Chapter 1Introduction

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1.0 Introduction

Industrial wastewater treatment covers the mechanisms and processes used to treat wastewater

that is produced as a by-product of industrial or commercial activities. After treatment, the

treated industrial wastewater (or effluent) may be reused or released to a sanitary sewer or to

surface water in the environment. Most industries produce some wastewater although recent

trends in the developed world have been to minimize such production or recycle such wastewater

within the production process. However, many industries remain dependent on processes that

produce wastewaters.

The principal objective of wastewater treatment is generally to allow human and industrial

effluents to be disposed of without danger to human health or unacceptable damage to the natural

environment. Irrigation with wastewater is both disposal and utilization and indeed is an

effective form of wastewater disposal (as in slow-rate land treatment). However, some degree of

treatment must normally be provided to raw municipal wastewater before it can be used for

agricultural or landscape irrigation or for aquaculture. The quality of treated effluent used in

agriculture has a great influence on the operation and performance of the wastewater-soil-plant

or aquaculture system. In the case of irrigation, the required quality of effluent will depend on

the crop or crops to be irrigated, the soil conditions and the system of effluent distribution

adopted. Through crop restriction and selection of irrigation systems which minimize health risk,

the degree of pre-application wastewater treatment can be reduced. A similar approach is not

feasible in aquaculture systems and more reliance will have to be placed on control through

wastewater treatment.

The most appropriate wastewater treatment to be applied before effluent use in agriculture is that

which will produce an effluent meeting the recommended microbiological and chemical quality

guidelines both at low cost and with minimal operational and maintenance requirements.

Adopting as low a level of treatment as possible is especially desirable in developing countries,

not only from the point of view of cost but also in acknowledgement of the difficulty of

operating complex systems reliably. In many locations it will be better to design the reuse system

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to accept a low-grade of effluent rather than to rely on advanced treatment processes producing a

reclaimed effluent which continuously meets a stringent quality standard.

Nevertheless, there are locations where a higher-grade effluent will be necessary and it is

essential that information on the performance of a wide range of wastewater treatment

technology should be available. The design of wastewater treatment plants is usually based on

the need to reduce organic and suspended solids loads to limit pollution of the environment.

Pathogen removal has very rarely been considered an objective but, for reuse of effluents in

agriculture, this must now be of primary concern and processes should be selected and designed

accordingly (Hillman 1988). Treatment to remove wastewater constituents that may be toxic or

harmful to crops, aquatic plant and fish is technically possible but is not normally economically

feasible. Unfortunately, few performance data on wastewater treatment plants in developing

countries are available and even then they do not normally include effluent quality parameters of

importance in agricultural use.

The short-term variations in wastewater flows observed at municipal wastewater treatment plants

follow a diurnal pattern. Flow is typically low during the early morning hours, when water

consumption is lowest and when the base flow consists of infiltration-inflow and small quantities

of sanitary wastewater. A first peak of flow generally occurs in the late morning, when

wastewater from the peak morning water use reaches the treatment plant, and a second peak flow

usually occurs in the evening. The relative magnitude of the peaks and the times at which they

occur vary from country to country and with the size of the community and the length of the

sewers. Small communities with small sewer systems have a much higher ratio of peak flow to

average flow than do large communities. Although the magnitude of peaks is attenuated as

wastewater passes through a treatment plant, the daily variations in flow from a municipal

treatment plant make it impracticable, in most cases, to irrigate with effluent directly from the

treatment plant. Some form of flow equalization or short-term storage of treated effluent is

necessary to provide a relatively constant supply of reclaimed water for efficient irrigation,

although additional benefits result from storage.

Wastewaters obtained from industries are generally much more polluted than the domestic or

even commercial wastewaters. Still, however, several industrialists try to discharge their

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effluents into natural river streams, through unauthorized direct discharges. Such a tendency, on

the part of industries may pollute the entire river water to a grave extent, thereby making its

purification almost an impossible task. Sometimes, the industries discharge their polluted

wastewaters into municipal sewers, thereby making the task of treating that municipal sewage, a

very difficult and costly exercise. The industries are, therefore, generally prevented by laws,

from discharging their untreated effluents. It, therefore, becomes, necessary, for the industry to

treat their wastewaters in their individual treatment plants, before discharging their effluents

either on land or lakes or rivers, or in municipal sewers, as the case may be. The characteristics

of the produced wastewater will usually vary from industry to industry, and also vary from

process to process even in the same industry. Such industrial wastewaters cannot always be

treated easily by the normal methods of treating domestic wastewaters, and certain specially

designed methods or sequence of methods may be necessary. In order to achieve this aim, it is

generally always necessary, and advantageous to isolate and remove the troubling pollutants

from the wastewaters, before subjecting them to usual treatment processes. The sequence of

treatment processes adopted should also be such as to help generate useful bi-products. This will

help economize the pollution control measures, and will encourage the industries to develop

treatment plants

1.1 Sources Of Industrial Waste Water

These are the sources of industrial waste water:-

1.1.1 Complex Organic Chemicals Industry

A range of industries manufacture or use complex organic chemicals. These

include pesticides, pharmaceuticals, paints, petrochemicals, detergents, plastics, paper pollution,

etc. Waste waters can be contaminated by feedstock materials, by-products, product material in

soluble or particulate form, washing and cleaning agents, solvents and added value products such

as plasticizers. Treatment facilities that do not need control of their effluent typically opt for a

type of aerobic treatment.

