operation & maintenance manual for effluent treatment plant

8/19/2019 OPERATION & MAINTENANCE MANUAL FOR EFFLUENT TREATMENT PLANT

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OPERATION & MAINTENANCE

MANUAL

FOR

EFFLUENT TREATMENT PLANT(Capacity = 30 M3 /Hr.)

INSTALLED AT

XYZ INDUSTRIES LTD.

BY

AQUATECH ENGINEERING SERVICES LTD.


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Aquatech Engineering Services Limited

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GLOSSARY OF TERMSBiochemical Oxygen demand (BOD): The strength of the wastewater is often determined by

measuring the amount of oxygen consumed by microorganism like bacteria in biodegrading theorganic matter. The measurement is known as the Biochemical Oxygen Demand (BOD).

Microorganisms such as bacteria are responsible for decomposing organic waste. When organic

matter such as dead plants, leaves, grass clippings, cellulose components, manure, sewage, organic

waste like dyes, fats and oils, or even food waste is present in a water supply, the bacteria will

begin the process of breaking down this waste. When this happens, bacteria in aerobic process,

robbing other aquatic organisms of the oxygen they need to live, consume much of the available

dissolved oxygen.

If there is a large quantity of organic waste in the water supply, there will also be a lot of bacteria

present working to decompose this waste. In this case, the demand for oxygen will be high (due toall the bacteria) so the BOD level will be high. As the waste is consumed or dispersed through the

water, BOD levels will begin to decline.

Nitrogen and phosphates in a body of water can also contribute to high BOD levels. Nitrates and

phosphates are plant nutrients and can cause plant life and algae to grow quickly. When plantsgrow quickly, they also die quickly. This contributes to the organic waste in the water, which is

then decomposed by bacteria. This results in a high BOD level. The temperature of the water can

also contribute to high BOD levels. For example, warmer water usually will have a higher BODlevel than colder water. As water temperature increases, the rate of photosynthesis by algae and

other plant life in the water also increases. When this happens, plants grow faster and also die

faster. When the plants die, they fall to the bottom where they are decomposed by bacteria. The

bacteria require oxygen for this process so the BOD is high at this location. Therefore, increased

water temperatures will speed up bacterial decomposition and result in higher BOD levels.

When BOD levels are high, dissolved oxygen (DO) levels decrease because the bacteria are

consuming the oxygen that is available in the water. Since less dissolved oxygen is available in thewater, fish and other aquatic organisms may not survive. Textile mill wastewater possesses a very

high BOD like 400 – 600 mg/l. It is necessary to reduce this BOD value up to a level less than 30

mg/l before discharging them into the environment like canals or rivers. If a water body of high

BOD is discharged into the sea or very large river then off course the concentration of BODdecreases due to dilution and have little or no harmful effect on the aquatic life or environment.

Therefore if it is possible to discharge a highly toxic effluent in sea or large river no treatment is

necessary.

Though it was not mentioned, the dissolved oxygen (DO) is a highly significant parameter todefine the BOD or COD of a wastewater. The amount of oxygen present in a certain amount of

water in dissolved state is known as DO. It is normally expressed as mg/l. Water may contain DO

ranging from 0 to 18 mg/l but in most cases of normal waters, DO lies between 7-9 mg/l. Aquatic

lives require certain level of DO to survive in the water. In case of wastewater the microorganisms

require oxygen to consume the organic wastes. As a result the DO of water decreases

tremendously and becomes a threat to the life of aquatic species. Textile effluents possess very


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low DO, which is unsuitable for discharging to the environment. During treatment of wastewater

air is blown through the effluent when oxygen is dissolved in the effluent as a result DO level

raises and as the DO increases the BOD/COD decreases.

Chemical Oxygen Demand (COD): This is a means of measuring the ability of wastewater to

sustain aquatic life, essential for the preservation of the environment. It also enables proper

assessment of treatment plant performance. Aquatic organisms and animals require dissolved

oxygen to flourish. The Chemical Oxygen Demand (COD) test gives an indication of the impact

of discharge waters on aquatic life by measuring the oxygen depleting nature of the discharge

water.

COD is based on the fact that nearly all-organic compounds can be fully oxidized to carbondioxide with a strong oxidizing agent under acidic condition. COD is another common measure of

water-borne organic substances — the process of measuring COD causes the conversion of all

organic matter into carbon dioxide. For this reason, one limitation of COD is that it cannot

differentiate between biologically active and those which biologically inactive. One major

advantage of COD over BOD is that COD can be measured in just three hours where as BOD

measurement takes at least five days. The value of COD is always higher than BOD, this is

because BOD accounts for only biodegradable organic compounds while COD accounts for allorganic compounds e.g. biodegradable as well as no biodegradable but chemically oxidisable.

Total suspended Solids (TSS): TSS is mainly organic in nature, are visible and can be removed

from the wastewater by physical/ mechanical means e.g. screening and sedimentation. TSS is

measured by filtering a certain quantity of effluent and then drying the filtrate at certaintemperature e.g. 105

0C followed by weighing. TSS is expressed as parts per million or in

milligram/litre. The pore size of the filter paper is very important in estimating the TSS, thenominal pore size 1.58 micro metre.

Total Dissolved Solids (TDS): TDS are the solids that are actually in solution, similar for

example to mix sugar into hot coffee. Dissolved solids generally pass through the system

unaffected. TDS is the sum total of all of the dissolved things in a given body of water. It is

everything in the water that's not actually water. It includes hardness, alkalinity, cyanuric acid,

chlorides, bromides, sulfates, silicates, and all manner of organic compounds. Every time we add

anything to the water, we are increasing its TDS. This includes not only sanitizing and pH

adjusting chemicals, but also conditioner, algaecides, and tile and surface cleaners. TDS alsoincludes airborne pollutants and bather waste as well as dissolved minerals in the fill water. TDSis referred to as the total amount of mobile charged ions, including minerals, salts or metals

dissolved in a given volume of water, and is expressed in units of mg per unit volume of water

(mg/L), or as parts per million (ppm).

Where do Dissolved Solids come from?

Some dissolved solids come from organic sources such as leaves, silt, plankton, and dyes and

chemicals used in processing, sewage. Other sources come from runoff from urban areas, roadsalts used on street during the winter, and fertilizers and pesticides used on lawns and farms.


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Dissolved solids also come from inorganic materials such as rocks and air that may contain

calcium bicarbonate, nitrogen, iron phosphorous, sulfur, and other minerals. Many of these

materials form salts, which are compounds that contain both a metal and a nonmetal. Salts usuallydissolve in water forming ions. Ions are particles that have a positive or negative charge.

Water may also pick up metals such as lead or copper as they travel through pipes used to

distribute water to consumers.

The effectiveness of water purification systems in removing total dissolved solids will be reduced

over time, so it is highly recommended to monitor the quality of a filter or membrane and replace

them when required.TDS may be the most misunderstood factor in the whole field of chemical processing and publichealth. In most cases it is misunderstood because no one knows exactly what effect it is going to

have on any particular body of water. TDS is directly related to the purity of water and the quality

of water purification systems and affects everything that consumes, lives in, or uses water,

whether organic or inorganic, whether for better or for worse.

Different standards advise a maximum contamination level (MCL) of 500mg/liter (500 parts per

million (ppm)) for TDS, however for domestic water suppliers maintain the TDS within 150 ppm.Off course some water supplies exceed this level. When TDS levels exceed 1000mg/L it is

generally considered unfit for human consumption. Most often, high levels of TDS are caused by

the presence of potassium, chlorides and sodium. These ions have little or no short-term effects,

but toxic ions (lead arsenic, cadmium, nitrate and others) may also be dissolved in the water.

At low levels, TDS does not present a problem. In fact, a certain amount of TDS is necessary for

water balance. Hardness and Total Alkalinity are both part of TDS. For textile processing theacceptable value of TDS is around 65-150 mg/l. The standards for bath and swimming pool are

between 1,000 and 2,000 ppm, with a maximum of 3,000 ppm. For irrigation the acceptable valuesof TDS are around 1500 ppm. Use of fertilizers increases TDS of the environment.

When the water evaporates, it leaves behind all of the solids that had been dissolved in it. This

principle is used widely to measure the TDS of a particular body of water. When everything else

seems to be all right, and the water still acts unlawfully, check the TDS.

High TDS can result in corrosion of metal equipment and accessories, even though the water is

balanced.High TDS can cause eye and skin irritation, even though the pH is right and there are nochloramines in the water. High TDS can permit an algae bloom, even with 2-3 ppm chlorine

residual.

If we drink water of high TDS some of this will stay in the body, causing stiffness in the joints,

hardening of the arteries, kidney stones, gall stones and blockages of arteries, microscopiccapillaries and other passages in which liquids flow through our entire body.


