Thesis: The Removal of COD and BOD from wastewater

The Removal of COD and BOD from Wastewater of The Civil Engineers Ltd., Unit-2: A Case Study

A project report submitted to the department of Environmental Sciences, Jahangirnagar University for partial requirement for the degree of Masters in Environmental Sciences and Management

Submitted by:

Md. Shaheruzzaman

Student ID: 180410

Registration number: WMES 00125

4^th Batch

Masters in Environmental Sciences and Management

Department of Environmental Sciences

Jahangirnagar University

Course No.: WMES 301    

September 2019

Supervised by:

Prof. Dr. Md. Khabir Uddin

Department of Environmental Sciences

Jahangirnagar University

Savar, Dhaka-1342

Certificate

This report has been complied according to the regulation of the Masters in Environmental Sciences and Management under weekend program in the Department of Environmental Sciences, Jahangirnagar University and approved in its style and content.

Prof. Dr. Md. Khabir Uddin Supervisor	Md. Shaheruzzaman Student

Dr. Shafi Mohammad Tareq

Coordinator

WMES Program

Department of Environmental Sciences

Jahangirnagar University

Declaration

I, Md. Shaheruzzaman, am presenting this project in partial fulfillment of the required degree of Masters in Environmental Sciences and Management. I, hereby declare that the work described in this project has been carried out under supervision of Dr. Md. Khabir Uddin, Professor, Department of Environmental Sciences, Jahangirnagar University, Savar, Dhaka-1342.

The work presented here is true and original. No part of this work has been submitted to any university or institute before for an award or degree.

Md. Shaheruzzaman Student ID: 180410 Registration number: WMES 00125 4th Batch Admission Session: September 2018 Masters in Environmental Sciences and Management Department of Environmental Sciences Jahangirnagar University

Prof. Dr. Md. Khabir Uddin Supervisor Department of Environmental Sciences Jahangirnagar University

Acknowledgement

First of all, I would like to thank almighty Allah for grant me the opportunity and my parents for their unconditional devotion and inspiration.

I wish to express my thanks and gratitude to my reverend teacher Dr. Md. Khabir Uddin, Professor, Department of Environmental Sciences, Jahangirnagar University, Savar, Dhaka, Bangladesh for his sincere guidance, constant supervision and constructive advice throughout the progress of this project work. Entirely he helped me a lot of by checking the proof and suggesting necessary corrections that improve the quality of the report.

Special thanks to the Coordinator of WMES Program Dr. Shafi Mohammad Tareq, Professor, department of Environmental Sciences, Jahangirnagar University for his support and direction. I would like to give special thanks to Prof. Dr. A H M Saadat, Chairman, department of Environmental Sciences, Jahangirnagar University for his nice cooperation and support.

I would like to thank all of my respectable teachers, university staffs and colleagues for their encouragement during project work.

Finally, I would like to give special thanks to my friends and colleagues, specially Jakaria, Mizan, Kazi Isa, Ashraf, Ayan Barua, Zia (Our Honorable and Valuable CR), Rakib, Perves, Nusrat Jahun Bithi, Mahfuz, Hosnul Ferdous Adity, Bashir, Imran, Alin Dewan, Sazzad, Rubel, Shuvo, Rashed, Rajib, Alvee, Mottaleb, Rakib, Kamal, Arif and Ansarul Karim Jamee, students, Batch 4, WMES, department of Environmental Sciences, Jahangirnagar University for their nice inspiration and direction.

Md. Shaheruzzaman

Student ID: 180410

Registration number: WMES 00125

4^th Batch

Admission Session: September 2018

Masters in Environmental Sciences and Management

Department of Environmental Sciences

Jahangirnagar University

Abstract

Bangladesh's export trade is now dominated by the ready-made garments (RMG) industry. There are 4621 garments factories in the year 2018-2019. In the fiscal year 2018-2019, total export was 40536.04 million USD, in this value RMG export was 34133.27 million USD, i.e., RMG sector export 84.21% of total export revenue. These industries are being used in various chemicals and large amounts of water during the production processes and also generate a substantial quantity of effluents, which can cause various environmental problems, if discharged to the environment without treatment. Effluent treatment plant or ETP is one type of wastewater treatment method, particularly designed to purify the industrial wastewater.

The present study was carried out to analyze the physicochemical parameters of textile effluents like pH, TDS, BOD and COD. At present COD and BOD parameter of ETP outlet is 223 mg/L and 61 mg/L respectively, which does not meet to the standard ECR, 1997. To meet the ECR1997, here applied activated sludge i.e., biological process on the existing ETP outlet water to reduce COD and BOD value. After treatment of biological process it is found the COD parameter is 143 mg/L and the BOD parameter is 26 mg/L. After research it is shown that COD and BOD parameters meet properly with the Department of Environment (DoE) standard the Environment Conservation Rules (ECR) 1997.