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1.1.2 Electric Power Plants

Fossil-fuel power stations, particularly coal-fired plants, are a major source of industrial

wastewater. Many of these plants discharge wastewater with significant levels of metals such

as lead, mercury, cadmium and chromium, as well as arsenic, selenium and nitrogen compounds

(nitrates and nitrites). Wastewater streams include flue-gas desulfurization, fly ash, and bottom

ash and flue gas mercury control. Plants with air pollution controls such as wet

scrubbers typically transfer the captured pollutants to the wastewater stream.

Ash ponds, a type of surface impoundment, are a widely used treatment technology at coal-fired

plants. These ponds use gravity to settle out large particulates (measured as total suspended

solids) from power plant wastewater. This technology does not treat dissolved pollutants. Power

stations use additional technologies to control pollutants, depending on the particular waste

stream in the plant. These include dry ash handling, closed-loop ash recycling, chemical

precipitation, biological treatment (such as an activated sludge process), and evaporation.

1.1.3 Food Industry

Wastewater generated from agricultural and food operations have distinctive characteristics that

set it apart from common municipal wastewater managed by public or private sewage

treatment plants throughout the world: it is biodegradable and non-toxic, but has high

concentrations of biochemical oxygen demand (BOD) and suspended solids (SS). The

constituents of food and agriculture wastewater are often complex to predict, due to the

differences in BOD and pH in effluents from vegetable, fruit, and meat products and due to the

seasonal nature of food processing and post-harvesting.

Processing of food from raw materials requires large volumes of high grade water. Vegetable

washing generates waters with high loads of particulate matter and some dissolved organic

matter. It may also contain surfactants.

Animal slaughter and processing produces very strong organic waste from body fluids, such

as blood, and gut contents. This wastewater is frequently contaminated by significant levels

of antibiotics and growth hormones from the animals and by a variety of pesticides used to

control external parasites.

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Processing food for sale produces wastes generated from cooking which are often rich in

plant organic material and may also contain salt, flavorings, coloring material and acids or alkali.

Very significant quantities of oil or fats may also be present.

1.1.4 Iron And Steel Industry

The production of iron from its ores involves powerful reduction reactions in blast furnaces.

Cooling waters are inevitably contaminated with products especially ammonia and cyanide.

Production of coke from coal in coking plants also requires water cooling and the use of water in

by-products separation. Contamination of waste streams includes gasification products such

as benzene, naphthalene, anthracite, cyanide, ammonia, phenols and cresols together with a

range of more complex organic compounds known collectively as polycyclic aromatic

hydrocarbons (PAH).

The conversion of iron or steel into sheet, wire or rods requires hot and cold mechanical

transformation stages frequently employing water as a lubricant and coolant. Contaminants

include hydraulic oils, tallow and particulate solids. Final treatment of iron and steel products

before onward sale into manufacturing includes pickling in strong mineral acid to remove rust

and prepare the surface for tin or chromium plating or for other surface treatments such

as galvanization or painting. The two acids commonly used are hydrochloric acid and sulfuric

acid. Wastewaters include acidic rinse waters together with waste acid. Although many plants

operate acid recovery plants (particularly those using hydrochloric acid), where the mineral acid

is boiled away from the iron salts, there remains a large volume of highly acid ferrous sulfate or

ferrous chloride to be disposed of. Many steel industry wastewaters are contaminated by

hydraulic oil, also known as soluble oil.

1.1.5 Mines And Quarries

The principal waste-waters associated with mines and quarries are slurries of rock particles in

water. These arise from rainfall washing exposed surfaces and haul roads and also from rock

washing and grading processes. Volumes of water can be very high; especially rainfall related

arising on large sites. Some specialized separation operations, such as coal washing to separate

coal from native rock using density gradients, can produce wastewater contaminated by fine

particulate hematite and surfactants. Oils and hydraulic oils are also common contaminants.

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Wastewater from metal mines and ore recovery plants are inevitably contaminated by the

minerals present in the native rock formations. Following crushing and extraction of the

desirable materials, undesirable materials may enter the wastewater stream. For metal mines, this

can include unwanted metals such as zinc and other materials such as arsenic. Extraction of high

value metals such as gold and silver may generate slimes containing very fine particles in where

physical removal of contaminants becomes particularly difficult.

Additionally, the geologic formations that harbor economically valuable metals such

as copper and gold very often consist of sulphide-type ores. The processing entails grinding the

rock into fine particles and then extracting the desired metal(s), with the leftover rock being

known as tailings. These tailings contain a combination of not only undesirable leftover metals,

but also sulphide components which eventually form sulphuric acid upon the exposure to air and

water that inevitably occurs when the tailings are disposed of in large impoundments. The

resulting acid mine drainage, which is often rich in heavy metals (because acids dissolve metals),

is one of the many environmental impacts of mining.

