“THE BALI WATER PROJECT”:

Small Scale Wastewater Treatment Systems and Surface Water Quality in Bali, Indonesia

A Master’s Thesis Presented to the Faculty California Polytechnic State University

San Luis Obispo

In partial fulfillment of the requirements for the degree of

Master of Science in Civil and Environmental Engineering

By

Daniel Garbely Matthew Merritt

Benjamin Monroe Sarah Munger

December 2002

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COPYRIGHT OF MASTER’S THESIS

I reserve the reproduction rights of this thesis for a period of seven years from the date of submission. I waive all reproduction rights after that time span has expired.

Daniel Garbely Date Matthew Merritt

Date

Benjamin Monroe

Date

Sarah Munger

Date

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MASTER’S THESIS APPROVAL TITLE: THE BALI WATER PROJECT:

SMALL SCALE WASTEWATER TREATMENT SYSTEMS AND SURFACE WATER QUALITY IN BALI, INDONESIA

AUTHORS: DANIEL GARBELY, MATTHEW MERRITT, BENJAMIN MONROE, SARAH MUNGER

DATE SUBMITTED: DECEMBER 2002

THESIS COMMITTEE MEMBERS: Dr. Yarrow Nelson Date

Dr. Robert Lang Date

Dr. Sam Vigil Date

Dr. Nirupam Pal Date

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ABSTRACT

THE BALI WATER PROJECT

DANIEL GARBELY, MATTHEW MERRITT, BENJAMIN MONROE, SARAH MUNGER

Current water quality and water treatment practices in Ubud, Bali, Indonesia were investigated by sampling two separate water supplies and developing prototype decentralized wastewater treatment designs. Collectively, this investigation and research was known as the Bali Water Project (BWP). The original goal of the project was to test and treat contaminated water from a small stream located near a rice field. The treatment system was to be a demonstration of low-tech water treatment that could be utilized in Bali. A thorough investigation of specific water quality parameters was performed for two streams that encompass the rice fields. After exploring different treatment options, a preliminary design of an Advanced Integrated Wastewater Ponding System (AIWPS), or “Oswald pond,” was completed. However, the AIWPS requires a minimum concentration of BOD to sustain its biological systems and after analyzing the water quality data, it was concluded that the water could not support biological treatment in an AIWPS. The members of the BWP determined that it would not be feasible to build a demonstration treatment system and were left to find a new demonstration site. An outfall from the Bali Spirit Hotel was discovered discharging raw kitchen wastewater into the Wos River. The Wos River runs through the town of Ubud and many hotels and resorts are located along this stretch. It was expected that there were more hotels discharging wastewater into the river so an investigation of how the water quality of the Wos changes as it flows through Ubud was begun. Water quality parameters were tested every other day at five sampling locations over the course of three weeks. The data did not show any clear trends in the change in water quality along the path of the river. However, the mean concentrations of phosphate and total chlorine were above EPA standards for streams and rivers at all five sampling sites. This is believed to be a result of the use of detergents and soaps that contain phosphates and bleach. The concentrations recorded are a cause of concern due to their effect on aquatic life because they can lead to eutrophication. As a potential method to reduce the amount of polluting wastewater being discharged to the Wos River, a decentralized wastewater treatment system was designed for the Bali Spirit Hotel. The design was intended to serve as a demonstration project that could be used for treatment systems at other hotels in the future. A sequencing batch reactor, an activated sludge reactor, a trickling filter and an intermittent sand filter with grease trap and septic tank were all designed and a comparison made between these designs. After an evaluation of the four designs it was concluded that the sequencing batch reactor was the most feasible option. A trickling filter preceded by a grease trap and septic tank was also recommended as an alternative solution. Water resources and wastewater treatment will be very critical to Bali’s future

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as tourism increases and the population continues to grow. These preliminary investigations into the current practices and state of water quality in the Wos River will provide a benchmark for further research, regulation and development of water quality and wastewater treatment in Ubud, Bali, Indonesia.

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ACKNOWLEDGEMENTS

The members of the Bali Water Project would like to thank the following people for all of

their support:

Dr. Robert Lang

Dr. Yarrow Nelson

Dr. Nirupam Pal

Dr. Sam Vigil

Ian Jasper

Chakra Widia and family

Management of Ibah Hotel & Resort

Management of Four Seasons Hotel & Resort

Allen Wilson

Mr. & Mrs. Garbely

Mr. & Mrs. Merritt

Mr. & Mrs. Monroe

Mr. & Mrs. Munger

Creek Environmental Laboratories

George Milanes

CH2M Hill

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TABLE OF CONTENTS

LIST OF TABLES..............................................................................................................vi

LIST OF FIGURES ...........................................................................................................vii

1 INTRODUCTION .........................................................................................................1

2 PROJECT BACKGROUND.........................................................................................5

2.1 Project Background .................................................................................................5

2.2 Water Resources on Bali .........................................................................................6

2.3 Pollution Problems on Bali ....................................................................................10

2.4 Pollution Problems in Ubud ...................................................................................12

2.5 Sampling Locations ...............................................................................................13

2.5.1 Rice Paddy Pollution .................................................................................14 2.5.2 Rice Paddy Sample Site Descriptions ........................................................15 2.5.3 River Pollution...........................................................................................19 2.5.4 Wos River Site Description .......................................................................22

3 PREPARATIONS & PROCEDURES ........................................................................26

3.1 Equipment ..............................................................................................................26

3.2 Sampling Procedures .............................................................................................27

3.2.1 Sample Types and Size ..............................................................................27 3.3 Constituent Description & Testing Procedures .....................................................28

3.3.1 Ammonia ...................................................................................................28 3.3.2 Biological Oxygen Demand (BOD) ..........................................................29 3.3.3 Free Chlorine .............................................................................................33 3.3.4 Total Chlorine ............................................................................................34 3.3.5 Total Coliform Bacteria .............................................................................36 3.3.6 Electrical Conductivity (EC), Salinity, & Total Dissolved Solids (TDS) .38 3.3.7 Dissolved Oxygen......................................................................................39 3.3.8 Nitrate ........................................................................................................40 3.3.9 Nitrite .........................................................................................................42 3.3.10 pH ..............................................................................................................43 3.3.11 Temperature ...............................................................................................45

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3.3.12 Turbidity ....................................................................................................45 3.4 Surveying ...............................................................................................................48

3.5 Problems and Modifications ..................................................................................49

3.5.1 BOD...........................................................................................................49 3.5.2 Total Coliform Bacteria .............................................................................51

4 CHARACTERIZATION OF RICE PADDY STREAM AND WOS RIVER ............53

4.1 Sampling the rice paddies and the Wos River .......................................................53

4.2 Preliminary results .................................................................................................53

4.3 Rice Paddy Sampling Site .....................................................................................55

4.3.1 Sampling Results .......................................................................................55 4.3.2 Data Analysis .............................................................................................57

4.4 Wos River Sampling Site.......................................................................................61

4.4.1 Sampling Results .......................................................................................61 4.4.2 Results of Water Quality Testing of the Wos River ..................................64

5 DISCUSSION OF WATER QUALITY RESULTS ...................................................78

5.1 Rice Paddy Site Conclusions .................................................................................78

5.2 Wos River Site Conclusions ..................................................................................79

5.3 Outfall Conclusions ...............................................................................................82

6 TREATMENT SYSTEM DESIGN.............................................................................84

6.1 Introduction............................................................................................................84

6.2 Design for Rice Paddy Demonstration Site ...........................................................84

6.2.1 Advanced Integrated Wastewater Ponding System (Oswald Ponds) ........84 6.3 Bali Spirit Design Options .....................................................................................86

6.3.1 Current Wastewater Practices in Bali ........................................................87 6.4 Design Approach ...................................................................................................92

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6.4.1 Wastewater Characterization.....................................................................93 6.4.2 Effluent Requirements ...............................................................................94

6.5 Trickling Filters .....................................................................................................94

6.5.1 Background on Trickling Filters................................................................94 6.5.2 Design Considerations for Trickling Filters ..............................................95 6.5.3 Design Process for Trickling Filters ........................................................105

6.6 Intermittent Sand Filter with Grease Trap and Septic Tank ................................118

6.6.1 Background ..............................................................................................118 6.6.2 Design Considerations .............................................................................120 6.6.3 Design Process .........................................................................................122 6.6.4 Conclusion...............................................................................................128

6.7 Traditional Activated Sludge System..................................................................135

6.7.1 Background ..............................................................................................135 6.7.2 Design Considerations .............................................................................136 6.7.3 Complete Mix Activated-Sludge Design Process....................................139 6.7.4 Discussion................................................................................................156 6.1.1 Conclusion...............................................................................................164

6.8 Sequencing Batch Reactor Activated Sludge System .........................................168

6.8.1 Background ..............................................................................................168 6.8.2 Design Considerations .............................................................................169 6.8.3 Sequencing Batch Reactor Design Process .............................................169 6.8.4 Conclusions on SBRs ..............................................................................177

6.9 Treatment and Disposal of Sludge .......................................................................185

6.9.1 Background ..............................................................................................185 6.9.2 Sludge Treatment Processes ....................................................................185 6.9.3 Conditioning and Dewatering..................................................................186 6.9.4 Digestion..................................................................................................188 6.9.5 Composting..............................................................................................189 6.9.6 Heat Drying and Other Thermal Processes .............................................190 6.9.7 Land Application .....................................................................................191 6.9.8 Discussion and Recommendation............................................................192

7 CONCLUSIONS .......................................................................................................195

7.1 Design Alternatives Evaluation...........................................................................195

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7.1.1 Design Criteria .........................................................................................195 7.1.2 Alternative Evaluation Matrix .................................................................198

7.2 Final Design Recommendations ..........................................................................204

7.3 Further suggestions and recommendations ..........................................................205

7.4 Signifigance of Pilot Plant Project.......................................................................206

REFERENCES ................................................................................................................209

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LIST OF TABLES

4.1 Results of Creek Environmental Laboratories' analysis of mid-day sample .........55 4.2 Results of Creek Environmental Laboratories' Analysis of midnight sample .......55 4.3 Rice paddy demonstration site sampling results....................................................56 4.4 BOD data from the rice field pilot plant sampling ................................................57 4.5 Sampling results from the first three Wos River Sites ..........................................62 4.6 Sampling results from the last two Wos River sites ..............................................63 4.7 Statistical analysis of Wos River sampling ...........................................................65 4.8 Statistical analysis of AquaTM bottled water.........................................................75 4.9 Sampling results from the Bali Spirit outfall and AquaTM bottled water ..............76 4.10 Statistical analysis of the Bali Spirit outfall testing...............................................77 6.1 Design assumptions for an onsite decentralized system at the Bali Spirit ............93 6.2 Design assumptions specific to trickling filters ...................................................110 6.3 Trickling filter design results ...............................................................................111 6.4 Trickling filter final design specifications ...........................................................113 6.5 Materials requirement for the trickling filter system...........................................115 6.6 ISF Total Dynamic Head .....................................................................................127 6.7 ISF Design Parameters ........................................................................................128 6.8 Materials requirement for the grease trap and ISF ..............................................129 6.9 Assumed values for complete mix activated sludge design ................................145 6.10 Design parameters for the activated sludge system.............................................161 6.11 Design parameters for secondary settling associated with the AS system..........161 6.12 Materials requirements for the activated sludge system......................................168 6.13 Phase timing for the SBR ....................................................................................177 6.14 Summary of SBR tank dimensions ......................................................................178 6.15 Materials requirements for SBR..........................................................................183 6.16 Summary of design parameters for SBR.............................................................184 7.1 Design ranking matrix .........................................................................................212

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LIST OF FIGURES

2.1 Trash dumped over hillside near initial pilot plant site. ........................................14 2.2 Varnish can in stream near initial pilot plant site. .................................................14 2.3 Ducks in rice paddies near initial pilot plant site...................................................15 2.4 Chakra’s map of rice paddies. ...............................................................................15 2.5 Rice Paddy Sampling Site Map .............................................................................16 2.6 Sampling location #1 at weir in rice paddies. ........................................................17 2.7 Wos River Sampling Site Map ..............................................................................18 2.8 Effluent debris below Bali Spirit Hotel .................................................................19 2.9 People doing laundry on banks of the Wos River. ................................................19 2.10 Outfall pipe below pool at Bali Spirit Hotel. .........................................................20 2.11 Trash on hillside below a hotel restaurant. ............................................................20 2.12 Effluent mixing with river water below Bali Spirit Hotel. ....................................24 2.13 Scum trail below Bali Spirit Hotel. ........................................................................24 3.1 Homemade Magnetic Stirrer..................................................................................50 4.1 DO Concentration Distribution vs. Sampling Location. .......................................58 4.2 Turbidity Quality Index. ........................................................................................59 4.3 Phosphorus Concentration Distribution vs. Sampling. ..........................................66 4.4 pH Distribution vs. Sampling Location. ................................................................67 4.5 Nitrate Concentration Distribution vs. Sampling Location. ..................................67 4.6 Nitrite Concentration Distribution vs. Sampling Location. ...................................68 4.7 Turbidity Distribution vs. Sampling Location. ......................................................69 4.8 TDS Concentration Distribution vs. Sampling Location. ......................................70 4.9 Electrical Conductivity Distribution vs. Sampling Location. ................................71 4.10 DO Concentration Distribution vs. Sampling Location. .......................................72 4.11 Total Chlorine Concentration Distribution vs. Sampling Location. ......................73 4.12 Free Chlorine Concentration Distribution vs. Sampling Location. .......................74 6.1 Treatment system at Ibah Hotel and Resort...........................................................88 6.2 Rainwater collection tanks at Udyana Lodge. .......................................................89 6.3 Decentralized wastewater treatment system at Udyana Lodge. ............................90 6.4 Solar panels used for lighting system at Udyana Lodge........................................90 6.5 Trickling filter profile view .................................................................................116 6.6 Trickling filter plan view .....................................................................................117 6.7 Northern wing plan view .....................................................................................131 6.8 Northern wing profile view .................................................................................132 6.9 Southern wing plan view .....................................................................................134 6.10 Southern wing profile view .................................................................................136 6.11 Intermittent sand filter profile view.....................................................................138 6.12 Main components of a complete mix activated sludge system............................139 6.13 Velocity Requirements for Inlet Port...................................................................165 6.14 Pipe sizing using slope of energy grade line. ......................................................165 6.15 Velocity Requirement with UPC minimum pipe diameter..................................166 6.16 Pipe sizing with UPC minimum pipe diameter. ..................................................166 6.17 Activated sludge plan view. .................................................................................170 6.18 Activated sludge profile view..............................................................................171

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6.19 Activated sludge detail ........................................................................................173 6.20 SBR plan view.....................................................................................................185 6.21 SBR cross-section plan........................................................................................186 6.22 SBR cross-section A-A........................................................................................187 6.23 SBR cross-section B-B ........................................................................................189 6.24 SBR cross-section C-C ........................................................................................191 6.25 SBR cross-section D-D........................................................................................192

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CHAPTER 1

INTRODUCTION

Each year more than three million people die world wide because of water related

diseases [38]. These diseases include cholera, typhoid, dysentery, and many more viral

and bacterial infections [6]. In most industrialized countries, the risk of exposure is very

low, but in developing countries some two billion people are at risk of contracting water

born illnesses [6]. According to the United Nations, 1.1 billion people do not even have

access to safe drinking water [22]. The risk is increased in developing countries because

of a lack of sanitation. Many of these problems could be eliminated with proper water

and waste treatment.

Reports from Indonesia’s Ministry of State for Population and Environment (SMPE)

have shown that at least twenty rivers in the archipelago of Indonesia have water

pollution problems of a significant nature. This pollution is partially due to inefficient or

absent wastewater treatment plants [11]. Fecal coliform contamination is found in 39%

of all of Indonesia’s urban water supplies [41]. This, in turn, results in over 100,000

incidences of water borne diseases each year, making water borne diseases the third

largest health issue in Indonesia [41]. These rivers are often contaminated from factories

that produce wood and pulp products, processed food, and textiles, creating areas with

high biological oxygen demand (BOD). Two rivers on the western side of Java are said

to have as much as “ten tons of chemical wastes dumped” in them daily [11]. To help

combat this problem, the SMPE created a program in 1989 known as PROKASH (Clean

Rivers). This plan encouraged provincial governors to set up local teams to identify the

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most polluted rivers in the region. Voluntary contracts were signed with factory owners

to reduce or eliminate their discharges into the rivers. The local teams would then

measure the quality of the factories’ effluent in order to determine of the amount of

pollution reduction achieved [32]. These programs had limited success, however, due to

the voluntary nature of the contracts. Many owners would sign the contracts, but few

actually made more than cursory changes to their processes. In 1990, BAPEDAL,

Indonesia’s environmental impact agency, established effluent standards for industries

including electroplating, caustic soda production, leather tanning, petrochemicals, pulp

and paper, textiles, rubber and sugar production, fertilizers, and plywood manufacturing.

Unfortunately, due to a lack of resources, BAPEDAL could not sufficiently monitor and

enforce these standards [32].

Bali, a small island to the east of Java in Indonesia, is one example of where water

quality is a pressing issue. According to a report on the state of Bali’s water resources, in

order to meet demands for the year 2015, it will be necessary to locate and develop 14.8

trillion liters per day of new water sources [20]. Even now, in some areas of Bali, the

locals must walk up to six hours in order to get fresh water from mountain springs [12].

The local water supply has been strained even more because of Bali’s rapid growth as a

tourist destination and producer of manufactured goods. According to one report, the

average hotel will use approximately 1.5 m3 of clean water per room per day [20]. To

reduce this amount, a few hotels have implemented water conservation techniques such

as low flow fixtures in bathrooms and rainwater collection, but most do not have the

knowledge or resources to implement such techniques.

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Hotel construction also introduces wastewater disposal issues. There is no government

regulation of hotel wastewater, so wastewater is often disposed with little or no treatment.

Most hotels use a septic tank system, where wastewater is allowed to infiltrate the ground

only partially treated. Some hotels are voluntarily installing wastewater systems to

maintain a high standard of water quality on their premises, but much of Bali’s

wastewater enters the groundwater aquifers substantially untreated.

In order to help alleviate the water problems in Bali, it was desired to construct a

wastewater treatment system that would serve as a pilot plant. This pilot plant would

demonstrate that the wastewater from a hotel can be treated and even reused on site. It

would show local officials the extent to which wastewater treatment can regenerate the

health of local rivers. The system would give these officials a standard from which they

can base the effectiveness of wastewater disposal at other hotels, serving as an example

of what other hotels can do to treat their effluent.

Before building a wastewater treatment pilot plant, an appropriate site must be found.

The construction site must have sufficient area to build and operate the system. In

addition, sloping hillsides will be favorable to limit the need for pumping, thus reducing

the cost of operation. Besides meeting the physical site requirements, the water to be

treated must contain a sufficient amount of pollution to warrant construction of the

demonstration project. To prove that a system is appropriate for use in Bali, the system

must be able to show a reduction in the amount of pollution in the water after treatment.

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This requires that the water entering the pilot plant contain substantial levels of BOD,

suspended solids, ammonia or some other pollutant to be removed.

While in Bali, the local water quality was characterized in order to find pollution problem

areas. Once an appropriate location was found, the wastewater characteristics were used

to create designs for several wastewater treatment systems that could treat the waste.

These designs were then evaluated against each other to produce the system to be

recommended for use as a pilot plant.

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CHAPTER 2

PROJECT BACKGROUND

2.1 Project Background The Bali Water Project began in the summer of 2001, when Bjamin Hittle, a business

student at UC Berkeley, traveled to the island of Bali and met Chakra Widia, a local

businessman who was very concerned with environmental issues in his hometown of

Ubud. In particular, Chakra was very concerned about local hotels dumping wastewater

into rivers used for swimming and bathing by the locals. After some research, Bjamin

came across a design for Oswald Ponds, an aerated lagoon system that could be used to

treat wastewater with very little maintenance and low operating costs [30]. Believing that

such a system would apply to the situation, Bjamin proposed it to Chakra as the perfect

solution for the problem. Chakra, very excited about being able to solve the water

pollution problems in his hometown, brought Bjamin to a local health official to describe

the Oswald Pond design. The official was skeptical about the idea, but told them that if

they could build a pilot plant and prove its effectiveness, he would consider creating

regulations requiring local hotels to treat their wastewater.

Chakra and Bjamin looked for land on which to build their pilot plant. They contacted

local farmers and landowners, and while many were excited by the project, none were

willing to donate their land. One farmer was willing to let them use his rice fields, but

wanted three million rupiah ($330US) per year for the use of the land. This was more

than Bjamin had expected or was willing to pay, so he suggested to Chakra the possibility

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of returning the next summer to build the ponds on the Widia property. The Widias own

a moderately sized piece of land has several rice paddies that Bjamin thought would

provide the perfect location to construct an Oswald pond system. After Bjamin's

departure from Bali, Chakra discussed the idea with his family and got permission to

build the system from his father.

In the spring of 2002, Dan Garbely, Ben Monroe, Matt Merritt, and Sarah Munger were

introduced to Bjamin through a Cal Poly professor. Bjamin had since done extensive

research on the Oswald ponds and had plans to not only construct a pilot plant, but also to

use the treated water for aquaculture, produce biosolids from the ponds for fertilizer,

bottle the treated effluent, and possibly capture the methane gas generated in order to

produce some electricity. Bjamin was a business student, however, and did not feel he

had the technical background to complete such a project. Seeing the project as a perfect

opportunity to apply their engineering skills and help a community, the Cal Poly students

decided to join Bjamin on his return trip to Bali that summer. To become more familiar

with Bali and developing country water quality issues in general, the students spent the

Spring of 2002 doing research and developing a plan for the project.

2.2 Water Resources on Bali Bali is an island located in the Indonesian archipelago and is approximately 5620 square

kilometers with mountains of around 2000 meters in elevation. To the north and south of

the central mountains are lowland agricultural lands. In the southern part of the island the

sloping land lends itself primarily to the rice crop, whereas the steep and cooler northern

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part grows more coffee and copra. There are also some arid regions in the western

mountain region and the eastern and northeastern slopes of Mount Agung. These parts of

the island are dry and therefore cannot support the wet-rice agriculture [26].

The climate on Bali differs greatly with respect to each region. The mean annual rainfall

on Bali ranges from less than 1000 mm on the eastern coast to over 3000 mm on the

southern slopes of Mount Agung. There is a well-defined wet season on Bali with 60-

90% of the total rainfall falling between the months of November and April [20]

.

The island of Bali has many sources of water including surface water, groundwater and

natural springs with an installed capacity of more than 88 million cubic meters per year.

In the past, these water sources have been developed primarily for the irrigation of 1073

km2 of rice paddies. There are a total of 822 irrigation weirs operated by the local water

agency to support this irrigation. In addition to these weirs, many smaller irrigation areas

have been developed and operated by the local rice growers associations called subaks.

The subak system helps to ensure that there is equal distribution to the rice paddies.

Unfortunately, the data for these smaller irrigation areas are not believed to be very

accurate[20]. Though records are kept for the diversions, it is believed that the amount

that is actually diverted is in excess of the true requirements for irrigation. These excess

diversions are not wasted, however, as they do contribute to groundwater and river

recharge through the irrigation system itself. The flow that is returned can then be reused

at the next diversion weir downstream.

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Although the island has many water resources, the recent increase in population and

tourism on the island is making it necessary to find new sources of water to meet the

increasing demands. Some of the options for new water supply sources that were

outlined in the 2000 Water Resources Report are [20]:

• Expansion of present sources – the expansion of current water supplies from

springs, streams and groundwater is the preferred option because it will minimize

the impact on the people and surrounding area when trying to locate new supplies.

Unfortunately, many of the existing water supplies are operating at their

maximum capacity or are already depleted. In these cases it is necessary to locate

new water supply sources.

• New Springs- this option involves locating springs that are not currently being

used for irrigation purposes. However, opportunities for this option are limited as

many of the springs are in use. It may be possible to work with the farmer to try

and arrange an agreement allowing both parties to use the water.

• Develop New Shallow Wells-this option is similar to that of the new springs. The

new development of shallow wells will have a direct impact on the surface water

flows and any downstream irrigation users.

• Develop New Groundwater Bores- this option has been widely used in Bali. The

water from these bores is generally of good quality and it is easy to locate the bore

close to the area it is needed. This option can be limited in areas where high

development of the groundwater resources has already occurred.

• River Abstractions (without storage)- there is large potential to develop the river

abstractions on several of the large rivers on Bali. However, to avoid adversely

9

impacting the agriculture in the area, water must be taken from the mouth of the

river. The water in the lower part of the river may be of lower quality due to

irrigation runoff and general pollution.

• River Abstractions (from in-channel storages)-this option would essentially act

like a dam within the riverbed, but there would still be a continuous flow. This

option can be accomplished using a gated weir or rubber dam to back up the flow

of the river. Sedimentation can occur behind the dam or weir, but this can be

remedied by flushing the system during the wet seasons high flows. Again, to

minimize the impact on existing agriculture lands, it will be necessary for the

developments to be located near the mouths of the rivers. The water quality near

the mouths of the rivers is generally poorer.

• Reservoirs (in-channel)- this option is similar to the river abstractions from in

channel storages in that it backs up the flow of the riverbed. It is different

because the structure that is used is permanent. This option is hydraulically

preferable because it allows for storage of the wet season flows. These storages

can later be released as needed during the dry season. Dams, however, are

expensive, often requiring land acquisition and relocation of people, and can be

unfriendly to the environment. Often times the potential dam sites are located far

away from the areas in need.

• Reservoirs (off-channel)- this option is similar to the in-channel reservoirs

because it allows the flow to remain constant throughout the year. This option

differs because the actual reservoirs that store the water is located away from the

river. The surplus flow during the wet season is diverted into the reservoir where

10

it is stored until it is needed. Again land acquisition and resettlement can be a

problem, but it is preferable to the irrigators because it will not disrupt the dry

season flow of the river.

• Lake Water- there are several lakes that could be considered for this option.

Unfortunately, the water quality in the lakes is poor and the water is located

approximately 40 km from the areas in need.

• Conversion of irrigated land-this option converts exis ting irrigated land to non-

irrigated agriculture. This option is attractive because river water would be used

for domestic water supply rather than for agriculture and the sites could be located

close to the areas in need. However, there would need to be significant

compensation costs and large political opposition.

Each of these options could help solve the eminent water shortage issue on the island;

however, these options will not be effective unless the quality of the water that is being

supplied is good. It is important that steps be taken to help ensure the quality of the water

sources on the island be kept in their pure and natural condition, this can be done by

addressing some of the pollution problems that are on the island.

2.3 Pollution Problems on Bali With the increase in population and tourism it is not only necessary to find new water

supplies, but to keep new and existing water supplies clean. It is becoming harder and

harder to find clean water on Bali and a lot of the problem lies within the culture itself.

The Balinese have always boiled water to drink and cook with, even when the tap water

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was safe enough to drink. According to one engineer, there was clean drinking water

available from the tap as early as 1970, but the boiling of water continued so disinfection

of water in treatment plants was discontinued to reduce maintenance costs[20]. Further

economic and political hardships in the last decade have caused the remaining treatment

plants to minimize their treatment or shutdown altogether. Many rural communities have

no access to treated water at all, and solely rely on deep underground aquifers, many of

which are being rapidly depleted.

There is also an island-wide problem with trash. Again this problem has roots within the

Balinese culture. In the past, all of the trash was placed in one central location within the

village or the family compound where it would naturally biodegrade. With the

introduction of plastic, the trash piles that used to biodegrade and naturally diminish, kept

growing and eventually end up in rivers and streams. So the Balinese people began to

burn the trash, releasing harmful dioxins into the air producing an even more serious

health threat to the public. Dioxin is a confirmed carcinogen that can cause reproductive,

developmental, and immune system problems and interferes with regulatory hormones

[8]. Since dioxin has a high resistance to degradation it is able to travel long distances

from the point of origin contributing to a trans-national pollution problem [8].

Tourism has also affected the environment on Bali, though some of these effects are

indirect and less obvious. Approximately 1.3 million tourists per year visit the island,

although this number has dropped a little since the terrorist attacks on September 11,

2001[26]. The most obvious environmental impact of the tourists is the conversion of

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agricultural land into hotels. This not only takes away from rice production but also

destroys the ecosystem in the rice paddies. Tourism has also caused an enormous

increase on the demand for water. According to the Lonely Planet Guidebook, in order to

accommodate for the air-conditioning, showers, cleaning, swimming pools and gardens,

many hotels will use over 570 liters of fresh water per day per room [26]. The average

hotel in the United States uses approximately 380 liters of fresh water per day per room

[28]. The majority of this water will soon have to be piped in from Bali’s central area,

depleting the water supply traditionally used for rice cultivation.

2.4 Pollution Problems in Ubud The town of Ubud is located in the southern region of Bali and is known for its art culture

and beautiful rice paddies. The average temperature is 26oC and the average rainfall is

approximately 2100 mm per year. The sources of water in Ubud are the same as the

majority of the island. Most villages have individual wells for each family compound.

Most families use this well-water for cooking, bathing and the toilet, but purchase bottled

water for drinking. Bathing and laundry are often still done in the nearby stream or river.

It is not uncommon to walk down the road in Ubud and find trash piles burning in the

rainfall runoff collection canals. These collection canals are concrete channels that run

parallel to the roads. The canals are located on both sides of the road and are

approximately 15 cm wide and 45 cm deep. Designed originally to collect rainfall runoff

the collection canals now collect everything from chickens to trash. This creates a larger

13

problem when it does rain, because the rain will move the trash to the outlet of the canal.

Often these outlets will dump on hillsides above rivers or directly into the river itself.

These collection canals also serve as an outlet from laundry facilities within the town of

Ubud. The canals within the town are frequently flowing full with frothy, cloudy water.

Sometimes people will bathe in these canals or use the water elsewhere on their property.

These pollution problems, unfortunately, are not only in the town of Ubud, they are an

island-wide problem.

The rivers that run through and around the town of Ubud, end up collecting the majority

of the trash. As stated earlier, this trash has many different origins. The majority of the

trash comes from the outlets of the collection canals. Additionally, a large portion comes

from people leaving their soap and shampoo packages along the banks of the river when

they are bathing or washing their clothes. A lesser portion is blown into the rivers during

windstorms.

2.5 Sampling Locations After exploration of the pollution problems both in the rice paddies and on the Wos

River, sampling sites where chosen that tried to encompass the problems as a whole. In

order for the data gathered at these sites to be considered useful, it was necessary that the

sites represent the affects of the pollution on the water quality. Also, at least one of the

sampling locations should serve as a basis. This basis would show how much the quality

14

Figure 2.2 - Varnish can in stream near initial pilot plant site.

of the water was degraded. These pollution problems and the sampling locations are

described below.