Contents

Certificate……………………………………………………………………..2

Declaration……………………………………………………………………3

Acknowledgement…………………………………………………………… 4

Abstract………………………………………………………………………. 5

Contents……………………………………………………………………….6

List of tables…………………………………………………………………..7

Chapter One-Introduction …………………………………………………..9-31

Wastewater

Sources of wastewater

Textile effluent in Bangladesh

Environmental impact of wastewater

Effluent treatment plant

Importance of wastewater treatment

The environment conservation rules, ECR 1997

Rationality

Objectives

Wastewater parameters

Chapter Two-Literature Review……………………………………………… 32-49

Production of textile effluent

Characteristics of textile effluent

Effect of textile effluent

Water pollution

Effluent treatment method

Biological Wastewater treatment method

Chapter Three- Materials and Methods………………………………………50-57

Study area

Materials

Apparatus and glassware

Laboratory equipments

Chemicals and reagents

Sample collection

Wastewater treatment by activated sludge

Analysis of water sample

Chapter Four-Results and Discussion…………………………………………58-66

4.2.1 pH test report of existing report

4.2.2 TDS test report of existing report

4.2.3 COD test report of existing ETP

4.2.4 BOD test report of existing ETP

4.3.1 COD test report after treatment by activated sludge

4.3.2 BOD test report after treatment by activated sludge

Chapter Five-Conclusion………………………………………………………67-68

Conclusion

References………………………………………………………………………69-72

List of tables

1.1  The standard ECR 1997……………………………………………………..27

2.1 Water pollution source and ranking in Bangladesh…………………………33

2.2 Physicochemical characteristics of waste water…………………………… 34

2.3 Effluent discharge from textile industry…………………………………….37

3.1 BOD measuring range and sample………………………………………….56

4.1 pH test report of existing ETP………………………………………………60

4.2 TDS test report of existing ETP……………………………………………..61

4.3 COD test report of existing ETP…………………………………………… 62

4.4 BOD test report of existing ETP………………………………………….…63

4.5 COD test report after treatment by activated sludge………………………...64

4.6 BOD test report after treatment by activated sludge………………………...65

Chapter One

INTRODUCTION

1.1 Water

Water is a transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. It’s chemical formula is H₂O, meaning that each of it’s molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H₂O at standard ambient temperature and pressure. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea.

Water covers 71% of the Earth's surface, mostly in seas and oceans. Small portions of water occur as groundwater (1.7%), in the glaciers and the ice caps of Antarctica and Greenland (1.7%), and in the air as vapor, clouds (formed of ice and liquid water suspended in air), and precipitation (0.001%).

Water plays an important role in the world economy. Approximately 70% of the freshwater used by humans goes to agriculture.  Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities (such as oil and natural gas) and manufactured products is transported by boats through seas, rivers, lakes and canals. Large quantities of water, ice and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of chemical substances; as such it is widely used in industrial processes and in cooking and washing. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing and diving.

1.1.1 Chemical and physical properties

Water is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue. This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the universal solvent for its ability to dissolve many substances. This allows it to be the solvent of life. It is the only common substance to exist as a solid, liquid and gas in normal terrestrial conditions.

States

Water is known to exist in three different states; as a solid, liquid or gas. Clouds, snow, and rain are all made of up of some form of water. A cloud is comprised of tiny water droplets and/or ice crystals, a snowflake is an aggregate of many ice crystals and rain is just liquid water.

Taste and odor

Pure water is usually described as tasteless and odorless, although humans have specific sensors that can feel the presence of water in their mouths and frogs are known to be able to smell it. However, water from ordinary sources (including bottled mineral water) usually has many dissolved substances, that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the portability of water by avoiding water that is too salty or putrid.

Color and appearance

The color of water varies with the ambient conditions in which that water is present. While relatively small quantities of water appear to be colorless, pure water has a slight blue color that becomes a deeper blue as the thickness of the observed sample increases.

Reactivity

Metallic elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides and releasing hydrogen. At high temperatures, carbon reacts with steam to form carbon monoxide.

Distribution on earth

Water covers 71% of the Earth's surface; the oceans contain 96.5% of the Earth's water. The Antarctic ice sheet, which contains 61% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the Earth's albedo.

Hydrology is the study of the movement, distribution and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology.

The collective mass of water found on, under and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1.338 billion cubic kilometers (321×10⁶ cu mi).

Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid and vapor states. It also exists as groundwater in aquifers.

Water is important in many geological processes. Groundwater is present in most rocks and the pressure of this groundwater affects patterns of faulting. Water in the mantle is responsible for the melt that produces volcanoes at subduction zones. On the surface of the Earth, water is important in both chemical and physical weathering processes. Water, and to a lesser but still significant extent, ice, are also responsible for a large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks, which make up the geologic record of Earth history.

Water cycle

The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater and plants.

Water moves perpetually through each of these regions in the water cycle consisting of the following transfer processes:

• Evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into the air.
• Precipitation, from water vapor condensing from the air and falling to the earth or ocean.
• Runoff from the land usually reaching the sea.

Most water vapor over the oceans returns to the oceans, but winds carry water vapor over land at the same rate as runoff into the sea, about 47 Tt per year. Over land, evaporation and transpiration contribute another 72 Tt per year. Precipitation, at a rate of 119 Tt per year over land, has several forms: most commonly rain, snow and hail, with some contribution from fog and dew. Dew is small drops of water that are condensed when a high density of water vapor meets a cool surface. Dew usually forms in the morning when the temperature is the lowest, just before sunrise and when the temperature of the earth's surface starts to increase. Condensed water in the air may also refract sunlight to produce rainbows.

Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is a hydrological transport model. Some water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood comes from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation.

1.1.2 Fresh water storage

Water occurs as both stocks and flows. Water can be stored as lakes, water vapor, groundwater or aquifers, ice and snow. Of the total volume of global freshwater, an estimated 69 percent is stored in glaciers and permanent snow cover; 30 percent is in groundwater; and the remaining 1 percent in lakes, rivers, the atmosphere and biota. The length of time water remains in storage is highly variable: some aquifers consist of water stored over thousands of years but lake volumes may fluctuate on a seasonal basis, decreasing during dry periods and increasing during wet ones. A substantial fraction of the water supply for some regions consists of water extracted from water stored in stocks and when withdrawals exceed recharge, stocks decrease. By some estimates, as much as 30 percent of total water used for irrigation comes from unsustainable withdrawals of groundwater, causing groundwater depletion.

1.1.3 Effects on life

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Without water, these particular metabolic processes could not exist.

Water is fundamental to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO₂ (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO₂ in the process (cellular respiration).

Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H⁺, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as a hydroxide ion (OH⁻) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7.

1.1.4 Human uses

a.       Agriculture

b.      As a scientific standard

c.       For drinking

d.      Transportation

e.       Chemical uses

f.       Heat exchange

g.      Fire considerations

h.      Recreation

i.        Water industry

j.        Industrial applications

k.      Food processing

l.        Medical use

m.    Law, politics and crisis

n.      In culture

o.      Philosophy

1.2 Wastewater

Wastewater (or waste water) is any water that has been affected by human use. Wastewater is used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff or storm water, and any sewer inflow or sewer infiltration. Therefore, wastewater is a byproduct of domestic, industrial, commercial or agricultural activities. The characteristics of wastewater vary depending on the source. Types of wastewater include: domestic wastewater from households, municipal wastewater from communities (also called sewage) and industrial wastewater from industrial activities. Wastewater can contain physical, chemical and biological pollutants.