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Microorganisms - Microscopic living objects, which require energy, carbon and small amounts of

inorganic elements to grow and multiply. They get these requirements from the wastewater and

the sun, and in doing so help to remove the pollutants.

pH – A term used to express the intensity of the acid or alkalinity source. pH represents the

effective concentration (activity) of hydrogen ions (H+) in water. This concentration could be

expressed in the same kind of units as other dissolved species, but H+ concentrations are much

smaller than other species in most waters. The activity of hydrogen ions can be expressed most

conveniently in logarithmic units. pH is defined as the negative logarithm of the activity of H+

ions:

pH = -log [H+]

where [H+] is the concentration of H

+ ions in moles per liter (a mole is a unit of measurement,

equal to 6.022 x 1023

atoms). Because H+ ions associate with water molecules to form hydronium

(H3O+) ions, pH is often expressed in terms of the concentration of hydronium ions. In pure water

at 22 C (72 F), H3O+ and hydroxyl (OH-) ions exist in equal quantities; the concentration of

each is 1.0 x 10-7

moles per liter (mol/L). Therefore, pH of pure water = -log (1.0 x 10-7

) = -(-7.00)

= 7.00. Because pH is defined as –log [H+], pH decreases as [H

+] increases (which will happen if

acid is added to the water). Since pH is a log scale based on 10, the pH changes by 1 for every

power of 10 changes in [H+]. A solution of pH 3 has an H

+concentration 10 times that of a

solution of pH 4. The pH scale ranges from 0 to 14. However, pH values less than 0 and greater

than 14 have been observed in very rare concentrated solutions.

The U.S. Environmental Protection Agency (U.S. EPA) sets a secondary standard for pH levels in

drinking water: the water should be between pH 6.5 and 8.5.

Very high (greater than 9.5) or very low (less than 4.5) pH values are unsuitable for most aquatic

organisms. Young fish and immature stages of aquatic insects are extremely sensitive to pH levels

below 5 and may die at these low pH values. High pH levels (9-14) can harm fish by denaturingcellular membranes.

Changes in pH can also affect aquatic life indirectly by altering other aspects of water chemistry.

Low pH levels accelerate the release of metals from rocks or sediments in the stream. These

metals can affect a fish’s metabolism and the fish’s ability to take water in through the gills, and

can kill fish fry.

The term "pH" was originally derived from the French term "pouvoir hydrogène," in English, this

means "hydrogen power." The term pH is always written with a lower case p and an upper case H.

Sludge-The settable solids separated from the liquid during sedimentation (clarification). The

sludge is very toxic in nature and needs to be dealt with very carefully. Under no circumstances it

should be mix with the environment again.


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1.

INTRODUCTIONAquatech Engineering Services, Dhaka, have prepared this operating and maintenance manual for

the Effluent treatment plant installed at ……………………., Chandora, Kaliakoir, Gazipur. Itrepresents the methodology of process operation of the effluent treatment plant and maintenance

of the plant equipments. The manual will be helpful to run the effluent plant effectively and

efficiently.

Every effluent treatment plant is unique with respect to its process flow sheet. This is because the

treatment scheme is adopted on the basis of design and input characteristics of the effluent as well

as the stipulated pollution level of the treatment. This in turn depends on the type of process, type

of generated waste, whether the treated waste will be discharged or recycled, the nature of waterreceiving body where the treated waste will be discharged (if any) and the pollution laws of the

concerned pollution authority. It must therefore be appreciated that effluent treatment plants are

tailor- made, and hence the mode of operation would be specific for the treatment envisaged.

The operating manual serves as an important guideline for the operating personnel responsible for

the start- up and maintenance of the equipment and facilities provided in the plant. The instruction

presents in this manual are based on the experience in operation of such plants. However, due tovariable nature of the effluents encountered in each plant, certain modification of processoperation may be necessary depending on the degree of variation in the raw effluent quality and

quantity.

This manual includes a brief description of the basis of design of the ETP, the adopted treatment

philosophy and the principles of treatment involved. The plant was designed to treat effluents

generated from the various sections of the knit fabric dyeing and finishing plant. The scheme

envisages treatment of two separate wastewater streams namely the less contaminated water and

more contaminated water. The less contaminated effluents are allowed to bypass many stagesbefore uniting together again with mainstream and finally discharged to the environment. This has

been done deliberately to reduce the treatment time and operating cost.


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2. Basics of effluent treatmentEnvironmental problems of the textile industry are mainly caused by discharges of wastewater.

Textile processing employs a variety of chemicals, depending on the nature of the raw materialand end product. Some of these chemicals are different enzymes, detergents, dyes, acids, sodas

and salts. Industrial processes generate wastewater containing heavy metal contaminants. Since

most of the heavy metals are non-degradable into non-toxic end products, their concentrations

must be reduced to acceptable levels before discharging them into the environment. Other wise

these could pose threats to public health and/or affect the aesthetic quality of portable water.

According to World Health Organization (WHO) the metals of most immediate concern are

chromium, zinc, iron, mercury and lead. Various types of treatment processes are adopted to dye

or print or finish the textile materials. Different types of textile process could generate differenttypes of effluent. Table 1.1 shows the Characteristics of wastewater produced by a typical knit

dyeing industry.

Table 1.1: Characteristics of Process Waste Streams of Knit dyeing and finishing.

SL.NO Processing

Unit

Possible pollutants

in the waste water

Waste water

volume

Nature of

waste

Water

01 Scouring NaOH,,Waxes, grease

Na2Co3, Na2O2, SiO2 And fragments of cloth.

Small 10 L/ kg

of cloth

Strongly alkaline,

dark color, highBOD (30% of

total)

02 Bleaching NaOCl, Cl2, NaOH,H2O2, Acids etc.

Mostlywashing

Alkalineconstitutes, approx

5 % of BOD

03 Dyeing Various dyes, salts,

alkalies, Acids,

Na2S,Na2S2O2 and soap

etc.

Large Strongly colored,

fairly BOD (6 %

of the total)

04 Finishing Different finishing agent, Very small Low BOD

The above table shows the detail discharges at various stages of processing, however the

overall discharges of a Knit Dye house are as follows;

Color (organic substance), Na2 SO 4 (inorganic), NaOH, NaHOCl (Sodium hypochlorite), Na2 SO 3,

Surfactant (LAS, BIAS, CIAS), (NH)3 SO4, H2O2,CH3COOH (Organic), paraffin (organic),

Cellulose, Oil (Organic), Soap (Organic); all these things are COD and BOD.

The fate of the above mentioned pollutant chemicals vary, ranging from 100% retention on the

fabric to 100% discharge with the effluent. Generally, a wet processing industry generates

wastewater possessing various level of toxicity. Textile finishing industry uses large amounts of


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water, mainly because of washing operations. If these wastewaters are discharged into the

environment they will cause serious and harmful impact not only on under ground and surface

water bodies and land in the surrounding area but also will have an adverse effect on the aquaticecological system. Effluents from textile mills also contain various types of metals, which has a

cumulative effect, and higher possibilities for entering into the food chain and may cause various

types serious diseases. Due to usage of dyes and chemicals, effluents are dark in colour, which

increases the turbidity of water body. This in turn hampers the photosynthesis process, causing the

death of many aquatic plants. If aquatic dyes then more oxygen will be required to consume them

by bacteria thus causing a reduction of dissolve oxygen in the water. Various types of dyes are

used in dyeing of various types of textiles fibres. Fixation capability of different dyes is different.

The higher the fixation capacity the lower is the pollution problem. Table 1.2 shows the quantityof unfixed dyes and pollutants of various colouration processes while table 1.3 shows the degreeof fixation of various dyes.

Table 1.2: Type of pollution associated with various coloration processes.

Fibre Dyes Class Type of pollution

Cotton Direct Dyes 1. Salts

2. Unfixed dye (5 – 30 %)

3. Copper salts, Cationic-fixing agents.

Cotton Reactive Dyes 1. Salts

2.

Alkali3. Unfixed dye (10 –40 %)

Cotton Vats Dyes 1. Alkali

2. Oxidizing agents3. Reducing agents

Cotton Sulphurs Dyes 1. Alkali

2. Oxidizing agent

3. Reducing agent

4. Unfixed dye (20 –40 %)

Polyester Disperse Dyes 1. Reducing agent

2. Organic acid

3.

Unfixed dye (5 – 20 %


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Table 1.3: Degree of fixation of various dyes.

Class of dye Degree of fixation (%)

Sulphur 60-70

Vat 80-95

Azoic 90-95

Reactive 50-80

Disperse 80-92

Pigment 99

1:2 Metal Complex Dyes on wood 95-99

Basic 97-98

Acid 80-93

The pollution level of textile wastewater is expressed in terms of BOD, COD, TSS, TDS, heavy

metals and also temperature of the discharging effluent. At higher temperature the rate of transferof gaseous oxygen into dissolved oxygen is reduced on the other hand at high temperature theactivities of various aquatic species increases so that they require greater amount of oxygen. Thusat high temperature the demand of oxygen increases while its supply decreases.