2.5.1 Rice Paddy Pollution The pollution in and around the rice

paddies was evident after an initial site

exploration. It was not uncommon to see

bits and pieces of plastic floating in the

irrigation canals or within the rice paddy

itself. The pollution worsens further

upstream. The soap and shampoo

packages indicated that people were using

the water for bathing and possibly laundry.

If there was a hillside nearby, it was not

uncommon find to trash where people had

just dumped it over the bank. A lot of this

trash then ended up in the canals or

streams that were providing water to the

rice paddies (Figure 2.1). Near the initial

pilot plant site there were often empty cans

of varnish in the stream (Figure 2.2). Just above this same stream there was an outlet pipe

that ran toilet water from the family compound directly into the stream. Another example

is ducks and a cow that was living among the rice paddies (Figure 2.3). The fecal matter

Figure 2.1 - Trash dumped over hillside near initial pilot plant site.

15

Figure 2.3 - Ducks in rice paddies near initial pilot plant site.

Figure 2.4 – Chakra’s map of rice paddies.

surely ended up in the rice paddy during

rains. The extent of the pollution in the

rice paddies prompted further exploration

of the rivers and streams that were

supplying the water for the irrigation of

the rice paddies.

2.5.2 Rice Paddy Sample Site Descriptions

After the exploration of the rice paddies it was determined that the sampling should be

performed at two separate locations. The rice fields are sloped from west to east and from

north to south. Running through the center of the field is a stream (Figure 2.4). Running

16

along the eastern border of the rice paddies is another smaller stream. This smaller

stream is the one labeled as S1 in Figure 2.4. Both of these streams run down-gradient

from north to south. Water from the larger stream is diverted into individual rice paddies

and then allowed to flow naturally from paddy to paddy until reaching the smaller stream.

One sampling location was chosen along each stream (Figure 2.5). This provided data for

both streams and allowed us to see if there was any significant difference between the

quality and quantity of the water entering versus the water leaving the rice paddies.

In one section of the larger stream there was a large cement spillway or weir (Figure 2.6).

It was at this point that much of the water was diverted for use in the rice paddies. This

site was chosen because it was representative of the water that flowed into all of the rice

paddies below and the flow was fairly constant. At this point in the stream, the water is

Figure 2.5 – Rice Paddy Sampling Site Map.

17

Figure 2.6 - Sampling location #1 at weir in rice paddies.

approximately 0.75 meters deep and 1.5 meters wide. The sampling point is surrounded

by ground vegetation and palm trees.

From the first sampling point, the water

flowed downhill, from paddy to paddy,

until it discharged into the second stream.

It was just downstream from this point that

a second, smaller sampling point was

chosen. It has a width of approximately

0.25 meters and a depth of 0.2 meters.

The stream’s bank is covered in a grassy ground covering and although there are no palm

trees directly adjacent to the sampling location, there are several in the vicinity.

18

Figure 2.7 - Wos River Sampling Site Map

19

Figure 2.8 - Effluent debris below Bali Spirit Hotel.

Figure 2.9 - People doing laundry on banks of the Wos River.

2.5.3 River Pollution The nearby Wos River was also sampled to see what kind of pollution was being

introduced. The Wos River runs from the Bali highlands, through Ubud and continues

toward the ocean. It has a wide range of seasonal flows. During the rainy season the river

is calm enough for swimming and bathing.

The initial exploration started at the outfall

of the Bali Spirit Hotel (Figure 2.7).

Aside from the obvious effluent pollution

in the river, the banks were littered with

plastic bottles, bags, and soap and

shampoo packages (Figure 2.8). This river

is also used for bathing and laundry. There

were several people doing their laundry

along the banks (Figure 2.9). As the

exploration proceeded up the river,

another outlet pipe was noticed coming

from Bali Spirit (Figure 2.10). Although,

no effluent was observed flowing from it,

it was speculated that it might be an

overflow for storm drains. Near the

bridge, just above Bali Spirit, it was noticed that there was an outlet for the rainfall runoff

collection canals. It was also noticed that no measures were being taken to collection any

20

Figure 2.10 - Outfall pipe below pool at Bali Spirit Hotel.

Figure 2.11 - Trash on hillside below a hotel restaurant.

runoff from the bridge. The exploration

continued through the town of Ubud,

where the pollution problems previously

stated, were evident.

Upon rejoining the Wos River at its

intersection with the Cerik River, the

pollution problems were similar to the

ones found around the Bali Spirit Hotel. There were plastic bottles, bags, and soap and

shampoo packages. This was another bathing spot. Also, near the bridge, just below the

intersection was an outlet for one of the collection canals. The hillside below this outlet

was also covered in trash and other debris.

Proceeding along the ridge, which

separated the Cerik and the Wos rivers, it

became evident how common it was to

dump trash over the hillside (Figure 2.11).

This trash will eventually end up in the

rivers either when it rains or when the

wind picks up. After crossing the river at

a bamboo bridge far from any villages or

hotels, it was noticed that the amount of trash in this area seemed to be far less than

anywhere else.

21

A second exploration of the river was done after samples had been collected for quite

sometime. The purpose of this exploration was to try to locate more point sources along

the river and to quantify the flow of the river. This meant walking/swimming the actual

river. The exploration started at what would be the farthest sampling site, the bamboo

bridge. There was also a minimal amount of trash at this site and it was discovered upon

talking to local that there was only one small village located upstream. The flow

measured at this point was equal to 0.816 m3/s.

Since there were only rice paddies between this point and the intersection of the Cerik

and Wos Rivers, the exploration continued at this point. Flow measurements were taken

both above and below the intersection. The measured flows were 0.625 m3 /s and 1.564

m3/s, respectively. Further downstream, approximately 50 meters from the bridge, there

was more bathing spots and another outfall that looked like it came from an apartment

complex as shown on Figure 2.7. It was unclear whether this outfall was for toilets or

gray-water. There was also a hose with running water that was being used for bathing

purposes and possibly laundry purposes as well. The flow measured at this point was

equal to 1.306 m3/s. Approximately another 25 meters beyond this point another outfall

pipe was located. It was unclear where the pipe was coming from, but it was speculated

that it was either a family compound or another apartment complex.

The exploration continued down the Wos River while no other outfalls were spotted, the

amount of trash was still largely present. It was collecting along the banks and in spots

22

with stagnant water. Probably the most impressive display of this was at a large pool of

water that was building up behind a couple of boulders. The amount of plastic bottles in

this area alone must have numbered in the thousands. The plastic bottles had also been

deposited along the banks of the river at different levels were the water had been. No

further flow measurements were taken due to the steep banks and high velocity of the

river.

It was thought that if one hotel was polluting the river with untreated wastewater that

there were probably more. Many of the hotels in Ubud lined the gorge through which the

Wos River ran and their respective discharges could be affecting the water quality of the

river in some manner. It was proposed that the water quality of the Wos River would

change negatively as it flowed through Ubud due to the affect of polluting discharges

from hotels and resorts. These two explorations help to determine and confirm which

points would best represent the pollution problems along the Wos River. These sampling

locations are discussed below.

2.5.4 Wos River Site Description Five sampling sites were chosen on the Wos River that would be easily accessible and

would provide a good representation of the fate of the contaminants as the river made its

way from the mountains through the town of Ubud. In order to understand specifically

how this type of pollution affected the water quality the sampling locations were chosen

to be both above and below known outfalls.

23

The first sampling point was about 2 km north of Ubud in a remote valley. The samples

were taken just downstream from a bamboo bridge that provided the only river crossing

in the valley. This point was to serve as the baseline for water quality as there was only

one village upstream from it.

The second sampling point was just above the intersection of the Cerik and Wos Rivers.

This point was in the village of Campuan just below a major vehicular bridge. This point

was a very popular bathing spot and a lot of garbage from the street above would wash

down during rainstorms.

The third sampling point was about 50 m downstream from the vehicular bridge and was

also used for bathing. Houses and apartment blocks on either side of the river discharge

wastewater and trash into the river near this spot. After the third point, the river became

very overgrown and accessibility was very limited. It was later determined that this area

was largely surrounded by rice paddies.

24

Figure 2.12 - Effluent mixing with river water below Bali Spirit Hotel.

Figure 2.13 - Scum trail below Bali Spirit Hotel.

The fourth point was several kilometers downstream at the intersection of the river with

another vehicular bridge. There were several residences as well as a midsized hotel,

called the Bali Spirit, in this area. The hotel had several outfalls directly into the river,

one of which was determined to be kitchen waste. The fourth sampling point was located

about 50 m upstream from the kitchen outfall.

The fifth sampling point chosen was the

effluent pipe at the Bali Spirit Hotel. The

outfall was a 102 mm pipe partially hidden

by vegetation. Periodically it would

discharge wastewater that was warm,

milky, oily and gritty (Figure 2.12). A

scum trail was left where the wastewater

flowed over the rocks into the stream and

in certain low points the scum had

collected and was up to 51 mm thick

(Figure 2.13). There was also a very

noticeable musty foul odor and where the

wastewater entered the stream the river

water was quite turbid. The outfall is

located below the restaurant at the Bali

Spirit Hotel and dishwashers and running

water could be heard as the wastewater was flowing from the outfall. It was determined

that the outfall discharge must be untreated kitchen wastewater and could possibly

25

include the wastewater from their laundry services. Due to the large rocks and the speed

of the river, sampling below the outfall was not possible. This limited the sampling sites

to these five.

26

CHAPTER 3

PREPARATIONS & PROCEDURES

3.1 Equipment Since there were minimal testing facilities in Bali, testing equipment was brought from

the United States. This equipment needed to be lightweight, portable, and easy to use in

a developing country running on 220V. In addition, the team would need to test for a

wide range of constituents to accurately determine how the water would need to be

treated. This made the choosing of the right equipment very important.

Because it was desired to prove the efficiency of a water treatment system, water quality

parameters were chosen that would be able to show the efficiency of biological waste

treatment. While many basic water quality parameters can be measured using simple

probes, testing for some pollutants is more complicated and requires laboratory

equipment and chemical reagents. After conferring with the Cal Poly environmental

engineering faculty and doing some research, the team decided to use the Hach Company

as their main equipment source. The Hach Company specializes in portable laboratory

kits and probes, so they seemed like the most logical choice. With a generous grant from

the Civil and Environmental Engineering Department, the team purchased the following

equipment from Hach:

• CEL/890 Advanced Portable Laboratory, which includes the DR/890

Colorimeter, Pocket Turbidimeter, sensION1 pH/mV/Temp Meter, sensION5

27

Conductivity/TDS Meter, and Digital Titrator, plus reagent sets for 26

parameters.

• SensION6 Dissolved Oxygen meter

• MEL/Membrane Filtration (MF) Total Coliform Lab

• Portable Incubator

• 300 mL BOD bottles

In addition, the stream flow measurement and basic surveying equipment were

purchased:

• Wading Rod

• Gurly meter

• Hand level

• Measuring tape

3.2 Sampling Procedures In order to get representative and accurate data, a sampling protocol was created and

followed every time samples were taken. These protocols were the basis of an overall

quality assurance project plan (QAPP), which is described in detail below.

3.2.1 Sample Types and Size Grab samples were collected twice a day at each site in one clean 600 mL plastic water

container and one 100 mL Nasco® Whirl-pak. All samples were numbered and

immediately transported back to the lab for analysis. The samples were never stored for

more than 2 hours before analysis making preservatives unnecessary, although each

28

Whirl-pak contained sodium thiosulphate to dechlorinate the sample for ammonia and

coliform testing. Time and date of the sample and sample taker were also recorded in a

logbook.

3.3 Constituent Description & Testing Procedures The samples were analyzed for the constituents listed below. A brief description of each

testing method is included, with specific procedure methods detailed in full.

3.3.1 Ammonia Ammonia is a form of nitrogen present in wastewater that can be used to indicate

pollution in the water. The bacterial decomposition of organic nitrogen and death and

decomposition of plant and animal proteins are both major sources of ammonia. The

relative amount of ammonia in water can also indicate the age of the wastewater.

Ammonia testing is performed on the HACH DR/890 Colorimeter using the salicylate

method (Method 8155) as detailed below. This tests for ammonia levels from 0 to 0.50

mg/L NH3—N and is used for water, wastewater, and seawater.

Ammonia testing procedure

1. Turn on the colorimeter by pressing the exit key. Press the PRGM key to enter

the preset Ammonia program.

2. Enter 64 and press ENTER. The display shows mg/L, NH3—N and the ZERO

icon. This lets you know you have entered the correct program.

3. Fill one clean sample cell with 10 mL of rinse of water. This will act as the blank.

4. Fill a second clean sample cell with 10 ml of the sample.

29

5. Add the contents of one Ammonia Salicylate Reagent Powder pillow to each

sample cell. Cap both cells and swirl vigorously to dissolve the reagent.

6. Press TIMER and then press ENTER. This will begin a three-minute reaction

period.

7. At the end of the three-minute period, the timer will beep. The display will show

15:00 TIMER 2. At this point, add the contents of one Ammonia Cyanurate

Powder Pillow to each sample cell. Cap both cells and shake vigorously to

dissolve the reagent.

8. Press ENTER to begin the fifteen-minute reaction period.

9. At the end of the reaction period, the timer will beep. Wipe off the blank sample

cell with a Kimwipe to remove any fingerprints or liquid on the cell. Place the

blank sample cell in the colorimeter, properly install the light shield, and press

ZERO. The cursor will move to the right twice and then show 0.00 mg/L NH3—N

to show that the meter has been zeroed.

10. Wipe off the prepared sample cell with a Kimwipe and place it in the colorimeter

making sure the light shield in tightly in place. Press READ on the keypad and

the display will show the concentration in mg/L NH3—N.

11. Record the result in the lab book and rinse out all of the equipment with clean

rinse water.

3.3.2 Biological Oxygen Demand (BOD) The BOD was tested using standard 300 ml BOD dilution bottles and Hach brand nutrient

solution. The BOD was measured two ways for quality assurance. The first method was

derived from Standard Methods and involves plotting the mg/L dissolved oxygen

30

remaining in each diluted sample versus the ml of sample diluted. Another method of

determining the BOD of each individual sample was to use equation 2-56 from Metcalf &

Eddy (2003). The dissolved oxygen is measured using a Hach sension 6 Dissolved

Oxygen meter. It is calibrated by HACH method 8166, using the HACH DR/890

Colorimeter and section 3.3.5 of the sension 6 Portable Dissolved Oxygen Meter

Instruction Manual.

Equipment calibration

1. Collect 400 ml of AQUA brand drinking water to be used as the sample.

2. Turn on the colorimeter by pressing the EXIT key. Press the PRGM key to enter

the prestored program number for the High Range Dissolved Oxygen method.

3. When prompted for the program, press 70 and ENTER. The display will show

mg/L O2 and the zero icon to show the correct program number was entered.

4. Fill a sample cell with at least 10 ml of sample. This will be the blank.

5. Fill the blue ampul cap with sample and collect at least 40-ml of sample in a 50-

ml beaker.

6. Using the 50-ml beaker with sample, fill a High Range Dissolved Oxygen

AccuVac Ampul with sample.

7. Without inverting the ampul, immediately place the ampul cap securely over the

tip of the ampul. Shake for 30 seconds.

8. On the colorimeter, press TIMER and ENTER. A 2 minute reaction period will

begin.

9. When the timer beeps, shake the ampul for another 30 seconds.

31

10. Place the blank into the cell holder. Tightly cover the sample cell with the

instrument cap.

11. Press ZERO. The cursor will move to the right, then the display will show 0.0

mg/L O2.

12. Place the AccuVac ampul into the cell holder. Tightly cover the ampul with the

instrument cap. Wait 30 seconds for the air bubbles to disperse from the light

path.

13. Press READ. The cursor will move to the right, then the result in mg/L O2 will be

displayed. This is the known dissolved oxygen present in the sample

14. Fill a standard 300-ml BOD dilution bottle with the sample water. Pour slowly,

making sure that the water runs down the side of the glass and that no bubbles are

formed.

15. Place the BOD bottle on a magnetic stirrer and insert the BOD funnel and stirrer

into the BOD bottle. Insert the dissolved oxygen probe into the BOD funnel.

16. Press the CAL key located in the lower left corner of the probe keypad. The Cal

icon will appear on the display with a flashing questions mark. The main display

will show the barometric pressure.

17. Press the READ ENTER key three times to skip to the display showing 100%.

18. Use the keypad to enter the known dissolved concentration determined in step 13.

Press the READ ENTER key. The meter will then return to the read mode and

calibration is complete.

32

Dilution water preparation

1. Collect 6 liters of AQUA drinking water in a large container.

2. Add the contents of one HACH nutrient slurry powder pillow.

3. Shake the container until the nutrient slurry is dissolved and well mixed.

BOD testing procedure

1. For each sample, three dilutions will be made. Use Table 2-16 of Metcalf & Eddy

to determine suitable dilutions based upon the expected BOD range. Dilutions of

50, 100 and 200 ml of sample were typically used.

2. Collect and label three BOD bottle with the sample #, dilution, date and time.

3. Measure the undiluted sample dissolved oxygen using the sension 6 dissolved

oxygen meter. Record.

4. Measure the desired amount of sample in a graduated cylinder. Slowly pour into

a standard 300 ml BOD bottle, being careful not to create any bubbles.

5. Fill the BOD bottle with nutrient solution, pouring slowly down the sides of the

glass, until the water is just above the neck of the bottle.

6. Place the BOD bottle onto the magnetic stirrer. Insert the BOD funnel and stirrer

into the BOD bottle. Insert the dissolved oxygen meter into the BOD funnel.

7. Determine the diluted dissolved oxygen. Record.

8. Repeat steps 4 through 7 for each desired dilution.

9. Fill a standard 300-ml BOD bottle with nutrient dilution water. Determine the

dissolved oxygen as before. Record. This will be the control.

10. Place all BOD bottles into the insulated coolers and cover.

33

11. After four days, remove the BOD bottles and measure the dissolved oxygen as

before using the magnetic stirrer, BOD funnel and dissolved oxygen meter.

12. Calculate the BOD of each sample using equation 2-56 of Metcalf & Eddy.

13. Plot dissolved oxygen remaining in mg/L of each diluted sample versus the

volume of sample diluted in ml. Determine a best- fit line.

14. The average BOD in mg/L is equal to the slope times 300 ml minus the y-

intercept.

15. Compare the average BOD versus the individual BOD calculated for each sample.

3.3.3 Free Chlorine Chlorine is one of the main components of detergents and soaps, which we suspected

might be present in the water. High levels of chlorine can be toxic to aquatic life and

beneficial bacteria. Free chlorine testing is performed using the HACH DR/890

Colorimeter. Method 10069, the DPD method will be used. This method tests for free

chlorine levels from 0 to 5.00 mg/L Cl2. This method is adapted from standard methods

and is used for water, wastewater, and seawater. Free chlorine is measured in the field

because plastic containers contain chlorine demand. This will affect the results by

absorbing the chlorine in the water.

Free chlorine testing procedure

1. Turn on the colorimeter by pressing the EXIT key. Press the PRGM key to enter

the prestored program for chlorine.

34

2. When prompted for the program, press 8 and ENTER. The display will show

mg/L Cl2, and the ZERO icon to show that the correct program was entered.

3. Fill two sample cells with 10 ml each of the sample. This must be done

immediately upon sample collection because the chlorine will degrade if stored.

4. Add the contents of one DPD Free Chlorine Powder Pillow to one of the sample

cells. This will be the prepared sample. Cap and swirl vigorously to dissolve the

reagent.

5. Within one minute of adding the reagent, fill each sample cell to the 25 ml mark

with rinse water. Cap and invert each cell twice to ensure mixing.

6. Using a Kimwipe, wipe off the sample cell containing the diluted sample without

reagent (the blank). This is to remove all fingerprints and liquid from the outside

of the cell. Place the blank in the colorimeter, put the light shield tightly on the

colorimeter, and press ZERO. The cursor will move to the right twice and the

display will show 0.00 mg/L Cl2 to show that the meter has been zeroed.

7. Wipe off the prepared sample with a Kimwipe and place it in the colorimeter,

making sure the light shield is tightly in place. Press READ and wait for the

display to show the concentration in mg/L Cl2.

8. Record this value in the lab book in the appropriate place and clean all equipment

with rinse water.

3.3.4 Total Chlorine Total chlorine testing is performed using the HACH DR/890 Colorimeter. Method

10070, the DPD method will be used. This method tests for total chlorine levels from 0

to 5.00 mg/L Cl2. This method is adapted from standard methods and is used for water,

35

wastewater, and seawater. Total chlorine is measured in the field because plastic

containers contain chlorine demand. This will affect the results by absorbing the chlorine

in the water.

Total chlorine testing procedure

1. Turn on the colorimeter by pressing the EXIT key. Press the PRGM key to enter

the prestored program for chlorine.

2. When prompted for the program, press 8 and ENTER. The display will show

mg/L Cl2, and the ZERO icon to show that the correct program was entered.

3. Fill two sample cells with 10 ml each of the sample. This must be done

immediately upon sample collection because total chlorine includes free chlorine

which oxidizes quickly with many inorganic and organic substances. Sample

storage will cause the concentration to degrade.

4. Add the contents of one DPD Total Chlorine Powder Pillow to one of the sample

cells. This will be the prepared sample. Cap the cell and swirl vigorously to

dissolve the reagent.

5. Press TIMER and then ENTER on the keypad, this will begin a two-minute

reaction period.

6. After the timer beeps, signaling the end of the reaction period, fill each sample

cell up to the 25 ml mark with rinse water. Cap both cells and invert twice to

ensure complete mixing.

7. Using a Kimwipe, wipe off the sample cell containing the diluted sample without

reagent (the blank). This is to remove all fingerprints and liquid from the outside

of the cell. Place the blank in the colorimeter, put the colorimeter light shield

36

tightly in place, and press ZERO. The cursor will move to the right twice and the

display will show 0.00 mg/L Cl2 to show that the meter has been zeroed.

8. Wipe off the prepared sample with a Kimwipe and place it in the colorimeter,

making sure the light shield is in place. Press READ and wait for the display to

show the concentration in mg/L Cl2.

9. Record this value in the lab book in the appropriate place and clean all equipment

with rinse water.

3.3.5 Total Coliform Bacteria Coliform bacteria are a rod shaped bacteria found in the human intestinal tract and have

been used as an indicator of human fecal contamination of water samples. To determine

whether the samples had any organisms, the sample would be analyzed in the lab using

the Hach MEL Total Coliform Laboratory kit. This kit used the membrane filter

technique to determine the number both total and E. Coli coliforms present in the sample.

Problems with the sterility of our dilution water required us to make several changes to

this test and are fully discussed in the Procedure Modifications section.

Dilution Technique

1. Wash hands.

2. Shake the sample collection container vigorously, approximately 20 times.

3. Use a sterile transfer pipet to pipet 11 mL of sample into a sterile dilution bottle.

4. Add 99 mL of Buffered Dilution Water to the bottle.

5. Recap the bottle and shake vigorously 25 times.

37

6. If more dilutions are needed, repeat Steps 3 to 5 using clean, sterile pipets and

additional bottles of sterile buffered dilution water.

Coliform testing procedure

1. Place a sterile absorbent pad in a sterile petri dish using sterilized forceps.

Replace petri dish lid.

2. Invert an m-ColiBlue24 Broth PourRite Ampule 2 to 3 times to mix the broth.

Break open the ampule. Carefully pour the contents evenly over the absorbent

pad. Replace the petri dish lid. Repeat steps 1 and 2 for each petri dish being

prepared.

3. Set up the Membrane Filter Apparatus. Using sterilized forceps, place a

membrane filter, grid side up into the assembly.

4. Shake the sample vigorously to mix. Pour sample or diluted sample into the

funnel. Use the vacuum syringe to filter the sample. Rinse the funnel walls 3

times with sterile buffered dilution water. Use 20 to 30 mL for each rinse.

5. Remove the vacuum syringe and lift off the funnel top. Using sterilized forceps,

transfer the filter to the previously prepared petri dish.

6. With a slight rolling motion, place the filter, grid side up, on the absorbent pad.

Check for air trapped under the filter and make sure the filter touches the entire

pad. Replace the petri dish lid.

7. Invert the petri dish and incubate at 35 ± 0.5°C for 24 ± 4 hours.

8. After incubating, count the colonies. Red and blue colonies indicate total

coliforms and the blue colonies indicate E. Coli.

38

3.3.6 Electrical Conductivity (EC), Salinity, & Total Dissolved Solids (TDS) The electrical conductivity of a sample is measured to determine the ability of the water

to conduct an electrical current and thus is an indicator of the amount of ions in the

solution. This can then be easily related to the total dissolved solids concentration and

the salinity of the water. Salinity is a measure of the salt concentration in a water sample.

The salinity of water most affects its ability to be used as irrigation water as increased salt

content in a soil can seriously effect plant growth. Dissolved Solids are those particles

present in the water that pass through a 2µm filter and can affect the suitability of the

water for irrigation [28]. Conductivity, Salinity, and TDS are all tested using the HACH

sensION5 Conductivity Meter, product number 51800-18.

Equipment calibration The HACH Conductivity meter is calibrated using a known standard of 1000 µS/cm.

1. Place the probe in the 1000 µS/cm standard and agitate to dislodge bubbles in the

probe cell. Avoid putting the probe on the bottom of the container or touching the

sides.

2. Press CAL on the keypad.

3. Use the arrow keys to scroll to the 1000 µS/cm calibration option. Press ENTER.

4. Wait for the reading to stabilize and the meter is calibrated.

Testing procedures for EC, Salinity, and TDS

1. Collect a sample from the river using a sampling bottle. Rinse the bottle several

times with the sample water before keeping a sample.

39

2. Turn on the probe by pressing the EXIT key. Place the probe in the sample bottle,

making sure that the probe does not touch the bottom or sides of the bottle.

3. To test conductivity, press the COND key and then press READ. Wait until the

reading stabilizes and then record it in the lab book.

4. To test salinity, press the SAL key and then press READ. Wait for the reading to

stabilize and then enter the reading into the lab book.

5. To test TDS, press the TDS key and then press READ. Wait for the reading to

stabilize and then record it in the lab notebook.

3.3.7 Dissolved Oxygen The amount of dissolved oxygen present in a sample is a direct measurement of how

suitable the water is for aerobic microorganisms as well as other aquatic life. Aerobic

microorganisms are responsible for the breakdown of many pollutants in wastewater and

the presence of dissolved oxygen is essential for the growth of these bacteria and to

minimize the formation of noxious odors. The dissolved oxygen probe was calibrated by

establishing the dissolved oxygen of a clean water sample using Hach colorimetric

method 8166, and then calibrating the probe with this known sample. This method is

detailed in the BOD section above. Once calibrated, the dissolved oxygen of the samples

was measured on site using a Hach SensIon6 portable probe.

Dissolved oxygen testing procedure

1. Insert the probe into the sample to the desired depth. The probe must be deep

enough to cover the thermistor (metallic button) located on the side of the probe.

40

2. Agitate the probe in the sample to dislodge air bubbles from the sensing area of

the probe tip.

3. Stir the sample vigorously with the probe or use a stir stand and stir bar. When

measuring deep bodies of water, create sufficient flow across the probe tip by

pulling on the cable to move the probe up and down. When using a stir stand and

magnetic stir bar, increase the speed of the stir bar until the displayed value no

longer increases with the stirring rate.

4. When the reading on the meter stabilizes, record or store the value in the meter

memory.

5. Press the CONC % key on the keypad to change the display from concentration in

mg/L to % saturation.

3.3.8 Nitrate Nitrate nitrogen is a completely oxidized form of nitrogen and can be potentially very

harmful to infants. Nitrate testing was performed using the HACH DR/890 Colorimeter.

Method 8039, the cadmium reduction method was used. This method tests for nitrate

levels from 0 to 30.0 mg/L NO3- - N using powder pillows. This method is used for

water, wastewater, and seawater.

Nitrate testing procedure

1. Press the exit key to turn on the colorimeter.

2. Press the PRGM key to enter the preset program for nitrate testing.

3. Enter 51 on the keypad and press ENTER. The display shows mg/L, NO3-N and

the ZERO icon to show that the correct program has been entered.

41

4. Fill one of the sample cells with 10 ml of the sample. This is done by first

measuring 10 ml of the sample into a graduated cylinder and then carefully

pouring it into the clean sample cell.

5. Open and add the contents of one NitraVer 5 Powder Pillow to the sample cell.

Place the cap on the sample cell. This is the prepared sample.

6. Press TIMER and then press Enter on the keypad. This begins a one-minute

reaction period. During this one-minute reaction period, shake the sample cell

vigorously. The timer on the colorimeter beeps, signaling the end of the reaction

period. Stop shaking.

7. After beeping, the display will show: 5:00 TIMER 2. Press ENTER to begin a

five-minute reaction period. Let the sample vial sit undisturbed during this

period.

8. Using the same method, fill a second sample cell with another 10 ml of sample.

This will act as the blank.

9. Wipe off the blank sample cell with a Kimwipe to remove fingerprints or liquid.

After the five-minute reaction period is finished, place the blank in the

colorimeter, put the light shield tightly in place, and press ZERO. The cursor will

move to the right twice and then the display will read: 0.0 mg/L NO3-N. The

colorimeter is now zeroed.

10. Wipe off the prepared sample cell with a Kimwipe and place it into the

colorimeter. Be careful to make sure the light shield is properly in place.

11. Press READ on the colorimeter and wait for the display to show a value in mg/L

NO3-N.

42

12. Record this reading in the lab book and rinse all equipment with clean water.

3.3.9 Nitrite Nitrogen as nitrite is an important parameter in water because it is an indicator of past

pollution and even at low concentrations can be extremely toxic to aquatic life.

Fortunately, it is relatively unstable and can be easily oxidized to nitrate. Nitrite testing

was performed using the HACH DR/890 Colorimeter. Method 8507, the diazotization

method was used with powder pillows. This method is USEPA approved for reporting

wastewater and drinking water analyses and tests for nitrite levels from 0 to 0.350 mg/L

NO2—N.

Nitrite testing procedure

1. Turn on the colorimeter by pressing the EXIT key.

2. Press PRGM on the keypad. The display will show PRGM ? to prompt for the

prestored program number.

3. Enter 60 and then press ENTER. The display will then show mg/L, NO2—N and

the ZERO icon to show that the correct program has been entered.

4. Fill a clean sample cell with 10 ml of sample. This is done by first measuring 10

ml of sample into a graduated cylinder and then carefully pouring it into the

sample cell.

5. Add the contents of one NitraVer 3 Nitrite Reagent Powder Pillow to the sample

cell. Cap the sample cell tightly and shake several times to dissolve the reagent.

This is now the prepared sample.

43

6. Press TIMER and then ENTER on the keypad. This will begin a fifteen-minute

reaction period.