1.1.6 Nuclear Industry

The waste production from the nuclear and radio-chemicals industry is dealt with as radioactive

waste.

1.1.7 Pulp And Paper Industry

Effluent from the pulp and paper industry is generally high in suspended solids and BOD. Plants

that bleach wood pulp for paper making may generate chloroform, dioxins (including 2,3,7,8-

TCDD), furans, phenols and chemical oxygen demand(COD). Stand-alone paper mills using

imported pulp may only require simple primary treatment, such as sedimentation or dissolved.

Increased BOD or COD loadings, as well as organic pollutants, may require biological treatment

such as activated sludge or up flow anaerobic sludge blanket reactors. For mills with high

inorganic loadings like salt, tertiary treatments may be required, either general membrane

treatments like ultra filtration or reverse osmosis or treatments to remove specific contaminants,

such as nutrients.

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1.1.8 Industrial Oil Contamination

Industrial applications where oil enters the wastewater stream may include vehicle wash bays,

workshops, fuel storage depots, transport hubs and power generation. Often the wastewater is

discharged into local sewer or trade waste systems and must meet local environmental

specifications. Typical contaminants can include solvents, detergents, grit, lubricants and

hydrocarbons.

Insecticide residues in fleeces are a particular problem in treating waters generated

in wool processing. Animal fats may be present in the wastewater, which if not contaminated,

can be recovered for the production of tallow or further rendering.

1.2 Treatment of Industrial Wastewater

Some of the methods through which industrial waste water can be treated:-

1.2.1 Brine Treatment

Brine treatment involves removing dissolved salt ions from the waste stream. Although similarities to seawater or brackish water desalination exist, industrial brine treatment may contain unique combinations of dissolved ions, such as hardness ions or other metals, necessitating specific processes and equipment.

Brine treatment systems are typically optimized to either reduce the volume of the final discharge for more economic disposal (as disposal costs are often based on volume) or maximize the recovery of fresh water or salts. Brine treatment systems may also be optimized to reduce electricity consumption, chemical usage, or physical footprint.

Brine treatment is commonly encountered when treating cooling tower blow down, produced water from steam assisted gravity drainage (SAGD), produced water from natural gas extraction such as coal seam gas, acid mine or acid rock drainage, reverse osmosis reject, pulp and paper mill effluent, and waste streams from food and beverage processing.

Brine treatment technologies may include: membrane filtration processes, such as reverse osmosis; ion exchange processes such as electro dialysis or weak acid cation exchange; or evaporation processes, such as brine concentrators and crystallizers employing mechanical vapour recompression and steam.

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Reverse osmosis may not be viable for brine treatment, due to the potential for fouling caused by hardness salts or organic contaminants, or damage to the reverse osmosis membranes from hydrocarbons.

Evaporation processes are the most widespread for brine treatment as they enable the highest degree of concentration, as high as solid salt. They also produce the highest purity effluent, even distillate-quality. Evaporation processes are also more tolerant of organics, hydrocarbons, or hardness salts. However, energy consumption is high and corrosion may be an issue as the prime mover is concentrated salt water. As a result, evaporation systems typically employ titanium or duplex stainless steel materials.

1.2.2 Solids Removal

Most solids can be removed using simple sedimentation techniques with the solids recovered as slurry or sludge. Very fine solids and solids with densities close to the density of water pose special problems. In such case filtration or ultra filtration may be required. Although, flocculation may be used, using alum salts or the addition of polyelectrolyte.

1.2.3 Oils And Grease Removal

The effective removal of oils and grease is dependent on the characteristics of the oil in terms of its suspension state and droplet size, which will in turn affect the choice of separator technology.

Oil pollution in water usually comes in four states, often in combination:

free oil - large oil droplets sitting on the surface; heavy oil, which sits at the bottom, often adhering to solids like dirt; emulsified, where the oil droplets are heavily "chopped"; and dissolved oil, where the droplets are fully dispersed and not visible. Emulsified oil droplets

are the most common in industrial oily wastewater and are extremely difficult to separate.

The methodology for separating the oil is dependent on the oil droplet size. Larger oil droplets such as those in free oil pollution are easily removed, but as the droplets become smaller, some separator technologies perform better than others.

Most separator technologies will have an optimum range of oil droplet sizes that can be effectively treated. This is known as the "micron rating."

Analyzing the oily water to determine droplet size can be performed with a video particle analyzer. Alternatively, there are commonalities in industries for oil droplet sizes. Larger droplets greater than 60 microns are often present in wastewater in workshops, re-fuel areas and depots. Twenty to 50 micron oil droplets often are present in vehicle wash bays, meat processing

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and dairy manufacturing effluent and aluminium billet cooling towers. Smaller droplets in the range of 10 to 20 microns tend to occur in workshops and condensates.