Households may produce wastewater from flush toilets, sinks, dishwashers, washing machines, bath tubs and showers. Households that use dry toilets produce less wastewater than those that use flush toilets.

Wastewater may be conveyed in a sanitary sewer which conveys only sewage. Alternatively, it can be transported in a combined sewer which includes storm water runoff and industrial wastewater. After treatment at a wastewater treatment plant, the treated wastewater (also called effluent) is discharged to a receiving water body. The terms wastewater reuse or water reclamation apply if the treated waste is used for another purpose. Wastewater that is discharged to the environment without suitable treatment causes water pollution.

In developing countries and in rural areas with low population densities, wastewater is often treated by various on-site sanitation systems and not conveyed in sewers. These systems include septic tanks connected to drain fields, on-site sewage systems (OSS), vermifilter systems and many more.

Wastewater may also be defined as the combination of the liquid or water-carried wastes removed from residences, institutions, commercial and industrial establishments after they have been used for various cultural, physiological and technical purposes. There is also an inherent difference between industrial and domestic wastewater. Industrial wastewater effluents carry more than twice much degradable organic matter as all the domestic combined.

Wastewater is about 99.4% water, with only 0.06% of the wastewater dissolved and suspended solid material. The cloudiness of wastewater is caused by suspended particles which in untreated wastewater ranges from 100 to 350 mg/l. A measure of the strength of the wastewater is biochemical oxygen demand, or BOD₅. The BOD measures the amount of oxygen microorganisms require in five days to break down wastewater. Untreated wastewater has a BOD₅ ranging from 100 mg/l to 300 mg/l. Pathogens or disease causing organisms are present in wastewater. Coliform bacteria are used as an indicator of disease causing organisms. Wastewater also contains nutrients (such as ammonia and phosphorous), minerals and metals. Ammonia can range from 12 to 50 mg/l and phosphorous can range from 6 to 20 mg/l untreated wastewater.

1.2.1 Sources of wastewater

Sources of wastewater include the following domestic or household activities:

• Human excreta (feces and urine) often mixed with used toilet paper or wipes; this is known as black water if it is collected with flush toilets
• Washing water (personal, clothes, floors, dishes, cars, etc.), also known as grey water.
• Surplus manufactured liquids from domestic sources (drinks, cooking oil, pesticides, lubricating oil, paint, cleaning liquids, etc.)

Activities producing industrial wastewater include:

• Industrial site drainage (silt, sand, alkali, oil and chemical residues)
• Industrial cooling waters (biocides, heat, slimes and silt)
• Industrial processing water
• Organic or biodegradable waste including waste from hospitals, abattoirs, creameries, and food factories
• Organic or non-biodegradable waste that is difficult-to-treat from pharmaceutical or pesticide manufacturing
• Extreme pH waste from acid and alkali manufacturing
• Toxic waste from metal plating, cyanide production, pesticide manufacturing, etc.
• Solids and emulsions from paper mills, factories producing lubricants or hydraulic oils, foodstuffs, etc.
• Water used in hydraulic fracturing
• Produced water from oil & natural gas production

Other related activities or events:

o   Urban runoff from highways, roads, car parks, roofs, sidewalks/pavements (contains oils, animal feces, litter, gasoline/petrol, diesel or rubber residues from tires, soap scum, metals from vehicle exhausts, de-icing agents, herbicides and pesticides from gardens, etc.)

• Agricultural pollution, direct and diffuse

• Heavy metals, including mercury, lead, and chromium
• Organic particles such as feces, hairs, food, vomit, paper fibers, plant material, humus, etc.
• Soluble organic material such as urea, fruit sugars, soluble proteins, drugs, pharmaceuticals, etc.
• Inorganic particles such as sand, grit, metal particles, ceramics, etc.
• Soluble inorganic material such as ammonia, road-salt, sea-salt, cyanide, hydrogen sulfide, thiocyanates, thiosulfates, etc.
• Macro-solids such as sanitary napkins, nappies/diapers, condoms, needles, children's toys, dead animals or plants, etc.
• Gases such as hydrogen sulfide, carbon dioxide, methane, etc.
• Emulsions such as paints, adhesives, mayonnaise, hair colorants, emulsified oils, etc.;
• Toxins such as pesticides, poisons, herbicides, etc.
• Pharmaceuticals and hormones and other hazardous substances
• Thermal pollution from power stations and industrial manufacturers

• Bacteria (for example Salmonella, Shigella, Campylobacter and Vibrio cholerae)
• Viruses (for example hepatitis A, rotavirus and enteroviruses)
• Protozoa (for example Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum) and
• Parasites such as helminths and their eggs (e.g. Ascaris (roundworm), Ancylostoma (hookworm) and Trichuris (whipworm)

1.3 Textile effluent in Bangladesh

Untreated textile waste water includes a large variety of dyes and chemicals that make the environmental challenge for textile industry not only as liquid waste but also in its chemical composition. Main contributor of toxicity in textile waste water is the wide range of dyestuffs, which are generally organic compounds of complex structure and is the first pollutant to be known in wastewater. As all of these are not contained in the final product, became waste and finds way in the waste stream. Due to the lacking of effective and cheaper approach, these compounds get released in to nearby system and consequently severe changes and disruptions of ecosystem services results from the negative impact of this invasive aquatic species.

