A VISION FOR FUTURE SLUDGE MANAGEMENT

IN ALEXANDRIA

Dr. Helaly Abdel Hady Helaly (1)

Chem. Hussein Mohamed Abdou Elashqar (2)

Dr. Samaa Maher Abdel Aziz (3)

(1) “General Manager of Industrial wastewater, Sludge and Reuse Sector, Alexandria Sanitary

Drainage Company”.

(2) " Manager of Landfill Composting Facilities (site 9N)".

(3) “Manager of Industrial Wastewater Studies and Research Department”.

Keywords: sludge production, Alexandria, future, wastewater quantities, sludge

dewatering, sludge handling, sludge treatment, compost marketing.

ABSTRACT

After full operation of secondary treatment at the East and West treatment

plants, the future production of sludge from these plants and from Amriya and Agamy

secondary treatment plants in addition to the rest 14 secondary treatment plants all

around Alexandria is expected to exceed than 1200 m3/d by 2015 thus the capacity of

the sludge disposal site should exceed. Therefore, the future sewage sludge

management represents a critical environmental issue in Alexandria, this management

includes sludge dewatering, handling, transportation cost to the disposal sites and the

final product marketing.

As the capacity of Alexandria sludge disposal system will be limited by the

increase in sludge production and the current management system, there is an

immediate need to investigate ways to establish a future management system and to

demonstrate successful operations at higher sludge producing rates.

Currently, Site 9N the sole disposal site in Alexandria include a composting

plant established when the site was initially developed as a dedicated disposal area for

sludge. Consequently, land spreading of the sludge on the dedicated disposal area has

ceased and all of the current production of raw sludge is now being composted using

the turned windrow technique.

The present study aims to evaluate the current efficiency of the sludge

management system and adopt a future vision for the Alexandria sludge system and

recommend modifications to protect public health and environment.

Introduction

Alexandria is the second largest main city in Egypt. It is the primary port home

for 40% of Egypt industrial base. In 1998, Alexandria population was 3.5 million and

it is estimated to reach 8 millions by year the 2030. Alexandria has attracted

considerable attention towards developing its basic structure and overcome some of

the problems facing its utilities.

In the late seventies, sanitary drainage activities covered only 40% of the total

inhabited area of the city. Even that the sewers were often worn out by time and

unable to handle the flows they receive. The problems of streak flowing have existed

due to the inability of pump stations and treatment plants to receive flows exceeding

their capacities. The city,s wastewater treatment facilities which are expected to serve

a population of about 4 million were not operated well and the collection system was

aging and limited in coverage. These conditions lead to frequent and unavoidable

operational failures which posed a direct threat to the public health, constrain

industrial development, and impacted the daily lives of the residents of the city.

Alexandria has two large primary treatment plants (East Treatment Plant (ETP)

and West Treatment Plant (WTP). The confined capacities of 607,000 and 400,000

m3/d were respectively, sludge processing and disposal facilities (600 tons/day),

collection system of large interceptors, tunnel collectors, pump stations, and

establishing a site for disposing the generated scum, grit, and sludge. The

implementation of wastewater project in the city of Alexandria resulted in large

quantities of sludge being produced (400 tons /day) average.

Future production of sludge from East and West treatment plants, Amriya and

Agamy will become more than double the current production. As a result, sludge

disposal site capacity has to exceed approximately 700 m3/d. This production level

expected around year 2010 with only primary treatment at East and west treatment

plants.

The installation of a secondary treatment at the East and West treatment plants

will result in the capacity of sludge site being exceeded when these units start full

operation. The key features of site 9N include the composting system and the

supporting facilities and equipment. Approximately 100 % of the dewatered sludge

and all the grit received from the treatment plants are disposed and incorporated into

composting plant located in the site which is about 140 feddan.

As the capacity of Alexandria sludge disposal site is limited by current

operation system, there is immediate need to investigate ways to increase site capacity

and to demonstrate successful operations at higher sludge producing rates.

The present study aims to evaluate the current efficiencies of the ASDCO

sludge disposal system with emphasis on site 9N as the main disposal facility and

recommend modifications to expand its capacity and life time than planned, to protect

public health and environment.

The quality and quantities of sludge produced at a municipal treatment facility are

controlled by the composition of the incoming wastewater and the required treatment.