7. When the time is finished it will beep. When this happens, fill another clean

sample cell with 10 ml of the sample, using the same method as the first one.

This sample cell will be used as the blank.

8. Wipe off the outside of the blank sample cell with a Kimwipe to remove all

fingerprints and liquid. Place the blank in the colorimeter making sure the light

shield is tightly in place. Press ZERO and wait for the cursor to move to the right

twice. The display will read: 0.000 mg/L NO2—N to show that it has been

zeroed.

9. Wipe off the prepared sample cell with a Kimwipe and place it in the colorimeter.

Be careful to check that the light shield in properly in place.

10. Press READ on the keypad and wait for the display to show a value in mg/L

NO2—N.

11. Record this reading in the la book and clean all equipment with rinse water.

3.3.10 pH The pH is a measure of the hydrogen ion concentration in both natural and waste waters.

Since biological life can only exist in a small concentration range, wastewaters with

extreme pH need to be treated so they do not negatively affect natural waters. The pH

was measured on site with a Hach SensIon1.

44

Calibration Procedure

1. Prepare two pH buffers, either 4.01 and 7.00 or 7.00 and 10.01.

2. Press I/O/EXIT to turn the instrument on. From the Reading mode, press CAL.

CAL and flashing ? will appear in the upper display area, along with Standard and

1.

3. Press READ/ENTER. The temperature and pH values will be updated until a

stable reading is reached.

4. When the reading has stabilized or been accepted, the standard number will

change to 2.

5. Remove the probe from the first buffer and rinse with deionized water. Place the

probe in the second buffer.

6. Repeat steps 5 and 6 for the third buffer and press EXIT.

7. Press READ/ENTER. The temperature and pH values will be updated until a

stable reading is reached.

8. When the reading has stabilized or been accepted, the slope value and the Store

and ? icons will appear. Verify the slope value is within ranged specified in the

electrode manual.

9. To save the calibration and return to the Reading mode, press ENTER.

pH testing procedure

1. Place the electrode in the sample. Press READ/ENTER. Stabilizing… will

appear, along with the sample temperature and the pH reading. These values may

fluctuate until the system is stable.

45

2. When the reading is stable Stabilizing… will disappear. If the Display Lock is

enabled, the display will “lock in” on the pH value and sample temperature.

3. Record the pH value.

4. Remove the electrode from the sample, rinse with deionized water and place the

electrode in the next sample. Repeat steps 1-3 for each sample.

5. When measurements are complete, press the I/O/EXIT key to turn the meter off.

Rinse the electrode with deionized water and blot dry. Replace the protective cap

on the electrode and put the electrode in the electrode holder.

3.3.11 Temperature The temperature of water is one of the most important characteristics to measure due to

its effect on aquatic life, biochemical reaction rates, gas solubility as well as many other

important parameters. The temperatures of our sampling sites were measured directly on

site with a Hach SensIon1. No calibration or specific measurement methods were

necessary.

3.3.12 Turbidity Turbidity measures the clarity of the water and can indicate the amount of suspended

matter present in the water sample. Turbidity was tested using the HACH Pocket

Turbidimeter Kit, catalog number 52600-00. (lot number L2144. The kit includes a

pocket turbidimeter, product number 52600-60 with a serial number of 020500004432.

Also included in the kit are six sample test vials, a 15 ml vial of silicone oil, catalog

number 1269-36, lot A2129, a StablCal 1.0 NTU standard solution, catalog number

46

26598-42, lot number A2067, and a StablCal 20 NTU standard solution, catalog number

26601-42, lot number A2093.

Equipment calibration

1. Pour 5-mL of properly mixed 1.0 NTU StablCal Standard into the clean, indexed

and oiled Pocket Turbidimeter sample cell.

2. Cap the cell, then remove dust particles by wiping the cell with the oiling cloth

immediately before inserting into the sample cell compartment.

3. Place the sample cell containing the 1.0 NTU standard into the instrument sample

cell compartment.

4. Cover the sample cell with the light shield and wait 30 seconds for the standard to

stabilize.

5. Press and hold the CAL key then press the READ key. Release both keys. After

a short delay, dA will flash alternating with the dark value (based on the last

calibration or the instrument default if no previous calibration exists).

6. To continue calibration, press and hold the READ key until the reading is stable.

Release the READ key to accept the new dark value.

7. Press the CAL key. After a short delay, the display shows C1.0 alternating with

the 1.0 NTU value using the last calibration or instrument default value.

8. To continue calibration, press and hold the READ key until the reading is stable.

Release the READ key to accept the new 1.0 NTU value.

9. Pour 5-mL of properly mixed 20 NTU StablCal Standard into the clean, indexed

and oiled Pocket Turbidimeter sample cell.

47

10. Cap the cell, then remove dust particles by wiping the cell with the oiling cloth

immediately before inserting into the sample cell compartment.

11. Cover the sample cell with the light shield and wait 30 seconds for the standard to

stabilize.

12. Press the CAL key. After a short delay, the display shows C1.0 alternating with

the 20 NTU value using the last calibration or instrument default value.

13. To continue calibration, press and hold the READ key until the reading is stable.

Release the READ key to accept the new 20 NTU value.

14. Press the CAL key to end the calibration. The instrument displays CLd to

indicate the new calibration has been entered. If no data points were changed, the

instrument displays Old to show the previous calibration has been retained.

Turbidity testing procedure

1. Remove one of the test vials and fill it with sample. Dump out the vial and refill

vial to just above the smaller portion of the vial.

2. Squirt some silicone oil on the bottom section of the vial and wipe down with the

oil rag. This is done to remove fingerprints and fill any scratches that may exist

in the plastic surface of the vial.

3. Place the vial in the turbidimeter with the black dot on the vial faces away from

you. Make sure to cover tightly with the light protection shield.

4. Hold down the READ button until the reading stabilizes. Let go of the button

once stabilized and record the reading in the appropriate section of the lab

48

manual. Rinse all used vials with clean water and return them to their proper

storage location.

3.4 Surveying A large tape measure and hand held eye level were included in the equipment brought to

Bali. In addition to the level and tape measure, a three meter long piece of bamboo was

used to measure the vertical differences. Starting as one end being zero, the bamboo was

marked every ten centimeters until the end of the three-meter pole was reached. Also, a

one-meter tall stand for the hand eye level was constructed.

In order to perform the surveying, one person stood in a stationary location along the rim

of the rice paddy while they held one end of the tape measure. The other person held the

other end and walked along the edge of the rice paddy to the nearest corner. The distance

between the two points was recorded. To find the elevation drop between the two points,

the hand level stand was placed at the beginning of the tape measure. The meter stick

was placed where the tape measure had ended. Using the meter stick as a reference, the

hand level was adjusted until level with a point on the meter stick. This point is then

recorded. The elevation difference between the two points is found by subtracting one

meter from the value recorded on the meter stick. After completing one point, the meter

stick is then moved to another corner of the paddy and the same procedure is completed

until all distances and elevations of the paddy are known.

49

3.5 Problems and Modifications Creative modifications were needed on certain tests due to the fact that this work was

being done in a developing country with very few resources available.

3.5.1 BOD The equipment that was chosen for the BOD test was difficult to use in Bali according to

the methods specified by the EPA. The first problem was the lack of an incubator in

which to store the samples during their 5-day incubation period. Although, the

temperature in Bali was fairly stable the average temperature was about 25ºC and there

was a ±5ºC variation that could the skew results. In an attempt to correct for this

variation the samples were kept in a light- tight cooler with Styrofoam insulation. While

the Styrofoam coolers helped to minimize the variation in temperature, there was still a

concern of keeping the samples above 20oC. After some research it was found that BOD

results have been found to be accurate with shorter incubation periods at higher

temperatures. It was decided to run the tests at 25ºC for four days instead of five. To be

consistent, all further BOD incubations were run at these conditions. The sample sizes

used to test for BOD were 50 ml, 100 ml, and 200 ml diluted with Hach nutrient solution

to fill the standard 300 ml BOD bottle. The results were not as expected. Problems arose

when attempting to graph the DO remaining vs. sample size as described by the EPA.

The results produced a positive slope instead of a negative one. This meant that the DO

remaining was higher for larger sample volumes. To explain the BOD results, further

research was done and it became evident that a magnetic stirrer was lacking.

Unfortunately, only a BOD accessory kit was included in the equipment from Hach,

which contained a funnel/stirrer for BOD bottles, but there was no way to spin the stirrer.

50

After about three attempts over the course of a week, a large speaker magnet, a motor

from a tape player and a Tupperware base, were put together as a stirrer as shown in

Figure 3.1. After several rounds of BOD testing, however, the results were still

confusing. The results gave no real indication of the amount of organic matter present in

the water. After running blanks on the dilution water it was discovered that the dilution

water had more oxygen demand than the river water samples. After rereading the

literature regarding BOD testing, two errors were discovered in the BOD testing. Since

there was a limited supply of Hach nutrient solution pillows, the dilution water that was

being used had been sitting for several

days. Secondly, AQUA brand drinking

water was being used instead of the

specified distilled water. Unfortunately,

there was no way to get distilled water

unless a still was constructed. Since time

and resources were the limiting factors, the

still was not constructed. Instead an

attempt was made to clean the dilution

water by running it through a 0.2-micron

activated carbon filter and only using the

dilution water on the day of the test.

These modifications made BOD testing Figure 3.1 - Homemade Magnetic Stirrer

51

difficult by the simple fact that there was only 15-300ml BOD bottles and limited space

in the makeshift incubators. This meant that the test could only be run every four days,

which made detecting and correcting problems a lengthy process.

3.5.2 Total Coliform Bacteria All coliform testing was performed using the Hach MEL Laboratory using microbial

filters to indicate total coliform numbers. The procedures were straight forward, but

multiple problems were encountered along the way. The first round of samples from the

rice paddy site were analyzed in California by from Creek Laboratories (Tables 4.1 &

4.2) prior to leaving for Bali. This gave a general order of magnitude of the bacteria

count. AQUA drinking water was used as the dilution water and diluted the samples to

10-3ml, 10-4 ml, and 10-5 ml of sample per 100ml of filtrate. All three of these samples

grew too many colonies to get an accurate count. On the second round, the dilution

factors were increased to 10-5, 10-6, and 10-7 ml per 100 ml of filtrate. The results were

inconsistent with higher dilutions having more colonies than lower dilutions. This led to

a careful examination of the methods and an attempt to eliminate any contamination that

could skew the results. It was theorized that contamination might be introduced during

the dilution of the samples. Due to the limited measuring equipment available, the same

graduated cylinders had been used throughout the dilution process. Although they were

rinsed with AQUA water between each measurement, it was decided to try and eliminate

any source of contamination by doing a three-rinse wash in-between each measurement.

This method added a considerable amount of time to the process, but it was hoped that

this would improve the results. Unfortunately it didn’t help. A blank run was on the

52

dilution water (AQUA) to see if that was the problem. As it turned out, the AQUA

drinking water had over 200 coliform colonies per 100-ml and had been skewing all of

the results. To alleviate this problem, the water was sterilized by boiling it and adding a

dilute chlorine solution. The first round using this water for dilution, the results were

found to be very high again, to the point of being unreadable, although the control was

blank. The next round the dilutions were increased and resulted in no colonies on the

filter. It was assumed that this meant that the dilutions were too high, so they were scaled

back to in the middle. The results showed no colonies on the filter. At this point, time

and supplies were starting to become low, so it was decided as a group to focus on other

tests.

53

CHAPTER 4

CHARACTERIZATION OF RICE PADDY STREAM AND WOS RIVER

4.1 Sampling the rice paddies and the Wos River Construction of any type of wastewater treatment system requires knowledge about the

system influent water. Once a sampling plan and laboratory were established, water

sampling and testing began at the proposed rice paddy demonstration site. Due to

complications at the rice paddy site, sampling and testing also soon began on the Wos

River. Presented in the following pages are the results of these tests and their statistical

analysis in addition to some data that was acquired prior to leaving for Bali.

4.2 Preliminary results The project was to be constructed in Bali, so very little information about the field

conditions was initially known. In order to make the design process easier, information

concerning the site layout, the flowrate, and the contaminants in the stream was necessary

before leaving for Bali.

Since the rice paddy demonstration site was located on the Widia family rice fields,

Chakra Widia was very familiar with the proposed construction site. Chakra created an

electronic map of the location where he expected to build the treatment system. The map

is shown in Figure 2.4 of the rice paddy sampling site description. The stream to be

treated runs along the east side of the rice paddies and flows from north to south. To the

54

east of the stream is a steep hillside. In addition, the map shows distance to rice fields,

vegetation, and rice paddy size.

Once it was known what the stream layout was, the approximate flow rate needed to be

determined in order to know how much flow the system would need to treat. If the flow

was very large, a method of diversion would need to be constructed in order to maintain

constant flow and not overload the system. Some field tests were performed to get an idea

of the amount of flow. Chakra measured two points one meter upstream and downstream

from each other on the creek and marked these points with a stick in the ground. Then,

using a stopwatch, Chakra placed a twig in the stream and found it took six seconds for it

to travel the measured meter. The stream width of 1.2 meters was constant over the

measured section of creek. The depth at the center of the creek and was 0.011 meters.

Using this data and an estimated trapezoidal cross sectional area, the flow within the

stream was calculated as 1.5 cubic meters per second.

After estimating the stream flow rate, it was important to find out the contaminant

concentrations in the stream in order to determine the best method of treatment. Chakra

sent two samples of the stream water to Cal Poly, one taken at midday, and one taken at

midnight. Each sample was taken in a plastic 400 ml bottle and shipped to Cal Poly via

airmail. The samples were taken to Creek Environmental Laboratories (San Luis Obispo,

California) where they were analyzed for other basic water quality parameters.

Unfortunately, the sample took over two weeks to arrive and many of the biological

55

parameters could not be analyzed. The results of the analyses for these two samples are

presented in Tables 4.1 and 4.2.

4.3 Rice Paddy Sampling Site 4.3.1 Sampling Results Seen below, Table 4.3 displays the results of the sampling performed at the rice field weir

pond and at the rice field stream sampling sites. Each parameter was sampled a total of

eight times at each location. Samples were taken in the morning and in the evening

through out the first week of arrival in Bali. The results shown in this table are described

in detail below.

Table 4.1 - Results of Creek Environmental Laboratories' analysis of mid-day sample from rice paddy lower stream.

Constituent Concentration UnitsTotal Alkalinity as Ca CO3 200 mg/LChloride 18 mg/LDissolved Oxygen 4.4 mg/LElectrical Conductance 390 umhos/cmNitrate as NO3 not detected mg/LNitrite as N not detected mg/LpH 7.1 unitsSulfate 12 mg/LSuspended Solids not detected mg/LTotal Dissolved Solids 310 mg/LAerobic Plate Count 170,000 CFU/ mLAluminum 0.36 mg/LCalcium 31 mg/LHardness 140 mg CaCO3/LIron not detected mg/LPotassium 11 mg/LMagnesium 15 mg/LSodium 26 mg/L

Table 4.2 - Results of Creek Environmental Laboratories' analysis of midnight sample from rice paddy lower stream.

Constituent Concentration UnitsTotal Alkalinity as Ca CO3 170 mg/LChloride 15 mg/LDissolved Oxygen 4.3 mg/LElectrical Conductance 400 umhos/cmNitrate as NO3 9.4 mg/LNitrite as N not detected mg/LpH 7.1 unitsSulfate 11 mg/LSuspended Solids 5 mg/LTotal Dissolved Solids 290 mg/LAerobic Plate Count 15,000 CFU/ mLAluminum 0.8 mg/LCalcium 28 mg/LHardness 130 mg CaCO3/LIron 0.8 mg/LPotassium 11 mg/LMagnesium 13 mg/LSodium 24 mg/L

56

Table 4.3 - Rice paddy demonstration site sampling results

Sample # Date TimeTemperatu

re, C pHTurbidity,

NTU TDS, mg/LEC,

umhos/cm Salinity, % DOi, mg/LNitrate, mg/L

Nitrite, mg/L

Ammonia, mg/L

1 6/30/2002 1:20pm 26.8 7.14 12.5 190.3 398 0.2 4.16 NM NM NM4 7/1/2002 11:15am 24.8 7.14 12.5 200 415 0.2 6.56 0.8 0.086 NM7 7/1/2002 6:00pm 26.6 7.1 8.5 187.1 387 0.2 5.56 0.8 0.085 0.059 7/2/2202 10:45am 25.8 7.14 10.2 183.7 381 0.2 6.39 2.5 0.121 0.1511 7/2/2202 5:15pm 27.2 7.14 10.5 177.6 369 0.2 4.44 1 0.109 NM12 7/3/2002 8:50am 24.1 7.17 9.2 190.9 396 0.2 5.44 0.8 0.117 0.4814 7/3/2002 5:00pm 25.6 7.15 9.2 186.7 387 0.2 4.14 0.1 0.166 0.316 7/4/2002 10:26am 24.2 7.2 9.5 178.9 371 0.2 5.61 0.6 0.075 0.14

Avg 25.6 7.15 10.3 186.9 388 0.2 5.29 0.9 0.108 0.224Std. Dev 1.2 0.03 1.5 7.2 15 0 0.95 0.7 0.031 0.169

2 6/30/2002 2:00pm 29.8 7.4 11.6 195.6 407 0.2 4.8 NM NM NM3 7/1/2002 11:00am 25.1 7.4 7.1 201 415 0.2 6.51 1 0.011 NM6 7/1/2002 5:53pm 26.8 7.23 9.3 179.4 373 0.2 6.2 1.1 0.051 0.078 7/2/2202 10:19am 25.8 7.32 10.8 194.4 403 0.2 7.52 2.7 0.179 0.0110 7/2/2202 5:10pm 26.9 7.31 13.6 194 402 0.2 4.85 1 0.053 NM13 7/3/2002 9:00am 24.2 7.24 8.1 177.7 418 0.2 5.17 0 0.046 0.0315 7/3/2002 5:10pm 25.7 7.25 6.1 200 415 0.2 4.91 1.5 0.107 0.0717 7/4/2002 10:31am 25.5 7.3 4.3 204 424 0.2 4.71 1.4 0.053 0.07

Avg 26.2 7.31 8.9 193.3 407 0.2 5.58 1.2 0.071 0.05Std. Dev 1.7 0.07 3.1 9.7 16 0 1.04 0.8 0.055 0.028

Rice Field Weir Pond

Rice Field Stream

57

In addition to the parameters in Table 4.3, a BOD test was also performed and these

results are presented in Table 4.4. Due to the previously stated problems with the BOD

testing, the BOD test results are not considered accurate, however, they do indicate that

the BOD concentration is equal to or lower than the concentration in the dilution water

because the dissolved oxygen remaining in the sample is independent of dilution.

After compiling the data, they were grouped by sampling location and parameter. This

allowed a statistical analysis to be completed. An average, standard deviation and a

confidence interval were determined for each sampling location and parameter. The

confidence intervals for some parameters appear to be quite large, but this is because of a

limited amount of data. Since BOD was only run twice on the weir location and once on

the creek, there was not enough data to perform a statistical analysis. Averages and

standard deviations are also included in Table 4.3.

4.3.2 Data Analysis An important factor to remember when analyzing the data is that all of the water that is

diverted from the upper stream and into the rice paddies eventually ends up in the lower

stream. Based on this, some conclusions can be made between the two sampling points.

Table 4.4 - BOD data from the rice field pilot plant sampling

Sample # Sample volume DOi DOf BOD(mL) (mg/L) (mg/L) (mg/L)

1 50 4.49 1.21 19.68100 4.53 1.19 10.02200 4.88 1.11 5.655

2 50 4.46 1.46 18100 4.51 1.13 10.14200 4.52 1.06 5.19

9 50 8.55 1.65 41.4100 8.23 1.24 20.97200 8.02 1.12 10.35

58

The mean temperature of the lower stream is slightly higher than that of the upper stream

(Table 4.3). This temperature difference is likely due to the water’s exposure to sun as it

flows through the shallow rice paddies. Dissolved oxygen also slightly increased from

the upper to lower stream (Table 4.3). It was first thought that photosynthesizing algal

blooms in the rice paddies caused the increase in dissolved oxygen. After plotting

dissolved oxygen versus time of day, it can be seen that this is not necessarily true

(Figure 4.1). The dissolved oxygen at the two rice paddy sampling sites is actually the

lowest during the period from 2 to 4 pm. This does not support the theory that

photosynthesis is playing a major role in stream aeration.

The turbidity was less in the lower stream than in the upper stream. Because turbidity is

related to suspended solids, one would think that the decrease from one stream to another

is caused by the decrease in stream velocity as it flows through the rice paddies. This

Figure 4.1 - Dissolved oxygen vs. time of day at the rice paddy weir pond

D.O. vs. Time of day

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

7:00 9:24 11:48 14:12 16:36 19:00

time of day (hour)

D.O

. (m

g/L

)

weir pond

rice stream

59

allows the suspended particles to settle out. An additional amount of particles may also

be removed by adsorption onto the soil or algae surfaces. According to Figure 4.2, turbid

water in the range of 8 to 10 NTU will have a water quality index of 70-80. This

suggests that the quality of the water is increased as it flows through the rice paddies.

The mean total dissolved solids concentration and mean electrical conductivity values

were higher at the lower stream sampling site. The lower creek is closest to residential

areas and many of the locals dump their solid waste into the creek ravine. Less than 100

meters upstream from the lower stream sampling site there is trash in the creek, as well as

on the adjacent hillside. In addition, all housing that borders the creek use septic tanks

for wastewater disposal. Excess salts leaching from the trash heaps or fugitive septic

leachate could explain the increase in total dissolved solids and electrical conductivity.

Figure 4.2 - Turbidity Quality Index (Adapted from http://www.fivecreeks.org/monitor/turbidity.html)

60

There was also a slight increase in pH from the weir pond sampling site to the stream

sampling site, but not enough to be significant.

The average nitrate concentrations were higher in the lower stream (Table 4.3). In

contrast, the ammonia and nitrite concentrations were lower in the lower rice stream.

This suggests that the rice paddies are providing some nitrification of the water. In

nitrification, ammonia is converted to nitrite and the nitrite is oxidized to nitrate by

microbes. This explains why the nitrate concentration increases and the nitrite and

ammonia concentrations decrease as the water flows through the rice paddies.

61

4.4 Wos River Sampling Site 4.4.1 Sampling Results The results of the Wos River testing are presented below in Tables 4.5 and 4.6. Each

sampling location, time and date of test is recorded along with the result of the individual

test. Some points are missing due to missed testing days because of inclement weather,

as well as fouled tests. There are also some significant outliers.

62

Table 4.5 - Sampling results from the first three Wos River Sites

Sample # Date Time Temp., C pHTurbidity

, NTUEC,

umhos/cmTDS, mg/L

Salinity, %

DOi, mg/L

Nitrate, mg/L

Nitrite, mg/L

Ammonia, mg/L

Phosphate, mg/L

Free Chlorine,

mg/L

Total Chlorine,

mg/L

7 7/7/2002 1:50pm 26.4 8.14 5.2 259 124.3 0.1 7.81 0.7 0.041 0 N/A N/A N/A8 7/9/2002 11:15am 26.6 8.16 4.6 260 126.3 0.1 7.38 0.4 0.03 0.01 1.28 0.04 0.0515 7/11/2002 1:50pm 25.7 N/A N/A 254 122 0.1 5.69 0.8 0.015 0 N/A 0.02 0.0718 7/13/2002 11:00am 24.9 N/A 4.1 254 122.1 0.1 6.26 0.7 0.015 0 0.91 0.04 0.0523 7/16/2002 10:10am N/A N/A 5.1 255 122.2 0.1 7.1 0.8 0.039 N/A 1.37 0.04 0.1129 7/18/2002 11:10am 24.9 N/A 6 256 122.6 0.1 7.21 0.8 0.014 N/A 1.92 0.04 0.0734 7/20/2002 10:15am 24.6 N/A 5.2 256 123 0.1 6.62 0.4 0.021 N/A 2.42 0.07 0.0540 7/23/2002 10:10am 24.7 8.17 5.1 259 124.1 0.1 6.44 0.6 0.019 N/A 1.15 0.04 0.0850 7/24/2002 12:50pm 26.3 8.22 4.6 259 124.7 0.1 6.82 1.8 0.026 N/A 0.77 0.02 0.0959 7/25/2002 2:00pm 25.7 8.23 8.3 258 123.6 0.1 6.16 0.5 0.007 N/A 0.93 0.04 0.06

5 7/7/2002 12:15pm 25 8.24 23.3 259 124 0.1 6.65 0 0.009 0.01 N/A N/A N/A10 7/9/2002 12:30pm 25.3 N/A 8.2 255 122.5 0.1 5.69 0.6 0.006 0 1.57 0.01 0.0416 7/11/2002 2:50pm 26.1 N/A N/A 257 123 0.1 5.59 0.9 0.024 0.02 2.11 0.06 0.0519 7/13/2002 12:15pm 24.7 N/A 7.2 255 122 0.1 5.61 0.7 0.007 0 0.97 0.34 0.0524 7/16/2002 10:50am 24.9 N/A 3.9 256 122.6 0.1 6.65 0.6 0.02 N/A 0.88 0.03 0.0531 7/18/2002 12:35pm 24.8 N/A 4.1 257 123.5 0.1 6.53 0.6 0.018 N/A 1.3 0.04 0.0735 7/20/2002 11:20am 24.8 N/A 3.7 258 123.5 0.1 6.31 0.6 0.004 N/A 0.92 0.02 0.0541 7/23/2002 11:00am 25.1 8.27 6.3 259 124.3 0.1 6.44 0.7 0.017 N/A 1.06 0.05 0.0651 7/24/2002 1:35pm 25.4 8.3 5.9 259 124.1 0.1 6.67 1.3 0.019 N/A 0.98 0.06 0.0357 7/25/2002 1:20pm 25.9 8.32 4.1 270 129.7 0.1 7.02 0.6 0.015 N/A 0.97 0 0.14

4 7/7/2002 12:15pm 25.4 8.23 17 258 123.7 0.1 6.82 0.5 0.014 0 N/A N/A N/A9 7/9/2002 12:15pm 25.2 8.25 4 254 122.4 0.1 5.8 0.9 0.013 0 1.56 0.07 0.0517 7/11/2002 2:55pm 25.5 N/A N/A 254 122.3 0.1 5.48 0.7 0.007 0.01 1.03 0 0.0220 7/13/2002 12:15pm 25 N/A 12.1 252 120.7 0.1 6.29 0.6 0.013 0 1.09 0 025 7/16/2002 11:00am 24.6 N/A 3.7 254 122.9 0.1 6.11 0.6 0.01 N/A 11.6 0.04 0.0430 7/18/2002 12:00pm 24.7 N/A 3.4 254 122 0.1 6.32 0.7 0.01 N/A 1.15 0 0.0136 7/20/2002 11:35am 24.9 N/A 4 256 122.7 0.1 6.09 0.5 0.025 N/A 0.97 0.03 042 7/23/2002 11:10am 25.3 8.22 7 257 123.1 0.1 6.39 0.5 0.014 N/A 1.13 0.02 0.0352 7/24/2002 1:55pm 25.9 8.27 5.9 257 123.3 0.1 6.48 0.6 0.014 N/A 0.96 0.01 058 7/25/2002 1:00pm 25.9 8.25 7.9 266 127.5 0.1 6.32 0.4 0.017 N/A 1.32 0.05 0.04

Bamboo Bridge

Above Intersection

After Intersection

63

Table 4.6 - Sampling results from the last two Wos River sites

Sample # Date Time Temp., C pHTurbidity,

NTUEC,

umhos/cmTDS, mg/L

Salinity, %

DOi, mg/L

Nitrate, mg/L

Nitrite, mg/L

Ammonia, mg/L

Phosphate, mg/L

Free Chlorine,

mg/L

Total Chlorine,

mg/L

3 7/7/2002 10:50am 25.1 8.27 4.7 263 126.5 0.1 7.27 1.4 0.037 0 N/A N/A N/A11 7/9/2002 1:35pm 26 N/A 9.2 264 126.8 0.1 6.23 0.5 0.008 0 N/A N/A N/A13 7/11/2002 10:00am 25.6 N/A N/A 261 125.4 0.1 6.23 0.5 0.012 0 1.01 0.07 0.0621 7/13/2002 2:00pm 25 N/A 8.6 261 125.3 0.1 5.34 0.7 0.019 0.01 7.3 0.18 026 7/16/2002 12:30pm 25.4 N/A 10.9 262 126 0.1 6.17 0.7 0.006 N/A 1.24 0.08 0.0532 7/18/2002 1:50pm 25.5 N/A 6.5 263 126.1 0.1 6.78 0.8 0.016 N/A 1.18 0.03 0.0337 7/20/2002 3:00pm 25.6 N/A 4.8 263 126.3 0.1 6.96 0.9 0.02 N/A 1.06 0.08 0.0543 7/23/2002 1:50pm 25.6 8.33 7.6 264 126.9 0.1 6.02 0.9 0.011 N/A 1.95 0.04 0.0647 7/24/2002 10:10am 25.1 8.33 7 268 128.3 0.1 6.34 1.9 0.023 N/A 1.31 0 056 7/25/2002 11:50am 26.8 8.3 4.9 266 127.7 0.1 5.7 0.6 0.021 N/A 1.54 0 0.08

2 7/7/2002 10:45am 24.7 8.21 4.4 265 127.1 0.1 8.05 0.6 0.015 0 N/A N/A N/A12 7/9/2002 2:05pm 26.5 N/A 8.6 261 125.3 0.1 6.63 0.3 0.003 0.01 1.23 0.02 0.0514 7/11/2002 10:00am 26.2 N/A N/A 264 126.6 0.1 6.06 0.7 0.02 0 1.46 0 0.0622 7/13/2002 2:15pm 25 N/A 9 261 125.6 0.1 7.3 0.7 0.015 0.01 1.22 0 0.0328 7/16/2002 12:50pm 25.4 N/A 4.7 263 126.2 0.1 6.5 1.3 0.032 N/A 0.87 0.01 0.9533 7/18/2002 2:15pm 26.1 N/A 8.9 263 126.3 0.1 6.36 0.7 0.018 N/A 1.91 0.12 0.0239 7/20/2002 3:15pm 25.5 N/A 8.1 266 127.7 0.1 7.5 0.8 0.017 N/A 1 0.03 0.0444 7/23/2002 2:10pm 26.1 8.31 6.3 272 130.7 0.1 6.82 0.9 0.019 N/A 0.99 0.02 0.0249 7/24/2002 10:45am N/A N/A 7.3 N/A N/A N/A N/A 0.7 0.024 N/A 1.38 0.16 0.1855 7/25/2002 11:30am 26.9 8.19 6.4 269 128.9 0.1 5.42 0.5 0.029 N/A 0.97 0 0.02

Below Bridge at Bali Spirit

Below Outfall

64

4.4.2 Results of Water Quality Testing of the Wos River The analysis of the Wos River testing is presented in Table 4.7. After presentation of the

results, a discussion of them follows. Each parameter is discussed and includes a graphs

display the parameter as a function of location. The mean value of the specific water

quality parameter was determined, as well as the standard deviation and the 95% upper

and lower confidence intervals. In general, data collected were within an acceptable

range and provided reliable results. In some specific cases, some outliers existed which

greatly skewed the confidence intervals. The statistical analysis is presented graphically

in a manner that will display the trend of the water quality as the Wos flows through

Ubud. There are five points to the graph, corresponding to each sampling location, and

displayed in geographical order.