Dyeing

Dyeing adds color to fabrics through the use of several chemicals and dyestuffs, depending on the fabric and processes used. Dyeing is performed in either continuous or batch modes. In the continuous dyeing processes, the fabric is passed through a dye bath of sufficient length. The dye is fixed to the fabric using chemicals or steam and then washed to remove any excess dyes and chemicals (Hendrickx, 1995). The batch dyeing process is similar, though the dye application stage occurs in a dyeing machine where the textile and dye solution are brought to equilibrium. The use of chemical or heat optimizes the batch process. Washing also follows the batch dye application stage. Common method of batch dyeing includes jig, jet, beam and beck processing. Each dyeing process requires a different dye bath ratio, or the amount of dye needed per unit of fabric. The dye bath ratio ranges from 5 to 50 depending on the type of dye, dyeing system and fabric type (EPA, 1998). The dyeing process can take place at different stages of the fabric development. Stock dyeing is used to dye textile fibers prior to their incorporation in to yarn. Yarn dyeing, including stock, package and skein dyeing, occurs once the fibers have been spun in to yarn but prior to the constriction of the fabric. Piece dyeing, dyeing of assembled fabric, is the most common dyeing method because it gives the manufacturer maximum flexibility with the color of the fabric. The largest volume of piece dyeing uses the continuous methods of beck and jig dyeing.

Mainly three dyes are used in dyeing industry:

1.      Reactive dyes

2.      Sulphur dyes

3.      Disperse dyes

1.3.1 Reactive dyes

Fibers reactive dyes derive their name from the fact that they form covalent bonds with the fiber molecules to be dyed. Molecules of fiber reactive dyes are much smaller than the complex molecule of direct dyes. Fiber reactive dyes are unique in that they become an integral part of the fiber that is dyed. Although more expensive then direct dyes, advantages of reactive dyes are excellent shade reproducibility and good leveling properties. These dyes can be subdivided in to either hot or cold dyeing groups, based on the temperature of application. Although silk and nylon can be dyed with fiber reactive dyes, the chief fibers dyes are cellulosic’s and wool. This dyes are also popular for printing textile, since even the brightest color are wet fast.

1.3.2 Sulphur dyes

Sulphur dyes are used primarily for cotton and rayon. The application of sulphur dyes requires carefully planned transformations between the water soluble reduced state of the dye and in soluble oxidized form. Sulfur dyes can be applied in both batch and continuous processes; continuous applications are preferred because of the lower volume of dye required. These dyes generally have a poor resistance to chlorine. In general, sulphur blacks are the most commercially important colors and are used where good color fastness is more important than shade brightness. Sulphur dyes are not applicable to wool or silk because the fibers are chemically damaged by the dyeing process.

1.3.3 Disperse dyes

Disperse dyes are colloidal and have very low water solubility’s. Most of these dyes are used for polyester, nylon, acetate and triacetate fibers. They are usually applied from a dye bath as dispersions by direct colloidal adsorption. Dye bath conditions ( temperature, use of carrier) are varied based on the degree of difficulty encountered by the dyes in penetrating the fiber being dyed. They are sometimes applied dry at high temperatures by means of a sublimation process followed by colloidal adsorption. High temperature sublimes the dye and once it is inside the fiber, the dye condenses to a solid colloidal state and adsorbed on the fiber.

1.4 Environmental impact of dyeing wastewater

It is evident that dyeing waste can cause severe damage not only to human being but to the environment and ecology, if the waste discharges without any treatment. The dyeing industries discharge their total emission to the surrounding environment, nearby open drain and in the surrounding air without any treatment or taking any preventive measure to abate or reduce the adverse effects. The waste streams of all the dyeing industries have a significant contribution to the destruction of the environment around.

Colored industrial effluents from the dyeing industries represent major environmental problems. Unbound reactive dyes undergo hydrolysis due to temperature and pH values during the dyeing processes. The strong color discharged dyes event at very smalls concentration has a huge impact on the aquatic environment caused by its turbidity and high pollution strength; in addition toxic degradation products can be formed.

There are many effects of wastewater. Here mentioned main three points.

o   Effect on ground water

o   Effect on human health

o   Emission to air

1.4.1 Effect on ground water

Ground water contaminated by chemical pollutants (e.g. BOD, COD) is major problem in dyeing industrialized areas. Typically, heavy metals containing wastes have been disposed of by discharging them to surface impoundments or stagnant ponds. Leakage from these stagnant ponds into ground water has been relatively common. Almost all reported incidents of heavy metals related groundwater contamination are of industrial origin.

1.4.2 Effect on human health

Heavy metal (i.e. chromium) is a major cause of allergic contact dermatitis among dye house workers and who perform dyeing operations and handle dyestuffs containing chromium.

1.4.3 Emission to air

The main emissions of atmosphere from textile dyeing and finishing processes are odors and particles. These emissions arise from dyeing, bleaching, heat setting, strengthening and other finishing processes. Their control represents a major challenge to the industry.

1.5 Effluent Treatment Plant (ETP)

Effluent Treatment Plant (ETP) or Wastewater treatment plant is a process design for treating the industrial waste water for its reuse or safe disposal to the environment. Wastewater treatment plant is a process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with minimum impact on the environment, or directly reused. The treatment process takes place in a wastewater treatment plant.

The treatment of wastewater is part of the overarching field of sanitation. Sanitation also includes the management of human waste and solid waste as well as storm water (drainage) management. By-products from wastewater treatment plants, such as screenings, grit and sewage sludge may also be treated in a wastewater treatment plant.

1.6 Importance of wastewater treatment plant

Direct discharge of untreated wastewater into the natural water bodies is not desirable, as the decomposition of the organic waste would seriously deteriorate in water quality. In addition, communicable disease can be transmitted by the pathogenic microorganisms. Nutrients such as nitrogen and phosphorous along with organic materials when discharged to the aquatic environment can also lead to excessive growth of undesirable aquatic life. When discharged in excessive amounts on land, can also lead to the pollution of underground water.