Each separator technology will have its’ own performance curve outlining optimum performance based on oil droplet size. The most common separators are gravity tanks or pits, API oil-water separators or plate packs, chemical treatment via DAFs, centrifuges, media filters and hydro cyclones.

A very important step in water and in wastewater treatment is the coagulation flocculation

process, which is widely used, due to its simplicity and cost-effectiveness. Regardless of the

nature of the treated sample (e.g. various types of water or wastewater) and the overall applied

treatment scheme, coagulation-flocculation is usually included, either as pre-, or as post-

treatment step. The efficiency of coagulation-flocculation strongly affects the overall treatment

performance; hence, the increase of the efficiency of coagulation stage seems to be a key factor

for the improvement of the overall treatment efficiency.

1.2.4 Other Treatment Processes Are:- Activated sludge

Aerated lagoon

Agricultural wastewater treatment

API oil-water separator

Carbon filtration

Chlorination

Clarifier

Constructed wetland

Extended aeration

Facultative lagoon

Fecal sludge management

Filtration

Imhoff tank

Industrial wastewater treatment

Ion exchange

Membrane bioreactor

Reverse osmosis

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Rotating biological contactor

Secondary treatment

Sedimentation

Septic tank

Settling basin

Sewage sludge treatment

Sewage treatment

Stabilization pond

Trickling filter

Ultraviolet germicidal irradiation

UASB

Wastewater treatment plant

1.3 Wastewater Disposal And Reuse Option

Combined sewer

Evaporation pond

Groundwater recharge

Infiltration basin

Injection well

Irrigation

Marine dumping

Marine outfall

Sanitary sewer

Septic drain field

Sewage farm

Sewerage

Stabilization pond

Storm drain

Surface runoff

Water reclamation

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Chapter 2Literature Review

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2.0 Literature Review

A lot of literature is available on waste water treatment. Some of them are discussed here.

P. Krzeminski et al. (2016) membrane filtration using ultra filtration (UF), nano filtration (NF) or

reverse osmosis (RO) membranes was evaluated as an efficient effluent polishing step at

municipal wastewater treatment plants (WWTPs)for the removal of selected contaminants of

emerging concern and for improvement of water quality according to water reuse requirements.

Water quality improved further with application of NF and RO. The results indicate that

membrane filtration can be effective post-treatment to improve overall water quality and a

measure to reduce potential risk in the receiving aquatic environment. This will help in

controlling the environment from pollution and reduction in consumption of fresh water.

Mohammad Al-Harahsheh et al. (2016) collected water sample from an effluent pond of a

phosphoric acid plant and characterized for its physical and chemical properties. This water

contains valuable components the utilization of which can contribute to the conservation of

natural resources. The collected samples were subjected to a hybrid process of chemical

precipitation followed by nano filtration. As a result both sulphate and fluoride ions were

separated which are heavy metals in nature and cause adverse effect on our environment.

Mohidus Samad Khan et al. (2014) explains that monitoring of ETPs also makes good business

sense: if you have invested large amounts of capital in an ETP it is only sensible to monitor to

check that you are getting good performance from your ETP. If you do sufficient monitoring you

should be able to get enough data to allow you to optimize performance and this may mean that

you can reduce expenditure on energy and on chemicals. Although monitoring ETP performance

may appear expensive it is essential and the suggestions made are feasible and not excessive

when the effects of textile effluents on the environment and human health are considered.

Srebrenkoska Vineta et al. (2014) proposed End-of-pipe technologies are used for wastewater

treatment and include sequential application of a set of methods: coagulation / flocculation,

flotation, adsorption, evaporation, oxidation, combustion, use of membranes, etc, that has been

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adapted to the particular situation of a textile plant. As a result of which consumption of water

will be decrease.

Farooq Sher et al. (2013) used aluminium sulphate [Al2 (SO4)3] and anionic polyacrylamide

(Magnafloc155) were used as coagulant and flocculent respectively. Sulphuric acid (H2SO4) and

lime solution [Ca(OH)2] were used to adjust the pH values during the treatment process. A series

of jar tests were conducted with different values of pH and dosing amounts of coagulant and

flocculant. These jar testing results have been further proved by a successful pilot scale trial at

the polymer plant which indicates that the chemical coagulation and flocculation process is a

feasible solution for the treatment of effluent.

N. D. Tzoupanos and A. I. Zouboulis (2013) incorporates various additives, inorganic or organic,

results in an increment of molecular weight and components size, which compensates efficiently

the decrease of charge neutralization capability in the new coagulants. Overall they present better

treatment performance, lower residual metal concentration and wider effective pH range.

Long Yan et al. (2011) introduced Fe particle and air into a traditional two-dimensional reactor

for petroleum refinery waste water. The effect of Fe particle and air on the electrochemical

process, and the optimal experimental conditions including initial pH, cell voltage were

investigated. The experimental results showed that the effluent with a satisfied COD removal

efficiency and low salinity was obtained when the initial pH was 6.5, cell voltage was 12 V and

fine Fe particle was introduced.