65

Table 4.7 - Statistical analysis of Wos River sampling.

Sample #Temperatu

re, C pHTurbidity,

NTUEC,

umhos/cm TDS, mg/L Salinity, % DOi, mg/LNitrate, mg/L

Nitrite, mg/L

Ammonia, mg/L

Phosphorus, mg/L

Free Chlorine,

mg/L

Total Chlorine,

mg/L

Avg 25.5 8.18 5.4 257 123.5 0.1 6.75 0.8 0.023 0.003 1.34 0.04 0.07Std. Dev 0.8 0.04 1.2 2 1.4 0 0.64 0.4 0.011 0.005 0.56 0.01 0.02Low C.I. 25 8.15 4.6 256 122.6 0.1 6.35 0.5 0.016 -0.002 0.95 0.03 0.06Up C. I. 26 8.22 6.2 258 124.3 0.1 7.15 1 0.03 0.007 1.73 0.05 0.08

Avg 25.2 8.28 7.4 259 123.9 0.1 6.32 0.7 0.014 0.008 1.2 0.07 0.06Std. Dev 0.5 0.04 6.2 4 2.2 0 0.51 0.3 0.007 0.01 0.41 0.1 0.03Low C.I. 24.9 8.25 3.4 256 122.6 0.1 6 0.5 0.01 -0.002 0.93 0 0.04Up C. I. 25.5 8.32 11.4 261 125.3 0.1 6.63 0.9 0.018 0.017 1.46 0.14 0.08

Avg 25.2 8.24 7.2 256 123.1 0.1 6.21 0.6 0.014 0.003 2.31 0.02 0.02Std. Dev 0.5 0.02 4.6 4 1.8 0 0.37 0.1 0.005 0.005 3.49 0.03 0.02Low C.I. 25 8.23 4.2 254 122 0.1 5.98 0.5 0.011 -0.002 0.03 0.01 0.01Up C. I. 25.5 8.26 10.2 259 124.2 0.1 6.44 0.7 0.017 0.007 4.59 0.04 0.03

Avg 25.6 8.31 7.1 264 126.5 0.1 6.3 0.9 0.017 0.003 2.07 0.06 0.04Std. Dev 0.5 0.03 2.2 2 0.9 0 0.58 0.4 0.009 0.005 2.13 0.06 0.03Low C.I. 25.2 8.28 5.7 262 125.9 0.1 5.95 0.6 0.012 -0.002 0.6 0.02 0.02Up C. I. 25.9 8.34 8.5 265 127.1 0.1 6.66 1.2 0.023 0.007 3.55 0.1 0.06

Avg 25.8 8.24 7.1 265 127.2 0.1 6.74 0.7 0.019 0.005 1.23 0.04 0.15Std. Dev 0.7 0.06 1.7 4 1.7 0 0.79 0.3 0.008 0.006 0.33 0.06 0.3Low C.I. 25.4 8.16 5.9 263 126 0.1 6.22 0.6 0.014 -0.001 1.01 0 -0.05Up C. I. 26.3 8.31 8.2 267 128.3 0.1 7.26 0.9 0.024 0.011 1.44 0.08 0.35

Below Outfall

Bamboo Bridge

Above Intersection

After Intersection

Below Bridge at Bali Spirit

* Confidence interval is for 95% C.I.

66

Although phosphorus levels were fairly high, Figure 4.3 shows there was no clear trend

of an increase or decrease of concentration as the river ran through Ubud. The

concentration remained fairly constant above the intersection, but then made a large jump

after the intersection. This indicates that there may be a significant phosphate source

along the Cerik River. The intersection of the Wos and Cerik rivers is a popular bathing

spot, so there may be residual phosphate at that point of the river that increases the

concentration.

pH consistently fell within a range of 8.15 and 8.35. In the graphical analysis the mean

pH values jump around.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Pho

spho

rus

Con

cent

ratio

n (m

g/L)

Average

Upper C.I.

Lower C.I.

Figure 4.3 - Phosphorus Concentration Distribution vs. Sampling Location

Downstream ⇒

67

Nitrate concentration also fell within a narrow range from 0.5 to 1.0 mg/L (Figure 4.5),

and no definitive trend in Nitrate concentration was observed along the Wos River.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Nitr

ate

Con

cent

ratio

n (m

g/L)

Average

Upper C.I.

Lower C.I.

Figure 4.5 - Nitrate Concentration Distribution vs. Sampling Location

Downstream ⇒

8.00

8.05

8.10

8.15

8.20

8.25

8.30

8.35

8.40

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

pH

Average

Upper C.I.

Lower C.I.

Figure 4.4 - pH Distribution vs. Sampling Location

Downstream ⇒

68

The nitrite concentrations were low, but this is because nitrite is quickly converted to

nitrate in natural waters. The mean value at the bamboo bridge was relatively high.

There was a drop in concentration above the intersection, and then the readings gradually

increased Figure 4.6.

0.00

0.01

0.02

0.03

0.04

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Nit

rite

Con

cent

rati

on (

mg/

L)

Average

Upper C.I.

Lower C.I.

Figure 4.6 - Nitrite Concentration Distribution vs. Sampling Location

Downstream ⇒

69

Figure 4.7 shows turbidity increasing after the Bamboo Bridge and then remaining

constant at around 7 NTU’s for the other sampling sites. This is considered a good value

for turbidity in stream water. The NTU value can be brought into real terms by these

comparisons: Drinking water has a turbidity of 0.5 NTU’s, while murky water has a

turbidity of 50.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Turb

idit

y (N

TU)

Average

Upper C.I.

Lower C.I.

Figure 4.7 - Turbidity Distribution vs. Sampling Location

Downstream ⇒

70

TDS concentration increased slightly downstream from the intersection along the Ubud

stretch of the Wos River. However, the levels recorded are considered very good for

surface water [15]. So, although total dissolved solids demonstrated an increase in

concentration along the Wos River, it is not of concern because of the low concentration.

120

122

124

126

128

130

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Tota

l D

isso

lved

Sol

ids

(mg/

L)

Average

Upper C.I.

Lower C.I.

Figure 4.8 - TDS Concentration Distribution vs. Sampling Location

Downstream ⇒

71

Electrical conductivity (EC) is closely related to TDS, so the trend observed for EC was

the same as that observed for TDS (Figure 4.9). Both parameters are measured by the

same probe and can be correlated by a coefficient.

252

254

256

258

260

262

264

266

268

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Ele

ctri

cal C

ondu

ctiv

ity

(um

hos/

cm)

Average

Upper C.I.

Lower C.I.

Figure 4.9 – Electrical Conductivity Distribution vs. Sampling Location

Downstream ⇒

72

Another good sign for the quality of the Wos River is the dissolved oxygen levels. They

were consistently at levels considered healthy for rivers [28]. The graph of the dissolved

oxygen concentration versus sampling location, shown in Figure 4.10, follows a parabolic

trend in which the concentration begins high, decreases and then increases back to the

same levels.

The temperature was similar at all sample sites, with less than 0.5oC variability as seen in

Table 4.7.

Upstream from the outfall, total chlorine values were consistently around 0.05 mg/L for

the first four sampling sites, but a significant jump below the outfall was observed

(Figure 4.11). Samples taken below the outfall had a higher mean value (0.15 mg/L) and

a very large confidence interval. This deviation was due to two samples that were taken

5.0

5.5

6.0

6.5

7.0

7.5

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Dis

solv

ed O

xyge

n (m

g/L)

Average

Upper C.I.

Lower C.I.

Figure 4.10 – DO Concentration Distribution vs. Sampling Location

Downstream ⇒

73

while outfall effluent was pouring into the river. This can be seen by looking at the

results in Tables 4.5 and 4.6 for samples taken below the outfall and from the outfall on

7/16/2002 and 7/24/2002. The chlorine values recorded on those two days below the

outfall are significantly higher than any other sample and cause a skewed mean value and

large confidence interval. This also shows the affect that the outfall has upon the Wos

River water quality.

In contrast to total chlorine, no significant trend in free chlorine was observed (Figure

4.12). Large range of readings were obtained for free chlorine at most of the sampling

sites. Due to several large confidence intervals, confidence in the validity of our free

chlorine results is not high.

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Tota

l C

hlor

ine

Con

cent

rati

on (

mg/

L)

Average

Upper C.I.

Lower C.I.

Figure 4.11 – Total Chlorine Concentration Distribution vs. Sampling Location

Downstream ⇒

74

Ammonia was also tested for a short period of time, however the values were so low, and

more often than not, zero, that it was decided to stop testing for that parameter.

Therefore, there is no graphical analysis for ammonia.

-0.01

0.01

0.03

0.05

0.07

0.09

0.11

0.13

0.15

Bamboo Bridge Above Intersection After Intersection Below Bridge Below Outfall

Free

Chl

orin

e C

once

ntra

tion

(m

g/L)

AverageUpper C.I.

Lower C.I.

Figure 4.12 – Free Chlorine Concentration Distribution vs. Sampling Location

Downstream ⇒

75

The Bali Spirit outfall wastewater and AQUA drinking water was also tested for specific

constituents. The results are presented below in Table 4.9. When testing certain

parameters such as phosphate and nitrate, the limits of the testing equipment were

reached. This resulted in the need to dilute the sample water with ‘DI’ water. True

deionized water was not available, however, so AQUA brand drinking water was used.

Unfortunately, the drinking water contained some amount of the nutrients being tested

for. To correct for this problem, the drinking water was tested and mean values of the

water quality parameters were determined and are displayed in Table 4.8. These mean

values were then used in a mass balance to determine the true quantity of nutrient in the

original solution. If a 1/10 dilution was performed and the resultant value was known as

well as the value for the dilution water, the true value for the sample could be found.

This concept is presented in the following equation.

Csample=(Ccombined*Vcombined-Cdilution water*Vdilution water)/Vsample Eqn. 4.1

Table 4.8 - Statistical analysis of AquaTM bottled water.

Constituent Nitrate, mg/L Nitrite, mg/L Phosphorus, mg/LLower 95% C.I. 0.9 0 1.2

Mean Value 1.1 0.016 1.3Upper 95% C.I. 1.3 0.032 1.4

76

Table 4.9 - Sampling results from the Bali Spirit outfall and AquaTM bottled water.

Sample # Date Time Temp., C pHTurbidity,

NTUEC,

umhos/cmTDS, mg/L

Salinity, %

DOi, mg/L

Nitrate, mg/L

Nitrite, mg/L

Ammonia, mg/L

Phosphate, mg/L

Free Chlorine,

mg/L

Total Chlorine,

mg/L

1 7/7/2002 10:45am 27.2 6.93 N/A 352 169.6 0.2 4 33 0.288 0.36 N/A N/A N/A27 7/16/2002 12:52pm 28.8 N/A 2530 399 192.4 0.2 1.62 35 0.57 2 0.91 N/A N/A38 7/20/2002 3:15pm 26.9 N/A 479 464 225 0.2 1.08 74 0.32 N/A 18.6 N/A N/A45 7/23/2002 3:00pm 29.3 N/A 81 431 208 0.2 N/A 19 0.34 1 N/A N/A N/A46 7/24/2002 10:00am 27.6 7.45 379 448 216 0.2 3.12 38 0.16 0.6 12.8 N/A N/A48 7/24/2002 10:35am 28.4 7.48 210 385 185.4 0.2 4.26 7 0.09 0.3 10.8 N/A N/A53 7/25/2002 11:00am 27.7 7.08 124 469 227 0.2 0.12 6 0.17 0 12.3 N/A N/A54 7/25/2002 11:15am 27.6 8.53 1110 1667 829 0.8 0.13 15 1.46 0.28 38.25 N/A N/A60 7/26/2002 9:00am 25.6 7.41 199 841 411 0.4 1.6 8 0.57 0.3 687.5 N/A N/A61 7/26/2002 9:15am 26.4 7.47 208 501 242 0.2 2.85 16 0.58 0.8 687.5 N/A N/A62 7/27/2002 12:15pm 26.6 7.33 906 597 290 0.3 0.13 38 2.12 N/A 13.2 N/A N/A

A1 7/8/2002 N/A 26.4 7.12 N/A 278 133 0.1 6.44 1.2 0.015 0 N/A N/A N/AA2 7/23/2002 N/A N/A N/A N/A N/A N/A N/A N/A 1.2 0.002 0 1.23 N/A N/AA3 7/26/2002 N/A N/A N/A N/A N/A N/A N/A N/A 0.9 0.03 0 1.35 N/A N/A

Outfall

Aqua Bottled Water

77

Testing of the outfall itself, showed that most of the mean values of the constituents are

above the mean values found for the Wos River (Table 4.10). The magnitude of the

turbidity of the effluent is about 100 times greater than the mean river value. The

phosphate level, with a mean value of 84.7 mg/L, is also extremely high, due to the soap

and detergent in the kitchen wastewater. The electrical conductivity and TDS of the

effluent was about double the mean value recorded for the river water. The dissolved

oxygen of the effluent was quite low, around 2 mg/L. The mean nitrate level of 16.4

mg/L was also significantly higher than the levels recorded in the river and is above the

EPA standard for water quality in a river [15]. Nitrite, with a mean value of 0.5 mg/L, is

insignificant because it will be quickly converted to nitrate, however that will increase the

nitrate concentration. Ammonia, with a mean value of 0.63 mg/L, is more of a problem.

It has been proven that ammonia at concentrations similar to that of the Wos River can be

fatal to certain species of fish [15]. The mean temperature of the outfall effluent was 27.5

degrees Celsius. This is 2 degrees higher than the mean value of the river.

Table 4.10 - Statistical analysis of the Bali Spirit outfall testing

Constituent

Temperature (

C) pHTurbidity NTU

Electrical Conducti

vity (umhos/c

m)TDS mg/L

Salinity, %

DOi mg/L

Nitrate mg/L

Nitrite mg/L

Ammonia mg/L

Phosphorus mg/L

Lower 95% C.I. 26.8 7.1 131 371 178 0.17 0.9 4.4 0.14 0.24 -19.7Mean Value 27.5 7.5 623 596 290 0.28 1.9 16.4 0.5 0.63 84.7Upper 95% C.I. 28.1 7.8 1114 820 403 0.39 2.9 28.3 0.87 1.02 189.1

78

CHAPTER 5

DISCUSSION OF WATER QUALITY RESULTS

5.1 Rice Paddy Site Conclusions Overall, the constituent levels found in the rice field streams were quite low. Due to

equipment problems and time limitations the exact BOD concentration levels are not

known. However, it appeared that nitrification was occurring in the rice paddies between

the upper and lower streams. The testing results also show that turbidity is removed

throughout the rice paddies and that the dissolved oxygen increases. All of these water

quality patterns suggest that the rice paddies are working similar to a natural wetlands

system and that some water treatment is naturally occurring.

The sampling of the water on either side of the rice fields found two interesting problems

with the quality of the water. These problems were the bacterial levels and the use of

pesticides. The occurrence of fecal coliform bacteria poses a health risk to the locals who

use the river for bathing and swimming. An exact coliform count for the rice paddy site

was never achieved. However, through numerous attempts at determining an accurate

coliform count during sampling and with the preliminary analysis data from Creek

Environmental Laboratories we can confidently state that the concentration ranges from

103 to 107 coliform units per one hundred milliliters. These levels are well above

drinking, bathing, and reuse standards for water [14, 36]. The high coliform counts are

due to livestock grazing around the rice paddies as well as people bathing in the river. In

addition, there is the possibility of septic tank leachate transporting high levels of

79

coliform bacteria into the surface waters. Eliminating the bacteria problem within the

creek would require some method of disinfection: whether it is chlorination, ozonation, or

ultra violet treatment. All three of these methods require a relatively large capital

investment and operational costs and were determined to be unfeasible for the pilot plant

location.

The second major problem discovered during the sampling of the rice paddies was that

the Balinese frequently use pesticides. Although the name for the pesticide is not

known, it is known that they are sprayed on each rice paddy six times a year. Due to lack

of appropriate equipment, the pesticide concentration within the water was not

determined, but could present a problem.

Although we don not have reliable BOD data, based upon the nature of the testing

problems it is safe to say that the average BOD is less than 30 mg/L. This concentration

will not support the continuous growth of microbes in a biological treatment system [30].

When combined with the fact that there are no feasible treatment options available for

pesticides and coliform bacteria at the rice paddy site, it was decided that the rice paddy

pilot plant project would be abandoned and another treatment site would be located.

5.2 Wos River Site Conclusions Some results of our analysis of the Wos River are quite encouraging, while some are a

cause for concern. The results of the nitrate, turbidity, TDS, EC, dissolved oxygen and

temperature samples all were within normal ranges and were encouraging for the health

80

of the Wos river. The mean nitrate levels were all below 1 mg/L. Compare this with the

EPA maximum contaminant level of 10 mg/L and it can be considered an acceptable and

safe concentration [15]. Turbidity was also within a good range. With consistent values

around 7 NTU’s, the Wos river water is healthy for the propagation of aquatic life [15].

A NTU value of 7 corresponds to a turbidity quality index of 80 on a 100-point scale (See

Figure 4.3). TDS and EC are about half of the typical values for normal streams and

rivers. A standard range of TDS in natural waters is between 300 and 500 mg/L [15].

The TDS concentration in the Wos River water is far below that and therefore not a

problem. Dissolved oxygen levels are high considering the nutrient levels in the water.

The EPA calls for a minimum of 5 mg/L DO for fresh water [15]. The DO levels in the

Wos River will not have a harmful affect upon the aquatic system.

The tested parameters that are cause for concern are phosphate and total chlorine. The

maximum level of phosphate recommended for streams and rivers is 0.1 mg/L. The

levels in the Wos River are 10 to 20 times this value. This is a cause for concern because

high nutrient levels, especially phosphate, can lead to eutrophication. Eutrophication is

an excessive growth of vegetation and algae that leads to low dissolved oxygen levels in

aquatic systems. Although the DO readings did not support the fact that eutrophication

had taken place in the river, it could become an environmental problem in the future. To

verify that eutrophication was or was not taking place, dissolved oxygen samples should

have been taken at sunrise when dissolved oxygen levels are at their lowest. However,

the Wos River moves very quickly and has many places where natural aeration occurs, so

the dissolved oxygen levels remain high even when being consumed by biological

81

processes. This would limit the harmful affects of eutrophication because dissolved

oxygen levels would consistently remain high. Eutrophication would be more of a

problem in stagnant bodies of water that receive flow from the Wos River. The high

nutrient concentration in the influent would allow for the onset of eutrophication in the

stagnant water because there is no naturally occurring aeration.

The high concentration of phosphate is due to the fact that phosphate containing

detergents are used in Bali. During our sampling it was not uncommon to see the

Balinese in the river bathing with soap or washing clothes with detergent. It is a

traditional practice in Bali, as in the rest of the world, to use rivers for bathing and

washing. However, up until recently they used a natural surfactant contained in the fruit

of the Kererek tree. According to our host, Chakra, these trees used to be prevalent on

Bali and were used as a natural soap for bathing, washing clothes and washing dishes.

The Balinese have abandoned the use of the Kererek fruit as a surfactant due to the ease

of use of commercial detergents; however this is now causing water quality problems.

Total chlorine is another significant problem. EPA recommends a maximum residual

chlorine concentration of 0.01 mg/L for the propagation of aquatic life in fresh water

[15]. The Wos river readings for total chlorine were consistently above that standard by

at least a factor of 4. This is harmful for the aquatic system and essentially limits the

growth of aquatic organisms. Again, this excess in chlorine, like the phosphate, is more

than likely due to the use of detergents and soaps in the river water. These detergents and

82

soaps contain some amount of chlorine bleach, which explains the high concentrations of

chlorine in the Wos River.

One possibility that could be further examined in the future is that the high levels of total

chlorine present in the Wos River water limited biological growth through disinfection

and therefore offset the fact that there were high phosphate levels. This could explain

why there weren’t any significant algal and biological growths observed in the Wos River

water.

5.3 Outfall Conclusions The analysis of the outfall effluent from the Bali Spirit Hotel was discouraging. The

effluent was very turbid and caused a noticeable change in the turbidity of the river water

where it entered the river (Figure 2.12). The TDS and conductivity were also above the

levels found in the river, which means that there is an excessive amount of salts being

discharged to the river water. Salinity of the effluent was also greater than that of the

river water, however not at a level that is harmful to the water quality [15]. Nitrate and

phosphate concentrations were well above EPA standards and provide significant

amounts of nutrients to the water near the outfall. The dissolved oxygen levels were very

low and could cause problems where the effluent enters the river by decreasing the

dissolved oxygen in that region. This combination of high nutrients and low dissolved

oxygen levels will only increase the chance that any stagnant receiving waters will have

eutrophication problems.

83

Based upon the testing and analysis of the outfall effluent it was concluded that the Bali

Spirit hotel was a possible pilot plant site. This would eliminate the discharge of the

untreated kitchen waste and reduce the pollution entering the Wos River.

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CHAPTER 6

TREATMENT SYSTEM DESIGN

6.1 Introduction Wastewater treatment for both the rice paddy demonstration site and the Bali Spirit Hotel

and Resort needed to be low cost, and low maintenance. Many treatment options were

explored when trying to determine which system would best fit the situations at both of

these locations. For the rice paddy demonstration site, advanced integrated wastewater

ponding systems were researched extensively, whereas, more traditional designs were

researched for the Bali Spirit Hotel and Resort. This chapter will review the research on

treatment designs and the conclusions that were reached.

6.2 Design for Rice Paddy Demonstration Site 6.2.1 Advanced Integrated Wastewater Ponding System (Oswald Ponds) It was determined that for a treatment system to be successful in Bali it would need to

have the following characteristics: have as few mechanical parts as needed, use as little

energy as possible, be reliable, and not require continual day to day operation and

maintenance [30]. The Advanced Integrated Wastewater Ponding System (AIWPS), or

“Oswald ponds”, were investigated because they were expected to have all of these

qualities. William J. Oswald developed Oswald ponds during 40 years of research at the

University of California, Berkeley. Oswald and his team of researchers modified existing

lagoon technology to create a more economical, reliable and effective treatment system.

The basic AIWPS consists of four main ponds in series: the advanced facultative pond

85

(AFP), the high rate pond (HRP), the settling pond and the maturation pond. More

advanced systems may have an extra AFP or include a disinfection process at the end

such as chlorination or ozonation. AIWPS have been utilized successfully for municipal

wastewater treatment in St. Helena, and Hollister, California. The pond system includes

the main unit processes found in mechanical treatment systems including primary

sedimentation, fermentation, aeration, secondary sedimentation and nutrient removal.

However, unlike the mechanical treatment systems, AIWPS do not require high-energy

inputs and large construction costs. AIWPS take advantage of natural biological

processes to digest and aerate the wastewater. The fermentation of sludge is allowed to

go to completion, greatly reducing the need for sludge removal; algae is used for aeration,

reducing expensive energy input; and the ponding system mainly consists of earthwork,

greatly reducing construction costs. Together, this results in an overall reduction in

capital and operating costs, when compared to traditional mechanical treatment systems.

[30]

The reduced cost and lack of complicated machinery make AIWPS ideal for use in

developing nations. When traditional mechanical systems are built in developing nations

many problems can arise. These include not having properly trained operators, not

having the resources to fix broken machinery and problems with supplies of necessary

chemicals and electricity. AIWPS do not require chemical inputs, have only limited

machinery and can be successfully run by one well-trained operator. The biggest

negative of the AIWPS is land use. For treating waste from municipalities of about

20,000 people, the land use requirement is on the magnitude of 104 m2. It will be smaller

86

for more decentralized systems, however an AIWPS will most always require more land

than most other treatment systems.

The land use requirement of AIWPS would not have been a problem at the proposed rice

paddy site, but this requirement made Oswald ponds unfeasible at the Bali Spirit Hotel.

Current wastewater treatment practices at other hotels in Bali and other decentralized

treatment options were therefore researched in order to identify possible treatment

options that would be feasible at the Bali Spirit Hotel site.

6.3 Bali Spirit Design Options

When the Bali Spirit Hotel was visited, an offer to design an upgrade to their current

wastewater treatment system was made. Unfortunately, the management was not

interested in our offer and was suspicious of the motivations behind the offer. The team

wanted to design a system that could be used to treat the kind of flows that they

experience. In order to come up with a good design, each member of the team researched

and designed an alternative treatment option. These options were then evaluated and the

best one chosen as the final design. Based upon the research done before arriving in Bali

and the investigation into current wastewater treatment practices in Bali, the following

design alternatives were identified:

• An attached -rowth trickling filter

• An upgraded septic tank system with grease trap and intermittant sand filter

• A traditional activated sludge system

• A sequencing batch reactor activated sludge system

87

• A constructed wetland

• Oswald pond

The constructed wetland and Oswald pond alternatives were emliminated due to lack of

available land area. The system would need to be compact in size, inexpensive, easy to

blend with the environment, have minimal odors, and treat the wastewater to the effluent

standards defined below. It was decided to use the Bali Spirit hotel as a basis for our

design and make some engineering assumptions to characterize the wastewater

6.3.1 Current Wastewater Practices in Bali

Bali Spirit Hotel After identifying the Bali Spirit Hotel as a potential demonstration site we visited them to

inquire about their current treatment practices and gather some information on the hotel.

The Bali Spirit has nineteen rooms that go for $50 to $150 a night. When asked about

their wastewater disposal, the Bali Spirit staff did not understand right away. After some

discussion, it was found that two septic tanks are used to handle the hotel’s black-water

disposal. One of the septic tanks is used for the seven original rooms and the other is

used for twelve newer rooms that have been built in the last five years. The current septic

tanks fill up with solids and need pumping twice a year. The size of the tanks is

unknown, so it is hard to predict sludge production. The gray-water from showers and

sinks is collected separately used for the landscaping. They explained that sometimes it

is very dry at their location and this is why they reused the grey-water for the landscape.

When asked about their restaurant they said that all of its waste also is sent to a septic

88

Figure 6.1 - Treatment system at Ibah Hotel and Resort.

tank, however our investigations indicate that the kitchen waste is discharged directly to

the Wos River untreated.

To better understand current wastewater disposal practices of hotels, several hotels in

different areas, and different price ranges were surveyed. Although no hotel or resort

admitted to discharging directly into the rivers and streams, a variety of different

practices were discovered as described below.

The first hotel contacted was the Ibah in

Ubud. The Ibah is an upper class resort

perched on a hill a couple hundred meters

above the Wos River. There are fifteen

rooms at this resort and they range in price

from $200 to $500 per night. Ibah is

aware of the problems with wastewater

and currently sends all of their wastewater

to an onsite decentralized treatment system. Although there were no English speaking

engineers on hand to discuss the system, a tour and photo opportunity were kindly

granted (Figure 6.1). The wastewater enters a large, open-air tank approximately three

meters long by two meters wide by two meters deep. Along the sides of this first tank are

large pipes used to aerate the effluent. This portion of the system appears to operate as an

activated sludge system. The Following the first tank are several smaller open-air tanks.

The first of these tanks was empty and the others appear to be operating as a series of

89

Figure 6.2 - Rainwater collection tanks at Udyana Lodge.

settling tanks. There was no overpowering smell, which suggests the absence of

anaerobic conditions. In the case of a power outage, this may become a problem because

aeration will stop. In the case of an outage, the system is designed to hold more than a

days worth of flow, so the tanks will just fill until operation can resume. Extended

outages may cause untreated discharges. The final tank had an effluent pipe, which

discharged to the vegetated hillside, eventually flowing down to the Wos River. Sludge

is currently pumped from the tanks every month. The sludge is then spread on the

surrounding vegetation.

The Udayana Eco Lodge, located on the south side of the island, was also visited. The

Udayana Lodge is currently undergoing its certification process for the Green Globe

ecotourism certification. There are sixteen rooms that go for about $50 a night. The

lodge is located on the drier portion of the island and has a great understanding of the

importance of water usage. During the

rainy portion of the year, rainwater is

collected and stored in underground storage

tanks (Figure 6.2). This collected rainwater

is then used in the sinks, toilets and showers

for up to five months in the dry season.

Groundwater is used to make up for the

remaining demand. All wastewater from the rooms and lodge restaurant is sent to a

decentralized onsite wastewater system consisting of three separate processes (Figure

6.3). The wastewater first enters a covered anaerobic biological treatment basin. From

90

Figure 6.3 Decentralized wastewater treatment system at Udyana Lodge.

Figure 6.4 Solar panels used for lighting system at Udyana Lodge.

the anaerobic section, the water is pumped to the top of an aerated packed bed filter.

Aeration is necessary because the system is enclosed in cement and natural aeration

cannot occur. Effluent from the filter is recycled back to the top of the filter to maintain

minimum wetting rates. Water not

recycled is sent to a third tank for settling.

The water is then stored in this final tank

until it is used on the lodge landscaping.

The sludge that is produced during the

treatment process is pumped once every

four years by a local company. This

company then takes the sludge to settling

ponds where it under goes further

treatment. In addition to conscience

water use, the lodge also uses solar water

heating and solar power for pumping and

some lighting and has an extensive

composing program (Figure 6.4). The

land surrounding the lodge is a preserve

for more than fifty species of birds and

more than sixty species of butterflies. The Udayana Lodge represents a prime example of

ecotourism that is important for the environmental sustainability of developing tourist

locations.

91

The management of the final resort did not wish to have their name entered in the report

but graciously allowed a tour and interview. They offer rooms for around $500 per night

and villas for upwards of $1500 per night and have individual treatment systems for each

villa and a centralized system for the remaining rooms. There is a packed bed biofilter

submerged in the backyard of each villa to treat wastewater. All biofilters used at this

resort are produced by Biotech and distributed by Fibertech from Java, Indonesia. The

effluent from each of these filters is discharged through two horizontal leaching lines

buried just below the ground’s surface. For the main hotel building, which housed the

lobby restaurant, and some service rooms, there was one large central system. This

system was designed to operate at fifty cubic meters per day, but as admitted by the

engineer, it sometimes operates at as much as 100 cubic meters per day, leading to

inefficient treatment during peak loads. The system consists of a primary activated

sludge process followed by a packed bed filter with recirculation. The effluent is then

settled and discharged. Although not currently in practice, they plan on reusing the

effluent for landscaping in the future.