1.7 The Bangladesh Environmental Conservation Rules, ECR 1997

1.7.1 Classification of industrial units based on its location and impact on environment

(A) Green category

1. Assembling and manufacturing of TV, Radio, etc.

2. Assembling and manufacturing of clocks and watches

3. Assembling of telephones

4. Assembling and manufacturing of toys (plastic made items excluded)

5. Book-binding

6. Rope and mats (made of cotton, jute and artificial fibers)

7. Photography (movie and x-ray excluded)

8. Production of artificial leather goods

9. Assembling of motorcycles, bicycles and toy cycles

10. Assembling of scientific and mathematical instruments (excluding manufacturing)

11. Musical instruments

12. Sports goods (excluding plastic made items)

13. Tea packaging (excluding processing)

14. Re-packing of milk powder (excluding production)

15. Bamboo and cane goods

16. Artificial flower (excluding plastic made items)

17. Pen and ball-pen

18. Gold ornaments (excluding production) (shops only)

19. Candle

20. Medical surgical instrument (excluding production)

21. Surgical instrument (excluding production)

22. Factory for production of cork items (excluding metallic items)

23. Laundry (excluding washing)

(B) Orange - A category

1. Dairy Farm, 10 cattle heads in urban areas and 25 cattle heads in rural areas

2. Poultry (up to 250 in urban areas and up to 1000 in rural areas)

3. Grinding/husking of wheat, rice, turmeric, pepper, pulses (up to 20 Horse Power)

4. Weaving and handloom

5. Production of shoes and leather goods (capital up to 5 hundred thousand Taka)

6. Saw mill/wood sawing

7. Furniture of wood/iron, aluminum, etc.,(capital up to 5 hundred thousand Taka)

8. Printing Press

9. Plastic & rubber goods (excluding PVC)

10. Restaurant

11. Cartoon/box manufacturing/printing packaging

12. Cinema Hall

13. Dry-cleaning

14. Production of artificial leather goods (capital up to 5 hundred thousand Taka)

15. Sports goods

16. Production of salt (capital up to 10 hundred thousand Taka)

17. Agricultural machinery and equipment

18. Industrial machinery and equipment                                                                                                      19. Production of gold ornaments                                                                                                               20. Pin, U Pin                                                                                                                                                 21. Frames of spectacles                                                                                                                                22. Comb                                                                                                                                                        23. Production of utensils and souvenirs of brass and bronze                                                                             24. Factory for production of biscuit and bread (capital up to 5 hundred thousand taka)                                      25. Factory for production of chocolate and lozenge. (Capital up to 5 hundred thousand taka)                26. Manufacturing of wooden water vessels

(C) Orange - B category

1. PVC items

2. Artificial fiber (raw material)

3. Glass factory

4. Lifesaving drug (applicable to formulation only)

5. Edible oil

6. Tar

7. Jute mill

8. Hotel, multi-storied commercial & apartment building

9. Casting

10. Aluminum products

11. Glue (excluding animal glue)

12. Bricks/tiles

13. Lime

14. Plastic products

15. Processing and bottling of drinking water and carbonated drinks

16. Galvanizing

17. Perfumes, cosmetics

18. Flour (large)

19. Carbon rod

20. Stone grinding, cutting, and polishing                                                                                                           21. Processing fish, meat, and food                                                                                                              22. Printing and writing ink                                                                                                                     23. Animal feed                                                                                                                                               24. Ice-cream                                                                                                                                                 25. Clinic and pathological lab                                                                                                                    26. Utensils made of clay and china clay/sanitary wares (ceramics)                                                                                    27. Processing of prawns & shrimps                                                                                                               28. Water purification plant                                                                                                                          29. Metal utensils/spoons etc.                                                                                                                                 30. Sodium silicate

31. Matches

32. Starch and glucose

33. Animal feed

34. Automatic rice mill

35. Assembling of motor vehicles

36. Manufacturing of wooden vessel

37. Photography (activities related to production of films for movie and x-ray)

38. Tea processing

39. Production of powder milk/condensed milk/dairy

40. Re-rolling

41. Wood treatment

42. Soap

43. Repairing of refrigerators

44. Repairing of metal vessel

45. Engineering works (up to 10 hundred thousand Taka capital)

46. Spinning mill

47. Electric cable

48. Cold storage

49. Tire re-treading

50. Motor vehicles repairing works (up to 10 hundred thousand Taka capital)                                           51. Cattle farm: above 10 numbers in urban area, and above 25 in rural area

52. Poultry: Number of birds above 250 in urban and above 1000 in rural area

53. Grinding/husking wheat, rice, turmeric, chilly, pulses – machine above 20 Horse Power

54. Production of shoes and leather goods, above 5(five) hundred thousand Taka capital

55. Furniture of wood/iron, aluminum, etc., above 5(five) hundred thousand Taka capital

56. Production of artificial leather goods, above 5(five) hundred thousand Taka capital

57. Salt production, above 10(ten) hundred thousand Taka capital

58. Biscuit and bread factory, above 5 (five) hundred thousand Taka capital

59. Factory for production of chocolate and lozenge, above 5 hundred thousand Taka capital

60. Garments and sweater production

61. Fabric washing

62. Power loom

63. Construction, re-construction and extension of road (feeder road, local road)

64. Construction, re-construction and extension of bridge (length below 100 meters)

65. Public toilet

66. Ship-breaking

67. G.I. Wire

68. Assembling batteries

69. Dairy and food

(D) Red Category

1. Tannery

2. Formaldehyde

3. Urea fertilizer

4. T.S.P. Fertilizer

5. Chemical dyes, polish, varnish, enamel

6. Power plant

7. All mining projects (coal, limestone, hard rock, natural gas, mineral oil, etc.)

8. Cement

9. Fuel oil refinery

10. Artificial rubber

11. Paper and pulp

12. Sugar

13. Distillery

14. Fabric dying and chemical processing

15. Caustic soda, potash

16. Other alkalis

17. Production of iron and steel

18. Raw materials of medicines and basic drugs

19. Electroplating

20. Photo films, photo papers and photo chemicals

21. Various products made from petroleum and coal

22. Explosives

23. Acids and their salts (organic or inorganic)

24. Nitrogen compounds (Cyanide, Cyanamid etc.)

25. Production of plastic raw materials (PVC, PP/Iron, Polyester in etc.)

26. Asbestos

27. Fiberglass                                                                                                                                             28. Pesticides, fungicides and herbicides