Various types of dyes and chemicals are used in textile wet processing industry. The pollution

capabilities of different chemicals are different. Some are highly polluted while some are less

polluted. Table 1.4 shows the pollution capability of various types of dyes and chemicals in textile

wet processing.

Table 1.4: Pollution capability of some of the chemicals/ products used in the Textile

Industry.

General Chemical Type Difficulty of Treatment Pollution

Category

Alkalies, Mineral acids Oxidizing agents Relatively harmless.

Inorganic pollutants. 1

Starch sizes, Vegetable oils, fats and waxesBiodegradable surfactants, Organic acidsReducing agents

Readily biodegradable. 2

Dyes and fluorescent brighteners

Fibres and polymeric impuritiesPolyacrylate sizes, Synthetic polymer finishes,

Silicones

Dyes and polymers,

Difficult to biodegrade.3

Wool grease, PVA sizes, Starch ether and esters,

Mineral oil, Surfactants resistant to

biodegradation, Anionic and nonionic softeners.

Difficult to biodegrade,

Moderate BOD. 4

Formaldehyde and methylol reactants

Chlorinated solvents and carriers

Unsuitable for

conventional


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Cationic retarders and softeners

Biocides

Sequestering agents, Heavy metal salts

biological treatment,

negligible BOD.

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The level of the polluting parameters is very high in textile mill wastewater as compared to the

their acceptable values recommended by the Department of Environment, Government of PeoplesRepublic of Bangladesh (GOB). Off course the acceptable level of the pollutants varies somewhat

form country-to-country and even within the country. The main reason for this is the wastewater-

receiving environment. If the effluent is discharged into a very big river or sea in that case vary

little or no treatment is necessary as the wastewater will have very little or no effect on such alarge water body. However if the same effluent is discharged into a small river or canal in that

case off course it will be necessary to treat the wastewater since the effluent will have significant

effect on the receiving water. Table 1.5 shows the values of the important pollutants found in the

wastewater of the ……………… Apparels Limited Table 1.6 shows the acceptable values of the

above pollutants of wastewater suggested by the Department of Environment, GOB. It will be

seen in table 1.5, that reference has been made about a range rather than a particular value of the

parameters. This is because the characteristics of textile wastewater are not always same which is

due to the variation of raw materials, dyes and chemicals etc. For example a factory sometimeprocess 100% cotton and sometime process 50/50 cotton & polyester blend or even 100 %

polyester. The three different cases will require different dyes and chemicals. For white goods no

dyes are used at all, in that case the effluent characteristics will be different from that of dyedeffluent. For sized fabrics the effluent characteristics will be different from that of knit fabrics.

The values shown in table 1.5 are presented from our long time experience about the effluent

characteristics of similar plants. The ETP is designed in a such a way so that if the your factory

changes the processing nature to some other products, even then the etp will be able to handle the

treatment efficiency without any problem.


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Hydraulic diagram of the plant


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3. Basis of the Plant Design3.1 Source

The raw effluent shall be discharge to the proposed effluent treatment plant from the dyeing and

finishing section of the ……………..Apparels Limited.

3.2 Quantity

The quantity of effluent to be treated shall be of the order of = 960 m3 / day.

3.3 Capacity of the Effluent Treatment Plant (ETP).

The effluent treatment plant has been designed on the basis of the following

• Dyeing capacity is 10,000 kg /day

• Contaminated effluent is 50%

• Less Contaminated effluent is 50%

• Operated continuously for 18 hours a day.

• Flow rate of treatment envisaged is 30 m3 / hr.

3.4 Inlet Effluent Characteristics

Sl.No Parameters Unit Values1 PH 8 –14

2 BOD mg/L 400 - 600

3 COD mg/L 800 - 1,200

4 TSS mg/L 200 - 500

5 TDS mg/L 3,000 - 6,000

6 OIL & GREASE mg/L 30 – 60

7 COLOUR Co-pt unit Dark Mixed

8 TEMPERATURE0C 60

0 C

3.5 Outlet Effluent Characteristics-Bangladesh Standard

Sl.

No.

Water quality

parameters

Unit Standard value for discharging into *

Inland river On land for irrigation

1 PH ---- 6-9 6-9

2 BOD mg/L


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4. Treatment PhilosophyAs was mentioned the method of treatment of wastewater varies a lot. It mainly depends on the

characteristics of effluent, volume of effluent, level of toxicity to be removed and the type of

environment to receive the effluent. It was also suggested by some standards that the effluent

might require very little or no treatment at all if the effluent is discharged into a very large river or

sea. The treatment process that has been adopted for the Effluent Treatment Plant installed at

……………………….. Limited is known as physico chemical and followed by biological. Thephysico chemical process consists of screening, coagulation and flocculation and sedimentation.

The physico chemical process removes a substantial part of all the parameters shown in table 3.4

The biological treatment is responsible for removal of the rest of the removable BOD and some

COD as well. The biological treatment is carried out by moving bed biofilm reactor (MBBR) inthe biological tank. MBBR is a new concept of wastewater treatment and was developed by a

Norwegian company known as AnoxKaldnes’. MBBR is a highly efficient method of reducing

the BOD of a body of wastewater.

Figure 1: Moving bed plastic media Figure 2: Bacteria in the plastic media

Figure 3: Bacteria in the plastic media Figure 4: Bacteria in the plastic grid media


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The MBBR™ biofilm technology is based on specially designed plastic biofilm carriers or

biocarriers that are suspended and in continuous movement within the biological tank or reactor of

specified volume. The design of associated aerators, grids, sieves, spray nozzles and other integralparts to the reactor is also of great importance in making up the system as a whole. The system is

suitable for treating both industrial as well as municipal wastewater. The textile effluent is led to

the MBBR treatment reactor where biofilm, growing within the internal structures of the

biocarriers, degrade the pollutants. These pollutants that need to be removed in order to treat the

wastewater are food or substrate for growth of the biofilm. The biocarrier design is critical due to

requirements for good mass transfer of substrate and oxygen to the microorganisms and there is a

continuous R&D in the area of the MBBR biofilm technology. Excess biofilm sloughs off the

biocarrier in a natural way. An aeration grid located at the bottom of the reactor supplies oxygen tothe biofilm along with the mixing energy required to keep the biocarriers suspended andcompletely mix within the reactor.

Treated water flows from reactor through a grid or a sieve, which retains the MBBR™ biocarriers

in the reactor. The various stages of the plant treatment procedure is elaborated as follows;

After biological treatment the effluent is passed through sand filter and finally though the activated

carbon filter. The activated carbon filter is highly successful in removing BOD, COD, TSS, TDS& color of the effluent.

4.1. PRE-TREATMENT

4.1.1 Screening - to remove coarse materials

4.1.2 Equalization & Skimming - to remove grease & oil and homogenize and to remove

some BOD & COD.

4.2. PRIMARY TREATMENT

4.2.1 Coagulation - to coagulate the suspended solid to coagulate

4.2.2 Flocculation - to flocculate by coagulants

4.2.3 Neutralization - to adjust the pH between 6.5 to 8.5

4.2.4 Sedimentation – to precipitate small suspended solids

All the above processes contribute to removal of substantial amount of all the polluting

parameters.


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4. 3. SECONDARY TREATMENT

Biological treatment (MBBR)- to remove BOD and COD & to decompose organic matter.

4. 4. TERTIARY AND OTHER TREATMENTS

4.4.1 Granular Media Filtration-to removes TSS and any other pollutants in the form

of particle. This filter is also useful to protect the Activated Carbon Filter (ACF)

from overloading by pollutants such as particulates, organics.

4.4.2 Activated Carbon Filter- Carbon adsorption is a proven process in tertiary

treatment for the processing biologically treated wastewaters, and is one of themany processes used in the advanced treatment of wastewaters. The ACF is used

to remove relatively small quantities of refractory organics, as well as inorganic

such as sulfides and heavy metals remaining in an otherwise well-treated

wastewater.

4. 5. SLUDGE MANAGEMENT & DISPOSAL

4.5.1 Sludge disposal – to separate the sludge from the thick slurry and then dispose of

the sludge as dried cake

5. PROCESS FLOW CHART


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6. Operational Processes


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6.1.Pre-Treatment

The effluent generated in a textile wet processing plant can be broadly classified into two classese.g i) Less contaminated and ii) Highly contaminated. The Less contaminated waters are mainly

generated due to machine washing, floor cleaning, waters coming from the last washing cycles etc.

These less contaminated waters pose very little threat to the environment; therefore they can be

discharged directly to the environment or may require little treatment. If however these waters are

mixed with the main effluent, then the volume of total effluent will be very high and as a resultoverall install capacity running cost of the ETP will be very high. Therefore the less contaminated

waters are stored in a separate tank and from time to time the effluent is pumped to the sand filter

followed by carbon filter and finally to the discharge outlet. The more contaminated waters are

guided through the bar screen to the equalization tank for various treatments.