Local Residences In addition to hotels and resorts, the current practice for water use and wastewater

disposal of family housing compounds was examined. In Bali, each family lives together

in a cluster of houses that is commonly referred to as a compound. Tap water for these

compounds comes from groundwater, and bottled water is used to drink. The wastewater

from these compounds is disposed of in septic tanks. There is usually one septic tank for

every one or two houses, depending on the house size. The septic tanks consist of a hole

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in the ground with four cement walls. The bottom is left open to the ground and the top

is capped with cement, leaving a small vent for maintenance. There are no leach fields

involved in the system, the water percolates into the soil. When a tank becomes full,

another hole is simply dug and the effluent is rerouted to this new tank. Special care is

taken to make sure that the groundwater well is not located hydraulically down gradient

from the septic tanks. Regardless, each family compound operates separately from

another, and one family’s effluent may become another’s tap water.

Summary of Current Practices As described above, there are several different options being used to treat wastewater in

Bali. Unfortunately, it appears that only the more expensive hotels are installing

decentralized systems other than septic tanks. Although it cannot be said for sure, the

septic tanks being used by these smaller hotels are most likely similar to the ones being

used in the family compounds. Most hotels need economic benefits to install a

decentralized system because there are no regulations or treatment standards.

6.4 Design Approach It was determined that a design for the Bali Spirit Hotel and Resort would be the best way

to help prevent pollution from entering the Wos River and demonstrate a wastewater

treatment option. To start the design process, it was necessary to determine what the

existing water quality was and what standards the effluent would be treated to before

being discharged back into the river.

93

Constituent Value UnitFlow 14250 L /day

People 38Flow 375 L / capita*day

Total Solids 917 mg/LTDS 639 mg/L

TDS-fixed 385 mg/LTDS-volatile 254 mg/L

TSS 283 mg/LTSS-fixed 64 mg/L

TSS-volatile 220 mg/LSetteable solids 14 mg/L

BOD 252 mg/LTOC 186 mg/LCOD 573 mg/L

Total N 52 mg/LOrganic N 19 mg/L

Free Ammonia 33 mg/LNitrites 0 mg/LNitrates 0 mg/LTotal P 9 mg/L

Organic P 3 mg/LInorganic P 7 mg/LChlorides 65 mg/L

Sulfate 38 mg/LOil and Grease 94 mg/L

VOC 308 mg/LTotal Coliform 1.E+08 mg/LFecal Coliform 1.E+06 mg/L

Table 6.1 – Estimated wastewater composition

* From reference [28].

6.4.1 Wastewater Characterization In order to complete the design, the constituents of the wastewater needed to be

characterized. During the discussions with the Bali Spirit Hotel it was determined that

they used approximately 20 m3 of water per

day. Of this flow it was assumed that 71%

of the used water would become wastewater

and need to be treated [34]. This

assumption resulted in a design flow of 375

L/capita-day. The specific constituent

concentrations were then estimated from

typical characteristics of low strength and

medium strength untreated domestic

wastewater [28]. The strength of the

wastewater is approximated based upon

flowrate, so that is why the characteristics

are interpolated for a design flow of 375

L/capita-day. This resulted in the final

characterization of the wastewater presented

in Table 6.1. As displayed in the table, the

design BOD is 252 mg/L.

94

6.4.2 Effluent Requirements There are no regulations in Bali concerning wastewater effluent discharge standards.

However, some effluent standards needed to be designed for. It was decided that U.S.

secondary treatment standards of 30 mg/L for BOD and TSS should be the basis for

design effluent [28].

6.5 Trickling Filters 6.5.1 Background on Trickling Filters Trickling filters are one of the oldest forms of biological wastewater treatment. They

consist of a column that is filled with a porous media. Wastewater is allowed to percolate

through the media, causing a thin, slimy film of bacteria to grow on the media. As the

water passes over this film, the nutrients and organic matter in the water are absorbed by

the bacterial film and used to construct more bacterial cells. Their simplicity of

construction and operation make trickling filters ideal for use in developing countries

such as Bali.

Trickling filters can be classified into two primary categories, rock media filters and

plastic media filters. Rock and plastic media filters are then classified by how heavily

they are loaded. Rock filters are typically loaded at three separate rates; low rate filters

are run at a rate around 2 cubic meters per square meter per day, intermediate rate filters

are operated around 7 cubic meters per square meter per day, and high rate filters are

typically loaded at 25 cubic meters per square meter per day [28]. Plastic media filters

can handle more variable flow depending on the shape of media, but usually run in the

range of 10 to 75 cubic meters per square meter per day [28]. Roughing filters are

95

trickling filters that run at high hydraulic loading rates. The high loading rate creates

shear on the biofilm layer, causing more biomass to slough off and eliminates the need to

clean the system as often. Roughing filters are good to avoid clogging problems, but

because of their short retention time, they require recirculation in order to reach

acceptable effluent levels [35]. These filters run with hydraulic loading rates from 40 to

200 m3/m2*day [28]. Trickling filters are also often used in series to account for variable

influent characteristics and inefficient treatment in the first stage. Plastic filters have an

advantage over rock filters for large systems because the weight of rock can be too great

for construction of large columns. Plastic media is much lighter and therefore can be

used for more applications.

6.5.2 Design Considerations for Trickling Filters

Filter Sedimentation A primary sedimentation tank usually precedes trickling filters. During primary

sedimentation as much as forty-five percent of the initial BOD can be removed with the

settled solids. In addition to reducing the BOD loading to the trickling filter, us ing

sedimentation prior to a trickling filter will reduce the amount of solids entering the filter

and thus reduce the amount of clogging that occurs with filter operation. For the system

in Bali, since the daily flow is not that great, a relatively small pretreatment

sedimentation tank is required.

Besides pretreatment sedimentation, the system design for Bali will also require a post

filter sedimentation tank. This is to ensure that the filter produces an effluent with low

96

BOD and suspended solids. Because the bacterial slime layer occasionally sloughs off

into the effluent, post sedimentation is necessary to remove any excess biosolids. Post

sedimentation should be a slightly larger tank than pretreatment in order to produce a

clarified effluent. For the design presented here, it was assumed that 30% of the initial

BOD is removed in the primary settling tank.

Because of the low flows associated with the Bali Spirit, plate settlers may also be used.

Plate settlers allow sedimentation to occur without using a large sedimentation basin

footprint [10]. In this form of sedimentation, plates are angled 45 to 60 degrees from the

horizontal. Typically, the flow enters the sedimentation zone at the bottom of the plate

and flows upward. This allows particles to settle out of suspension onto the plates. As

solids accumulate on the plates, the force of gravity moves the solid toward the bottom of

the plate. A hopper or some other collection device is usually located at the bottom of the

basin. As sludge accumulates in the hopper, it is pumped out to sludge disposal.

Filter Wastewater Distribution When using a trickling filter, it is important that the wastewater is evenly applied to the

media. Uneven distribution of water may allow some areas of the filter to dry out. This

will result in death of the bacteria biofilm in this portion of the filter, allowing future

wastewater to pass through this section untreated. To avoid this, a proper distribution

system must be designed. Typical distribution systems for trickling filters use a rotary

distributor. The influent is distributed through two or more arms that are mounted on a

pivot in the top center of the filter. Most filter distribution systems are controlled by a

rotary motor. This ensures that the water is dispersed at an even rate. [28]

97

The filter will occasionally need to have water applied at a rate several times higher than

usual to clean off excess biomass that has accumulated over time. This process is known

as sloughing and is the main operating principal behind roughing filters. Regular

sloughing is necessary to avoid clogging of the media.

As discussed in Metcalf and Eddy [28], most filter distributors apply water to the media

at a rate that takes one to five minutes per revolution of the distributor arms. This allows

even distribution, however, it has been found that filters dosed at a rate of 30 to 55

minutes per revolution will out-perform filters dosed in the 1 to 5 region, but this is not

always practical. For low BOD loads, an appropriate distributor arm speed will cover the

filter surface with 30 mm of water per pass or less. During periods of flushing or

sloughing, the filter should be dosed with greater than 200 mm per pass. In order to

determine the rotational speed that the distributor should run at, the following equation

can be used [28]:

( )( )[ ]( )( )( )60

)10(1 3

DAqR

n+

= (Eqn 6.1)

where: n = rotational speed of the distributor, rev/min

q = influent applied hydraulic loading rate, m3 / m2 * h

R = Recycle ratio

A = number of arms on the distributor

DR = dosing rate, mm/pass of the distributor arm

98

Minimum Wetting Rates and Recirculation In order to prevent bacteria from dying it is recommended that a minimum wetting rate of

0.5 liters per square meter per second be used. When dealing with low flows,

recirculation will be necessary to maintain a minimum wetting rate. Recirculation is

necessary only to maintain minimum wetting rates. Except for filters with high hydraulic

loading rates, any recirculation above the minimum rate will only produce minor changes

in effluent quality [28]. The recirculation ratio, R, can be found by using the following

process:

Minimum wetting rate = 0.5 = q + qr (Eqn 6.2)

where: q = the application rate without recirculation, L/m2 * day

qr = the recirculation application rate, L/m2 *day

This can then be used to find the ratio, R:

qq

R x= (Eqn 6.3)

The recirculation ratio, R, is used in several computations and is necessary for hydraulic

sizing requirements.

Airflow in Filters In order to assure that the trickling filter process remains aerobic, there must always be an

adequate flow of air within the media. Wind can create airflow in open-air filters.

Airflow is also created by a temperature difference between the water and the outside air.

If the water is colder than the ambient temperature, then the air inside the media pore-

99

space will be colder and denser than the ambient air, therefore causing the air molecules

to fall within the filter. The reverse is true for ambient temperatures that are cooler than

the wastewater. In this situation, the air in the filter becomes warmer as it is in contact

with the water longer, creating an upward draft of warm air. Because of its tropical

climate, Bali has very warm and air. If the temperature of the water is too close to the

ambient temperature, then there may not be enough natural force to cause the airflow. In

these situations, blowers should provide additional airflow. As described in Metcalf and

Eddy’s fourth edition, Equations 6.4 through 6.13 show the method of determining the

pressure drop required by a forced aeration system. A properly aerated trickling filter

will help limit fly population and unattractive odors.

Proper construction will also help induce natural draft. Over sizing collection and

effluent drains, installing ventilation manholes, and installing a ventilation grate for

cleaning access in the underdrain will all help create natural airflow. Additional forced

aeration may be necessary if these adjustments do not create enough draft. Natural draft

pressure in filters can be determined by comparing the difference in temperatures of the

water and the air. The amount of pressure induced by natural draft is found using

empirical Equations 6.4 and 6.5 [28].

ZTT

Dmc

air

−=

11353 (Eqn. 6.4 )

where: Dair = natural draft pressure induced by temperature difference, mm Tc = colder temperature, degrees K Tm = log mean of the temperatures, degrees K Z = the filter depth, meters

100

−

=

1

2

12

lnTT

TTTm (Eqn. 6.5)

where: T2 = warmer temperature, K T1 = colder temperature, K In order to determine if this natural draft is sufficient, the airflow rate required to

maintain aerobic conditions must be calculated. First the necessary oxygen supply rate

must be determined.

[ ]( )PFeekgkg

R BB LLo

17.09 2.180.020 −− +

= (Eqn. 6.6)

where: R0 = rate of oxygen uptake, kg O2 / kg BOD applied LB = organic loading rate, kg BOD/ m3 day PF = peaking factor, maximum to average organic loading Once the amount of oxygen required is known, the total airflow rate at standard

conditions (ARstd) can be found.

)min/1440)(/10(

)/58.3(3

23

daykggkgOmQSR

AR oostd = (Eqn. 6.7)

This value is then corrected to the operating temperature (TA).

+

=15.273

15.273 AoT

TARAR

A (Eqn. 6.8)

where: TA = ambient air temperature, degrees C The value is also adjusted to correct for lower oxygen saturation.

−

+=100

201 A

TT

ARARA

(Eqn. 6.9)

101

Once the oxygen airflow rate is known for the operating conditions, the pressure drop

must be determined to know how much total air should be added to the system.

( ) ( )( )ALp eDN /10*36.1 5

33.10−

= (Eqn. 6.10) where: Np = adjusted depth for aeration, m D = filter depth, meters L/A = as defined below, kg/ m2*h

=

Lkg

mL

qAL 110

3

3

(Eqn. 6.11)

AsQ

q = (Eqn. 6.12)

where: Q = flowrate, m3/h As = surface area of the filter, m2

This value of Np is then adjusted to correct for head loss through the packing media and

for inlet and outlet losses. After a satisfactory value of Np is obtained, the pressure drop

through the filter is determined.

=∆

gv

NP p 2

2

(Eqn. 6.13)

where: ∆P = pressure drop from bottom to top of filter tower, N/m2

v = AR/ As, m/s Once the pressure drop and natural draft are calculated, they should both be converted to

the same units. This allows the two values to be compared. If the natural draft value is

greater, then no forced aeration is necessary. If the pressure drop is greater, additional

oxygen will need to be supplied.

Filter Media

102

Trickling filters are primarily constructed using rock or plastic packing media. Redwood

was also used, but because of increased scarcity, it is no longer found in new plants.

Each type of media has its own pros and cons.

All trickling filters in the U. S. used rock until the late sixties. Rock was an obvious

choice because it is easy to get, cheap, and durable. The two most common rock media

used are high-quality granite and blast furnace slag. River gravel also works well [28].

Rock media requires grading to assure that ninety-five percent of all media is within 75 to

100 millimeters [29]. Smaller or larger rock will be susceptible to clogging and not allow

adequate airflow. Rock media has other limitations. Due to the weight of rock, filter

depths usually do not exceed 3 meters [29]. Because of this, heavily polluted influent

wastewater must use several filters in series.

Plastic packing media allows for a maximum amount of surface area per volume as well

as minimizing density. This allows filters to be built to almost any height desired. Most

plastic media resembles a honeycomb with several small chambers for the water to flow

through. The inside of these chambers often have a corrugated surface to provide a

surface for slime growth and to slow down the water, thus increasing detention time.

Plastic media is available in two different forms, vertical and cross flow. Vertical flow

allows the water to percolate down through the media, altering its course on the way

down to increase contact with the film. Cross flow allows the water to enter the media

through its upper surface, but then sends the water diagonally downward until it exits into

another section of media. Crosflow is good because it allows the water to disperse

103

horizontally as well as vertically. Both types of plastic media are good because of their

ability to handle high flows without clogging.

Nitrification in Trickling Filters Since the Bali Spirit Hotel is near the Wos River and the amount of ammonia in the

effluent is assumed to be 33 mg/L (Table 6.1), it is important that nitrification occurs in

the treatment of its wastewater. Ammonia is toxic to fish in relatively low amounts and

must be degraded before being discharged into the river. In addition to being toxic to

aquatic life, ammonia also contributes additional oxygen demand and will degrade the

health of the river if discharged without nitrification. The method to design a filter for

nitrification based on packing media specific surface area is shown below. In order to

design for nitrification, the rate of nitrification must be determined using the following

empirical equation [28]:

( )44.0

82.0−

=

TKNBOD

Rn (Eqn 6.14)

where: Rn = nitrification rate, g N/ m2 * day BOD/TKN = influent BOD to TKN , g/g The amount of nitrogen removal desired per day can be found by multiplying the decimal

amount of nitrogen removal desired, the flow, and the concentration of TKN as follows:

TKN removal per day = (Q)(TKN)(0.9) (Eqn 6.15) where: Q = average daily flow rate, m/d TKN = concentration of TKN present in the influent, mg/L 0.9 = 90 % desired removal of TKN Using this value and the rate of nitrification, the amount of packing surface required to

achieve nitrification can be found. Using this surface area and the specific surface area of

104

the packing material, the necessary volume of packing material can be calculated.

Knowing the volume and assuming a depth, a filter surface area can be calculated. For

nitrification with rock media it is recommended that the filter be loaded at a BOD loading

of 0.08 kg BOD per day or less in order to achieve ninety percent nitrification [28].

Trickling filters are also used for nitrification after water has been treated with activated

sludge or some other biological treatment process. Waters with low BOD levels allow

nitrifying bacteria to grow on the filter media, thus promoting more nitrification.

Head Loss in Trickling Filters As with most treatment processes, there is a loss of hydraulic head as the water flows

through the process. This head loss must be determined and an appropriate pump should

be selected to provide the additional head necessary. The loss associated with the water

passing through the filter is assumed to be one meter from the top of the filter media to

the exit at the under drain. In addition to head loss in the filter, there are also losses that

occur in the piping. These losses are determined by using the Darcy-Weisbach equation

[27].

g

VDL

fhf2

2

= (Eqn. 6.16)

where: hf = friction head loss, feet f = coefficient of friction L = Length of pipe in question, feet D = Pipe diameter V = velocity of fluid in the pipe, ft/ sec g = force of gravity, 32. 2 ft/sec2 There are also losses that occur when the fluid enters or exits the pipe and when the pipe

bends at 90 or 45 degrees angles. These are considered minor losses and are found by

105

using a variation of the Darcy-Weisbach equation that uses a loss coefficient k [27].

This equation is of the form:

gV

kh f 2

2

= (Eqn. 6.17)

where: hf, V, and g = as defined previously k = loss coefficient associated with a specific minor loss. 6.5.3 Design Process for Trickling Filters

Preliminary Filter Designs and Equations There are several formulations in use for trickling filter design. Some are based on

empirical data such as the ones presented by the National Research Council (NRC). This

was one of the first relationships for trickling filter efficiency [Sarner 1980]. Several

other empirical equations based on first order decay have also been developed. These

include equations by Eckenfelder [35] and Germain and Schultz [29]. Several other

formulations exist, but these ones are commonly used and will be evaluated in the design

of a trickling filter for the Bali Spirit hotel.

The NRC equations for first and second stage filters are typically applied to rock media

[29], but also have been used for plastic media as well [Sarner 1980]. These equations are

as follows:

For first stage filters:

106

( )( )( )

+

=

FVW

E1

1

4432.01

100 (Eqn 6.18)

where: E1 = BOD removal efficiency of the first stage at 20 degrees C including recirculation, %

W1 = BOD loading to the filter (kg/d) V = volume of the filter media (m3) F = Recirculation factor

( )

2

101

1

+

+=

R

RF (Eqn 6.19)

For the values assumed for the Bali Spirit: W1 = 2.51 kg BOD /day V = 2.35 m3

R = 1.38 F = 2.31 This produces a first stage efficiency, E1, of 76.8%.

For a second stage filter:

( )( ) ( )( )

−+

=

FVW

E

E2

1

2

14432.0

1

100 (Eqn 6.20)

where: E2 = BOD removal efficiency of the second stage filter at 20 degrees C, % E1 = Fraction of BOD removal in the first stage filter W2 = BOD loading applied to the second stage filter, kg/d The efficiency of the second filter was found using the following assumed values: E1 = 0.768 W1 = 0.24kg BOD /day V = 3 m3

R = 2 F = 2.3

107

This produced an efficiency, E2, of 54.9%. For temperature correction the following equation is used: ( ) 20

20 035.1 −= TT EE (Eqn 6.21)

where: ET = BOD removal efficiency at temperature T, degrees C, % E20 = BOD removal efficiency at 20 degrees C, %

Using equation 6.21 with an ambient temperature of 25 degrees C [23], and the

efficiencies E1 and E2, the operating efficiencies can be determined. Operating

efficiencies were found to be:

E1T = 91.2 % E2T = 65.2 %

As it can be seen, warmer temperatures can increase the operating efficiency greatly.

Design parameters fro the NRC preliminary designs are found in Table 6.3. The

following equations are typically used to design plastic media trickling filters. As

mentioned previously, all of these are based on empirical data and first order decay [28].

kSdtds

−= (Eqn 6.22)

where: k = an experimentally determined rate constant S = BOD concentration at time t One variation of this equation is the form used by Germain and Schultz.

( )( )

−

=nq

Dk

o

e eSS

(Eqn 6.23)

where: Se = BOD concentration of the final settled filter effluent, mg/L So = BOD concentration of influent to filter, mg/L k = wastewater treatability and packing coefficient, (L/s)0.5/m2

D = packing depth, m

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q = hydraulic application rate of primary effluent, excluding recirculation, L/m2*s n = constant characteristic of packing used

The Schultz equation was also used for trickling filter preliminary design.

An effluent concentration, Se was found to be 25 mg/L BOD for the first stage filter,

when using the following values:

So = 252 mg/L k = 0.21 (L/s)0.5/m2 before temperature correction D = 3 m

q = 0.1 L/m2*s n = 0.5

A second stage design was also produced using similar assumptions. The parameters

determined for the second filter are shown in Table 6.3.

Another variation of the first order decay is the form presented by Eckenfelder [28].

( )

+

−

=mza

QRAs

k v

n

eSiSe 1

* (Eqn 6.24)

where: Se = effluent BOD concentration, mg/L Si* = influent BOD concentration including recycle, mg/L k = temperature and epth corrected removal rate constant As = cross-sectional surface area of the filter, m2

R = Recycle ratio Q = Influent flowrate with out recycle, m3/day m, n = empirical constants av = specific surface area of the packing media, m2/m3 z = filter depth, m

Applying the assumed data for the Bali Spirit, these variables have the following values:

Si* = 56.9 mg/L As = 1.28 m2

R = 0 Q = 14.25 m3/day

109

m, n = 1, 0.7 av = 55 m2/m3 z = 3 m

In the use of these equations, the value of k needs to be adjusted for different degradation

at different filter depths. This is done by using:

( )5.05.0

12 21

21

=

SS

DD

kk (Eqn 6.25)

where: k2 = normalized value of k for the site-specific packing depth and influent

BOD concentration k1 = k value at a depth of 6.1 meters and influent BOD of 150 mg/L S1 = 150 mg BOD/ L S2 = site-specific influent BOD concentration, mg BOD/L D1 = 6.1 meters packing depth, m D2 = site-specific packing depth, m Using filter depth and BOD values as shown above, and a k value of 0.1, a new k value of

0.23 can be calculated and then produce the final effluent concentration value of 19

mg/L. Equations 6.24 and 6.25 are also used for the design of a second stage filer using

the Eckenfelder equations. Summaries of both Eckenfelder designs are seen in Table 6.3.

Because there are several equations that describe the treatment efficiency of trickling

filters, all three designs were evaluated and the best option was used. Looking at

multiple designs allows the best design to be used and it is also a good double check to

see that design parameters are similar for all designs. This guarantees accuracy of the

design. The equations used are Eqns. 6.4, 6.6, 6.9, and 6.10. To use these equations, the

general design assumptions were applied as well as the additional assumptions stated in

Table 6.2.

110

Using this information, the previous three separate trickling filter designs were created.

All three designs utilized two trickling filters. The first filter was designed to knock

down the amount of BOD to acceptable concentrations. The second filter was designed

using the organic loading rate of 0.08 kg BOD/ day*m3 [28], which allows nitrification to

occur. If it were not desired to achieve nitrification, one filter would perform sufficient

treatment. Table 6.3 shows the results for each design as well as average values for all

three designs.

As it can be seen in Table 6.3, all designs use filters with a depth of three meters due to

the difficulty of working with one much bigger. For the first filter, diameters range from

1 meter to 1.55 meters and the recycle ratio varies from 0 to 3.78. All designs for the first

filter produce an effluent quality of 25 mg/L BOD or less. This value is below the United

Sates EPA Secondary Effluent discharge standard of 30 mg/L and therefore should

provide enough treatment in terms of BOD. Organic loading rates to these filters are also

within the recommended loading ranges for high rate rock and plastic filters. However,

Table 6.2 - Design Assumptions Specific to Trickling Filter

Parameter Value Units Reference #

k1 0.21 (L/s)0.5/m2 27Maximum air temperature 32 Degrees Celsius indo.comMinimum air temperature 17 Degrees Celsius indo.comSchultz n value 0.5 27Eckenfelder k value 0.1 variable 33Eckenfelder m value 1 33Eckenfelder n value 0.7 33Max filter Depth 3 meters 27

Plastic Media Specific Surface Area 90 m3/m2 33

Rock Media Specific Surface Area 55 m3/m2 33

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the hydraulic loading rate of the design using the NRC equation is above the suggested

40 m3/m2*day [28]. All other designs meet the suggested rates.

The second stage filter designs also have a depth of three meters with diameters ranging

from 2.58 to 1.13 meters. The recycle rate required for these designs to meet the

Table 6.3 - Trickling Filter Design Results

Parameter Eckenfelder Schultz NRC average Units

Media rock plastic rockFirst FilterDepth, D 3 3 3 3 mSurface Area, As 1.28 1.58 0.79 1.32 m2

Diameter, d 1.28 1.42 1 1.28 m

Volume, V 3.84 4.73 2.36 3.64 m3

Recycle ratio, R 0 3.78 1.38 2.04Effluent Concentration, Ce1 19.57 25 16.83 18.8 mg/L = g/m3

Organic Loading, OLR 0.95 0.79 1.65 1.08

kg BOD / m3

*dayHydraulic Loading, HLR 50 32.57 67.48 48.19 m3/m2 daySecond FilterDepth, D 3 3 3 3 mSurface Area, As 5.23 1.48 1 2.47 m2

Diameter, d 2.58 1.38 1.13 1.65 m

Volume, V 15.68 4.45 3 7.41 m3

Recycle ratio, R 2.53 3.5 2.03 2.39Effluent Concentration, Ce2 1.13 2.66 7.6 3.8 mg/L = g/m3

Organic Loading, OLR 0.08 0.08 0.08 0.08

kg BOD / m3

dayHydraulic Loading, HLR 12.27 34.56 53.46 36.31 m3/m2 day

112

minimum wetting rate ranges from 2 to 3.5. Taking this into account, the settled effluent

from all of these two filter systems will be lower than 10 mg/L BOD. Since the organic

loading rate of the secondary filter is 0.08 kg BOD/ day*m3, all three designs will also

achieve around ninety percent nitrification. The hydraulic loading rates for the second

stage filter designs are all in the range of high rate filters and exceed the ranges for low

rate filters. Because these are second stage filters, and the influent BOD concentrations

are considerably lower than that for the first stage, the high hydraulic loading rates should

still produce a well treated effluent.

Filter Design Conclusions and Recommendations After analyzing all three filter designs, a final design was selected. The specifications for

the final design are shown in Table 6.4 and figures displaying the trickling filter design

are shown in Figures 6.5 and 6.6. This final design was selected because it was a good

representative of all three designs created. This design met all effluent, recirculation, and

loading parameters, therefore making it a desirable design. Rock media was selected

because it is easy to find on Bali, and the efficiencies are easy to predict based on a large

amount of past data.

113

As it can be seen in Figure 6.5, the filters will stand three meters tall and have an inner-

wall diameter of 1.4 meters. Hydraulic loading rates are around 45 m3/m2 day and

organic loading rates are 0.9 kg BOD / m3 day for the first filter and 0.11 kg BOD / m3

day for the second filter (Table 6.4). Although the loading on the second filter is above

the desired amount to achieve ninety percent nitrification, it is still loaded with a low

organic rate and some nitrification should occur. Although nitrification is important,

because the effluent will be entering a river with high year round flows, the effect on the

Table 6.4 - Trickling filter final design specifications

Parameter NRC Units

Media rockFirst FilterDepth, D 3 m

Surface Area, As 1.41 m2

Diameter, d 1.4 m

Packing Volume, V 4.5 m3Recycle ratio, R 3.3

Effluent Concentration, Ce1 10.55mg/L = g/m3

Organic Loading, OLR 0.89

kg BOD /

m3 day

Hydraulic Loading, HLR 44.98 m3/m2 day

Second Filter

Depth, D 3 mSurface Area, As 1.41 m2Diameter, d 1.4 mPacking Volume, V 4.5 m3Recycle ratio, R 3.3

Effluent Concentration, Ce2 4.1mg/L = g/m3

Organic Loading, OLR 0.11kg BOD / m3 day

Hydraulic Loading, HLR 45.38 m3/m2 day

114

surface water should be minimal. Also, the recirculation ratio of 3.3 is within the range

of 1 to 4 as suggested by Tchobanoglous [35].

Because the flow is so low, the wastewater will be distributed by two rotating arms run

by an electric motor to ensure even distribution. The motor will be programmed to

operate at two minutes per revolution which will give a dose of 30 mm each time the arm

passes over a section of media.

Pumps will be required prior to the both filters. The headloss through the distribution

arms is assumed to be three feet or about one meter [28]. The elevation head required by

the pump will be four meters, which is the height of the filter plus the loss associated with

the filter media. Because the system is working with such low flows, the headloss

through the pipes is less than one centimeter and therefore will be neglected because they

have no significant contribution. The flow required by the pumps will be 14.25 m3 per

day for the primary pump, 61.3 m3 per day for the pump between filters, 47 m3 per day

for the recycle pump, another pump of 14.25 m3 per day to pump to the clarifier. Each of

the two pumps preceding a filter will be required to provide a head of 4 me ters. The

recycle pump should provide no more than one meter of head, and the pump to the

clarifier will need to provide about four meters of head as well.

The existing septic tanks will be used for primary sedimentation. Because they are

already in place, this will reduce the cost of installing a complete primary sedimentation

system. Plate settlers are desired for use in the secondary sedimentation system.

115

Information on LamellaTM settlers was provided by one distributor, but it was just an

overall description of their operation. Lamella settlers require the use of coagulant and

are not desired to be used because of the operating cost of using coagulant. However,

plate settlers are very simple in operation and will be fitted to a tank of appropriate size

for the Bali Spirit Hotel application.

The natural draft induced by the temperature difference between the air and the

wastewater provides 0.034 mm of pressure. This value is greater than the 0.0000695 mm

H2O required for forced ventilation to maintain an aerobic environment. Because of this,

a forced air system will not be recommended. The filter should be designed with all the

proper specifications to ensure that the natural draft is allowed to occur.

Table 6.5 - Materials required for the Trickling Filter System

Material Quantity Units

reinforced concrete 4 m3

75 to 100 mm diameter river rock 8.5 m3

30 mm PVC pipe 14 msludge pumps 1pumps 4electric rotary motor 2piping for distribution 3 mpackaged plate settling system 1

vitrified clay 2.3 m2

116

117

118

6.6 Intermittent Sand Filter with Grease Trap and Septic Tank 6.6.1 Background This treatment option consists of a grease trap followed by a traditional septic tank and an

intermittent sand filter (ISF) for final clarification. An ISF is utilized rather than a

standard leach field so that the effluent can be utilized for irrigation prior to being

directly discharged to the Wos River. The grease trap will only treat the wastewater from

the kitchen, dishwashing and laundry services. This is estimated to be 15% of the daily

750 L/unit*day wastewater flow. The restaurant facilities are located in the southern

wing of the hotel with the 12 newer rooms. The northern wing of the hotel contains 7

rooms. Currently Bali Spirit treats each wing with separate septic tanks. This method of

splitting the treatment will continue so as not to affect the existing plumbing. The

Southern wing will have a treatment train that consists of a grease trap, septic tank and

ISF. This treatment system will treat the higher volume of flow due to the fact that there

are more rooms and that the restaurant facilities are located here. The northern wing’s

system will only utilize a septic tank and ISF. There is no need for a grease trap since it

is only receiving wastewater from the hotel rooms and not the restaurant.