29. Phosphorus and its compounds/derivatives

30. Chlorine, fluorine, bromine, iodine and their compounds/derivatives

31. Industry (excluding nitrogen, oxygen and carbon dioxide)

32. Waste incinerator

33. Other chemicals

34. Ordnance

35. Nuclear power

36. Wine

37. Non-metallic chemicals not listed elsewhere

38. Non-metals not listed elsewhere

39. Industrial estate

40. Basic industrial chemicals

41. Non-iron basic metals

42. Detergent

43. Land-filling by industrial, household and commercial wastes

44. Sewage treatment plant

45. Lifesaving drugs

46. Animal glue

47. Rodenticide

48. Refractories

49. Industrial gas (Oxygen, Nitrogen & Carbon-dioxide)

50. Battery

51. Hospital

52. Ship manufacturing

53. Tobacco (processing/cigarette/Biri-making)

54. Metallic boat manufacturing

55. Wooden boat manufacturing

56. Refrigerator/air-conditioner/air-cooler manufacturing

57. Tyre and tube

58. Board mills. 59. Carpets

60. Engineering works: capital above 10 (ten) hundred thousand Taka

61. Repairing of motor vehicles: capital above 10 (ten) hundred thousand Taka

62. Water treatment plant

63. Sewerage pipe line laying/relaying/extension

64. Water, power and gas distribution line laying/relaying/extension

65. Exploration/extraction/distribution of mineral resources

66. Construction/reconstruction/expansion of flood control embankment, polder, dike, etc.

67. Construction/reconstruction/expansion of road (regional, national & international)

68. Construction/reconstruction/expansion of bridge (length 100 meter and above)

69. Murate of Potash (manufacturing)

1.7.2 Standards for waste from industrial units or projects waste

Table 1.1: The standard: The Environment Conservation Rules, ECR 1997

SN	Parameter	Unit	Places for determination of standards
			Inland surface water	Public sewerage system connected to treatment at second stage	Irrigated land
1	Ammonical nitrogen (as elementary N)	mg/L	50	75	75
2	Ammonia (as free ammonia)	mg/L	5	5	15
3	Arsenic (as)	mg/L	0.2	0.05	0.2
4	BOD5 at 20°C	mg/L	50	250	100
5	Boron	mg/L	2	2	2
6	Cadmium (as CD)	mg/L	0.50	0.05	0.05
7	Chloride	mg/L	600	600	600
8	Chromium (as total Cr)	mg/L	0.5	1	1
9	COD	mg/L	200	400	400
10	Chromium (as hexavalent Cr)	mg/L	0.1	1	1
11	Copper (as Cu)	mg/L	0.5	3	3
12	Dissolved Oxygen (DO)	mg/L	4.5-8	4.5-8	4.5-8
13	Electro-conductivity (EC)	micro ohm/ cm	1200	1200	1200
14	Total Dissolved Solids	mg/L	2100	2100	2100
15	Fluoride (as F)	mg/L	2	15	10
16	Sulfide (as S)	mg/L	1	2	2
17	Iron (as Fe)	mg/L	2	2	2
18	Total Kjeldahl Nitrogen (as N)	mg/L	100	100	100
19	Lead (as Pb)	mg/L	0.1	1	0.1
20	Manganese (as Mn)	mg/L	5	5	5
21	Mercury (as Hg)	mg/L	0.01	0.01	0.01
22	Nickel (as Ni)	mg/L	1.0	2.0	1.0
23	Nitrate                 (as elementary N)	mg/L	10	Not yet fixed	10
24	Oil and Grease	mg/L	10	20	10
25	Phenolic Compounds (as C6H5OH)	mg/L	1.0	5.0	1.0
26	Dissolved Phosphorus (as P)	mg/L	8	8	15
27	Radioactive substance	To be specified by Bangladesh Atomic Energy Commission
28	pH		6-9	6-9	6-9
29	Selenium (as Se)	mg/L	0.05	0.05	0.05
30	Zinc (as Zn)	mg/L	5	10	10
31	Total Dissolved Solids	mg/L	2100	2100	2100
32	Temperature	Centig rade	40 45	40 45	40-Summer 45- Winter
33	Suspended Solids (SS)	mg/L	150	500	200
34	Cyanide (as Cn)	mg/L	0.1	2	0.2

1.8 Rationality

Washing industry in Bangladesh is very vital part for export garments product. This industrial activity needs large amount of water and also produce huge amount of wastewater. This wastewater contains abnormal parameters and various hazardous materials such as abnormal pH, BOD, COD, Color, TDS, TSS, heavy metal and so many toxic substances. Abnormal water parameters are not good for the environment. If the toxic effluent is discharged into open water body such as river without any treatment, the normal parameters of the natural and normal water body will be changed. The change of normal water parameters of natural water body will be destroying the ecological system. By this effect will be vanish the total flora and fauna. It discharge becomes to deteriorate of our daily life style.  The normal life cycle of aquatic habitats of the water body are inhibited or sometimes may extinct, which also effects on aquatic ecosystem as well as the total environment. For this reason the textile effluent need to be treated as properly and timely. Proper treatment of wastewater is save our natural environment.

1.9 Objectives

The objectives of the project work:

1.      1. To determine the water parameters like pH, TDS, COD and BOD of existing ETP inlet and outlet water.

2.      To reduce and control COD and BOD parameter and to meet the standard ECR1997.

1.10 Wastewater parameters

pH

It may be defined as the base-10 logarithm of hydrogen ion concentration of a solution.

pH= -log[H⁺]

The neutral pH of water is 7. The pH value below 7 called acidic medium. The pH value  above 7 called basic medium. Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. (www.britannica.com/science/pH)

Total Dissolved Solids (TDS)

Total Dissolved Solids (TDS) is defined as all inorganic and organic substances contained in water. In general, TDS is the sum of the cations and anions in water. Ions and ionic compounds making up TDS usually include carbonate, bicarbonate, chloride, fluoride, sulfate, phosphate, nitrate, calcium, magnesium, sodium and potassium, but any ion that is present will contribute to the total. The organic ions include pollutants, herbicides and hydrocarbons. In addition, soil organic matter compounds such as humic/fulvic acids are also included in TDS. (en.wikipedia.org/wiki/Total_dissolved_solids)

Chemical Oxygen Demand (COD)

COD is the amount of oxygen required to chemically oxidize the biodegradable and non-biodegradable organic matter. COD often is used as a measurement of pollutants in wastewater and natural water. It is expressed in milligrams per liter (mg/L) which indicates the mass of oxygen consumed per liter of solution.