6.1.1 Screening (To remove coarse and float materials.)

The raw waste water (Raw Effluent) from the process of the plant would first be screened through

a manual bar screen strainer channel, where all particles with dia.> 5 MM as well as small pieces

of the fiber and floating suspended matters like polythene paper, polythene bags, rags and othersmaterials are removed by bar screen net. The bar screen consists of parallel rods or bars and is also

called a bar rack. These devices are used to protect downstream equipment such as pumps, lines,

valves etc. from damage and clogging by rags and other large objects. The bar screen is cleanedmanually by means of rakes. The screening is disposed off suitably after they are de-watered. The

screened clean effluent flows by gravity to an equalization tank.

6.1.2 Equalization and Skimming (To remove grease & oil and homogenize)

The raw wastewater from the screen channel is collected in the equalization tank, where it is

equalized with respect to its characteristics, homogeneity, flow and an uniform pollution load as

well as to make bacteria acclimatized. High-speed aerating devices are fixed at the bottom of the

equalization tank, which blows air through the waste at a rate about 0.1 CUF of air per gallon of

effluent. The rising air tends to coagulate the grease and oils and cause them to rise to the surface

where they can be removed by a scraper mechanism. Besides, the airflow accomplishes a proper

equalization of both varying loading and fluctuating PH values. The equalization tank is designedfor hydraulic retention time of around 6 hours. Certain amount of COD will also be removed by

the dissolved air flotation process. The following benefits are derived from the flow equalization

process;

1. Biological treatment is enhanced, as the shock loadings are eliminated or minimized, inhibiting

substances diluted, and pH stabilized.

2. Chemical treatment is improved if chemical dosing is controlled to provide consistentperformance

3. The effluent quality and thickening performance of secondary sedimentation units are improved

through constant solids loading.


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4. Effluent surface area requirements are reduced, filter performance is better, and more uniform

filter-backwash cycles are possible.

6.2. Primary-Treatment

6.2.1 Coagulation and Flocculation (To remove color and effluent suspended)

The homogenized effluent will then be pumped to a flash-mixing tank followed by a flocculation

tank. In the flash-mixing tank coagulants like lime (Calcium Hydroxide) and flocculants like ferrous sulfate (FeSO4) are dosed. This is done for coagulation and removal of the total dyeparticles. The basic idea of adding coagulant is to bring together all the suspended and dye

particles so that they can be precipitated out in the flash mixing tank and flocculation tank bycoagulation and flocculation mechanism. The chemical reaction that occurs in the coagulation and

flocculation process is shown below;

CaO + H2O Ca (OH) 2

The above reaction take place in lime dosing tank when lime reacts with water and we get calcium

hydroxide solution. This solution reacts with the ferrous sulphate solution, which as follows

Ca (OH) 2 + FeSO4 CaSO4 + Fe (OH) 3

+ FeSO4 (Unreacted) + Fe (OH) 2

Adequate quantity of polyelectrolyte polymer solution is dosed in the flocculation tank to enhance

the process of colour removal by the flocculation process. A substantial amount BOD and COD

etc. are removed in the coagulation and flocculation process.

6.2.2 Precipitation and Sedimentation in Tube Settler -1. (To remove the flocs materials)

From the flocculation tank the effluent is taken by natural gravity in to the tube settler- 1 tank

where the dyes and suspended particles are precipitated. The flocs formed are removed in the

downstream tube settler –1 by the help of tube settler media. The effluent will further flow by

overflow system to the pH correction tank where requisite quantity of acid will be dosed and pH

will be adjusted as per the requirement.

6.2.3 pH Correction (To adjust the inlet pH)

The effluent from tube settler- 1 tank is then taken by overflow method to the pH correction

channel for neutralization, where 33% HCl acid is dosed for neutralizing the pH value around 7 to

8. The pH correction channel is designed for hydraulic retention time of around 1 -2 minutes and

is provided with slow speed agitator for thoroughly mixing of waste with acid to maintained pHvalue.

6.3 Secondary-Treatment


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6.3.1 Biological Treatment in the Fluidized Aerobic Bio-Reactor (also called MBBR) # 1 & 2

(To reduce the remaining BOD / COD aerobically).

The neutralized effluent is then taken by gravity in to the biological treatment aeration tank for

biological degradation of available organic matter to reduce the remaining BOD and COD

aerobically. The biological treatment tanks are designed on extended aeration principle. The

fluidized Aerobic Bio-Reactor I & II includes two tanks of any shape filled up with small carrier

elements. The two tanks are also called Moving Bed Biofilm Reactor (MBBR). The media

elements are made up of special grade plastic of controlled density such that they can be fluidized

using an aeration device. In course of treatment a bio-film develops on the elements, which move

along with the effluent in the reactors. The movement within the reactors is generated byproviding aeration with the help of diffusers placed at the bottom of the reactor. The thin bio-film

on the elements enables the bacteria to act upon the biodegradable matter in the effluent and

reduce the BOD content while the rapid and turbulent movement of the effluent in the presence ofoxygen available from the air, certain amount of COD is also removed. The chemical reactions

that took place in the FAB reactor can be defined according to the following three processes;

A. Oxidation process

COHNS + O2 + Bacteria + DAP & UREA CO2 + NH3 + Energy

+ Other end Products

DAP and Urea is used as food for the microorganism.

B. Synthesis Process

COHNS + O2 + Bacteria C5H7NO2 (New bacteria)

C. Endogenous Respiration

C5H7NO2 + 5O2 CO2 + NH3 + 2H2O

Apart from the above basics reaction there are some other reactions that take place in the FAB

reaction tanks. During aeration the oxygen reacts with C, S and N which is shown below.

C + O2 CO2

S + O2 SO2

N + O2 NO2


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Some untreated ferrous sulfate and ferric hydroxide reacts with oxygen and the reactions are as

follows,

FeSO4 + O2 Fe2 (SO4) 3

Fe (OH) 2 + O2 Fe (OH) 3

When the plant is kept shut down for short period of time, at that time, off course, it will be

necessary to continue the aeration of Biological reactor 1 & 2. The biological degradation process

in enhanced by the adding some Dia-mmonium Phosphate (DAP) and UREA, which acts as food

for the microorganism. Therefore it will be necessary to supply food for the bacteria. Thus a

combined solution of Urea and DAP are dosed in the biological tank to feed the bacteria.

6.3.2 Tube Settler –2 (To remove the biological solids generation. )

From the biological reactor the treated effluent flows by gravity to the tube settler –2. The

biological solids generated are removed from the tube settler –2 by the help of tube settler media.

6.3.3 Filter Feed Sump (To collect effluent for next processes)

The treated effluent from tube settler- 2 overflow in to the filter feed sump. From the filter feed

sump the effluent is pumped to the pressure sand filter at first and then through activated carbon

filter. From here the disinfected effluent is pumped by means of the pressure sand filter feed pump

to the pressure sand filter. The pump is normally operated in automatically with interlock to thelevel switch in the filter sump.

6.3.4 Pressure Sand Filter (To remove suspended matter)

From the filter feed sump the effluent is pumped to the pressure sand filter. The filtration takes

place in the downward mode. The filter is filled with a layer of graded sand media supported by a

layer of graded gravel. The suspended matters in the effluent are filtered out in this unit; the

effluent is then flown into the activated carbon filter.

It was mentioned in the section 6.1 that the less contaminated waters are collected in the separate

tank and then pumped to the sand filter tank followed by carbon filter and discharge outlet. It isnecessary to backwash the sand filter every eight hours.

6.3.5 Activated Carbon Filter (To absorbed the dissolved organic matter)

The treated and filtered effluent from the pressure sand filter flows into the activated carbon filter.

In this unit too the feed flow is downward through a layer of granular activated carbon filter in

which dissolved organics of the effluent are absorbed. It is necessary to backwash the carbon filterevery eight hours.

6.3.6 Treated Effluent Disposed Off (Ready for disposed off)


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The treated effluent emerging from the ACF is directly disposed off through the out let channel to

environment.

6.3.7 Sludge Treatment and handling

The sludge generated in the flash mixing tank, flocculation tank, tube settler-1, tube settler-2 and

biological reactor is taken to a sludge sump. Here also aeration is carried out. The waste is then

pumped to a Sludge Thickener tank where the sludge is concentrated at the bottom of the tank.

The thickened sludge from the thickener is pumped to centrifuge pump for de-watering. At first

the centrifuge is started and then the thickener feed pump is started. As the slurry of sludge flowspolyelectrolyte solution is dosed in the centrifuge as a result the sludge will be separated from thewater. The centrifuge is run for 20 to 30 minutes and then switched off.