The sludge characteristics, in turn, affect the alternatives available for

treatment, beneficial use and disposal. Different sludge treatment processes will yield

different types and volumes of sludge which can effect the beneficial use/disposal

options available. The proposed beneficial use / ultimate disposal of the sludge solids

dictate the extent to which the sludge must be treated prior to disposal. Various

alternatives for sludge treatment and disposal are presented in Figure (1), Table (1).

Figure (1): Sludge Disposal Alternatives

Table (1): Sludge treatment processes and their functions

Unit Processes Function

Thickening

gravity, flotation, belt thickeners

Water Removal

Volume Reduction

Blending

Biological Stabilization

Aerobic Digestion

Anaerobic Digestion

Composting

Pathogenic Destruction

Volume and Weight Reduction

Odor Control

Putrescibility Control

Gas production (methane)

(Anaerobic Digestion)

Conditioning

Chemicals, heat, fly ash

Improve Dewatering rate

Improve Solids capture

Improve compactability

Belt Filters Water Removal

Solids capture

Change to Damp Cake

Volume and Weight reduction

Dewatering

Vacuum Filter

Belt Filter press

Filter press

Centrifuge

Water Removal

Solids capture

Change to Damp Cake

Reduces Fuel Requirements for

Incineration/Drying

Drying Beds

Heat Drying

Water removal

Incineration Destruction of solids

Water removal

Conversion

Sterilization

Final Disposal irrigation and croplands

Energy

Land reclamation and Landfill

ocean disposal (Banned in USA)

Incineration

Wet oxidation

Location and capacity (current and planned) of all WWTPs:

Alexandria has 18 wastewater treatment plants, ranging from 3,000 m3/day

to 607,000 m3/day. Total capacity is about 1.4 MCM/day, of which 1.3 MCM/day is

concentrated in 4 large treatment plants. About 1 MCM/day is currently upgraded to

secondary. 0.3 MCM is already secondary. Planned capacity increase is 0.55

MCM/day.

The East Treatment plant is currently a primary treatment plant under

upgrading to secondary activated sludge treatment and discharges to Dayer El-Matar

drain to Lake Maryout. Abis Villages 6 secondary treatment plants; The 10th Abis TP

discharges to El Amlak drain, Nasriya TP to Dayer El Matar drain, Abis 1st and 2nd

TPs to Mansheya Drain, Abis 3rd TP to Mansheya 3 drain and Abis 4th to Mansheya 4

drain.

The West Treatment plant (primary under upgrading to secondary Activated

sludge treatment) discharges directly to Lake Maryout. The Km 26 secondary

activated sludge treatment plant does not discharge its effluent but it is reused by Alex

West Tourist Compound adjacent to the treatment plant.

Iskan Moubarak secondary TP discharges to Amriya drain, while Khorshid

& Zawayda TP and El Maamoura TP are secondary treatment plants and discharge to

Amiaa Drain. El Hannovile secondary treatment plant (Ard El Hesh) discharges near

El Dekhila Harbour. El Seiouf secondary treatment plant disharges to El Qalaa Drain.

El Agamy Km 21 Treatment plant will discharge to West Noubariya drain.

And El Amriya secondary treatment plant will discharge to Noubariya canal. While el

Noubaria secondary treatment plant discharges to El-Shagaa drain.

New Borg El-Arab secondary Aerated lagoon treatment plant discharges to

its surrounding forest area which is considered reused. It is proposed to discharge the

rest unreused effluent to the West Noubaria Drain.

Sludge generation (location, quantity, quality), processing and disposal.

The sludge from both ETP and WTP is mechanically dewatered at the WTP.

The liquid primary sludge is pumped from the ETP to the WTP where it is co-settled

with sewage and the sludge is dewatered by the belt press to about 30% dry solids (ds).

Sludge production is currently about 450 m3/d, equivalent to about 50,000 tonnes dry

solids (tds per year). This will increase when the WWTPs are extended (currently under

development) and secondary treatment is installed (planned for 2010), reaching about

80,000 tds by 2015. Table (2) shows the current and future sludge production in

Alexandria.

The generated amount of sludge from the East Treatment plant that resulted from

clarifiers is about 3000-4000 m3/d , solid concentration 2-3%, it is diluted to 1-2% then

pumped through middle zone tunnel (12 km length, 5 m depth), to WTP, then

dewatered by mechanical dewatering facility.