Chemical Oxygen Demand or COD is a measurement of the oxygen required to oxidize soluble and particulate organic matter in water. In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution which in SI units is milligrams per litre (mg/L). A COD test can be used to easily quantify the amount of organics in water. The most common application of COD is in quantifying the amount of oxidizable pollutants found in surface water (e.g. lakes and rivers) or wastewater. COD is useful in terms of water quality by providing a metric to determine the effect an effluent will have on the receiving body. (http://en.wikipedia.org/wiki/Chemical_oxygen_demand)

Biological Oxygen Demand (BOD)

Biochemical Oxygen Demand (BOD, also called Biological Oxygen Demand) is the amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.

BOD is the amount of dissolved oxygen (DO) needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The BOD value is commonly expressed in mg of oxygen consumed per liter of sample during 5-days of incubation at 20 degree celsius temperature. BOD test time required 5 days for this it is called BOD₅.

(en.wikipedia.org › wiki › Biochemical_oxygen_demand)

Chapter Two

LITERATURE REVIEW

2.1 Production of textile effluent

The textile and clothing industries provide the single source of growth in Bangladesh. Rapidly developing economy exports of textiles and garments are the principal source of foreign exchange earnings. In the fiscal year 2018-2019, total export of Bangladesh was 40536.04 million USD, in this value RMG export was 34133.27 million USD, i.e., RMG sector export 84.21% of total export revenue.

Nazmul et al., 2014, Rodrigez et al., 2002 and Delec et al., 1998 studied on textile effluents from production in Bangladesh. Textile mills are major consumption of water with an average consumption of 160 kg per kg of finished product and consequently the most polluting industries casing intense water pollution (Bhatnagar et al., 2014). This wastewater comprises different effluent coming from different manufacturing operation such as sizing, desizing, scouring, bleaching, dyeing, soaping and softening operation (Tzitzi et al., 1994). These functions are responsible to suspended solids, high temperature, unstable pH, high chemical oxygen demand, high biochemical oxygen demand and high colorization (Lin et al., 1994). Textile effluent color is produced by laboring dyes and pigments are produced annually worldwide of which about 20% are assumed to be discharged as industrial effluent during the textile dyeing processes (Muhammad et al., 2008). Worldwide about 106 tons and more than 10,000 different synthetic dyes and pigments are produced annually in dyeing and printing industries.

Table 2.1: Water pollution source and their ranking in Bangladesh (Hannan et al., 2011)

Industry	Water pollution	Pollution product	Ranking
Agriculture	Moderate	1.08	3
Textile	Big	3.35	1
Transport	Small	0.02	6
Construction	Small	0.14	5
Paper	Very Big	0.67	4
Leather	Extreme	1.88	2
Sugar	Extreme	1.72	2

2.2 General characteristics of textile dye effluent

Textile dye effluent carries various harmful materials. The characteristics of this effluent inhibit normal parameter of water and which place this effluent is discharged the water quality of those area/water body become polluted. As a result total water quality system of this area is affected by such kind of pollution. Textile industries are major sources of these effluents (Ghoreishi, S.M. and Haghighi, 2003). In the table 2.2 wastewater characteristics are shown. Due to the nature of their operations which requires high volume of water that eventually results in high wastewater generation. They are one of the largest water users and polluters (Babu, 2007).

Table 2.2: Physico-chemical characteristics of textile waste water                  (Saravanamoorthy et  al., 2007)

Characteristics (mg/L)	Textile waste water
Color	Dark brown
Odor	Unpleasant
pH	8.1-9.1
EC d Smpl-1	6.2
TSS	250-300
TDS	1600-3900
BOD	42
COD	142
Bicarbonate	1500
Chloride	526
Sulphate	Present
Calcium	580
Magnesium	140
Sodium	45
Potassium	28

2.3 Effect of textile effluent

2.3.1 Environmental effect of textile dye effluent

The key environmental issues inter-linked with textile manufacturers are use of water, its treatment and disposal of liquid effluents (Morali et al.,2016). Here, dyes are contributing to overall toxicity at all processing stages. Therefore, it is responsible for high level of BOD, COD, colour, surfactants, fibres, turbidity and contains toxic heavy metals (Silva et al., 2014).

In addition, dyeing process usually contributes chromium, lead, zinc and copper to effluents (Nergus et al., 2005). Hence, the released effluents from the effluent treatment plants (ETPs) of industries must meet the national effluent discharge quality standards (Evans et al., 2009) where common effluent treatment plant (CETP) facilitates the industries in easier control of pollution with low-cost as well acts as a step towards cleaner environment.
In as much efficiency and effectiveness of an ETP is very important (Kanade et al., 2015), so, the CETP is a better and economically viable option for industrial effluents treatment (Bhattacharya et al., 2016).

There are currently above 30,000 industrial units in Bangladesh; thereof, about 24,000 are small and cottage industries (Ahmed et al., 2012). The DoE, recently, has identified 900 large polluting industries, have no treatment facilities for effluents and straightly discharge to adjacent soils and water bodies (Tayagi et al., 2015) else, release their daily generated wastes into the ecosystem, on which local people depend on for their livelihoods (Chowdhury et al., 2006).

Amidst, textile is one of the most important and rapidly developing industrial sectors in Bangladesh based on earning foreign exchange and labor employment (BGMEA 2013). But these industries generate commingled a large quantity of contaminated effluents that pollute the environment (Awomeso et al., 2012). To mitigate the risks associated with the discharge of textile effluents, an ETP is required (Kumer et al., 2011) but due to high installation and operation cost, most of the textile industries don’t run ETP; occasionally, operate when buyers or DoE inspect the factory (Chowdhury et al., 2006).