The de-watered sludge is transformed into cake form. The dried cake may be disposed of to

deliver in the brickfield for burning. The overflow from the sludge thickener will be flow back to

equalization tank for further treatment.

In some cases due to the nature of the wastewater characteristics it is not possible to dewater thesludge into a cake form, in that case the sludge is collected in the form of slurry in a bucket just

below the centrifuge pump. After collection of the sludge, it is strongly advised to dispose the

sludge in such a way so that it will not come in contact with the environment. A best way to

handle this sludge is to throw them in a deep hole, when the hole is nearly filled then it will be

necessary to bury the sludge by means of soil.

In every two days the sludge cake is taken out by opening the cover of the centrifuge. After taking

out of the cake the centrifuge is washed and clean by water. The water that has been separated

from the sludge will be flown back to equalization tank for treatment.

7. Operational Procedure


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7.1 Preparation of the chemical dosing

Before starting the operation it will be necessary prepare all the necessary chemical solutions. The

procedures of preparing the solutions are described below.

7.1.1 Preparation of the Lime solution

The daily requirement of the lime solution is calculated and shown in section 8.1. During

preparing the dosing solution of lime a 5% solution is prepared. In this regard the dosing tank,

which is fitted with a motor and stirrer, is at first filled with 1000 litres of water. After that 50 kgs

of lime is added and the motor is switched on to stir the solution. The stirring should be continuedon a 24-hour basis i.e. as long as the plant runs. After that the solution is ready for dosing in the

flash-mixing tank. It is necessary to adjust the stroke of the dosing pump to get the desired flow.

7.1.2 Preparation of the Ferrous Sulphate (FeSO4) solution

The daily requirement of the ferrous sulphate is calculated and shown in section 8.2. During

preparing the dosing solution of ferrous sulphate a 10% solution is prepared. In this regard thedosing tank, which is fitted with a motor and stirrer, is at first filled with 1000 litres of water.After that 100 kgs of ferrous sulphate is added and the motor is switched on to stir the solution.

The stirring is continued for nearly 1 hour. After that the solution is ready for dosing in the flash-

mixing tank. It is necessary to adjust the stroke of the dosing pump to get the desired flow.

7.1.3 Preparation of the Poly Electrolyte (PE) solution

The daily requirement of the PE solution is calculated and shown in section 8.3. During preparing

the dosing solution of lime, a 0.05% solution is prepared. In this regard the dosing tank, which isfitted with a motor and stirrer, is at first filled with 1000 litres of water. After that 500 gms of PE

is added and the motor is switched on to stir the solution. The stirring should be continued on a

24-hour basis i.e. as long as the plant runs. After that the solution is ready for dosing in the flash

mixing tank as well as centrifuge tank. It is necessary to adjust the stroke of the dosing pump to

get the desired flow.

7.1.4 Preparation of the Acid solution

The daily requirement of the Acid solution is calculated and shown in section 8.4. During

preparing the dosing solution of acid, a 2.5% solution is prepared. In this regard the dosing tank,

which is fitted with a motor and stirrer, is at first filled with 1000 litres of water. After that 70

litres of 33% HCl is added. After that the solution is ready for dosing in the flash-mixing tank. It is

necessary to adjust the stroke of the dosing pump to get the desired flow.

7.1.5 Preparation of the Diammonium Phosphate (DAP) and Urea solution


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The requirement of the DAP and Urea is calculated and shown in section 8.5. During preparing the

dosing solution of DAP and Urea a 5% mixed solution is prepared in the same dosing tank. In this

regard the dosing tank, which is fitted with a motor and a stirrer, is at first filled with 1000 litres ofwater. After that 50 kgs of DAP and Urea (35 kgs Urea and 15 kgs DAP) are added and the motor

is switched on to stir the solution. The stirring should be continued for half of an hour. After that

the solution is ready for dosing in the biological tank. It is necessary to adjust the stroke of the

dosing pump to get the desired flow.

7.2 Method of seeding bacteria in the FAB reactor # 1 & 2.

The following steps are to be followed during start up of FAB reactor.

1. Check whether civil work is complete in all respects as far the civil GA drawings.

2. Check any leakage

3. After completing the civil work, assemble air pipes. Fill the water tank. Take trial for air

diffusion. Aeration has to be uniform and there should not be any leakages in the air grid.

4. If aeration is o.k. drain water and pour FAB media in the reactor.

5. Fill the tank up to the water level

6. Add 10 tons of filtered cow dung. Ensure that cow dung is free of foreign material andfibres. Make 5-10% slurry. Filter it through 2-3 mm opening mesh. During the addition of

slurry in FAB keep the blowers on. Cow dung should be fresh (3 to 4 days) . We can also

have aerobic culture in FAB in place of cow dung. Add this slurry uniformly in all the

compartments.

7. Aerate the dilute slurry continuously for about 5-6 days.8. Dilute effluent can be loaded after this gradually; (Starting with 10% of design BOD load,

for initially 7-8 days thereafter the load can be increased after every 4-5 days by 10%provided BOD reduction is continuously 70-75% is observed at the increased BOD load.

If, in cases, the bacteria of the biological reactor dye for any reason like wrong acidity or

alkalinity, nor aeration shock load etc, in that case it will be necessary to seed the bacteria

again. This has to be done by means of adding 10 tons of cow dung as was mentioned in

section 6 above. It is not very easy to detect the presence of bacteria in the biological tank. By

means of using a microscope it will only be possible to test the presence of bacteria in the

effluent. Apart from this by testing the BOD of the effluent before and after the biological

reactor treatment it will be possible to say whether there is any bacteria in the reactor or not. Ifthe quantity of BOD is same before and after the biological reaction then we can say that thereare no bacteria to reduce the BOD. On the other hand, if the BOD is reduced, after, treatment

in the biological reactor then we can say that there is bacteria in the biological tanks.

7.3 Important processing tips


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7.3.11. Drain the sludge settled at the bottom of the tube settler at periodic interval to avoid carry

over of sludge.2. Changeover from operating to stand by equipment every day.

3. Regularly follow the lubrication and maintenance schedule for all mechanical moving

items.

4. Take samples from the locations specified. Analyze them and maintain logbook regularly

to ensure better control over operation of the plant.

7.3.2

1. Do not let effluent –having pollutants more than specified range in the plant .2. Do not enter in to the closed tank without opening the manhole/without draining the

contents of the tank.

3. Do not handle chemicals, dosing system without taking precautions.

4. Do not allow acidic pH < 6 or alkaline pH > 8.5 or hot (temp > 400C)

5. Do not drain the FAB reactor under normal operation.

7.4 Trouble Shooting guide

7.4.1 Aeration Problem

Low DO and/or septic odor in FAB reactor

Possible cause Necessary Check and possible correctiveactions

Under aeration 1. Check DO, should be in the range of 1.0 to

3.0 mg/L throughout in the tank.

2. Check the air quality delivered by blower, in

case the quantity is less than design; check theblower for any mechanical problem. In case of

any mechanical problem refer the blower

manual for the maintenance.

3. Check for adequate mixing in FAB reactor.

Blower operation not continuous The blower should be in continuous operation

Grid are damaged In case the grid is damaged, this will result in

excessive turbulence but low oxygen transfer.

The corrective action should be taken nfor

reparing the diffuser/grid.

High inlet Organic i.e BOD/COD load 1.In case the BOD/COD load is higher than

design, the same to be controlled prior to E.T.P.

If the increase is for a small period the flow to

the plant to be reduced to decrease the kg

BOD/COD loading.

2.Solid level in the FAB reactor very high, the


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settled solids (if any) to be drained. The

draining frequency can be ascertained based on

the site condition.

7.4.2 Foaming Problem

Possible cause Necessary check and possible corrective actions

Over aeration Check BOD loading (kg/d), in case the BOD

level is much lower than the design basis.

Adjust the air quantity to the bio reactor and

maintain minimum D.O level as 2.0 mg/l

Low bacterial level in the FAB reactor Seeding should be done preferably by using

activated sludge from an well-operated plant

Note- The foaming problem usually occurs during start-up and is only temporary. If you are under

starting up do not be alarmed by it.

7.4.3 Low oxygen uptake in FAB reactor

Possible cause Necessary check & possible corrective actions

High Temperature At high temperature there will be decreasedoxygen utilization.

Maintain the inlet effluent temperature between

250C to 35

0C maintain organic removal

pH out of range Eliminate source of pH upsetAdjust pH in FAB reactor to between 6.5 and

8.5

Spill Eliminate source of spill

Evaluate effect of spill on active Bio Mass.

Low organic loading Adjust the air supply according to the inlet

BOD load, simultaneously maintain the DO

level >2.0 mg/l.

7.4.4 Low Bio Growth in the FAB reactor

Possible Cause Necessary Check & Possible Corrective Actions

High Temperature High process temperature can result in

decreased oxygen utilization and as a result low

bacterial growth. Apart from this at high

temperature there is possibility of dyeing of themicroorganisms.