Table (2) : Current and Future sludge production in Alexandria main

treatment plants (m3/d)

Year ETP/WTP Amriya

TP

Hannoville

TP

Total

Current 450 450

2009 669 169/109 352 1,190/1,130

2010 724 169/109 364 1,257/ 1,197

2015 724 169/109 376 1,269 / 1,209

2020 759 169/109 388 1,316 / 1,256

2025 759 445/285 400 1,604 / 1,444

The amount of sludge generated from the West treatment plant is also about

3000-4000 m3/d with solid concentration of 3-5% , then to the mechanical dewatering

facility, The produced sludge is 8704 Ton/month; Used polymer 6927 kg

polymer/month; Polymer cost 182873 L.E/month.; Dewatering efficiency 27.9%.

The generated sludge from El-Hannoville TP and Iskan Moubarak TP is

dewatered by centrifugation, with solid concentration of 25-30%, transported to 9N.

The Mex/Dekhila/Agamy WWTP is initially expected to produce 200 m3/d of

20% ds, increasing to 400 m3/d by 2025. This will be a conventional primary

sedimentation and activated sludge plant. The total quantity of sludge that will be

produced by Alexandria will be about 1,200 m3/d by 2015, equivalent to about

150,000 tds/y.

The produced composted sludge has an average of 34 % Organic matter, 3%

Total Nitrogen, 175 mg/kg available phosphorus. The heavy metals contents of the

compost are within the required limits of Egyptian regulations.

Sludge Treatment and Disposal system:

Site 9N is located 35 km west of Alexandria. The site receives sludge cake

from the MDF and grit, scum and screenings removed from the ETP and WTP. Grit,

sand and screenings generated from the ETP and WTP are transported to site 9N by

dump trucks. Currently, the total quantities transported of sludge are 83212 m3/year,

of sand is 7973 m3/year and of screenings is 1749 m

3/year, and from Industrial solid

waste 3338.85 m3/year according to values of year 2008/2009.

At Site 9N, a composting plant is established when the site was initially

developed as a dedicated disposal area for the sludge. Consequently, land spreading of

the sludge on the dedicated disposal area has ceased and all of the current production

of raw sludge is now being composted using the turned windrow technique as shown

in Figure (2).

Figure (2) : Composting Processes of Dewatered Sludge.

Mature compost is used as a bulking agent to improve the aeration of the

composting process and is mixed on a 1:1 volume basis with the fresh dewatered raw

sludge, delivered daily to Site 9N. Specialized windrow turners are used for mixing

the materials and for process (temperature, moisture) control in the windrows. Some

mixing and turning is also done by mechanical shovel. A 30-day period is allowed for

the active composting phase in windrows, following which the compost is removed to

a curing and stockpile area where it is allowed to mature for several weeks, but the

compost may be stored for many months before sale and use.

Based on these assumptions, 1 m3 of dewatered sludge is converted into 0.4

m3 of matured compost. Therefore, at the current sludge production level, compost

production is likely to be about 66,000 m3/y, rising to 184,000 m

3/y by 2015, and

234,000 m3/y by 2025, based on the estimated increases in sludge production

Assessment of the current Mechanical Dewatering Facility (MDF) conditions:

1- Hydrogen sulfide problems, which resulted from the septic condition of sludge at

the equalization tanks and different location of sludge dewatering operations, thus

affecting life time of the MDF components.

2- Produced quantities of dewatered sludge (30%) of the designed value.

3- Reduction in sludge dewatering production results in accumulation of the sludge in

the end effluent channel of the WTP, affecting primary treatment operation efficiency.

According to ASCDO committee (no. 931 dated 30/11/2008) recommended the

following to improve MDF performance:

1- Starting rehabilitation of current belt press components.

2- Keep the safe level of H2S concentration.

3- Repairing and operating the blowers to ensure continuous mixing of liquid sludge

in equalization tanks, homogenizing SS concentration and prevents septic

conditions.

4- operating MDF hydrogen sulfide control unit.

5- Rehabilitation of computer systems.

Control of odor emissions from the current wastewater treatment plants by

taking appropriate operating measures is not implemented to mitigate any

noncompliance.

It is a must to increase the efficiency of mechanical dewatering operations to

guarantee dewatering all sludge from primary treatment plants.

Assessment of Sludge/Solids Disposal Facility (9N)

Composting significantly reduces the volume of sludge. During the

composting process, there is a substantial loss of water during composting (reducing

from 70% to 10% moisture content) but the density of the product will become less

than that of the sludge because of its open texture (reducing from 1 to 0.7 m3/t). The

amount of dry solids will also be reduced through the mineralization of organic matter

(20% loss assumed). The volume of the compost will be increased by using matured

added to facilitate the composting process, but this is in effect internal relying within

Site 9N and so does not influence the net volume of compost produced for marketing.