A grease trap is used to intercept the oil and grease contained in restaurant wastewater

before it reaches the septic tank. It is utilized to isolate the oil and grease so they do not

foul the other unit operations. In grease traps the wastewater is introduced near the

bottom of the tank. As the grease and oil cool, they solidify and rise to the top of the

tank. The wastewater will also contain organic material and settleable solids, so it will

also act as a septic tank and biological degradation will occur. Due to the high

119

concentration of grease and oil in restaurant wastewater, a grease trap will need to be

monitored and pumped more often than a standard septic tank.

A standard septic tank is essentially a combined settling and skimming tank, as well as an

anaerobic digester and sludge storage tank. The wastewater is introduced near the middle

of the tank and the floatables rise to the top to form a scum layer while the settleables fall

to the bottom to form sludge. As the sludge layer accumulates, dissolved oxygen levels

decline and anaerobic digestion occurs. Septic tanks are found in many shapes and sizes,

including rectangular boxes, long tubes and tall barrels. An effluent filter vault can also

be implemented to ensure that no untreated solids escape the septic tank. In standard on-

site systems the septic tank effluent is then discharged through a leach field, where the

wastewater percolates through the soil. This is not always an option due to lot size and

soil limitations, as well as treatment standards.

An intermittent sand filter allows for the further treatment of wastewater to higher

standards, as well as for the collection of the treated effluent to be utilized in irrigation,

through mechanical, biological and chemical treatment. An ISF differs from a typical

sand filter because the wastewater is applied in doses and a constant head is not formed

over the sand. This allows for a more complete bio logical degradation of the wastewater,

rather than simple mechanical filtering in continuous flow sand filters. A dose of effluent

is pumped from the septic tank about 18 to 24 times a day and applied uniformly over the

surface of the sand filter through a series of laterals and orifices. A dosing rate in the

range of 18 to 24 times per day has been proven to be the most efficient (32). The

120

laterals are evenly spaced across the surface of the filter. Each lateral has orifices

through which the wastewater is discharged and applied to the filter. The effluent is then

allowed to percolate through the media and is collected in an underdrain. During

percolation the wastewater is mechanically filtered of large particles and nutrients are

removed through biological processes. The sand filters out BOD, TSS, turbidity and

ammonia. Lightly loaded ISF’s also can drastically reduce total and fecal coliform and

viruses [34]. An ISF is typically a rectangular bed of sand 0.5-1 meter deep. The bed is

lined with a PVC liner and also contains layers of rock and gravel to aid in drainage and

distribution. An ISF can be located above or below ground. The treated effluent from an

ISF can be utilized for irrigation through drip systems or discharged to surface water.

6.6.2 Design Considerations A grease trap and septic tank are similar in design because they are based upon many of

the same design parameters. The difference is in a grease trap a certain concentration of

grease is being removed by flotation, were as in a septic tank a given BOD concentration

is being removed by settling and biological decay. The hydraulic detention time (HDT)

and the ability to handle peak flows are the most important design parameters. The

standard peaking factor used in wastewater treatment design is 1.5 times the average

daily flow [34]. There is also another multiplier depending upon the desired pump-out

interval of the system. The design HDT is a combination of the standard multiplier for

pump-out intervals and peaking factors. A HDT of 3 days in a grease trap is more than

sufficient to provide adequate separation during average flows, as well as accommodate

peak flows [34]. For a septic tank, the HDT can vary from 3-6 days. This value also

121

provides an estimate of expected pump out interval because the pump out interval

multiplier is inclusive in the HDT. Depth is also important. A minimum depth of 2

meters should be used in both grease traps and septic tanks to accommodate proper

sludge and scum stratification.

The most important parameters when designing an ISF are the average daily flow,

hydraulic loading rate (HLR), organic loading rate (OLR), dosing frequency, dosing

volume per orifice and duration of flow per dose. The HLR affects the size of the ISF:

the higher the HLR, the smaller the surface area of filter needed. A lightly loaded ISF

will perform better and achieve better effluent quality. A typical HLR is 50 L/m2-d, with

the standard range being from 40-60 L/m2-d. The OLR is the product of the HLR and the

BOD concentration. The BOD of the septic tank effluent is multiplied by the HLR to

determine the OLR. A typical OLR is less than 0.005 kg BOD/ m2*d. Dosing frequency

is how often the effluent is applied to the filter and dosing volume per orifice is how

much effluent is discharged per orifice during one dose. The minimum dosing frequency

recommended is 18 times/day, but can be as high as 48 times/day. The dosing volume

per orifice ranges from 0.6-1.1 L/orifice*dose and a typical value is 0.9. This value is

dependent upon the stated parameters as well as others such as number of laterals and

number of orifices. There are no standards for duration of flow per dose, however it is

important because the engineer needs to know how long to pump during each dose. [34]

122

6.6.3 Design Process The grease trap operates on a fairly simple concept: give the grease and oil enough time

to cool and separate and then discharge the clarified wastewater for further treatment.

The grease is then removed by pumping out the scum layer that is formed. By

multiplying average daily flow and HDT a tank volume can be determined. From the

minimum depth and volume an area can be found. The length and width can then be

manipulated based upon site criteria, however it is always better to have the tank longer

in the direction of flow to enhance settling and flotation.

In this design, two new septic tanks will be designed to replace the existing ones, so each

septic tank will need to accommodate a different average daily flow. The HDT of five

days used in this design will provide for the handling of a peaking factor of 1.5 and

provide sludge storage for up to four years. A standard depth of 2 meters is used and the

area is determined in the same manner as the grease trap. Once again, the length and

width are determined based upon site criteria. In this particular design the width and

length were chosen to accommodate effluent filter vaults and sampling ports, while still

providing enough length for settling.

The initial BOD of the wastewater was assumed to be 252 mg/L as discussed in section

6.2.1. Due to the lack of empirical formulas for predicting septic tank effluent BOD

some more assumptions need to be made. First, the septic tank is assumed to act as a

settling tank in which it is common to achieve 25% BOD removal from the settling of

solids [28]. For the remaining BOD suspended in the wastewater first-order degradation

123

is assumed to occur for the entire HDT. After 25% BOD removal from settling the

wastewater will have a BOD concentration of 189 mg/L. That value will decay for the

duration of the HDT of five days at a rate of 0.1 day-1 to achieve a septic tank effluent

BOD of 115 mg/L.

The ISF filter surface area is found by dividing the peak daily flow by the HLR. The

peak daily flow is assumed to be 2.5 times the average daily flow, which is a standard for

ISF design [34]. This peaking factor is for safety so that the system is never overloaded.

The HLR chosen for this design is 50 L/m2*d for both systems. This value was chosen to

keep the OLR near 0.005. This HLR resulted in a filter surface area of 489 m2 for the

larger ISF and an area of 223 m2 for the smaller ISF. Once the area is determined, the

dimensions of the filter must be set. ISF’s are usually wider than they are long due to the

head loss associated with the distribution laterals. No more than 5% of the residual head

can be lost from the first orifice to the last in any given lateral; therefore short laterals

should be used. This is determined through head- loss calculations and will be described

later. The resulting filter dimensions are 17.5 m by 14 m for the larger ISFs and 22 m by

10 m for the smaller ISF.

The number of laterals and orifices per lateral are determined from the filter dimensions.

A standard wallspace of 0.3 m between the outside laterals and the wall of the filter, a

lateral spacing of 0.6 m and orifice spacing of 1.2 m are used. The number of laterals can

be found by subtracting the wallspace on both sides from the width of the filter and

dividing by the lateral spacing of 0.6 m. Then add one lateral to account for the first

124

lateral in the spacing. The resulting number may be a decimal, so round to the nearest

whole number to determine the actual number of laterals used. The number of orifices

per lateral is determined by subtracting 1 m from the length of the filter and then dividing

by the orifice spacing of 1.2 m. Once again round down to a whole number to find the

actual number of orifices.

The volumetric flow per dose is determined by dividing the average daily flow by the

dosing rate. For both systems a dosing rate of 18 doses/day was chosen [34]. This is the

minimum recommended, but was used in order to achieve a dosing volume per orifice

closer to the typical value of 0.9 l/orifice*dose. The volumetric flow per lateral per dose

is then found by dividing the above by the number of laterals. The important design

parameter dosing volume per orifice is then determined by dividing the flow per lateral

per dose by the number of orifices per lateral.

Next, using equation 6.26, find the rate of discharge from an individual orifice (Qn). [34]

( )( )( ) ( ) 5.02 245.2 nn ghDCq = (Eqn 6.26)

where qn = discharge from orifice n, L/lateral*dose

C = orifice discharge coefficient, 0.63

D = diameter of orifice, mm

g = acceleration due to gravity, 9.81 m/s2

hn = head on orifice n, m

125

Here some assumptions are made. 1.5 m of residual head (hn) at the last orifice is

assumed so that there is enough pressure to keep the orifice clean and unclogged. An

orifice discharge coefficient of 0.63, obtained from literature, is also assumed [34]. The

diameter of the orifice is taken to be 3 mm based upon typical design standards [34]. The

volumetric flow per lateral (Qlateral) is then found by multiplying Qn by the number of

orifices per lateral. Similarly, the volumetric flow per dose (Qdose) is found by

multiplying Qlateral by the number of laterals. The duration of flow per dose (tdose), in

seconds, is obtained by dividing the volumetric flow per dose by Qdose and multiplying by

60 sec/min.

Once the sizing is completed, the head loss calculations must be completed and the pump

size is determined. The head loss is found for the supply pipe, the distribution manifold

and the laterals. Estimations are made for the hose and valve assembly, the fittings and

the elevation differences. Head loss in these pipes is calculated using the Hazen-

Williams formula [34]:

( )( ) ( ) 87.485.1

5.10 −

= D

CQ

LH f (Eqn 6.27)

where hf = headloss through pipe, m

L = length of pipe, m

Q = pipe discharge, m3 /d

C = Hazen-Williams discharge coefficient

D = inside diameter of pipe, mm

126

For each supply pipe or lateral, the head loss is calculated for that particular length of

pipe and flow rate. For the supply manifold and lateral, which have holes for pipes and

orifices, the head loss is assumed to be 1/3 of the value calculated for a closed pipe [34].

This is because there is less head loss in pipes in which water is discharged along the

length of the pipe.

To calculate the percentage loss of residual head in a lateral mentioned earlier, it is

assumed that the residual head of 1.5 meters is achieved at the final orifice. The head at

the first orifice can be calculated by using equation 6.28 [34].

12hmhn = (Eqn 6.28)

where m = constant with decimal value less than 1.0

h1 = head on first orifice, m

In this equation hn is the head on the nth orifice in the lateral. The head in the first orifice

is represented by h1. If h1 is assumed to be the residual head of 1.5 meters plus the head

loss associated with the lateral and hn is assumed to be the residual head of 1.5 meters, m

can be solved for. Once you have determined m, subtract it from 1 and multiply by

100%. If this value is less than or equal to 5% then the head loss in the lateral is

acceptable. For the southern wing treatment system’s ISF the laterals were sized at 25

mm class 200 PVC pipe. A 25 mm pipe was needed rather than the standard 19 mm

because the head loss was greater than 5% in the pipe. With the 25 mm lateral the head

loss was 1.0%. The northern wing utilizes 19 mm class 200 PVC laterals, which incurs a

head loss of 1.2% from the first orifice to the last. The head loss results are presented in

Table 6.6 below.

127

The southern wing treatment system had a head loss of 21 meters and needs a pump to

deliver 949 L/min of septic tank effluent. For the northern wing, the pump is required to

achieve 15.7 meters of head at 412 L/min.

Table 6.7 - ISF Design Parameters

OLR (kg/m 2*d)

# of Laterals

# of Orif ices per lateral

Dosing rate ( t imes /d )

Dos ing volume

per orif ice (L/orif ice*

dose)

td o s e ( sec )

Grease Trap

Q T (L/d) HDT (days ) Volume (m 3 ) D e p t h ( m ) W i d t h ( m ) L e n g t h ( m )

Nor thern Wing N / A N/A N/A N/A N/A N / A

Southern Wing 2138 3 6.4 2.0 1.5 2.1

Sept ic Tank

Q T (L/d) HDT (days ) Volume (m 3 ) D e p t h ( m ) W i d t h ( m ) L e n g t h ( m )

Nor thern Wing 4463 5 22.3 2.0 2.0 5.6

Southern Wing 9788 5 48.9 2.0 3.0 8.2

Intermit tent Sand Fi l ter

Q a v g (L/d) Q p e a k (L/d) HLR (L/m2*d) No. of Fi l ters W i d t h ( m ) L e n g t h ( m )

Nor thern Wing 4463 11156 50.0 2 22.0 10.1

Southern Wing 9788 24469 50.0 2 11.2 10.0

Intermit tent Sand Fi l ter

Nor thern Wing 5.7E-03 36 7 18 0.98 32.8

18 0.94 34.4Southern Wing 5.7E-03 58 10

Table 6.6 - ISF Total Dynamic Head

Northern Wing Sorthern WingFriction loss in supply pipe 11.95 7.56 m

Hose and valve assembly (estimated) 1.52 1.52 mFittings (estimated) 0.30 0.30 m

Friction loss in manifold 2.65 1.68 mFriction loss in lateral 0.03 0.03 m

Residual head on orifices 1.52 1.52 mElevation differencs (estimated) 3.05 3.05 m

Total Dynamic Head 21.03 15.67 m

Total Dynamic Head

128

When a design is complete it is important to be able to predict the quality of effluent.

Some more complicated treatment systems utilize empirical equations in the design that

predict effluent quality. Unfortunately, there are no such equations for ISF’s. However,

there have been studies that document removal rates of certain constituents that can be

expected. A number of studies demonstrate a greater than 90% removal rate of BOD in

well designed ISF’s [34]. If a removal rate of 90% is achieved, then the final effluent of

our treatment systems should have a BOD less than 10 mg/L. Table 11-5 [34] reports an

expected fecal coliform removal of about 99% in ISF’s. Most design guidelines report

expected effluent quality. Reference 32 reports an expected BOD less than 15 mg/L, TSS

less than 15 mg/L, fecal coliform less than 103/100 ml, ammonia less than 1 mg/L and

nitrate less than 30 mg/L. This same quality can be expected from this proposed design.

6.6.4 Conclusion The proposed grease trap, septic tank and ISF system is a good choice for a decentralized

system for the Bali Spirit Hotel. The design relies on tried and true treatment operations

that are simple, dependable and low energy. The grease trap and septic tank can be built

where the existing tanks are at the Bali Spirit. They will be relatively inexpensive to

Table 6.8 - Materials Required for the Grease Trap and ISF

Material Quantity Unit

Reinforced Concrete 14 m3

Sand 470 m3

13-19 mm Rock 215 m3

10 mm Pea Gravel 107 m3

30 mm PVC Liner 712 m2

19 mm Class 200 PVC Pipe 346 m25 mm Class 200 PVC Pipe 793 m38 mm Class 200 PVC Pipe 18 m51mm Class 200 PVC Pipe 18 m

Effluent Filter Vault Pumps 2Pumps 2

129

build and require minimal maintenance and monitoring when compared to more

advanced systems. The ISF requires regular maintenance and monitoring, but it is of a

fairly simple manner. This is a positive feature because of the lack of qualified trained

operators in Bali. The major drawback for the ISF is the land requirement. The 712 m2

needed is definitely more than is available at the Bali Spirit, especially considering the

hilly nature of the terrain. This system may best be utilized with a trickling filter instead

of an ISF to minimize the land use requirement, while still achieving the same level of

performance. Another positive to this design is the fact that it has separate treatment

systems. This will minimize the need to alter the existing plumbing and provides

construction sites where their septic tanks already exist. The system, as it is designed,

will be able to treat the characterized wastewater at or near the desired effluent standards.

This design is a viable option due to its simple technology, reliable operation and cost

effectiveness. However, the land requirement for the ISF will render this option

unfeasible for the Bali spirit site.

130

131

132

133

134

135

6.7 Traditional Activated Sludge System 6.7.1 Background The activated-sludge process is now routinely used in the United States in the biological

treatment of wastewater. The antecedents of the activated-sludge process have been

dated back to the 1880’s. The process has evolved greatly since then due to the need for

higher-quality effluents from wastewater treatment plants, technological advances, and

increased understanding of microbial processes. [28]

The activated-sludge process was named because the microorganisms used in the

biodegradation of the waste are recycled back to the front of the treatment process. This

results in a more active biodegradation of the waste. In the aeration basin, mixing and

aerating the influent wastewater with the microbial suspension occurs. By definition the

activated-sludge process contains three basic components, first a reactor in which the

microorganisms responsible for the treatment process are kept in suspension and aerated.

Second, is the liquid-solids separation. This usually occurs in a sedimentation tank

following the reactor. Finally, there is a recycle system for returning solids removed

from the liquid-solids separation unit back into the reactor. These components are shown

in Figure 6.7. One of the more important features of the activated-sludge process is the

Recycle

Influent

Reactor Separator

Waste

Figure 6.12 Main Components of Complete Mix Activated-Sludge System

136

formation of flocculent settable solids. These solids are removed by gravity settling in

the sedimentation tanks [28].

Primary sedimentation is generally used before the activated-sludge process to remove

settleable solids. Once the settleable solids have been removed, the biological process

that is involved in activated-sludge is more efficient at removing the soluble, colloidal

and particulate organic substances. Primary sedimentation is often omitted in small

communities due to the less operator- intensive methods that are traditionally used at these

sites. It is also omitted due to the odor problems that can occur in areas of the world that

have hot climates. [34]

6.7.2 Design Considerations When designing an activated-sludge system, it is important to consider the following

items:

§ Selection of reactor type § Biological kinetic relationships § Solids retention time and loading criteria § Sludge production § Oxygen transfer rates and requirements § Nutrient requirements § Settling characteristics of sludge § Disposal of sludge

Selection of Reactor Type

Different design options that use the activated-sludge process include batch reactors,

complete-mix with recycle and plug-flow with recycle. It is important to take into

consideration the following items when deciding which reactor type will best suit the

situation [28].

137

§ Reaction kinetics § Oxygen transfer requirements § Characteristics of wastewater to be treated § Environmental conditions of the surrounding area § Presence of substances that could be inhibitory or toxic in wastewater § Costs § Ability to expand to meet future needs

While each reactor has advantages and disadvantages, the complete mix activated-sludge

reactor will be the focus of this section. A batch reactor will be discussed later in the

chapter.

Kinetic Relationships The kinetic relationships are used to determine the growth rate of the biomass. The

relationships are also used to determine the amount of substrate that will be utilized and

the rate at which is will be used. It is important to use these kinetic relationships to

ensure that the microorganisms survive. Once the microorganisms start to die off the

efficiency of the plant starts to deteriorate. Often times when treatment plants are

operated with low amounts of microorganisms the effluent will contain small amounts of

organic debris, which is extremely hard to remove using sedimentation [35].

Solids Retention Time and Loading Criteria The most common parameters that are used to design activated-sludge processes are the

solids retention time (SRT), the food to biomass ratio (F/M) and the organic loading rate.

The SRT is used as a basic operating parameter, whereas the F/M and organic loading

rate can be used to compare operating conditions.

138

Sludge Production It is necessary when designing an activated-sludge system to also incorporate how much

sludge will be produced and how it will be disposed. If this parameter is under estimated

the efficiency of the system could be compromised. The sludge will accumulate in the

activated-sludge process if it cannot be processed fast enough by the system. The excess

sludge will exit the secondary clarifier in the effluent, therefore degrading the quality of

effluent leaving the plant and potentially violating discharge limits.

Oxygen Requirements Oxygen is required to biodegrade the carbonaceous material that is found in wastewater.

The bacteria that perform this biodegradation oxidize a portion of the biodegradable

chemical oxygen demand (bCOD) to provide the necessary energy. The rest of the

bCOD is used for the growth of additional cells. Oxygen within the system will also be

consumed through endogenous respiration. The amount that is consumed will be

dependent on the SRT of the system.

Nutrient Requirements Since the activated-sludge system is a biological system it is necessary to have the

appropriate nutrients available to feed the bacteria. The nutrient requirements can be

determined from the daily biomass production rate. This is done later in the chapter

using equation 6.36. It should be noted that there could be nutrient limitations and

nutrients may need to be supplemented to ensure survival of the microorganisms.

139

Settling Characteristics The settling characteristics are important when designing the secondary clarifier. This

portion is important for the liquid-solids separation. It must provide adequate

clarification for the effluent and solids thickening for the activated-sludge solids. It is

common to base the design of the secondary clarifier on the surface overflow rate and the

solids loading rate. The overflow rates are based on the wastewater flow rates because it

is equivalent to the upward flow velocity. The solids loading rate represents a

characteristic value of the suspension that is under consideration. If the solids loading

rate becomes too high the effluent quality will start to deteriorate.

Disposal of Sludge In wastewater treatment sludge is produced during many of the processes that are found

in a common treatment plant. Some of the sources of sludge are screening and grit

removal, primary and secondary settling tanks and digesters. Therefore it is important to

know how to handle and dispose of the sludge. The options for treatment and disposal of

sludge will be discussed in further detail later in this chapter.

6.7.3 Complete Mix Activated-Sludge Design Process In the complete mix activated-sludge process the effluent from the primary sedimentation

tank and recycled return are introduced at several points within the reactor. Since the

reactor is completely mixed, the organic load, oxygen demand, and substrate

concentration are uniform throughout the tank. The computational approach that was

used for this design is listed below:

1. Obtain influent wastewater characterization data

140

2. Determine the effluent requirements

3. Select an appropriate nitrification “safety factor”

4. Select a minimum dissolved oxygen concentration for the aeration basin

5. Determine the nitrification maximum specific growth rate

6. Determine the net specific growth rate and the SRT at this growth rate

7. Obtain the design SRT

8. Determine the biomass production

9. Perform a nitrogen balance to determine NOx

10. Calculate the volatile suspended solids (VSS) mass and total suspended solids

(TSS) mass for aeration basin

11. Select a design mixed liquor suspended solids (MLSS) concentration and

determine the aeration basin volume and hydraulic detention time

12. Determine the overall sludge production rate

13. Calculate the oxygen demand

14. Determine if alkalinity addition is needed

15. Design the secondary clarifier

16. Design pipe network

Obtain Influent wastewater characterization data The influent wastewater characterization data that was used in the design of a complete

mix activated-sludge system can be found in Table 6.1. Table 6.1 summarizes the flow

data to be 14.5 m3 /day with a BOD concentration of 252 mg/L, TSS concentration of 283

mg/L and a total nitrogen content of 52 mg/L. Further assumptions were made to help

with the design process. These assumptions can be found in Table 6.9 and are based off

of average operating values of complete mix activated-sludge processes [28].

141

Determine the Effluent Requirements The wastewater will be treated to secondary standards discussed in section 6.2.2. These

standards require that both the effluent BOD and TSS be reduced to 30 mg/L.

Nitrification Safety Factor The nitrogen safety factor is used to account for peak and average loading rate of TKN

for the solids retention time (SRT) and to provide extra nitrifying bacteria to account for

peak TKN loadings. By multiplying the design SRT by the safety factor, the amount of

nitrifying bacteria is increased to meet the NH4-N concentration during peak loads. This

is done to ensure that the effluent concentration requirement for NH4-N is met. The

ranges for the safety factor are 1.3-1.5. This design used a conservative assumption of

1.5.

DO Concentration in Aeration Basin The amount of oxygen that is needed in the aeration basin is equal to the amount that the

bacteria need to oxidize the organic material. The minimum dissolved oxygen (DO)

Table 6.9 - Assumed Values for Complete Mix Activated-Sludge Design

Parameter Value Parameter ValueY 0.4 Kn 0.74Yn 0.12 kdn 0.08µn,m 0.75 µm 6Ks 20 Ko 0.5kd 0.12 F 0.9α 0.6 β 0.95θµn 1.07 θµm 1.07θKn 1.053 θkd 1.04θkdn 1.04 θKs 1θfd 0.15

UnitsUnitsg VSS/g bCODg VSS/g NOxg VSS/g VSS*dg bCOD/m3g VSS/g VSS*d

g NH4-N/m3g VSS/g VSS*dg VSS/g VSS*dg/m3

142

concentration for the aeration basin is 2 mg/L [28]. DO concentration higher than 2 mg/L

may improve nitrification rates, but concentrations greater than 4 mg/L do not increase

operations significantly.

Determine the Nitrification Maximum Specific Growth Rate The nitrification maximum specific growth rate is based on the temperature in the

aeration basin and the DO concentration. Since the average temperature was 26oC, the

value must be corrected for the change in temperature from the standard of 20oC. This

was done using the following equation [28]:

20,

−= TmTm θµµ (Eqn 6.29)

Where µm,T = maximum specific bacterial growth rate at operating temperature, g new cells/g cells d

θ = Temperature-activity coefficient, 1.07 T = Operating temperature, 26oC µm= maximum specific bacterial growth rate, 6 g new cells/g cells d Using these values in equation 6.29 the resulting maximum specific growth rate at 26oC

is 9 g VSS/g VSS*d.

Net Specific Growth Rate and SRT The growth rate of nitrifying bacteria is determined by the nitrogen concentration and the

amount of dissolved oxygen in the activated-sludge. This is done by solving the

following equation out of the Metcalf and Eddy fourth edition [28]:

dnon

nmn k

DOKDO

NKN

−

+

+

=µ

µ (Eqn 6.30)

Where µn = specific growth rate of nitrifying bacteria, g new cells/g cells*d

µnm = maximum specific growth rate of nitrifying bacteria, 1.13 g new cells/g cells*d

143

N = nitrogen effluent concentration, 0.5 g/m3 Kn = half velocity constant, substrate concentration at one-half the maximum specific substrate utilization rate, 1.01 g/m3 kdn= endogenous decay coefficient for nitrifying organisms, 0.10 g VSS/g VSS*d DO = dissolved oxygen concentration, 2 g/m3 Ko = half-saturation coefficient for DO, 0.5 g/m3

The resulting specific growth rate of nitrifying bacteria is 0.20 g new cells/g cell*day. The solids retention time is the average time the activated-sludge solids are in the system.

For a complete mix activated-sludge system it is the inverse of the specific growth rate

[28].

n

SRTµ1

= (Eqn 6.31)

Where SRT = solids retention time, days µn = specific growth rate of nitrifying bacteria, 0.20 g new cells/g cells*d

Therefore, the solids retention time is equal to 5.07 days.

Design SRT The design SRT applies the factor of safety to the theoretical SRT. This allows for any

fluctuations that may occur between the peak and average flow rates. This design SRT is

calculated with the following equation [28]:

Design SRT = (Safety Factor)(Theoretical SRT) (Eqn 6.32) Using the assumed safety factor of 1.5 and the theoretical solids retention time solved for

using equation 6.31, the design solid retention time is 7.61 days.

Sludge Production It is necessary to estimate the amount of sludge that will be produced to design handling

and disposal/reuse facilities. The method that was used to determine the sludge

144

production is based on the wastewater characterization. First it is necessary to determine

the effluent soluble substrate concentration. The effluent soluble substrate concentration

for the complete mix activated-sludge process is a function of the SRT and the kinetic

coefficients for growth and decay. This can be solved using equation 6.33. Using the

effluent soluble substrate concentration and equation 6.34 to account for the heterotrophic

biomass growth, cell debris from endogenous decay, nitrifying bacteria biomass and non-

biodegradable volatile suspended solids, the amount of sludge produced can be

determined. It is also necessary to estimate the concentration of NH4-N in the influent

flow that is nitrified. It is necessary to estimate this value because a proper nitrogen

balance depends on the amount of biomass produced. This assumption can be done by

assuming that it is equal to 80% of the TKN in the influent flow. The error that is

associated with this assumption is negligible [28].

( )[ ]

( ) 11

−−+

=dm

ds

kSRTSRTkK

Sµ

(Eqn 6.33)

where S= concentration of growth limiting substrate in solution, mg/L kd = endogenous decay coefficient, 0.15 d-1

Ks = half-velocity constant, 20 mg/L Y = biomass yield, 0.4

Other terms previously defined The resulting concentration of growth limiting substrate in the solution is equal to 0.65 g

bCOD/m3.

( )( )

( )( ) ( )( )

( )( )SRTk

NOQYSRTk

SRTSSQYkfSRTk

SSQYP

nd

xn

d

odd

d

obiox +

++

−+

+−

=111, (Eqn 6.34)

where Px,bio = biomass as VSS wasted, g/d Q= Inflluent flow, 14.5 m3/d

145

So = influent concentration, 403.2 mg/L kdn =endogenous decay coefficient for nitrifying organisms, 0.10 d-1 fd = fraction of cell mass remaining as cell debris, 0.9 g/g Yn= net biomass yield, 0.12 g VSS/g bsCODr NOx = nitrogen oxidized, 41.6 mg/L Other terms previously defined Using the values from Tables 6.1 and 6.8 and the result from equation 6.33, the biomass

produced is equal to 1.35 kg VSS/day.

Determine NOx

NOx is the amount of TKN that is oxidized to nitrate. This can be determined by

performing a mass balance on the system that accounts for the influent TKN, nitrogen

removed for biomass synthesis and un-oxidized effluent nitrogen. This balance can be

done using the following equation [28]:

Q

PNTKNNO biox

ex,12.0

−−= (Eqn 6.35)

where TKN = total TKN concentration, 52 mg/L Ne = effluent NH4-N concentration, 0.5 mg/L Other terms previously defined

The nitrogen balance performed using equation 6.35 results in 40.1 g/m3 of nitrogen to be

oxidized during the process.

Mass of TSS and VSS The volatile suspended solids determined using the same equation as the biomass, but it

also includes the non-biodegradable VSS in the influent.

( )( )

( )( ) ( )( )

( )( ) ( )nbVSSQ

SRTkNOQY

SRTkSSQYkf

SRTkSSQY

Pdn

xn

d

odd

d

oVSSx +

++

+−

++

−=

111, (Eqn 6.36)

where Px,VSS = net waste activated sludge produced each day, kg VSS/d nbVSS = non-biodegradable volatile suspended solids, 142.4 mg/L

146

Other terms previously defined This results in a net waste of 3.49 kg/day. To determine the mass it is necessary to

multiply by the SRT, resulting in a mass of 18.41 kg [28].