E. Yuliwati et al. (2011) proposed the refinery wastewater process was conducted using an

experimental set-up consisted of an SMUF (submerged membrane ultra filtration) reservoir, a

circulation pump, and an aerator. In this experiment the influence of air bubble flow rate

(ABFR), hydraulic retention time (HRT), mixed liquor suspended solid (MLSS) concentration,

and pH on the performances of modified polyvinylidene fluoride (PVDF) was investigated. The

process performance was measured in terms of the membrane water flux and chemical oxygen

demand (COD) removal efficiency. Experimental results showed that a ultra filtration process

using modified PVDF membranes has a great potential for refinery produced wastewater

treatment.

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Khannous, L. et al. (2011) used ANOVA (Analysis Of Variance) analysis for the treatment of

effluent generated from pastas industries. The result shows that the control of the wastewater

temperature is important in the treatment process. In fact, an increase of temperature partially

destroys the current fauna and flora in the environment.

Yusuf Yavuz et al. (2010) introduced direct and indirect electrochemical oxidation by using

boron doped diamond anode (BDD). The results obtained from electrochemical methods were

compared to each other. Complete phenol and COD (chemical oxygen demand) removal can be

achieved in almost all electrochemical methods, except electro coagulation. Electro coagulation

was found to be ineffective for the treatment of PRW (Petroleum Refinery Wastewater).

M.J. Ayotamuno et al. (2007) treated flocculation effluent of liquid-phase oil-based drill-cuttings

(LPOBDCs) in a batch adsorption process, using powdered activated-carbon (PAC) in order to

improve the quality of the flocculation effluent before its surface injection. This flocculation is

very harmful to the environment and leads to environmental degradation because this

flocculation effluent contains high concentrations of chromium (Cr6+), which is a heavy-metal

pollutant. At the end of the process, the Cr6+ content was further reduced and shows a

significant improvement on the quality of the flocculation effluent.

J Roussy et al. (2005) used biopolymers (chitosan and tannin) to treat an ink-containing effluent

generated in the processing of packaging. The process was particularly efficient under acidic

solutions, the amount of coagulant and flocculant to be used were significantly reduced by

limiting the pH to 5.

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Chapter 3System Domain

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3.0 System Domain3.1 A typical coagulation and Flocculation system

Coagulation-flocculation is a chemical water treatment technique typically applied prior to

sedimentation and filtration (e.g. rapid sand filtration) to enhance the ability of a treatment

process to remove particles. Coagulation is a process used to neutralize charges and form a

gelatinous mass to trap (or bridge) particles thus forming a mass large enough to settle or be

trapped in the filter. Flocculation is gentle stirring or agitation to encourage the particles thus

formed to agglomerate into masses large enough to settle or be filtered from solution.

To separate the dissolved and suspended particles from the water coagulation and flocculation

processes are used. Coagulation and flocculation is relatively simple and cost-effective, provided

that chemicals are available and dosage is adapted to the water composition. Regardless of the

nature of the treated water and the overall applied treatment scheme, coagulation-flocculation is

usually included, either as pre-treatment (e.g. before rapid sand filtration) or as post-treatment

step after sedimentation (see also centralized water purification plants).

Fig.3.1 Coagulation

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3.2 Coagulation Principle

Coagulation destabilizes the particles’ charges. Coagulants with charges opposite to those of the

suspended solids are added to the water to neutralize the negative charges on dispersed non-

settable solids such as clay and organic substances.

Once the charge is neutralized, the small-suspended particles are capable of sticking together.

The slightly larger particles formed through this process are called microflocs and are still too

small to be visible to the naked eye. A high-energy, rapid-mix to properly disperse the

coagulant and promote particle collisions is needed to achieve good coagulation and formation of

the microflocs. Over-mixing does not affect coagulation, but insufficient mixing will leave

this step incomplete. Proper contact time in the rapid-mix chamber is typically 1 to 3 minutes.

Fig.3.2 Flocculation

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3.3 Flocculation

Flocculation, a gentle mixing stage, increases the particle size from submicroscopic microfloc to

visible suspended particles.

The microflocs are brought into contact with each other through the process of slow mixing.

Collisions of the microfloc particles cause them to bond to produce larger, visible flocs. The floc

size continues to build through additional collisions and interaction with inorganic polymers

formed by the coagulant or with organic polymers added. Macroflocs are formed. High

molecular weight polymers, called coagulant aids, may be added during this step to help bridge,

bind, and strengthen the floc, add weight, and increase settling rate. Once the floc has reached its

optimum size and strength, the water is ready for the separation process

(sedimentation, floatation or filtration). Design contact for flocculation range from 15 or 20

minutes to an hour or more.

3.4 Coagulation Flocculation Separation

In water treatment, coagulation and flocculation are practically always applied subsequently

before a physical separation. The Coagulation-Flocculation process consists of the following

steps:

Coagulation-flocculation: The use of chemical reagents to destabilize and increase the

size of the particles; mixing; increasing of flog size,

A physical separation of the solids from the liquid phase. This separation is usually

achieved by sedimentation (decantation), flotation or filtration.