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Maintain the inlet effluent temperature between

250C to 350C to maintain organic removal

pH out of range Eliminate source of pH upset as it will

adversely affect the Biological process.

Adjust pH in FAB reactor in between 6.5 and

8.5

Insufficient aeration Insufficient aeration may lead to decrease in

bacterial population. The aeration should be

continuously carried. Even if the effluent is not

available for a short span in a day blowersshould not be stpped.

Shock loading The effluent having pollutant level very high

should be segregated and stored separately.

The effluent having toxic pollutant should be

prevented from entering the ETP.

7.4.5 High suspended solids level in the tube settler II outlet effluent

Possible cause Necessary Check & Possible Corrective Actions

Media position Check the position of tube settler media by

lowering the water level, in case any short

circuiting is there, the same is required to be

corrected by correctly positioning the media as

per the drawing.

Excessive storage of sludge in the tube settler. The sludge needs to be drained periodically

from the tube settler. In case the sludge level

increases in the tube settler the same will result

in sludge carry over.

Trough are not cleaned The trough should be cleaned manuallyperiodically.

7.4.6 High COD (or BOD) level in tube settler II outlet effluent

Possible cause Necessary Check & Possible Corrective

Actions

Low Bio mass Seeding of FAB reactor may be required.

High organic loading and/or excessive flow Increase in the inlet BOD/COD load in

comparison to Design. If the increase is for a


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short time decrease the flow to maintain the kg

BOD loading as far design.

High effluent suspended solid (SS) If COD increase is attributable to high effluent

suspended solids, refer to corrective actions for

“high effluent suspended solids”

Inadequate DO Check organic loading by measuring COD.

Increased oxygen utilization can result fromincreased organic loading. Refer to corrective

actions for “low oxygen level in FAB Reactor”


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8.Estimation of various chemicalsThe requirements of various chemicals must be determined by means of jar test. It is strongly

recommended to conduct the jar test whenever any major changes occurs either in selection of

process, dyes, or raw material characteristics. Different process condition due to change of rawmaterial or change of brand of dyes will lead to different types of effluent characteristics.

8.1 Estimation of quantity of lime (Calcium Hydroxide) :-

From our experience of running plants and jar tests, the quantity of required lime can be estimated

as follows;

If the flow of effluent is 30 M3 /Hr.

Dose optimized by jar test = 833 mg / l.

Therefore,30 M

3 /hr. X 833 mg /l X 24 hrs.

CaO required = --------------------------------------------- = 600 Kg / day.

1000

= 25 kg/hr

8.2 Estimation of quantity of Ferrous Sulphate FeSO4.

Based on experience or by jar tests findings the dosages can be stabilized. e.g.

If flow of effluent is 40 Cum / Hr.

Dose optimized by jar test = 833 mg / l.

Therefore

30 M3 /hr. X 833 mg /l X 24 hrs.

FeSO4 required = ------------------------------------------------- = 600 Kg / day.

1000

= 25 kg /hr

8.3 Estimation of quantity of Polyelectrolyte.

Based on experience or by jar tests findings the dosages can be stabilized. e.g.

If flow of effluent is 30 Cum / Hr.

Dose optimized by jar test = 4.16 mg / l.

Therefore,30 M3 /hr X 4.16mg / l X24 hrs

Polyelectrolyte required = -------------------------------------------- = 3 kg / day

1000


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= 0.125 kg / hr

(This amount will be required for dosing in the flash mixing as well as centrifuge feed pump)

8.4 Estimation of quantity of Hydrochloric Acid ( HCl)

These can be optimized by using Jar test procedure given bellow Based on experience or by jar tests findings the dosages can be stabilized. e.g.

If flow of effluent is 30 M3 /Hr.

Dose optimized by jar test = 375 mg / l

Therefore

30 M3 / hr X 375 mg/l X24 hrs

HCl –33% required = ---------------------------------------------- = 270 Kgs / day

1000

= 11.25 kgs / hr

8.5 Estimation of quantity of DAP and Urea

Assume BOD content of the feed to the system = 200 mg/ l.

Flow of effluent to the system is 30 M3 / hr.

30 X 200 X 24Total BOD load = ------------------------ = 144 Kgs /day.

1000

Basis for activated sludge process is BOD : N : P = 100 : 5 : 1.

144 X 5

For 192 kgs / day BOD Nitrogen required. = -------------- = 9.6 kg /day.

100

144 X 1Phosphorus required = --------------- = 1.44 Kg / day.

100

Now, DAP contains 17.9 % phosphorus, for 1.92 Kg phosphorus, DAP required.

1.44 X 100

= ------------------ = 8.04 Kgs / day17.9

=0.34 kg / hr

DAP contain 18 % Nitrogen, therefore Nitrogen provided by 8.04 kg DAP is


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8.04 X 18

= ------------------- = 1.45 kg.100

Nitrogen shortfall = 8.04– 1.45 = 6.60 Kg / day.

Now, urea contains 46 % Nitrogen, so for 7.68 Kg Nitrogen, Urea required is

6.60 X 100= ----------------------- = 14.35 Kg / day.

46

= 0.60 kg / hr.

Therefore, Urea required is 14.35 kg/day

DAP required is 8.04/day

Note: The Urea and DAP solutions are required to feed the bacteria i.e. they works as

nutrient for the microorganisms. If, for any reason, the plant is kept shut down due to

closure of the factory or something like this, even then it will be necessary to run the

biological reactor along with dosing DAP and Urea solutions. This is because if the biological

reactors are shutdown the bacteria will dye and then again it will be necessary to seed thebacteria according to the procedure outlined in section 7.2.

Chemical Consumption/day @ (100% Efficiency)

Chemicals Quantity/day Quantity / hr

CalciumHydroxide(Lime Crystal)

85% Purity

600 Kg /day 25.00 kgs/ hr

Ferrous sulphate (FeSO4) 85%

Purity

600 Kg/ day 25.00 kgs/ hr

Polyelectrolyte(Anionic PE 100%Purity)

3 Kg /day 0.125 hg/ hr

Hydrochloric acid 33% purity 270 Kg /day 11.25 kgs / hr

Dia ammonium phosphate 8.04 Kg /day 0.34 kg / hr

Urea 14.35 Kg /day 0.60 kg / hr

Note: The actual quantities will depend on chemicals purity , effluent characteristics and jar test.

The above indicate consumption pattern. These are not guarantee figures


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9. Commissioning of the Plant

a. At first sufficient effluent is allowed in the equalization tank. After that aerationshould be continued. After aeration for about an hour or two the effluent is pumped to the

flash mixing tank.

b. Lime and Ferrous Sulphate solution should be dosed as soon as the effluent

accumulated in the flash mixing tank. Soon after dosing, the colour of the effluent will be

changed and the dissolved matters will form small flocks. The effluent will then be flown tothe flocculation tank by overflow and gravity principle.

c. Polyelectrolyte is then dosed when the small sludge particles will concentrated at the

bottom of the tank.d. From the flocculation tank the effluent is over flown to the tube settler 1 where the effluent

is flown upwards through the tube media. Under this condition a substantial amount of

sludge will be accumulated at the bottom of this settler tank.

e. The effluent is then goes to the pH correction channel due to the over flow. It is necessary

to check the pH of the effluent at this stage and if the pH is above 7 then acid solution is

dosed to bring down the pH within a range of 6.5 to 8.5.

f. The effluent is then goes to the Fluidized Aerobic Biological reaction tank #1 due to the

over flow and gravitation method. Microorganisms like bacteria are seeded in FluidizedAerobic Biological reaction tank #1 & 2 tank, which is described in section 7.2.

g. Nutrients are dosed in the FAB reactor for nursing microorganisms like bacteria. When

this tank is filled with, the effluent is then flows to the Fluidized Aerobic Biologicalreaction tank # 2. At this stage the remaining BOD/COD will be reduced. From the

Fluidized Aerobic Biological reaction tank # 2, the effluent enters into the tube settler # 2.

This is also happen due to overflow.

h. As the effluent flows through the tube media the sludge is settled at the bottom of the tank.i. From the tube settler tank # 2 the effluent goes to the filter feed sump due to gravity. From

the filter feed sump the effluent is pumped to the pressure sand filter or Granular MediaFiltration-to remove carbonaceous BOD and nitrogenous and residual in solubilised

phosphorous. This filter is also useful to protect the down stream Activated Carbon Filter

(ACF) from overloading by pollutants such as particulates, organics.

j. The effluent is then flows to the Activated Carbon Filter. Carbon adsorption is a proven

process in tertiary treatment for the processing biologically treated wastewaters, and is one

of the many processes used in the advanced treatment of wastewaters. The ACF is used to

remove relatively small quantities of refractory organics, as well as inorganic such as

sulfides and heavy metals remaining in an otherwise well-treated wastewater.k. The water at this stage is safe to be released into the environment.