The total suspended solids concentration includes the VSS plus the inorganic solids that

may be found in the influent. The inorganic solids add to the solids production of the

system, therefore it is necessary to add a term to equation 6.36. The biomass terms in

equation 6.36 contain inorganic solids as well as VSS. The VSS fraction of the total

biomass is assumed to be approximately 85%, therefore it is necessary to divide each

biomass term by 0.85. (See Equation 6.37)

( )( )

( )( ) ( )( )

( )( ) ( ) ( )oo

dn

xn

d

odd

d

o

TSSx VSSTSSQnbVSSQSRTk

NOQYSRTk

SSQYkfSRTk

SSQY

P −+++

++

−

++

−

=85.0

185.0

185.0

1,

(Eqn 6.37)

where Px,TSS = total mass of dry solids wasted, kg TSS/d TSSo = influent wastewater TSS concentration, 283 mg/L VSSo = influent wastewater VSS concentration, 220 mg/L Other terms previously defined.

The total mass of dry solids wasted is then equal to 4.67 kg/day. To determine the mass it

is necessary to multiply by the SRT, which results in a total mass of 35.5 kg [28].

Volume and Hydraulic Residence Time It is necessary to know the volume of the aeration basin and the hydraulic detention time

to determine the dimensions of the aeration tank. The volume is determined by dividing

the mass of the total suspended solids, found using equation 6.37, by an assumed

concentration of mixed liquor suspended solids. The MLSS range for complete mix

147

activated-sludge is between 800-6500 mg/L. This designed assumed a median value of

3000 mg/L [28].

MLSS

SRTPV TSSX *,= (Eqn 6.38)

where V = aeration tank volume, m3

MLSS = Mixed Liquour Suspended Solids, 3000 mg/L Other terms previously defined

The resulting volume of the aeration tank is 12 m3. It is often necessary to divide the

volume into two or more tanks. This is useful if one tank needs servicing, it can be taken

off- line without interrupting service. Since, the volume of the tank is relatively small it

was decided to have one aeration tank.

The hydraulic residence time that is necessary in each tank is determined by dividing the

volume of each tank by the average flow rate [28].

QV

=τ (Eqn 6.39)

where τ = detention time in aeration tank, hours Other terms defined in pervious paragraphs.

After solving this equation the resulting hydraulic residence time is equal to 18.94 hours.

Observed Yield To complete the design it is necessary to calculate the observed yield for both the TSS

and VSS. These can be calculated using the following equations [28]:

( ))SSQdbCODremove o −= (Eqn 6.40)

( )

dbCODremove

PY TSSx

TSSobs,

,

6.1= (Eqn 6.41)

148

( )

=

TSSVSS

dbCODremove

PY TSSx

VSSobs,

,

6.1 (Eqn 6.42)

where bCOD removed = biodegradable chemical oxygen demand removed, 6.0

kg/d Yobs,TSS = observed yield, 1.24 g TSS/g substrate removal Yobs,VSS = observed yield, 0.64 g VSS/g substrate removal Other terms previously defined

Oxygen Demand The oxygen that is needed in the aeration system is dependent on the amount needed for

the removal of carbonaceous material and the amount needed for the ammonia and nitrite

oxidation to nitrate. These are accounted for and calculated using the following equa tion

[28]:

( ) ( )xbioxoo NOPSSQR 33.442.1 , +−−= (Eqn 6.43) where Ro = total oxygen required, g/d Other terms previously defined

Using equation 6.43 and the terms that have been solved for using pervious equations, the

resulting oxygen demand is 0.28 kg/hour.

Aeration System Design The design of aeration tanks depends on many factors, such as land availability, tank

geometry, system flexibility and building and operational costs. One of the most

important features is system flexibility. Often times it will be necessary to perform

routine maintenance tasks on the aeration tank or system. During these times it would be

helpful to be able to divert the flow to another tank rather than shut the entire plant down.

These other tanks should be able to handle 60-75% of the average flow [19]. However,

149

due to the small amount of flow that is available for this design, there will not be any

redundancy of aeration tanks.

There are many different tank geometries that can be used. Circular and rectangular

tanks are the most popular. Square tanks are not commonly used because there is a

tendency for sludge to build up in the corners. The tank geometry has a strong influence

on the configuration of the aeration system. For rectangular tanks there are four types of

configurations for the aeration system, the ridge-and-furrow, spiral flow, inka tanks and

the cross-roll system. These systems vary on how and where the aerators are placed in

the tank. Again, the best aeration system varies with each situation. This design used the

cross-roll aeration configuration [18].

In designing an aeration system one of the first steps in this process is to account for any

pressure changes due to change in elevation. This done was using the following

equations [28]:

( )

−−

=RT

zzgMe

PP ob

o

b (Eqn 6.44)

where Pb/Po = relative pressure at elevation of system g = acceleration due to gravity, 9.81 m/s2 M = mole of air, 28.97 kg/kg mole zb= elevation of system, 250 m zo= elevation at sea level, 0 m T = average temperature, 299 K R = universal gas constant, 8314 kg*m2/s2*kg mole*K This results in a relative pressure of 0.97 at the elevation of the system.

150

26CPP

Co

bstH = (Eqn 6.45)

where CstH = oxygen concentration at temperature and elevation of system, mg/L C26 = oxygen concentration at 26oC, 7.93 mg/L

Therefore, the oxygen concentration at 26oC and 250 meters above sea level is equal to

7.71 mg/L.

γ

atmo

b

Hatm

PPP

P =, (Eqn 6.46)

where Patm,H = atmospheric pressure at elevation of the system, kPa Patm = atmospheric pressure, 101.3 kPa γ = specific weight of water, 9.7 kN/m3

The atmospheric pressure at 250 meters above sea level is equal to 10.08 meters. Determine the oxygen concentration in the tank assuming that a percentage of the oxygen

concentration leaves the tank. This percentage is usually in the range of 18-20%. This

design assumed a median value of 19% of the oxygen concentration is leaving the tank

[28].

+

+

=

2119

21

,

,,

Hatm

effdepthwHatmsthtHs P

PPCC (Eqn 6.47)

where CstH= average dissolved oxygen saturation concentration in clean water in

aeration tank at temperature 26oC and altitude 250 m, mg/L

Csth = oxygen saturation concentration in clean water at temperature 26oC and altitude 250 m, 7.71 mg/L

Pw,eff,depth = pressure at depth of release of air, 99 kPa Other terms previously defined.

This results in an average dissolved oxygen saturation concentration in clean water in the

aeration tank at 250 meters above sea level and a temperature of 26oC of 7.89 mg/L.

151

The determination of the standard oxygen transfer rate is done using equation 6.48.

( ) ( )T

tHs

s

CCF

CAOTRSOTR −

−

= 2020, 024.1βα

(Eqn 6.48)

where SOTR = standard oxygen transfer rate in tap water at 20oC and zero

dissolved oxygen, kg O2/h

AOTR = actual oxygen transfer rate under field conditions, 0.28 kg O2/h

β = salinity-surface tension correction factor, 0.95

C = operating oxygen concentration, 2 mg/L

T = operating temperature, 26oC

α = oxygen transfer correction factor for waste, 0.5

F = fouling factor, 0.9.

Cs,20 = dissolved oxygen saturation concentration in clean water at 20oC and 1 atm, 9.07 mg/L

Other terms previously defined

Therefore, the standard oxygen transfer rate is equal to 0.75 kg/hour. Next determine the

flow rate of the air.

Air Flowrate = SOTR (Eqn 6.49) [(E)(60 min/h)(kg O2/m3 air)] Where E = oxygen transfer efficiency of fine bubble diffusers, 35% This results in an airflow rate of 0.13 m3 /min. The last step in designing an aeration tank is to size the blower/pump that will be needed

to bubble air through the diffusers. To size an appropriate blower it is necessary to use

both the air flow rate and the power requirement. The power requirement can be

determined using the equation seen below [28]:

152

−

= 1

7.29

283.0

1

2

pp

newRT

Pw (Eqn 6.50)

where Pw = Power Requirement, kW w= weight of the flow of air. 0.15 kg/s R= Universal Gas Constant 8.314 kJ/kmol*K T = Operating Temperature, 299 K 29.7 constant n = 0.283 e = efficiency of blower, 0.70 p2 = pressure at outlet, 1.15 atm p1 = pressure at inlet, 0.98 atm Therefore, the power needed to aerate the tank is 3000 watts.

Alkalinity Addition Alkalinity is often needed to aid in the nitrification process. Often it is necessary to add

alkalinity to maintain the pH in the range from 6.8 to 7.4. To determine if it is necessary

to add alkalinity to the system a mass balance must be performed on the alkalinity of the

system [28].

Alkalinity to maintain pH~7 = Influent Alk – Alk used + Alk to be added (Eqn 6.51) Where alkalinity at pH 7 = 202.6 mg/L Influent alk = 140 mg/L Alk used = 80 mg/L Therefore, 2.14 kg/day of alkalinity as CaCO3 needs to be added to the system to ensure

that pH remains at approximately 7.

Secondary Clarifier The last step in the process is the design of the secondary clarifier. This is where the last

sedimentation takes place before the effluent is discharged. Part of the sludge from this

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step will be recycled back into the aeration basin. It is important to determine what

percentage will be recycled. This is done using the concentration of sludge [28].

XXrX

R−

= (Eqn 6.52)

where R = recycle ratio X = concentration of MLVSS, 3000 mg/L Xr = concentration of MLVSS to be recycled, 1000 mg/L

This result in approximately 75% of the sludge will be recycled back to the aeration

basin.

To determine the area of the secondary clarifier it is necessary to assume a hydraulic

application rate. The area is determined by dividing the average flow of the system by

the hydraulic application rate. The range for hydraulic application rates is 16-28

m3/m2*day. This design assumed an application rate of 20m3/m2*day and the resulting

area is 0.79 m2. It is necessary to divide this total area into two or more tanks to facilitate

in maintenance on the tanks. Due to the small size of the tank, it was determined that one

clarifier was sufficient.

Pipe Design An important feature in any water or wastewater treatment plant is the pipe network that

connects all of the unit processes together. There are four important aspects of this

network that need to be taken into consideration when designing a network for the

system. First, is the type of material that the pipe will be made of. The United State

Environmental Protection Agency has selected a few materials that are appropriate for the

transfer of wastewater; they are concrete, ductile iron, thermoplastics, thermosets, and

154

vitrified clay. The applicability of pipes made of different materials depends on the site

and the system that the pipe will be used for [37].

Second, it is important to know the amount of headloss that will occur within the pipe

network. If this headloss is too great it may be necessary to pump the wastewater

between unit processes. The headlosses that should be taken into consideration are due to

the friction of the water and the pipe surface and headloss due to bends, expansions,

contractions, and valves. These headloss values are called friction headloss and minor

headloss. Headloss due to pipe friction can be calculated using the Darcy-Weisbach

equation, defined earlier in equation 6.16. The minor headlosses are calculated using the

equation 6.17 defined earlier in the chapter.

Third, when determining the size of the pipe that will be used it is necessary to make sure

that the size that has been chosen will be best for the system. The slope of the energy

grade line can be used in determining the suitability of the selected pipe diameter. The

slope of the energy grade line can be calculated by dividing the headloss in the pipe by

the length of the pipe. In general, this value should fall between 0.5 and 1.5% [34]. If

the value is too low, then the pipe is oversized and material cost will be excessive. If the

value is too high, then higher pumping costs will results in order to overcome the

excessive friction losses.

Finally, the fourth component taken into consideration when designing the pipe network

is the head works for each of the unit processes. Depending on the process that is being

155

analyzed it may be necessary to try to avoid introducing a vertical component to the flow

of the wastewater. In general, there are three types of inlet designs that can be used, first

is a full-width inlet channel with inlet weirs. Second, is inlet channels with submerged

ports or orifices and the third option is inlet channels with wide gates and slotted baffles.

Good distribution across the tank can usually be obtained if the velocities can be

maintained between 3-9 m/min [28].

Checks and Balances The last step in the design of a complete mix activa ted sludge system is to check some of

the parameters. It is important to check the F/M ratio, solids loading rate and the

volumetric loading rate. The F/M ratio should be between 0.2-0.6 kg BOD/kg

MLVSS*day. The volumetric loading should in the range of 0.3-1.6 kg BOD/m3*day

and the solids loading rate should be in the range of 4-6 kg/m2*h. This is done using the

following equations [28]:

F/M ratio

XVQS

MF o=/ (Eqn 6.53)

Volumetric Loading

VQS

L oorg = (Eqn 6.54)

Solids Loading

( )( )A

MLSSQrQLoading

+= (Eqn 6.55)

where F/M = food to biomass ratio Qr = Flow recycled back to aeration tank, m3/d

156

Using the parameters solved for throughout this section of the chapter the F/M ratio is

equal to 0.21 g/g*day, the volumetric loading is equal to 0.32 kg/m3*day and the solids

loading is equal to 4.18 kg/h*m2.

6.7.4 Discussion The results of the complete mix activated-sludge system can be found in Table 6.10 and

6.11. Many assumptions were made during the design process. This section will discuss

the assumptions and decision that were made to reach the final design parameters. This

design was based off of removing both carbonaceous BOD and nitrification. Another

design was done to remove carbonaceous BOD only, the results of this design can be

found in Appendix A.

Table 6.10 - Design parameters for activated sludge System.

P a r a m e t e r Va lue U n i t s

Vo lume 1 2 m 3

A r e a 8 m 2

L e n g t h 5.33 mW id t h 1.5 mD e p t h 1.5 mD e t e n t i o n T i m e 7.61 d a y sS l u d g e P r o d u c t i o n 35.52 k g T S S

18.41 k g V S SF / M L o a d i n g 0.21 g / g * dV o l u m e t r i c L o a d i n g 0.32 k g / m 3 * dO 2 D e m a n d 0.28 k g / hS O T R 0.75 k g / h

A i r F l o w r a t e 0.13 m 3 /min

M L S S 3000 g / m 3

M L V S S 2015 g / m 3

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One of the first assumptions that were made was the nitrogen safety factor. As stated

earlier, this safety factor helps to account for the operational variations in controlling the

solids retention time and to add excess nitrifying bacteria to handle to peak TKN

loadings. This will help to ensure that the effluent NH4-N concentration in not exceeded.

This design assumed a conservative value of 1.5 [28].

The next decision that was made was to have only one aeration tank. The total volume

that was calculated for the aeration tank was 12 m3. Normally, this volume would be

split into at least three or four different aeration tanks. This ensures that at least 60-75%

of the flow will still be treated if any one tank needs to be serviced [19]. This volume

could be split, but since the flow within the system is low, it was decided to have only

one tank. If the tank does need to be serviced the flow could possibly be diverted and

stored until the necessary repairs have been completed.

Table 6.11 - Design parameters for Secondary Settling associated with AS System

Parameter Value units

Volume 1.18 m3

Area 0.75 m2

Diameter 1 mDepth 1.5 mDetention Time 1.88 hRecycle Ratio 0.75Solids Loading Rate 4.18 kg/h*m2Effluent BOD 8.95 g/m3Additional Alkalinity 0.86 kg/d CaCO3

158

The dimensions of the aeration tank were decided to be 1.5 m deep, 1.5 m wide and 5.33

m long. Approximately 0.5 m of the tank will be underground and there will be a

freeboard of 0.3 m to allow for rainfall (Figure 6.8). These dimensions were chosen to

allow for easy maintenance. Since approximately 1.3 meters of the tank will be above

ground this will allow a person of average height to visually inspect the tank. The width

of the aeration tank was chosen to maximize the amount of contact with oxygen that is

being dissolved and the amount of mixing.

As stated earlier, there are many different types of flow that can occur in an aeration tank.

For this design the spiral flow and the cross-roll flow were considered. The difference

between these two types of flow is the placement of the aerators. In the spiral flow the

aerators are placed along one edge of the tank, whereas in the cross-roll flow the aerators

are spaced along the entire width of the tank at intervals of 2 times the depth [19]. For

this design the spiral flow the aerators would have to be placed at a minimum spacing of

0.2 meters. This resulted in 13 aerators for the entire length of the tank. The cross-roll

flow only needed 4 aerators. The decision was made to use the cross-roll flow design and

extra two aerators were placed in the design to help ensure proper aeration and mixing.

The next decision was whether the aerators would be stationary or removable. There are

two major disadvantages from using stationary diffusers. First, the diffusers are hard to

access when maintenance is required. Second, it is difficult to rearrange the air

distribution by rearranging the diffusers. Both maintenance and rearrangement of the

diffusers would require that the aeration tank be emptied [19]. Since it was decided

159

earlier that there would be only one aeration tank, it would be necessary to have a

removable aeration system. A swing arm was designed to allow each set of aerators to be

removed without the need to empty the aeration tank (Figure 6.9). The swing arm was

designed out of aluminum alloy 6061, 51 mm diameter pipe. The thickness of the pipe

will be 6.35 mm. The aluminum alloy 6061 was chosen because it has good corrosion

resistance and it is relatively light [31]. As can be seen in Figure 6.10, the air supply

hose will run the length of the swing arm into a “T” at the end of swing arm. There are

two 610 mm long aerators one either end of the “T”, each with a diameter of 61 mm.

This will leave approximately 140 mm between the aerator and the wall of the aeration

tank. The vertical length of the swing arm needs to be 1.8 meters to ensure that the

aerators are sitting 19 mm from the bottom of the tank. To ensure that a maintenance

worker would be able to lift the aeration system from the tank, a maximum force that

would need to be exerted by the worker would be 133 N. To help maintain that this

would be the maximum force it would be necessary to have a lever arm of 1.9 meters

long. Once the aeration system has been lifted from the water, it can then be pivoted out

for maintenance. This way the worker is not trying to work on the aeration system while

it is hanging out over the water.

The inlet system for an aeration tank was the next design decision to be considered. It

was decided that an inlet port would be used because it provided a good distribution

across the entire width of the tank. As stated earlier it is necessary to maintain the flow

velocity between 3 to 9 m/min [28]. The next decision was to decided what size pipe

should be used to maintain this velocity. It was necessary to use a minimum pipe

160

diameter of 66 mm to meet the minimum velocity requirement of 3 m/min (Figure 6.11).

The next factor in deciding the pipe diameter was the slope of the energy grade line.

Again, as stated earlier, it is necessary to have the slope of the energy grade line fall

between 0.5 and 1.5% [34]. It was determined that in order to meet the minimum slope

of 0.5% it would be necessary to use a pipe with a diameter of 33 mm (Figure 6.12). The

final factor that was used in determining the pipe diameter was the Uniform Plumbing

Code. The UPC states that a minimum pipe diameter of 51 mm must be used (Figures

6.13 and 6.14). Therefore, a pipe with a diameter of 64 mm was chosen. The reason

that the slope of the energy grade line was overlooked was that it was more reasonable to

ensure a minimum velocity rather than the appropriate cost.

Figure 6.11 - Velocity Requirements for Inlet Port.

161

Figure 6.12 - Pipe sizing using slope of energy grade line.

Figure 6.13 - Velocity Requirement with UPC minimum pipe diameter.

162

Next, it was necessary to determine the material that the pipe would need to be made out

of. As stated earlier there are many different choices in deciding which type of pipe

material should be used. Concrete pipe was the final decision because it is inexpensive,

has good resistance to corrosion and can with stand the forces of being buried.

Next, the design of the clarifier was to be considered. Based on an overflow rate of 20

m3/m2*day the calculated area of the clarifier is 0.75 m2. A depth was assumed at 1.5 m

to be consistent with the aeration tank. This results in a total volume of 1.18 m3.

Clarifiers can be designed in either rectangular shape or circular. This design used a

circular configuration to help with the ease of sludge disposal. The inlet pipe of the

clarifier stands approximately 0.4 m. It was not necessary to have flow distribution since

the flow within the system is low.

Figure 6.14 - Pipe sizing with UPC minimum pipe diameter

163

Finally, it is necessary to check that the food to mass ratio, volumetric loading and solids

loading rate are all within the recommended operating ranges. The first check is the food

to mass ratio, the normal operating range is 0.2-0.6 kg BOD/kg MLVSS*d and the value

calculated in the design was 0.21 kg BOD/kg MLVSS*d [28]. The next check of the

volumetric loading rate is also within the given range of 0.3-1.6 kg BOD/m3*d. The

value calculated in the design process was 0.32 kg BOD/m3*d [28]. The recommend

operating range is 4-6 kg/m2*d [28]. The result from the design was a solids loading rate

of 4.18 kg/m2*h. All of the required checks have been met with this design, but are at the

lower end of the recommended ranges.

The materials that will be needed for the construction of a complete mix activated sludge

system are listed Table 6.12:

Table 6.12 - Material requirements for Activated Sludge System.

Material Quantity Units62 mm diameter and 610 mm long Urethane membrane 6 unitsStainless steel clamps 62 mm in diameter 12 clamps62 mm diameter and 610 mm long PVC pipe 6 piecesCast mount diffusers 3 pieces62 mm, 5 meter long plastic tubing 3 piecesColeman powermate air compressor 1 pump51 mm diameter, 2 meter long aluminum alloy 6061-76 tubing 9 piecesHinges 3 piecesPivots 3 pieces64 mm diameter concrete piping 12 metersCentrifugal Nonclog Sludge pump 1 pump

Reinforced concrete 5.4 m3

164

6.1.1 Conclusion The activated-sludge process has proven effective over the years in many situations.

The checks that are used to make sure that the system is within the operating ranges have

proven that the system is operating within the required parameters. The resulting design

consists of one aeration tank with a volume of 2.79 m3 and a secondary clarifier with an

area of 0.38 m2.

While the design checks have met the requirements a complete mix activated-sludge

system maybe unpractical for this situation. The amount of flow that needs to be treated

is relatively small. Due to the small volumes required for both the aeration tank and the

secondary clarifier it is unnecessary to have multiple aeration tanks and clarifiers.

Normally, the two or more of these processes would aid in any maintenance problems

that may arise. Again, the flow that was designed for is small and the flow could

potentially be stored if the process would needed maintenance. The activated-sludge

system may allow for future expansion, but at the moment it is an excessive solution.

165

166

167

168

6.8 Sequencing Batch Reactor Activated Sludge System 6.8.1 Background A sequencing batch reactor (SBR) is an activated sludge wastewater treatment system

that operates on a fill and draw batch process. Unlike other activated sludge systems

where there are separate tanks for each unit process, SBRs can achieve equalization,

mixing, aeration, and clarification in one reactor. This provides for a relatively compact

system that is suited for low or intermittent flow conditions. For continuous flow

applications, two or more reactors can be used so that one reactor can be filling while the

other is reacting.

All SBRs share the same five process steps that operate in the following sequence. The

first step is the filling of the reactor. The reactor is already partially full with activated

sludge acclimatized to the wastewater and thus can speed up the start up time of the

biological reaction. Once the reactor is full, the reaction phase begins with aeration of

the wastewater using fine or course bubble aerators. During the reaction phase, aerobic

bacteria biologically degrade the organics in the wastewater. Nitrification and phosphorus

removal can also happen in this phase. After the reaction phase, the tank enters the

settling phase where the sludge settles to the bottom of the reactor. This is followed by

the draw phase where a decanter is used to remove the treated effluent. Wasting of

excess biomass may also occur during this step to keep the ratio of substrate to biomass

constant from cycle to cycle. Unlike other conventional activated sludge systems, there

is no recycling of activated sludge since the tank already contains the sludge needed for

the reaction. Primary sedimentation is also usually not needed with SBRs unless the

BOD or TSS are greater than 400 to 500 mg/L. Due to its all- in-one natural and relative

169

automated operation, an SBR seemed like an appropriate choice for the treatment of the

wastewater at the Bali Spirit Hotel.

6.8.2 Design Considerations When designing an SBR, it is very important to consider certain design parameters to

ensure efficient operation of the system. The first step is to fully evaluate the influent

characteristics of the wastewater and how these characteristics will affect the design. It is

also necessary to determine the effluent requirements as required by regulatory agencies

in the area. The important characteristics include maximum daily flows, BOD, TSS, pH,

alkalinity, and temperature of the wastewater, TKN, NH3-N, and total phosphorus. Other

parameters that are important to consider when designing a SBR include Food to Mass

ratio, Treatment cycle duration, hydraulic retention time, number of basins, volume of

basins, decant volume and detention times.

6.8.3 Sequencing Batch Reactor Design Process An iterative computational design approach is used in which many of the important

design parameters are first assumed and then analyzed in a spreadsheet to determine the

optimum design. The steps to this process are outlined and explained in detail below:

1. Obtain influent wastewater characterization data and define effluent requirements.

2. Select number of SBR tanks.

3. Select the react/aeration, settling and decant times. Determine the fill time and

the total time per cycle. Determine the number of cycles needed per day.

4. From the total cycles per day, determine the fill volume per cycle.

170

5. Select the MLSS concentration and determine the fill volume fraction relative to

the total tank volume. Determine the decant depth. Using the computed depths,

determine the SBR tank volume.

6. Determine the SRT for the SBR process design developed.

7. Determine the amount of TKN in the influent that is nitrified.

8. Calculate the nitrifier biomass concentration and determine if the aeration time

selected is sufficient for the nitrification efficiency needed.

9. Adjust the design as needed – additional iterations maybe needed.

10. Determine the decant pumping rate.

11. Determine the oxygen required and average transfer rate for aeration system

design.

12. Determine the amount of sludge production/removal rate.

13. Calculate the F/M ratio and BOD volumetric loading.

14. Prepare design summary.

Wastewater Characterization and Effluent Requirement The wastewater and effluent requirements are detailed in background section of this

chapter.

Select the Number of SBR Tanks Due to the relatively small amount of flow, only two tanks were deemed necessary for

this design. To allow for continuous flow, one tank will always be in the fill phase while

the other tank is in the react/settle/decant phases.

Select Phase Timing Phase timing is very important in the design of an SBR. In order to allow each tank to

treat small amounts of waste several times during the day the phase timing was selected

171

as shown in Table 6.13. Note that the fill phase is equal to the react, settle and decant

phases combined.

Determine Fill Volume To compute the fill volume, the total cycle time and the number of cycles per day were

calculated. The total cycle time is the sum of the phase timings or 8 hours equates to 3

cycles per tank per day for a total of 6 cycles. Therefore the fill volume of 2.4 m3/fill is

simply the total flow rate (7.125 m3 /day/tank) divided by the total number of cycles (3).

Determine Tank Depth and Volume The tank depth of 3 m was an assumed value so to figure out the actual dimensions of the

tank the total volume must be found. To do this a mass balance based on the solids in the

reactor must be developed.

Mass of solids at full volume = Mass of settled solids

sst XVXV = (Eqn 6.56)

Where: Vt = total volume m3 X = MLSS concentration at full volume, g/m3 Vs = settled volume after decant, m3 Xs

= MLSS concentration in settled volume, g/m3 Estimate Xs

on an assumed SVI value of 150 mL/g Determine the settled fraction and provide a 20 percent liquid above sludge blanket so

that the solids are not removed by the decanting mechanism.

Table 6.13 - Phase Timing for the SBR.

Fill 4 hReact 2 hSettle 1 hDecant 1 hTotal Cycle Time 8 hNumber of Cycles per day 3 cycles/day

Phase Timing

172

By then determining the fill fraction, it can be compared to the selected value of 0.33 to

see if is acceptable. The fill fraction turns out to be 0.37 so the selected value is fine.

That value is then used to determine the total volume of each tank.

33.0f

t

VV = (Eqn 6.57)

From here the dimensions of the tank can be found as summarized in the Table 6.14.

Determine the SRT The solids retention time (SRT) is a very important parameter because in activated sludge

systems, it affects not only the process performance, but also the tank volume, sludge

production and oxygen requirements. In this design the SRT was determined by trying to

obtain a relationship between equation 6.36 and the following equation, and solving for

(PX,TSS)SRT.

( ) ( )MLSSTSSx XVSRTP =, (Eqn 6.58) A spreadsheet was used to equate the two equations and to solve for the SRT. In this

design the SRT = 14.36 days which falls in the range of typical values for a SBR

designed to remove both BOD and achieve nitrification.

Table 6.14 - Summary of SBR tank dimensions

Tank Dimensions

Length 1.55 m

Width 1.55 m

Depth 3 m

Volume per tank 7.2 m3

Number of tanks 2

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Determine the amount of TKN removed Due to the long design SRT, the SBR will achieve a certain amount of nitrification of the

TKN present in the influent. It must be determined if the reaction time is enough to

achieve an effluent concentration of 0.5 g/m3 of NH4 -N. To do this, the amount of NH4

–N oxidized is calculated by performing a nitrogen balance using equations 6.35 and

6.33.

Once NOX is determined, oxidizable NH4-N is added per cycle is known, but since there

is sludge remaining from the previous cycle, it is necessary to determine the total amount

of oxidizable N still available in the tank before the fill. After that is determined, batch

kinetic equations should be used to verify if the react period aeration time selected for the

design is sufficient to provide the desired amount of nitrogen degradation [28].

( ) tDOK

DOY

XNNNN

Kon

mnnto

t

on

+

=−+

µln (Eqn 6.59)

where Kn = half velocity constant, substrate concentration at one-half the maximum specific substrate utilization rate, mg/L No = NH4-N concentration at t=0 mg/L Nt = NH4-N concentration at time t, mg/L DO = dissolved oxygen, mg/L Ko = half-saturation coefficient for DO, mg/L

Yn= net biomass yield, g VSS/g bsCODr Xn = nitrifying bacteria concentration, mg/L t = time, d

unm = maximum specific growth rate of nitrifying bacteria, g new cells/g cells*d

For this design the desired about of nitrification occurs in just 1.9 hours, therefore no

additional aeration is needed during the fill phase.

174

Determine the decanting rate The decanting rate is found by simply dividing the fill volume per tank by the decant

time. This will then be used to size the floating decanting pump. This system would

float on the top of the water line and, during the decant phase, draw from the reactor

about 0.3 m below the water surface. This will minimize the amount of floatable solids

entering the effluent. The pump will be timed to draw a specific amount of water and

then shut off to avoid the discharge of settled solids.

Determine oxygen required and average transfer rate The microorganisms in the activated sludge process use oxygen while they consume the

organics in the wastewater. To determine the oxygen required use equation 6.43 defined

previously in this chapter.

To find the average oxygen transfer rate the oxygen required is divided by the total daily

aeration time. Because the oxygen demand will be higher at the beginning of the aeration

period, the oxygen transfer rate should be multiplied by a peaking factor (2 in this design)

to account for these startup demands as well as peak loads.