The common reagents are: mineral and/or organic coagulants (typically iron and aluminium

salt, organic polymers), flocculation additives (activated silica, talcum, activated carbon…),

anionic or cationic flocculants and pH control reagents such as acids or bases. Certain heavy

metal chelating agents can also be added during the coagulation step.

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Fig.3.3 Typical Method of Flocculation

3.5 Jar Test

The jar test is used to identify the most adapted mix of chemical compounds and concentrations

for coagulation-flocculation. It is a batch test consisting of using several identical jars containing

the same volume and concentration of feed, which are charged simultaneously with six different

doses of a potentially effective coagulant. The six jars can be stirred simultaneously at known

speeds. The treated feed samples are mixed rapidly and then slowly and then allowed to settle.

These three stages are an approximation of the sequences based on the large-scale plants of rapid

mix, coagulation flocculation and settling basins. At the end of the settling period, test samples

are drawn from the jars and turbidity of supernatant liquid is measured. A plot

of turbidity against coagulant dose gives an indication of the optimum dosage (i.e. the minimum

amount required to give acceptable clarification). The criteria thus obtained from a bench jar test

are the quality of resultant floc and the clarity of the supernatant liquid after settling. The design

of the full-scale plant process is then done based on the bench-scale selection of chemicals and

their concentrations.

Unfortunately, the jar test suffers from a number of disadvantages, despite its widespread

application. It is a batch test, which can be very time-consuming. And the results obtained from a

series of jar tests might not correspond to the results obtained on a full-scale plant.

The jar test – a laboratory procedure to determine the optimum pH

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and the optimum coagulant dose

A jar test simulates the coagulation and flocculation processes

Fig.3.4 Flocs After Jar Test

Adjusting optimum pH for gaining economic amount of chemical usage for treatment

Fill the jars with raw water sample

(500 or 1000 mL) – usually 6 jars

Adjust pH of the jars while mixing

using H2SO4 or NaOH/lime(pH: 5.0; 5.5; 6.0; 6.5; 7.0; 7.5)

Add same dose of the selected Coagulant (alum or iron) to each jar (Coagulant dose: 5 or

10 mg/L)

Rapid mix each jars at 100 to 150 rpm for 1 minute. The rapid mix helps to disperse

the coagulant throughout each container

Reduce the stirring speed to 25 to 30 rpm and continue mixing for 15 to 20 mins. This

slower mixing speed helps promote floc formation by enhancing particle collisions,

which lead to larger flocs

Turn off the mixers and allow flocs to settle for 30 to 45 mins

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Measure the final residual turbidity in each jar

Plot residual turbidity against pH

Optimum pH: 6.3

Fig.3.5 Turbidity-Ph Graph

Optimum coagulant dose

Repeat all the previous steps

This time adjust pH of all jars at optimum (6.3 found from first test) while mixing using

H2SO4 or NAOH/Lime

Add different doses of the selected coagulant (alum or iron) to each jar (Coagulant dose:

5; 7; 10; 12; 15; 20 mg/L)

Rapid mix each jars at 100 to 150 rpm for 1 minute. The rapid mix helps to disperse the

coagulant throughout each container

Reduce the stirring speed to 25 to 30 rpm for 15 to 20 mins

Turn off the mixers and allow flocs to settle for 30 to 45 mins

Then measure the final residual turbidity in each jar

Plot residual turbidity against coagulant dose

Now the coagulant dose with the lowest residual turbidity will be the optimum coagulant dose

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Fig.3.6 Turbidity-Alum Graph

Optimum coagulant dose: 12.5 mg/L

Typical coagulants

Aluminum sulfate: Al2(SO4)3.14 H2O

Iron salt- Ferric sulfate: Fe2(SO4)3

Iron salt- Ferric chloride: Fe2Cl3

Polyaluminium chloride (PAC): Al2(OH)3Cl3

Aluminium Chemistry

With alum addition, what happens to water pH?

Al2(SO4)3.14 H2O Û 2Al(OH)3¯+ 8H2O + 3H2SO4-2

1 mole of alum consumes 6 moles of bicarbonate (HCO3-)

Al2(SO4)3.14 H2O + 6HCO3- Û 2Al(OH)3¯+ 6CO2 + 14H2O + 3SO4

-2

If alkalinity is not enough, pH will reduce greatly

24

Lime or sodium carbonate may be needed to neutralize the acid.

(Optimum pH: 5.5 – 6.5)

Iron Chemistry

FeCl3+ 3HCO3- Û Fe(OH)3¯+ 3CO2 + 3Cl-

With iron salt addition, what happens to water pH?

(Wider pH range of: 4 – 9; Best pH range of 4.5 – 5.5)

1 mole of FeCl3 consumes 3 moles of bicarbonate (HCO3-)

If alkalinity is not enough, pH will reduce greatly due to hydrochloric acid formation. Lime or

sodium carbonate may be needed to neutralize the acid. Lime is the cheapest.