The assessment indicated that the thermophilic composting temperatures of 55–65ºC

are evolved during composting. The temperature of the compost is stable within this

range for up to two months and is relatively insensitive to the frequency of turning.

The compost windrows do not require many turnings to maintain efficient processing,

which is desirable for moisture retention since high moisture loss is likely to limit

microbiological activity.

Sludge Handling, Treatment and Disposal

The goal of any wastewater residual solids disposal system is to dispose of

solids in a cost-effective manner that protects the public health and the environment.

Sludge disposal has historically been a major challenge in the wastewater

treatment field. Approximately half of the operation and maintenance costs for a

typical wastewater treatment operation are incurred in the sludge disposal processes.

Current means of disposal in use in the U.S. include incineration, landfilling, ocean

disposal and land spreading. All of these means have drawbacks; they are either too

costly to operate or they may create a potential threat to the public health and

environment. Therefore, an economical sludge disposal process that ensures

protection of public health and the environment must be developed.

Table (3) : Expected Sludge Production from different wastewater treatment plants

Area Treatment

plant

Amount of sludge produce ton/day (25% solids)

2010 2011 2012 2013 2014 2015

Wes

t

West TP 228 234 294 324 324 648

El Hannovile 60 60 60 60 60 60

Iskan Moubarak 18 25.2 25.2 25.2 25.2 25.2

Km 26 4.8 12 12 12 12 12

Km 21 180 192 204 216 216 216

Amrya 0 0 108 120 144 144

King Mariot 0 0 36 48 60 60

Abo talat 0 0 12 12 12 12

Borg Elarab (old) 52.8 52.8 52.8 52.8 52.8 52.8

Borg Elarab (new) 0 0 84 96 108 138

Ea

st

East TP 330 330 720 720 720 720

Elsiouf 8.4 8.4 8.4 8.4 8.4 8.4

Elmammoura 2.4 8.4 24 30 36 42

Khorshid 18 48 54 54 54 54

Abis (6TP) 21.6 21.6 21.6 21.6 21.6 21.6

Daily total 924 992.4 1716 1800 1854 2214

Monthly total 27723 29775 51483 54003 55623 66423

Annual total 337295 362261 626375 657035 676745 808145

Suggested scenario for Sludge management in Alexandria

This scenario aims to manage the sludge production in the near future 2015. All

Alexandria wastewater treatment plants will be in operation, so the sludge

management will depend on collection of all sludge produced from the new small

treatment plants and large treatment plants. Then, the dewatered sludge will be

transported to treatment sites by large vehicles in order to be treated and disposed.

Figure (3): Flow diagram of the sludge treatment by using windrow

composting

Figure (4) : Unloading of Sludge.

Figure (5) : Covering of dewatered sludge with composted sludge.

Figure (6): Turning of windrows with composting machine.

The steps of the plan could be as follows:

1- Sludge handling

a- The sludge produced from East wastewater treatment plants

The East Treatment plant is a central plant located east of Alexandria which will

produce around 720 ton/day dewatered sludge. The dewatered sludge produced from

all small treatment plants in the east of Alexandria will be collected there. The small

secondary treatment plants are:

• Maamoura T.P. will produce around 42 ton/day of sludge.

• Khorshid and Zawieda T.P will produce around 54 ton/day.

• EL seiouf T.P. will produce around 8.5 ton/day of sludge.

• The Abis treatment plants (six treatment plants) will produce around

21.5 ton/day of sludge.

b- Sludge produced from Amyria and Agami wastewater treatment plants

The sludge produced from Iskan Moubarak T.P. (will be around 25 ton/day) and will

be transported to Amyria T.P. which will produce around 144 ton/day. All sludge

produced from both treatment plants will be transported to site 9N.

c- The Km 21 treatment plant which will produce around 216 ton/day of sludge will

be the collection point of sludge produced from both Hannoville T.P. and Km 26 T.P.

• Hannoville T.P. will produce around 60 ton/day of sludge.

• Km 26 T.P. will produce around 12 ton/day of sludge.

d- The sludge produced from West wastewater treatment plants

The sludge produced from the West treatment plant will be around 648 ton/day which

will be transported directly to site 9N.

2- Sludge treatment system

Composting area of site 9N is 140 feddans which has been used for sludge

composting as shown on Figure (7).

Figure (7) : Location of Site 9N and the proposed extension area.