Aeration system design Once this peak oxygen transfer rate has been calculated it can be used to determine the

actual airflow rate needed for the aeration system. As with the traditional activated

sludge design, adjustments for pressure, elevation and temperature need to be made

(using equations 6.44 through 6.47) to determine the concentration of oxygen in the

aeration tank. This concentration is then used to calculate the standard oxygen transfer

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rate (SOTR) using Eqn. 6.48 (assuming a = 0.5, ß = 0.95, & the diffuser fouling factor =

0.9). The SOTR is the oxygen requirement in clean water at 20°C and 0 mg/L dissolved

oxygen and can be used to find air flow rate and thus appropriate diffuser modules. The

airflow rate for this design was determined to be about 0.34 m3/min using Equation 6.49.

Nine-0.2 m fine pore membrane discs were chosen to provide aeration for each tank.

They will each have an air flow rate of 0.06 m3/min, providing a total aeration of 0.51

m3/min per tank. This excess aeration will provide adequate protection against diffuser

fouling and failure, with minimal increases in power requirements.

To determine the power requirements of the blowers, the pressure head of the tank and

the headloss through the piping must be determined. The maximum headloss is calculated

using the Bernoulli equation with minor losses through two 90° bends, one cross fitting,

three ball valves and three check valves. There is one blower installed on each tank to

provide aeration for that tank. In case of a blower failure, however, they are piped so

either can be taken out of service while the other provides aeration to both tanks.

Determine the amount of sludge production Sludge production is an important parameter as it is a measure of process performance.

By calculating sludge production, BOD and suspended solids removed by the treatment

system can be determined. The amount of BOD removed and the observed yield of TSS

and VSS are determined using equations 6.37 and 6.40 through 6.42.

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Sludge Storage Since there needs to be residual sludge in an SBR reactor, only small amounts of sludge

are wasted on a daily basis. A small storage basin is designed to hold the sludge for at

least one month. When the basin is full, it will be pumped out by a septic tank disposal

truck. To design this basin the volume of sludge wasted per day needs to be determined

using the following equation [29].

CMs

Vsγ

= Eqn 6.60

Where Vs = Volume of sludge, m3 Ms = Mass of Sludge, kg ? = Specfic Gravity of sludge, 1.02 C= Concentration of sludge, 8000 mg/L About 3 m3 of sludge is wasted on a weekly basis; therefore the volume of the basin will

be 12 m3 to be able to store the wasted sludge for one month.

Calculate F/M ratio and BOD volumetric loading As a further check of process performance the F/M ratio and BOD volumetric loading

should be calculated using equations 6.53 and 6.54.

Materials List To estimate the capital cost of building a SBR, a materials list has to be generated and

carefully evaluated. Due to the near complete automation of this system, many parts may

have to be imported to Bali, which will sharply increase costs. A detailed materials list is

presented in Table 6.15 below.

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As is shown, many of the parts necessary for the construction of a SBR are available on

Bali, but some of the most essential ones are not. Although the importation of these

materials will increase costs, it should not do so to the point of being prohibitive.

6.8.4 Conclusions on SBRs A sequencing batch reactor activated sludge system could prove to be a very good option

for treating the wastewater generated by the Bali Spirit Hotel because the construction of

the system is relatively simplistic, and the automation of the controls should make the

operation and maintenance easy for one or two trained personnel. This automation will

come with the price of a high capital cost, but its ease of use should more than make up

for it over the lifetime of the system. The plant also has a relatively small footprint of 4

m x 4 m including the entire treatment system, pumps and controls. These could all be

easily enclosed within a building to minimize hotel guest contact. This would also

contain any odor or noise problems that may occur. It is also very energy efficient

requiring only sporadic use of low flow, high efficiency pumps and blowers. Most

importantly, the quality of the effluent will be significantly higher than current practices

Table 6.15 - Material requirements for SBR

75mm PVC Cross Fitting 275mm PVC End Caps 6Actuated Ball Valves 4100mm Schedule 40 PVC 10 mSubmerged Sludge Pumps 2100mm Schedule 40 PVC 10 m100mm PVC 90° Bends 4½ HP Decant pump 275mm flexible tubing 20+ mAutomated Control System 1Misc. Wiring

Reinforced Concrete 8.2 m3

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and will not pose a threat to the ecology of the discharge stream. A design summary is

presented in the Table 6.16.

Table 6.16 - Summary of design parameters for SBR

Design Parameter Value Unit

Average Flow 14.25 m3 /dAverage BOD load 3.59 kg/dAverage TKN load 735 g/dNumber of tanks 2 numberFill Time 4 hReact Time 2 hTotal Aeration time 2 hSettle time 1 hDecant time 1 hCycle time 8 hTotal SRT 14.36 dTank Volume 7.2 m3

Tank Depth 3 mTank Width 1.55 mTank Length 1.55 mFill volume/cycle 2.4 m3

Fill volume/tank volume 0.33 ratioDecant depth 0.33 mTank depth 3 mMLSS 3500 g/m3

MLVSS 2422 g/m3

F/M 0.1 g/g dVolumetric BOD load 0.49896 kg/m3dDecant pumping rate 0.0396 m3/minSludge production 3.51 kg/dObserved yield 0.98 g TSS/g BODObserved yield 0.61 g TSS/g bCODAverage oxygen required/tank 3 kg/dTotal aeration time/d-tank 6 hPeak O2 transfer rate 1.16 kg/h

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180

181

182

183

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6.9 Treatment and Disposal of Sludge 6.9.1 Background In wastewater treatment, sludge is produced during many of the processes that are found

in common treatment plants. This sludge contains organic matter as well as inorganic

elements. These components may be used beneficially after appropriate treatment.

The organic matter in sludge contains macro and micronutrients and water that is

important for plant growth. Some of the nutrients that are found in sludge are nitrogen,

phosphorus, potassium, sulfur, calcium, magnesium, iron, boron, manganese, copper,

zinc, and molybdenum. A few of the nutrients, however, can be detrimental to plant or

animal life if they are above certain concentrations. Many of the inorganic elements

found in sludge can adversely affect plants and animals if the levels are excessive. Some

of these elements are arsenic, cadmium, chromium, copper, lead, mercury, molybdenum,

nickel, selenium and zinc [21]. These elements also build up after continued application

to the soil over time.

6.9.2 Sludge Treatment Processes Processing or disposing of sludge is extremely difficult for three reasons. First, the

sludge contains materials that were offensive in the wastewater to start with. Second, the

sludge contains a lot of bacteria and settled solids, which means that it is organic and will

decay. Third, only a small portion of the sludge is actually solid, meaning that the water

must be separated out. There are many different methods that can be used to treat the

sludge from a wastewater treatment plant. Some of the methods are conditioning,

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thickening, stabilization, dewatering, drying, and disinfection [35]. Any of these methods

or combination of these methods could be used effectively. The best method or

combination depends on the situation and the characteristics of the sludge. This section

will go through each of the main processes and make a suggestion as to which methods

will best treat the sludge from the Bali Spirit Hotel.

6.9.3 Conditioning and Dewatering Conditioning and dewatering is an important step that needs to be taken when reusing or

disposing of sludge. This step helps to prepare the sludge for other processes such as

incineration, drying, composting, or beneficial uses, such as land application.

Conditioning and dewatering can reduce the volume and weight of sludges by as much as

20-fold, although a 10-fold reduction is more common [21].

Conditioning is the first step that prepares the liquid sludge to separate into the liquid and

solid fractions. Changing the chemical and/or physical properties of the sludge can help

condition it. Next, it is necessary to actually separate the liquid portion from the solid

portion of the sludge. This step is called dewatering and is usually accomplished using

mechanical means, although passive means such as drying beds or freeze/thaw lagoons

can be used where the weather permits. Often times thickening is used as the first step of

the dewatering process, but it can also be used as a stand-alone process.

Conditioning can be done through the use of chemical or physical means, including:

• Organic and inorganic chemical addition

• Thermal treatment (with or without increased pressure)

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• Freeze/thaw

• Addition of bulking material

Unfortunately, conditioning represents a significant cost. However, it is impractical to

try to dewater sludge without conditioning.

Dewatering sludge depends on sludge characteristics, the type of conditioning that has

been used and the type of thickening or dewatering device being used. The thickening

process can be done through the use of four different processes [21].

• Gravity Belt thickening

• Centrifuges

• Flotation thickening

• Gravity thickening

Some of the processes that can be used to dewater the sludge are as follows:

• Belt filter presses

• Centrifuges

• Pressure filters

• Vacuum filters

• Screw presses

• Rotary presses

• Drying beds and freeze/thaw lagoons

• Bag Dewatering

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Each of these processes has advantages and disadvantages associated with it. With the

exception of a conventional drying bed, freeze/thaw lagoons and bag dewatering, each

process requires energy for moving parts.

6.9.4 Digestion Digestion of sludge from wastewater treatment processes has been used for many years to

stabilize and reduce the volume of sludge and to reduce the pathogen content. Since

options for disposing of sludge are decreasing, it is becoming more and more important

for digestion and other treatment methods to accomplish greater treatment so the sludge

can be used for beneficial purposes.

Digester configurations have been fairly standard in the past [21]. The two most

common types of digesters are aerobic and anaerobic digesters. However, improvements

to digestion processes have been directed toward an increase in efficiency, reducing

maintenance and reducing the amount of pathogens. Some of these improvements

include:

• Egg-shaped anaerobic digesters- this type of digester has improved the efficiency

and reduced the required maintained of the traditional anaerobic digester

primarily through modifying the shape of the reactor configuration.

• Autothermal Thermophilic Aerobic Digestion (ATAD) – this type of digester has

improved the efficiency and increased the amount of pathogen reduction of the

conventional aerobic digester.

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• Pre-Staged ATAD- this type of digester can be used upstream of an anaerobic

digester to help increase the destruction of pathogens. This type of digester is

typically retrofitted into existing plants that are using anaerobic digesters.

While digestion can be extremely efficient at removing pathogens, it can also be costly.

Depending on the type of digester that is being used it may be necessary to provide

mixers, aeration systems, scum removal, foam control, decanting of supernatent and

pumps [21]. These requirements suggest that sludge digestion is not that feasible for just

the Bali Spirit Hotel.

6.9.5 Composting Composting is a natural process in which aerobic, thermophilic microbiological

degradation occurs to turn organic wastes into a stabilized and useful product. The

product is often times free of odor and pathogens. It will not attract rodents or insects

and can be used for horticulture or landscaping purposes. The composting process

stabilizes the waste biologically. This means that the organic components of the waste

are broken down until they are stable or resistant to biological change. Other wastes are

broken down over time, but the process can be slow. This does not affect the use of the

material.

Composting is a living process; therefore it is necessary to take care of the process with

the appropriate care and feeding. It is necessary to have the right environmental

conditions, such as temperature, oxygen levels and moisture content of the composting

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piles. As well as the appropriate nutrient requirements so the degradation process can

occur. These conditions depend on the type of solids that are being composted.

Unfortunately, depending on the amount of sludge being composted, the land

requirement can be quite extensive. It also can be labor intensive when first starting a

composting system [21].

6.9.6 Heat Drying and Other Thermal Processes Heat or thermal treatment of sludge can be used for several purposes, such as:

• Promoting separation of solids from liquids

• Reducing pathogens and vector attraction

• Enhancing waste-activated sludge digestibility

• Incineration

• Drying and production of fertilizers

There are two main methods for drying sludge. These two methods are air (solar) drying

and heat drying. Air-drying is fairly low cost method of drying the sludge on a open

surface until the desired solids content is reached. This depends on the weather and the

availability of land. Heat drying can be done through many different methods a few are

listed below:

• Rotary Drum Dryers

• Fluid Bed Dryers

• Flash Dryer

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• Conveyor Dryer

• Indirect multi-tray Dryer

Some of these dryers take more energy than others, but there is also a problem with

pollution control. It is necessary to control the particulate matter and gaseous pollutants

that can result when exposing sludge to high temperatures. Heat drying may not take up

as much land, but there is definitely the possibility for high operational costs, depending

on the fuel that is used [21].

6.9.7 Land Application Land application is a term used to describe the application of sludge to land for purposes

of agricultural production, production of other non-agricultural crops or use as a soil

amendment/fertilizer to help reclaim disturbed areas, such as roads or construction areas

[21].

Application of sludge to the land often times results in an improvement in soil properties

primarily because the sludge contains two key components, plant nutrients and organic

material. Plant nutrients encourage growth of vegetation, whereas the organic material

can have a significant influence on the physical, chemical and biological properties on the

soil. However, toxic trace metals can sometimes have a negative impact on the soil.

Therefore it is important to know the content of the sludge.

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When applying sludge to land, it is important to designate a specific area. When

designating this area, it is necessary to consider the items listed below:

• Proximity to Surface Waters

• Proximity to public access

• Proximity to drinking water supplies

• Distance to groundwater

• Transportation from facility to site

• Storage

• Method of application

• Type of agriculture

Land application can be very beneficial, but there are costs involved. The major costs of

the system are transportation, storage, site preparation, application and incorporation into

the soil [21].

6.9.8 Discussion and Recommendation The sludge disposal methods discussed in this section each have advantages and

disadvantages. The best method clearly depends on the situation that it will be used for.

The Bali Spirit Hotel has specific needs that need to be met. Since the hotel is relatively

small, there is not a lot of land available to build a large system, nor is there a lot of

money that can be spent on capital and operational costs. As with the rest of the

treatment design it would be best if the sludge could be treated and disposed of in a low

energy, cost effective way.

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The low energy need makes it difficult to recommend a system that would need constant

power, such as heat dryers, and digesters. The need for a low cost method also makes it

difficult to recommend chemical conditioning and thickening. Although it can be

expensive, some type of conditioning is essential to help with the dewatering of the

sludge. The addition of bulking material can be used to help condition the sludge from

the Bali Spirit. Dewatering can still be costly because of energy input. While it would be

ideal to use drying beds, this would fail during the monsoon season on Bali. Therefore,

the best dewatering technique would be to bag dewater. Bad dewatering is recommended

for treatment plants that are treating less than 760,000 liters per day [21]. There are no

moving parts so the cost can be reduced significantly. After dewatering, disposal of the

sludge would have to be done through land application. It is possible that the sludge

could be sent to a landfill, but necessary precaution should be taken to ensure that the

sludge has a significantly reduced pathogen content. Using sludge on the local

agriculture is not an option because the majority of the agriculture is wet-rice, which

would cause leaching of sludge material. Finally, the option of using the sludge as fill

material for roads and construction sites has a largest potential. The growth on the island

should produce enough construction sites and roads that will require enough extra soil to

handle the disposal of large amounts of sludge produced in the future.

As stated earlier, the Ibah Hotel and Uydana Lodge currently dispose of the sludge by

spreading it on the surrounding vegetation and sending the sludge to settling pounds,

respectively. For now these are probably the best option for the Bali Spirit Hotel. Since

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spreading the sludge on the land without sediment runoff control can cause the spread of

pathogens, nutrients, and metals, this option is not recommended. However, because the

Bali Spirit Hotel currently has their septic tanks pumped by a local waste company, the

best option for sludge disposal would be to continue having it pumped by the same

company. This company then takes it to the settling ponds that receives the sludge from

the Udayana Ecolodge. This disposal method utilizes the best available technology for

sludge disposal in Bali. It will not induce any costs additional to what the Bali Spirit

already pays for their waste disposal. If the Bali Spirit Hotel continues to expand, then

further options should be explored for onsite treatment and reuse of the sludge.

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CHAPTER 7

CONCLUSIONS

7.1 Design Alternatives Evaluation In order to evaluate the design options, there must be a method for comparison. To do

this, a set of design criteria was developed and given a weighted value depending on the

importance of the criteria. Each design option was ranked relative to each other based on

how well they met the criteria

7.1.1 Design Criteria

Effluent Quality Since improving the quality of the effluent is the primary purpose these designs this

criteria was given a weight of 30%. For the purposes of the Bali Spirit Hotel, the water is

desired to have BOD removed to meet U.S. EPA secondary standards of 30 mg/L. In

addition, the amount of TKN should be reduced by more than 50 percent. This is because

the effluent is to be discharged into the Wos River. A discharge of high nitrogen levels

can be toxic to aquatic life. A system with the cleanest achievable effluent is desired.

Construction and Capital Costs Since the project is going to be built in Bali, the cost of materials and labor in particular,

will be considerably less than in the United States, but in relative terms will still be

significant. Any equipment that is specialized or must be imported from outside of Bali

will require a more expensive cost. The size of each alternative will also have a big

influence on materials cost and construction time. The existing system consists of two

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subsurface septic tanks. The cost of rebuilding similar tanks will be used as neutral for

evaluation purposes. It was agreed that designing a system of low cost would be a

secondary goal of each system, therefore this criteria was given a weight of 20%.

Operation and Maintenance Cost Associated with the everyday operation of an onsite wastewater system are several

additional costs. As is the case in most situations, pumping is required to transport the

wastewater from one location to the next. These pumps will use energy and therefore

increase the amount of operating cost. In addition to pumping, treatment systems often

require supplemental aeration. Just as with pumping, aeration requires electricity use,

increasing operational costs. If the system requires an operator to be onsite continuously,

this system will much more expensive than the current use of self-operating septic tanks.

Systems with more mechanical and moving parts usually require more maintenance

because of increased wear and tear. Again, since this secondary goal of each system is

low cost, this criterion was given a weight of 20%.

Land Use Since the project is going to be built on the Bali Spirit Resort and Spa property, the

amount of space available is limited. The hotel has already expanded once in the recent

past and may wish to expand again within the near future. In order to accommodate this,

the treatment option selected should have a relatively small surface area. This will ensure

that the system will allow for any future developments. The amount of land that each

system requires is important because acquiring more land to handle a treatment system

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could be rather difficult, although not impossible, for the hotel. This criterion was given

a weight of 15%.

Ease of Operation and Maintenance After construction, each system must be maintained to guarantee the quality of effluent.

Some systems operate quite simply and only require that someone check to make sure

things are working properly. Other systems are slightly more complex and need a routine

sludge wasting. In the most complex situation, computer software is necessary and a

specially trained person will be required to operate the system. Most system need to have

a trained operator, but it may be as simple as the existing septic tank system, where it is

only required that the tank be free of clogging and are pumped twice a year. This

criterion could result in having to hire someone or simply train existing personnel to

operate the system. This criterion was given a weight of 5% because it is not

unreasonable to hire someone or expand the responsibility of existing personnel.

Ease of Construction As mentioned in construction costs, the size of each alternative will have an effect on the

amount of time required to build it. It is highly likely that untrained and usually unskilled

workers perform construction; the design should be quite simple. A complex design will

be more difficult to explain to laborers and therefore will likely take more time. Septic

tank construction is very simple because it only requires the excavation of earth, pouring

of cement, and connection of plumbing. Again, it may be hard to explain the design to

the labors, but this is a one-time cost, therefore this criterion was given a weight of 5%.

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Aesthetics The Bali Spirit is an upper end hotel where tourists expect to enjoy their vacation. The

implementation of a wastewater treatment system should not interfere with the enjoyment

that the guest receives from staying at the Bali Spirit. Optimal systems are small and

easy to disguise with other buildings or landscaping. A frequent problem associated with

wastewater is presence of an unpleasant odor. Systems causing odor problems should be

avoided. Overall, the system used should not hinder the vacation atmosphere created by

the Bali Spirit. Aesthetics were agreed to be lowest criteria on the list, therefore this was

given a weight of 5%.

7.1.2 Alternative Evaluation Matrix This section gives an overview on how each design system scored on the design criteria

and why the system was given that score. Overall, there was a narrow range of final

weighted totals between all of the designs. The lowest score was the complete mix

activated-sludge with a value of 5.45 and the highest score was 6.3 for the sequencing

batch reactor. Table 7.1 at the end of this section gives a complete summary of the scores

for each system.

Sequencing Batch Reactor The sequencing batch reactor design came in with the highest weighted score of 6.3 and

was chosen as the final design recommendation. A large part of this high score was due

to the 8 that was assigned to the effluent quality category. The SBR will have excellent

BOD and nitrogen removal and remove up to 99% of the suspended solids. This well-

treated effluent should comply and exceed USEPA secondary standards and contribute to

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a significant improvement in the quality of the Wos River water. This quality, however,

comes at a cost. Due to the fact that some of the components of the system will need to

be imported to Bali, the SBR only received a score of 5 on the capital cost category.

Similarly, the SBR will require some maintenance and electricity to run effectively so the

O&M costs category was also assigned a 5. The SBR scored a 6 in the land use category

because it takes up about 9.6 m2 of land area on the Bali Spirit property. The entire

system, however, will be contained in a 4m x 4m building that will conceal it from the

hotel guests and reduce odors, thus a score of 7 was assigned to the aesthetics category.

One of the biggest selling points of the SBR is its ease of operation and construction and

these categories were assigned a 7 and 6 respectively. The construction of this SBR will

simply require a partitioned concrete square to be built, after which piping, pump s, and

control system can easily be added. Once it is constructed, the system runs automatically

with only periodic maintenance of pumps and blowers needed. The automated control

system will effectively run the operation of the plant. In conclusion, the implamentation

of an SBR system at the Bali Spirit should serve as an example of effective wastewater

treatment for the entire island.

Trickling Filter The trickling filter design received a weighted ranking of 6. In the wastewater effluent

quality category, a value of 8 was awarded. This value was chosen because the first filter

is designed to remove BOD to acceptable levels and the second filter further treats the

water by performing nitrification, thus producing a well- treated effluent. A ranking of 4

was chosen for capital cost because in addition to buying simple construction materials

such as concrete, rebar, etc., the construction of the trickling filters also includes the

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purchase of five pumps, a rotary motor for distribution, and a plate settling system. The

operation and maintenance of the system will only require daily inspection to make sure

everything is operating properly and enough energy to supply the pumps. Because of

these needs for operation, the filter received a ranking of 5 in this category. Land use for

the filter received a 7 because the filters are built tall instead of wide, allowing a smaller

area to be used. Ease of operation also received a 7 because once the system is in

operation; an operator only needs to check that everything is functioning properly. Ease

of construction however, received a 3. Because the system requires the use of

mechanical parts, installation of proper ventilation ports, and semi complex piping, the

trickling filters will not be easy for the local Balinese to construct. The filters will be

fairly self-contained and look like another outbuilding, but odor problems may arise with

improper operation and that is why the design only received a 5 for aesthetics.

Grease Trap and Intermittent Sand Filter The grease trap, septic tank and ISF system received an overall ranking on the weighted

scale of 5.85. It received a ranking of 6 for effluent quality because it will treat the waste

stream to acceptable standards, but not as well as the SBR or trickling filter. A score of 6

was given for capital cost because of the amount of excavation and backfill needed for

the construction of the ISF. This will be the largest and most significant part of

construction. The operation and maintenance cost of the ISF system is fairly low, so it

received a ranking of 8. The grease trap and septic tank need periodic testing for sludge

and sludge removal. The ISF only needs periodic monitoring for clogged orifices and

effluent quality sampling. The biggest problem with the ISF is the land use requirement.

The land use needed is so large that it renders the system unfeasible and a ranking of 2

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was given. The entire system is low maintenance and does not require day to day

monitoring or upkeep, therefore an ease of use ranking of 7 was given. The ease of

construction was ranked at 4, again due to the large size of the ISF. For aesthetics a

ranking of 8 was given because the entire system can be implemented below existing

grade. The relative ranking of the ISF to the other systems was third out of four designs.

Complete Mix Activated Sludge The complete mix activated-sludge system design received an overall ranking of 5.45.

This was the lowest score amongst all of the designs. This system received a 7 for

effluent quality because this system has a high potential for efficient removal of BOD.

The capital cost of the system received a 4. This is primarily due to the aeration system

for the design. The components of the aeration system could be rather difficult of find on

the island of Bali. The operation and maintenance cost of the system could be intensive,

especially during the start up. The aeration system has the potential to become clogged if

any settling were to occur immediately after the inlet ports or through out the aeration

tank. The land use of the complete mix activated-sludge is fairly minimal when

compared to the other systems. The overall footprint of the system is approximately 12

m2; therefore this system received a score of 8 in the land use area. For the ease of

operation criteria, the complete mix activated-sludge system scored a 4 because there is a

high opportunity for the system to fail. Therefore, it would require more supervision.

The ease of construction is a little more complicated because of the use of pumps and the

excavation that needs to take place. It received a 5 in this category. The complete mix

activated-sludge system scored low for aesthetics, 4, because it is an open system

therefore increasing the potential for odor problems. Also the majority of the system is

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located above ground and the pumps for the aeration system need to be running

constantly. This creates an eye-sore and a noisy environment.

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Criteria Weight ScoreWeighted

ValuesWeighted

ValuesWeighted

ValuesWeighted

ValuesEffluent Quality 0.3 8 2.4 8 2.4 6 1.8 7 2.1Cost-Capital 0.2 5 1 4 0.8 6 1.2 4 0.8Cost-O &M 0.2 5 1 5 1 8 1.6 5 1Land use 0.15 6 0.9 7 1.05 2 0.3 8 1.2Ease of Operation 0.05 7 0.35 7 0.35 7 0.35 4 0.2Ease of Construction 0.05 6 0.3 3 0.15 4 0.2 5 0.25Aesthetics 0.05 7 0.35 5 0.25 8 0.4 4 0.2Totals 1 44 6.3 39 6 41 5.85 37 5.75

Sequencing Batch Reactor Trickling Filter ISFComplete Mix Activated

Sludge

Table 7.1 – Design Ranking Matrix

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7.2 Final Design Recommendations Based on the results of the design criteria evaluation matrix, the sequencing batch reactor

(SBR) design was chosen as our final design for the treatment of wastewater at the Bali

Spirit Hotel. The SBR is a simple self-contained unit that, once set up, will run

automatically with minimal maintenance or process adjustment. The volume of each of

the two tanks will be about 7.2 m3 and will be contained within a small building that will

muffle blower noise, prevent rainwater intrusion, and minimize hotel guest contact with

the system. The construction of the system should also be relatively easy to do with

materials available on Bali. The tanks will be a simple concrete structure 1.55m on a side

and 3m deep. There will be a series of aerators placed on the floor of the structure with

piping to the blower running out the side. There will also be an inlet for the influent

midway up one side of the unit and a sludge-wasting pump on the bottom. A sludge

storage tank will be located directly next to the treatment units and will contain the

wasted sludge for at least 30 days. A floating decanting pump will remove the treated

water and discharge it to the Wos River. Most of these materials are available on Bali

and should be easy to locate and install. There are several critical parts, however, that

will need to be imported including actuated ball valves, aerators, sludge pumps and the

automated control system. This part of the system, in particular, is crucial because it

controls which tank the influent flows into, as well as the timing of the different phases.

Although it may be expensive to import and train someone to use this equipment, I think

the benefit of having an automated unit would make up for these costs. One of the most

important reasons the SBR was chosen was the quality of effluent that it would produce.

In an 8-hour treatment cycle the BOD would be reduced to less than 1mg/L and the NH4-

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N would be reduced to 0.5 mg/L. This would produce effluent cleaner than the U.S. EPA

standards and would be the first step towards having a cleaner, healthier Wos River [28].

7.3 Further suggestions and recommendations If the Bali Spirit Resort does not desire to use the SBR system, another design option that

would be appropriate to use is a grease trap and septic tank followed by a trickling filter

instead of the ISF. The ISF was deemed unfeasible to the large land requirement. This

combination is good because the septic tank will remove much of the solids load to the

trickling filter and perform some pretreatment, allowing better treatment by the filter.

The trickling filter will provide treatment surpassing an ISF, and require a much smaller

footprint to accomplish it. Another advantage of this system is that all of the unit

operations are simple to operate and classically have been utilized in on-site systems.

This will provide some familiarity to the Balinese operators and ease the complexity of

the system. There are no automated controls and the only maintenance is monitoring of

sludge production. The main drawback to this system is its required use of a secondary

settling system. This design option is very feasible for implementation at the Bali Spirit

Hotel and should be considered if the SBR is not accepted.

Besides the combination mentioned in the previous paragraph, it was also determined that

whichever design is chosen, a grease trap should be installed between the kitchen and the

treatment system. This will greatly increase the efficiency and lifespan of the system.

Greases and oils can clog piping, foul biological treatment processes and reduce

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infiltration capacity, so it is important to remove them as early as possible in your

treatment process.

At present, the treated effluent is being discharged to the Wos River. While touring the

Bali Spirit’s premises, the management indicated that it can be very dry at their location

sometimes, and that is why they recycle shower effluent for use on the landscaping. In

order to further reduce the amount of groundwater being pumped for landscaping, it is

recommended that the Bali Spirit look into using the treated wastewater effluent for

landscaping as well. This would require the installation of a subsurface irrigation system

and additional pumping. These additions require extra cost and the Bali Spirit

management must determine if the money saved by reducing groundwater pumping is

enough to justify water reuse.

7.4 Signifigance of Pilot Plant Project The pilot plant designed for the Bali Spirit Resort should allow government officials to

see an onsite wastewater treatment system in operation. They can observe the quality of

the influent and see the visual difference of the effluent. With sufficient observations by

these officials, regulation may be implemented. If government officials create and

enforce regulation on hotel wastewater effluent, then the hotels will be required to install

wastewater treatment systems. The system at the Bali Spirit Resort and other existing

systems will serve as examples for hotels in need of constructing a system. In addition,

as more systems get built, the ir use will become more familiar to the Balinese. As this

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happens, the use of onsite systems will hopefully spread from hotels, to individual family

compounds or even whole villages.

With the installation of onsite treatment systems in the Ubud area and the rest of Bali, the

amount of pollution entering the rivers will decrease. The river will no longer have to

handle the burden of partially treated septic tank leachate and untreated hotel effluent

pipes. This will reduce the total amount of BOD entering the river, the amount of

coliform bacteria entering the river, and the amount of ammonia entering the river. By

doing this, the amount of stress placed on lowland receiving waters is also limited.

Since much of Bali’s water supply, even drinking water, comes from local rivers, the

reduction of pathogens in the water is important. Although disinfection is not occurring

at the pilot plant because of operating costs and the hazards presented with onsite

chemical storage, the amount of coliforms in the water is being reduced in the secondary

treatment process. Elimination of direct discharge to the river coupled with coliform

reduction in the process will decrease the amount of pathogens found in the local waters.

As a result of this, the amount of waterborne disease occurring in Bali will also decrease.

This will lead to an increased trust in the local water supply and further support for

environmental regulation.

Once the Balinese people see the benefit of environmental pollution prevention, they can

begin to remediate their many problems. Rivers polluted with untreated wastewater are

just a small portion of the many issues the Balinese currently face. The success achieved

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by the implementation of treatment systems can show the way that other problems may

be tackled. Perhaps next, a village will create a small scale recycling, composting, and

garbage collection system so that other villages can use them as an example to reduce

trash accumulation and air emissions from burning waste. The problems that need

tackling are endless and it is hoped that the onsite wastewater pilot plant will serve as the

first step in the direction toward reducing pollution.

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REFERENCES

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