3.6 Design of Flocculator (Slow & Gentle mixing)

Flocculators are designed mainly to provide enough inter particle contacts to achieve particles

agglomeration so that they can be effectively removed by sedimentation or flotation.

Fig.3.7 Mechanical Flocculator

3.7 Methodology

25

water treatment

Cross flow Flocculator (sectional view)

Plan (top view)

L

H

W

S.No. Chemical Name PPE To Be Used Solution Vs Water

1 Ferric Chloride

Mask

Goggle

Gum Boots

Chemical Suit

Nitrile Gloves

Ferric Chloride – 20

lits.

Water – 80 lits.

2 Lime Goggle

Gum Boots

Nitrile Gloves

Lime – 10 Kgs.

Water – 90 lits.

3 Polyelectrolyte Goggle

Nitrile Glove

PolyE – 10 gms.

Water – 100 lits.

Fig.3.8 Chemical Table

Fill the effluent in tank until top.

Fill the complete reaction tank with effluent then open the valve and allow the settling

(final) tank to fill i.e. 1000 lits.

Again fill the reaction tank up to the bottom rib of tank i.e. 200lits and open the valve.

In final tank there will be 1200lits. Effluent for treatment.

Do the dosing of ferric chloride solution and mix properly by mixture till the Ph value

becomes 2 to 3. Take the solution in glass biker and check Ph every time and maintain it.

Do the dosing of lime solution and mix properly by mixture till the Ph value become 6.5

to 7.5. Take the solution in glass biker and check Ph every time and maintain it.

Do the dosing of Polyelectrolyte solution and mix properly by mixture till the proper

formation of clots.

Checking of clots – Mix the polyelectrolyte in effluent in small quantity.

Take the effluent in biker and check the clot formation.

Once see the proper formation and then see the settling.

Settling should be in 5 to 10 min.

26

Wait for 2 to 2.30 hrs. to allow the treated effluent to settle down.

Once it settle down then start the sludge pump and collect the sludge in drying bed mean

while close the valve of equalization tank and open the valve of drying bed.

Collection of sludge in drying bed till the clear water coming to the bed.

Once the clear water coming to the bed then close the valve of drying bed and open the

valve of equalization tank which is place on drying bed.

Remove the all treated water from tank and tank is ready to make the next batch of the

effluent.

Fig.3.9 Typical Diagram Of ETP

3.8 Operation and Maintenance of Flocculator

The operation of coagulators, flocculators and clarifiers requires trained operators. Maintenance

work should be undertaken regularly. The key aspects of operation and maintenance of

coagulators, flocculators and clarifiers are:

Chemical stock: There should be a good stock (at least sufficient for one month of operation).

Dosing control: Correct dosing of coagulant chemicals is very important for efficient and

effective removal of suspended solids. Samples of raw water should be taken regularly, and

tested with a range of coagulant concentrations to determine the optimum dose rate of coagulant.

The results should be used to adjust the coagulant dose.

Rapid mixing of the water and coagulant chemicals at the point where the chemicals are added is

essential.

27

Flocculation should be achieved by gentle mixing so as to maximize the number of collisions

between suspended particles and flocs, without breaking the flocs up through rapid mixing.

Plant layout: The flocculator and clarifiers should be located close to one another and water

should flow slowly between them so as to not break up the flocs.

During the course of coagulation-flocculation treatment, a substantial amount of sludge coming

from the settling process is generated. This sludge can be reused as fertilizer for agriculture when

no toxic compounds are present. In the presence of toxic sludge the solid waste has to be treated

or disposed of in an environmentally proper manner.

Coagulation-flocculation Industrial grade aluminum sulphate (Al2(SO4)3 14H2O) was used as

the coagulant was used as the flocculant aid, respectively. The chemical compounds were

obtained from Fisher Scientific U.K. Ltd. They were prepared by dissolving the powder with

distilled water. The coagulation-flocculation experiments were carried according to Ghafari et al.

(2009) using the jar tests in 500 ml beakers. The sample was immediately stirred at a constant

speed of 200 rpm for 2 min (rapid mixing), followed by a slow stirring at 40 rpm for 10 min

(slow mixing). After preliminary investigations, the setting time was fixed at 30 min

3.9 Safety Instruction

Check all PPE before start any work.

Wear all the PPE before start the work. Use special PPE during work involving any

harmful chemicals.

Do not touch any equipment if you are not trained.

Follow all the safety procedure.

Before handling & Using chemical refer MSDS.

Always stand opposite site of wind direction while chemical pouring.

Use Eye Wash bottle when you feel any problem in eye and immediate report to

respective members.

Don’t do bypass anything.

Always use right PPE for right operation.

28

Fill incident report from in case of any incident.

If you are in any trouble ask ETP site Security guard to help.

29

Chapter 4

Problem Formulation

30

4.0 Problem Formulation

Major problems which are generated before the treatment is usage of chemicals for treatment.

Major problems which are generated after the treatment is sludge formation.

Particular pollutants can be removed from the wastewater using coagulation/flocculation, which

would otherwise be impossible without adding these chemicals.