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10. Plant Shutdown

In cases when the factory is kept shut down for a short period of time then there will not be any

effluent, in that case it will be necessary to continue aeration and nutrient dosing in the Fluidized

Aerobic Biological reaction tank # 1 & 2, otherwise the bacteria will dye. If the bacteria dye then

it will be necessary to seed bacteria again following section 7.2.

11. Maintenance of the plant11.1 Bar Screen:

The bar screen should be cleaned everyday

11.2 Equalization pump:

The lube oil should be checked before starting the pump. The valve of the suction line should be

opened and cleaned once every seven days.

11.3 Flash Mixing and flocculation agitator:

Apply lube oil before starting the agitator motor. The lube oil should be checked after every sevendays.

11.4 Air Blower:

Check the lube oil before starting the air blower. If there is no lube oil then apply lube oil and start

the blower. The lube oil pump should checked frequently.

11.5 Sludge transfer pump and centrifuge feed pump:

After starting the sludge transfer pump and centrifuge feed pump it should be observed for a short

period of time. If no sludge is found then stop the pump and open and clean the delivery line.

11.6 Agitators of all the dosing tanks:

Check the lube oil every seven-day. Apply lube oil if finishes.

11.7 Flash mixing, flocculation and tube settler tank # 1:

The tanks should be cleaned very well in every three months. The tube settler media should alsobe cleaned.

11.8 Tube settler tank # 2:


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This tank should be cleaned after every six months time.

11.9 Sand Filter:[

It is necessary to backwash the sand filter every eight hours.

11.10 Carbon filter:

It is necessary to backwash the carbon filter every eight hours.

11.11 Centrifuge:

After removal of the cake, the inside of the centrifuge should be cleaned. Check the belt of the

motor frequently, if loose change it so that it can rotate freely and easily.

11.12 Painting the plant:All the pipes and M.S tanks should be painted every year. The painting instruction and other

details are given in Appendix-III

11.13 Information about various equipments, parts and accessories:

SR. NO DESCRIPTION SPECIFICATION01 Bar Screen Type – Coarse

Model- Aquatech-03

Quantity – 1 ( One )

Size – 450 MM X 500 MM.

Materials of construction – Mild Steel

Epoxy Paint.

Origin- Bangladesh.

02 Aeration Grids for equalization tank. Type – Air diffuser

Model- Aquatech -03

Quantity- 1 Lot

Size- 80 MM, 40 MM.

Material of construction- “U” PVCTemperature – 80 0C

Origin – Bangladesh.


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03. Effluent transfer pump for equalization

tank.

Type – Horizontal, Centrifugal, non Clog

Model- JOHNSON

Capacity – 30 m3 / Hr.

Head – 16 MWC

Motor- 3.7 KW, Volt-400, 3 P, 50 Z.

RPM- 2,900 RPM

Quantity- 1 (One)

Size- Suc. -80 MM Del.- 50 MM.Material of construction- CI

Temperature – 800C

Origin – India.

With base frame, coupling, bolts etc.

04 Air blower for equalization tank. Type – Twin lobe, rotary air

Cooled, Horizontal

Model-Everest Transmission.

Capacity – 110 m3 / Hr.Discharge pressure – 4,500MMWC

Motor- 3.7 KW, Volt-400, 3 P, 50Hz.

RPM- 1,450 RPM

Quantity- 1 (One)Size- Suc. - 100 MM Del.- 80 MM.

Material of construction- CI

Origin – India.With base frame, V belt, Pressure gauze,

filter, silencer and non-return valve etc.

05 Air blower for biological reaction tank Type – Twin lobe, rotary air

Cooled, Horizontal

Model- Everest Transmission.

Capacity – 440 m3 / Hr.Discharge pressure – 6,500MMWC

Motor- 15 KW, Volt-400, 3 P, 50Hz.

RPM- 1,450 RPMQuantity- 1 (One)

Size- Suc. – 100 MM Del.- 80 MM.

Material of construction- CI

Origin – India.With base frame, V belt, Pressure gauze,

filter, silencer and non-return valve etc.


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06. Flash Mixture Mechanism. Type – Pitch blade turbine impeller

Vertical.

Model- Aquatech- FM-03

Capacity – Heavy duty, suitable for

Flash mixing tank.


RPM- 1,450 RPM

Quantity- 1 (One)Material of construction- CI

Origin – Bangladesh.Gear box- Aquatech

Reduction ratio- 15: 1

07. Flocculation Mixture Mechanism Type – Pitch blade turbine impellerVertical.

Model- Aquatech- FM-03

Capacity – Heavy duty, suitable for

Flash mixing tank.


RPM- 1,450 RPM

Quantity- 1 (One)

Material of construction- CIOrigin – Bangladesh.Gear box- Aquatech

Reduction ratio- 15: 1

08 Tube Settler Media for tube Settler #1

Material of construction- PVC .Model – Aquatech- TSM-03

Type - Hexagonal

Inclination angle – 600 deg.


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12 Sludge thickener mechanism. Type – Suitable of thickener tank

Model- Aquatech- STM-03

Quantity- 1 ( One )

Material of construction – MildSteel.

Epoxy painted.Motor– 1.5 KW, Volt-400, 3 P, 50

Hz

RPM- 1,000 RPM

Gear box- reduction ratio. - 70:1

Origin- Bangladesh.

13 Sludge Centrifuge for cake making. Capacity – 100 Kg / batch

Quantity- 1 (One)

Model- Aquatech- HC-03

Type- Hydro extractor centrifuge

Material of construction – Mild

steel

Basket size-Dia-850 MM X 550MM

Motor- 7.5 KW, V-400, 3 P, 50

SR. NO DESCRIPTION SPECIFICATION

09 Tube Settler Media for tube Settler # 2

Material of construction- PVC .

Model – Aquatech- TSM-03

Type- Hexagonal

Inclination angle – 600 deg.

10 Biological FAB Media for biological

Reaction tank # 1 & 2.

Type – Corrugated

Model- Aquatech-FAB-03

Quantity – 2 ( Two )

Materials of construction –

Polypropylene

Size- 20 MM x 16 MM height

Origin- Bangladesh.

11 Aeration grids for biological reaction tank. Type – Air diffuserModel- Aquatech -03

Quantity- 1 LotSize- 80 MM, 40 MM.Material of construction- “ U “

PVC

Temperature – 80 0C



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Hz.

RPM- 1450 RPM


14 Filter feed sump pump Type – Horizontal Centrifugal

PumpModel- Submersible

Capacity – 30 M3 / Hr.

Discharge pressure- 15 MWCHead – 35 MWC

Motor- 3.75 KW, Volt-400, 3 P,

50 Z.

RPM- 2900 RPM

Quantity- 1 ( One )

Size- Suc. -65 MM Del.- 50 MM.Material of construction-

Body-CI


Origin – India.

With base frame, coupling, bolts

etc.

15 Less contaminated water pump Type – Horizontal/Centrifugal

Model- Submersible/centrifugalCapacity – 30M3 / Hr.

Discharge pressure- 15 MWC

Head – 35 MWC

Motor- 3.75 KW, Volt-400, 3 P,

50 Z.RPM- 2900 RPM

Quantity- 1 (One)

Size- Suc. -65 MM Del.- 50 MM.

Material of construction-

Body-CI


Origin – India.

With base frame, coupling, boltsetc.

16 Thickener feed pump for sludge sump. Type – Horizontal Screw pump

Model- Alpha Helical

Capacity – 6 m3 /hr.


Head – 16 MWCMotor- 3.75 KW, Volt-400, 3 P,

50 Z.

RPM- 2900 RPM

Quantity- 2 (Two)


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Body-CI


Origin – India.


etc

17 Centrifuge feed pump of hydro extractorFor sludge cake making

Type – Horizontal, Centrifugal,Screw, non-Clog.

Model- Alpha Helical

Capacity – 5M3 /Hr.


Head – 16 MWC

Motor- 1.5 KW, Volt-400, 3 P, 50Z.

RPM- 1,450 RPM

Quantity- 1 (One)



Body-CI


Origin – India.With base frame, coupling, boltsetc

19 Lime (Calcium hydroxide) Preparation tank

agitator mechanism.

Location of dosing – Flash mixing

Tank capacity – 1,000 liter.

Quantity- 1( One)

Material of construction- PVC

Agitator mechanism- 1 ( One )

Motor- 0.75 KW, V-400, 3 P, 50

HzRPM – 1000 RPM

Origin- Bangladesh + India

20 FeSO4 (Ferrous Sulphate ) preparation tankagitator mechanism.

Location of dosing – Flash mixingTank capacity – 1,000 liter.

Quantity- 1(One)

Material of construction- PVCAgitator mechanism- 1 (One)

Motor- 0.75 KW, V-400, 3 P, 50

Hz

RPM – 1000 RPM

Origin- Bangladesh + India


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21 Polyelectrolyte (PE-100 % purity) tank

agitator.