Site 9N is the most suitable location for composting operation, where it is downwind

of the near houses and can easily be managed as a composting area. The composting

area contains 180 windrows of 250 length, 1.5m height and 4m width. The distance

between each two windrows is 5 m. For building a windrow, 35 – 40 trucks

containing 20 m3 of sludge cake are required (700 m

3 – 800 m

3), construction of one

windrow takes from 2-3 days. The spoil material storage area is utilized for

emergency use. For adopting windrow composting method to treat non stabilized

primary sludge the windrows are covered after each turning with a 5 cm layer of

matured compost to minimize the flies' attraction, especially during first week of

composting period. Also, ten centimeters matured compost is used during

construction at the bottom to prevent septic condition at the lower layer of the

windrows.

The expected total quantity of dewatered sludge produced in Alexandria will be

around 2000 ton/day. This quantity will be sent to site 9N for treatment and disposal.

Currently Site 9N has two areas for sludge composting, south and north composting

areas 30 hectares each. In addition to a storage area of about 15 hectares. The total

capacity of sludge treatment at site 9N is about 150,000 tons, which is equal to sludge

produced from Alexandria treatment plants during 75 days. The sludge treatment

process takes three months (two months fermentation period and one month curing

period) which indicates that the composting area at site 9N is not enough to receive

the sludge in the nearest future (2015), therefore it is important to find another new

composting site with an area of about 200 feddans. The site suggested is the extension

of site 9N to the west direction which has a large unused desert area surrounded by

agriculture fields Figure (7). The suggested new site should be designed as the

follows:

1- Composting field 120 feddan serviced with ground and surface water

protection system.

2- Storage area about 40 feddan which must be beside the composting area.

3- Site utilities about 40 feddan which include the following:

- Administrative buildings

- Maintenance work shop.

- Temporary storing area for equipments.

- Equipment washing area.

- Roads and trees surrounding the site area. (as shown in Figures (8,9))

Figure (8): Suggested new site design.

North Composting area

South Composting area

Figure (9): Suggested new site after extension.

3- The sludge produced from Borg El -Arab wastewater treatment plants

The sludge produced from Borg El-Arab treatment plants -about 200 tons/day- will

need to be treated in situ, and so we need to establish two sites for sludge treatment in

Borg El-Arab city. The area of each sludge treatment site should be about 70 feddans,

60% of the proposed site should be used for sludge treatment, 20% for sludge storage

and 20% for traffic building and equipments. The suspected new site design is as the

follow as shown in Figure (10).

1- Composting field 42 feddan serviced with ground and surface water protection

system.

2- Storage area about 14 feddan which must be beside the composting area.

3- Site utilities about 14 feddan which include the following:

- Administrative buildings

- Maintenance work shop.

- Temporary storing area for equipments.

- Equipment washing area.

- Roads and trees surrounding all site.

Figure (10): Suggested new sludge treatment site for Borg ElArab.

The sludge management system of Borg El Arab city will depend on the characteristic

of each dewatered sludge batches. As a result of laboratory chemical analyses, batches

characterized with high contents of hazardous industrial waste must be collected and

transferred to site 9N for sanitary landfill. The batches satisfy with the Egyptian

criteria for sludge reuse especially in terms of heavy metals will loaded into windrow

composting area.

References:

1- Integrated Urban Water Management (IUWM), CEDARE/SWITCH project

(2010), "New Strategies for Wastewater Management and Reuse in

Alexandria in 2037"

2- Malina Joseph F.,. Sludge Handling, Treatment and Disposal Processes.

Workshop on Domestic wastewater treatment and sludge Disposal

processes. The American University in Cairo. 17-20 April 1995..

3- Sludge Handling and Conditioning, Operations Manual. U. S. EPA,

Washington, (1978).

4- Wastewater Research Group (WRC), Alexandria Effluent and sludge

Reuse Study . Alexandria, ARE., January 2000.

5- Wastewater Research Group (WRC), Alexandria Effluent and sludge

Reuse Study . Alexandria, Final Report March 2001.

6- Egyptian Code ECP 501-2005, (2005). “Egyptian standards for use of

treated wastewater in agriculture". World Academy of Science, Engineering

and Technology 57 2009.

7. Master plan of Alexandria wastewater system 2007)

8. M. Ghazy, T. Dockhorn, and N. Dichtl, Sewage Sludge Management in Egypt:

Current "Status and Perspectives towards a Sustainable Agricultural Use, World

Academy of Science, Engineering and Technology 57 2009.