Limited investment is required for these tanks and dosage units.  However, a major disadvantage

of this technique is the operational costs. In some cases, considerable quantities of coagulant and

flocculant are needed to achieve the required level of flocculation. A certain quantity of chemical

sludge is also formed, which is normally processed externally.  These costs can escalate,

particularly with large volumes of wastewater.

The correct dosage of chemicals is also very important for the process to work correctly. This is

not straightforward with wastewater with a widely varying composition. Effective buffering of

wastewater offers a good solution in this case.

4.1 Coagulation Reagents

Numerous chemicals are used in coagulation and flocculation processes. There are advantages

and disadvantages associated with each chemical. Following factors should be considered in

selecting these chemicals:

Effectiveness.

Cost.

Reliability of supply.

Sludge considerations.

Compatibility with other treatment processes.

Secondary pollution.

Capital and operational costs for storage, feeding, and handling. Coagulants and coagulant aids

commonly used are generally classified as inorganic coagulants and polyelectrolyte.

31

Polyelectrolytes are further classified as either synthetic-organic polymers or natural-organic

polymers. The best choice is usually determined only after jar test is done in the laboratory.

Following table lists several common inorganic coagulants along with associated advantages and

disadvantages.

4.2 Polyelectrolytes

Polyelectrolytes are water-soluble polymers carrying ionic charge along the polymer chain and

may be divided into natural and synthetic polyelectrolytes. Important natural polyelectrolytes

include polymers of biological origin and those derived from starch products, cellulose

derivatives and alginates. Depending on the type of charge, when placed in water, the

polyelectrolytes are classified as anionic, cationic or nonionic.

Anionic—ionize in solution to form negative sites along the polymer molecule.

Cationic—ionize to form positive sites.

Non-ionic—very slight ionization.

4.3 Major Problems Or Challenges Being Faced By Wastewater Management

Plant.

Energy Consumption

Energy consumption is one of the largest expenses in operating a wastewater treatment plant.

Wastewater treatment is estimated to consume 2 - 3% of a developed nation’s electrical

power, or approximately 60 tWh (terawatt hours) per year. In municipal wastewater treatment,

the largest proportion of energy is used in biological treatment, generally in the range of 50 -

60% of plant usage.

Staff

Operators of wastewater treatment facilities must be adequately trained and certified individuals.

They are on call 24 hours a day and are responsible for overseeing everything from pipe leaks

and valves to electrical and instrumentation equipment. This work becomes especially

demanding during changes in influent and seasonal changes.

Sludge Production

32

Sludge is the residue generated during physical, chemical and biological treatment. A major

environmental challenge for wastewater treatment is the disposal of excess sludge produced

during the process. 

Mechanical Issues

Mechanical issues refer to when an important piece of equipment is off line due to mechanical or

electrical problems. Mechanical can include pumps, screening equipment, blowers, clarifier, and

sludge handling equipment, or some other piece of instrumentation for process control or

measuring the flow. These also may include electrical problems such as lack of power, loss of

phase, power bumps, and lightning strikes, which can cause equipment to be off line due to

blown fuses, motors, wiring, and tripped breakers, or damage to the electrical switchgear

(breakers, starter contacts, starter coils etc.) motors or wiring.

Biological Issues

Biological issues are where the biomass has been affected and the bacteria are shocked, stunted,

or killed back and then begin starting over to rebuild sufficient bacterial numbers to break down

and clean the water. The biological treatment biomass consists of a mix of different bacteria,

algae, plant material, and other organisms that function together to remove the nutrients and

break down the proteins, amino acids, and other waste products in the sewage. This process is

described as Nitrification and Denitrification in the treatment process.

33

Chapter 5Proposed Plan for Dissertation- II

34

5.0 Purposed Plan for Dissertation- II

We will work according to the future scenario in which there will be some changes in the

composition of effluent because companies are changing the chemicals and oils which are used

for the process for cutting or machining of mechanical components.

There might be some changes will make in the rules and regulation of the legal requirement of

the establishment of ETP Plants in Mechanical Industry. So, we have to make establishment

according to the legal requirements and also for the sludge disposal.

Sludge disposal and usage of chemical for the treatment are the major hazards. Sludge and

chemicals impacts on our environment and also the health of the affected employees.

These above improvements will be done by the implementation of the following:-

Implement safety guidelines of the chemistry of the chemicals which are used in the mechanical

plant for cutting of components.

Storage of the chemicals and sludge would be according to the revised Factory’s Act 1948.

By giving trainings to the affected employees and also to the operator of the ETP plant will

minimize the risk of hazard and severity.

Conducting lab experiments will be taken according to the BSL(Bio Safety Level) in the

chemistry lab so that there should be less risk of hazards.

The Major focus on the future plan is on the emergency plan of the ETP.

If in case there will be any fire or disaster happened then what to do in that particular situation

because it will definitely damage the property and also harmful for the health of people and

serious impacts on our environment.

35

Chapter 6

References

36

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40