Location of dosing – Flocculation

mixing.

Tank capacity – 1,000 liter.

Quantity- 1(One)


Agitator mechanism- 1 (One)

Motor- 0.75 KW, V-400, 3 P, 50

HzRPM – 1000 RPM

Origin- Bangladesh + India.[

22 HCL (Hydrochloric acid) dosing tank

agitator mechanism

Location of dosing – PH

correction mixing.Tank capacity- 1000 liter

Quantity – 1 (One)

Material of construction – PVC

23 Nutrient (Urea & DAP) dosing tank agitator

mechanism.

Location of dosing – Biological

reaction tank.

Tank capacity – 1,000 liter.Quantity- 1(One)


Agitator mechanism- 1 ( One )

Motor- 0.75 KW, V-400, 3 P, 50

HzRPM – 1000 RPM

Origin- Bangladesh + India.

24 Activated carbon and sand filter feed

Pump.

Type – Horizontal,

Centrifugal/Sub

Model- KSB/JOHNSON

Capacity – 30m3 / Hr.


Head – 16 MWCMotor- 7.5 KW, Volt-400, 3 P, 50

Z.RPM- 1450 RPM

Quantity- 1 (One)


Material of construction

Body-CI


Origin – India.


etc


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25 Pressure sand filter. Quantity- 1 (One)

Type- Down flow.

Model- Aquatech sand filter.

Diameter- 1,600 MM

Height on straight- 1,800 MM

Design pressure- 3.5 kg/cm2


steelTreated flow rate- 30 m3 / Hr

Deep of media- 900 MMMedia fill- Sand media and Gravel

support.

Duty- Filtration.

26 Activated carbon filter Quantity- 1 (One)

Type- Downflow.

Model- Aquatech sand filter.

Diameter- 1,600 MM

Height on straight- 1,800 MM

Design pressure- 3.5 kg/cm2


steelTreated flow rate- 30 M3 / HrDeep of media- 900 MM

Media fill- Granular Activated

carbon support.

Duty- Filtration.

27 Interconnection piping Quantity- 1 (One) lot

Butterfly valve, Gate valve,

Elbow, Tee, Flange, Pressure

gauge, Ball valve, Non return

valve etc.

11.14Electrical Scope of Supply

SR. NO Items Unit

01 Glands for cables 1 Lot

02 Motor (As required for the equipment listed in mechanical

List) Crompton / Kirloskar/ China

1 Lot

03 Main Distribution Board with MCCB, MCB, Ammeter,Voltmeter with selector switch, Indicator lamp, Overload relay

with complete distribution board.

1 (One)

04 Power cable from distribution board to different motor. 1 Lot


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Local made

05 Power cable from different motor to operating panel board 1 Lot

06 Suitable cable tray made by M.S. angle & flat bar. 1 Lot

07 Structural steel support for cable tray lying in the plant. 1 Lot


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12. List of Appendixes

Appendix-I Description and Operation of Pressure Sand Filter & Activated Carbon Filter

Appendix-II Technical information about Pump

Appendix-III Technical information about Air Compressor

Appendix-IV Information about Painting

Appendix –1

Technical specification of Pressure Sand Filter and Activated Carbon filter.

Pressure Sand Filter

1. No of unit : One (1)

2. Type : Cylindrical

3. Capacity at normal flow : 30 M

3 /hr

4. Size of unit Diamater : 1600mm

Height : 1800mm

5.Material of Construction : M.S

6. Pressure condition at Minimum working : 2 kg/cm2


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Maximum working : 3.5 kg/cm2

7. Painting details, Internal : Epoxy

External : At first red oxide and then epoxy

8. Support details : M.S construction built in four legs

provided.

9. Manhole details, Number : One (1)

Type : Circular

Size : 450mmMaterial : M.S

10. Handhole details, Number : One(1)Type : Circular

Size : 150mm

Material : M.S

11. Supporting Bed Type : Graded Garvel

Specification : (1½”- 1”, 1"- ¾”, ¾” - ½”, ½” - 1/8”,

Mesh)

Bed Depth :900mm

12. Pipeline details, Size :100 NB

Material :M.S

Make : Aquatech

End connection :Flanged

13. Valve details Size :100 NBType :Butterfly

Activated Carbon Filter

1. No of unit : One (1)

2. Type : Cylindrical

3. Capacity at normal flow : 30 M3 /hr4. Size of unit Diamater : 1600mm

Height : 1800mm

5.Material of Construction : M.S

6. Pressure condition at Minimum working : 2 kg/cm2

Maximum working : 3.5 kg/cm2

7. Painting details, Internal : EpoxyExternal : At first red oxide and then epoxy

8. Support details : M.S construction built in four legs


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provided.9. Manhole details, Number : One (1)

Type : Circular

Size : 450mm

Material : M.S

10. Handhole details, Number : One(1)

Type : Circular

Size : 150mm

Material : M.S11. Supporting Bed Type : Graded Garvel and activated carbon

Specification : (1½”- 1”, 1"- ¾”, ¾” - ½”, ½” - 1/8”,Mesh)

Bed Depth :900mm

12. Pipeline details, Size :100 NB

Material :M.S

Make : Aquatech

End connection :Flanged

13. Valve details Size :100 NB

Type :Butterfly

Operation of Pressure Sand Filter & Activated Carbon Filter

The filtration section mainly comprises of following equipment

1. Pressure Sand Filter (PSF)

2. Activated Carbon Filter (ACF)

Water from Tube Settler II flows by gravity into the filter feed sump. This is almost treatedeffluent, which is then passed through the pressure sand filter (PSF) and then Activated Carbon

Filter (ACF).

Operation:

The Plant is designed to provide trouble free service. Each of the above filter units needs to bebackwashed once in 24 hour or whenever pressure drop across PSF and ACF reaches 0.7 kg /cm 2 g

whichever is earlier.


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The Pressure Sand Filter & Activated Carbon Filters are backwashed in staggered fashion which isdescribed below.

Backwash of PSF

The following steps to be followed

Step-1 Air scouring of PSF

Close inlet valve V1 and outlet Valve (i.e inlet valve V1 of ACF). Open the air scouring valve V6& air vent valve V7. Switch on the blower and continue air scouring for about 5 minutes. Air

scouring of PSF is done to ensure thorough backwash of the filter.

Valve position[[[[[[[[[[[[[

Open V6 ,V7

Close V1,V3,V4,V5,V8,V9

Step-2 Backwashing of PSF

Open backwash inlet valve V3 and backwash outlet valve V4 . Continue backwash of the filter for

8-10 minutes. Water during backwash flows in the upward direction thereby cleaning the filter off

dirt accumulated at the top of the filter media . Backwash water comes out of backwash out let andsame shall be drained . Flow rate for filter backwash shall be 60 m3 /hr .

Valve position

Open V3 ,V4, V8

Close V1, ,V5,V6,V7, V9

Step-3 Rinsing of PSF

Close backwash inlet & out let i.e. V3 & V4 and open service inlet valve V1 and rinse out let

valve V5. Rinse water comes out of backwash outlet and the same shall be drained. Continue

rinsing for 5 minutes. Rinse flow rate shall be same as service flow rate i.e. 30m3 /hr.

Valve position

Open V1 ,V5

Close V3, ,V4,V6,V7,V8,V9

B. Backwash of ACF

Step-1 Backwashing of ACF

Close rinse outlet valve V5 of PSF, service inlet and outlet valve V1 & V2 of ACF. Open

backwash inlet and outlet valve V3 & V4 of ACF. Backwash water flows in upward direction in


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ACF thereby backwashing the media. Continue backwashing for about 10-15 minutes . Backwash

water comes out from backwash outlet and the same shall be drained .Flow rate for ACF

backwash 30 m3 /hr.

Valve position

Open ACF V3 ,V4, V8

Close ACF V1, ,V2,V5,V6,V7,V9

PSF All the valve of sand filter close

Step-2 Rinsing of ACF.

Now close the backwash inlet & outlet valve V3 & V4 of the ACF . Open service inlet valve V1of PSF and service inlet & outlet valve V1 & V2 of ACF rinse outlet valve V5. Continue rinsing

for about 3-5 minutes. Rinse water comes out from backwash outlet and the same shall be drained.

Flow rate for ACF rinsing 30m3 /hr.

Valve position

Open ACF V1 ,V5, V8PSF only V1, V8 (All the other valve of PSF closed )

Close ACF V2,V3,V4 ,V6,V7,V9

Step-3 ACF in service mode.

Valve position

Open ACF V1 , V8, V2 all the other valves closed.

For valve number refer interconnecting piping diagram of PSF and ACF


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Appendix-II Technical information about Pump


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Appendix-III Technical information about Air Compressor


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Appendix-IV Information about Painting

operation & maintenance manual for effluent treatment plant

Documents