Anyway, recently many industries are making progress in establishing and operating their own ETPs to comply with national and international requirements. Regretfully, advanced wastewater treatment technologies; e.g. - advanced oxidation process, aerated lagoon, bioreactor, constructed wetland, membrane bioreactor, nano-technology, ion-exchange, desalination and reverse osmosis etc. are not popular for industrial and municipal wastewater treatment in Bangladesh till now (BTMA Annual report 2012) inversely, technologically ahead countries are recovering valuable nutrients, elements and metals from wastewater but Bangladesh lags behind yet (Ahmed et al., 2012).

Further, ETP, which is closely linked to remove excess level of different pollutants from industrial effluents, has not really been quested to explore their efficiency of effluents treatment here to in Bangladesh. Therefore, the absence of any known study on the efficiency of established ETPs has coupled the problems. Thereat, efficiency analysis of ETPs is momentous to improve its current performance and so the research work was carried out to assess the efficiency of ETPs.

2.3.2 Water pollution

Textile industries release large amount of effluents to aquatic systems, which contain toxic and hazardous pollutants degrading the environment (Dubey, 2010). Water pollution is considered to be the biggest environmental threat all over the world. In India government is investing more to control water pollution but the results are below the satisfactory level. The consumption for the textile industry includes various processes such as sizing, dyeing, and other end product processes. The major problem arises when these chemicals are directly discharged into water bodies thus causing water pollution. This water pollution not only affects human beings and house hold animals but also aquatic animals to the same extent. In recent years the fatality of death endorsed because of water pollution everywhere and majority of the diseases are due to this pollution (Chikogu, V., 2012). In order to reduce water pollution some measures should be taken for betterment of life. Before entering into major treatment it will be easy to carry over preliminary steps for removing hazards. Table 2.3 shows pollutant generation from textile industries.

Table 2.3: Effluent discharge from textile industry

SN	Process	Chemical discharge	Pollution	Health effects
1	Sizing	Benzene	Resin, fate, waxes, starch and glucose	Carcinogenic, mutagenic and affect central nervous system
2	Bleaching	Cyanide	Wax, grease, soda ash sodium and silicate	Prolonged exposure will affect kidney and liver and leads to death
3	Dyeing	Sulphate	Sulphides, acetic acid and mordant	Eye and respiratory problem
4	Printing	Nitrate, Phosphate	Starch, gums and mordant acid	Harmful health hazards
5	Finishing	Lead	Starch, salt and finishing agent	Suppression of hematological System

2.4 Textile effluent treatment method (physicochemical)

Adsorption

Zhu et al., 2011 and Zhao et al., 2012 studied on adsorption. They found adsorption has widely received significant attention over the years due to its vast advantages in terms of operational, technically and feasibility. It is the most used method in physicochemical wastewater treatment, which can mix the wastewater and the porous material powder or granules, such as activated carbon and clay, or let the wastewater through its filter bed composed of granular materials. Through this method, pollutants in the wastewater are adsorbed and removed on the surface of the carbon of the porous material or filter. Commonly used adsorbent are activated carbon, silicon polymers and kaolin. Different adsorbents have selective adsorption of dyes. So far activated carbon is still the best adsorbent of dye wastewater. The chrome can be removed 92.17% and COD can be reduced 91.15% in series adsorption reactors.

Coagulation, flocculation and sedimentation

Coagulation, flocculation and sedimentation are the most used methods, especially in the conventional treatment process. Chemical coagulation includes all of the reactions and mechanisms involved in the chemical destabilization of particles and in the formation of larger particles through perikinetic flocculation (aggregation of particles in the size range from 0.001 to 1 µm). Alum, Ferrous sulphate, Poly aluminium chloride can be used as coagulant to destabilized the colloidal particles. Normally the colloids bring negative charges, so that coagulants are usually inorganic or organic cationic coagulants (with positive charge in water). The metallic hydroxides and the organic polymers, besides giving the coagulation can help the particle aggregation into flocks, thereby increasing the sedimentation. Flocculation is a transport step that brings about the collisions between the destabilized particles needed to form larger particles that can be removed readily by setting or filtration. The combined action of coagulation, flocculation and setting is named clariflocculation. Setting needs stillness and flow velocity, so these three processes need different reactions tanks. This processes use mechanical separation among heterogeneous matters, while the dissolved matter is not well removed (clariflocculation can eliminate a part of it by absorption into the flocks). The dissolved matter can be better removed by biological or by other physical chemical processes (Sheng et al., 1997). But additional chemical load on the effluent (which normally increases salt concentration) increases the sludge production and leads to the uncompleted dye removal.

Chemical oxidation

Chemical operations, as the name suggests, are those in which strictly chemical reactions occur, such as precipitation. Chemical treatment relies upon the chemical interactions of the contaminants we wish to remove from water and the application of chemicals that either aid in the separation of contaminants from water or assist in the destruction or neutralization of harmful effects associated with contaminants. Chemical treatment methods are applied both as stand-alone technologies and as an integral part of the treatment process with physical methods (Ranganathan et al., 2007). Chemical operations can oxidize the pigment in the printing and dyeing wastewater as well as bleaching the effluent. Currently, Fenton oxidation and ozone oxidation are often used in the wastewater treatment.

Ozone oxidation

It is a very effective and fast Decolouring treatment, which can easily break the double bonds present in most of the dyes. Ozonation can also inhibit or destroy the foaming properties of residual surfactants and it can oxidize a significant portion of COD. Moreover, it can improve the biodegradable and toxic components through the conversion (by a limited oxidation) of recalcitrant pollutants into more easily biodegradable intermediates. As a further advantage, the treatment does increase neither the volume of wastewater nor the sludge mass. Full scale applications are growing in number, mainly as final polishing treatment, generally requiring up-stream treatments such as at least filtration to reduce the suspended solids contents and improve the efficiency of decolourisation. Sodium hypochlorite has been widely used in the past as oxidizing agent. In textile effluent it initiates and accelerates azo bond cleavage. The negative effect is the release of carcinogenic aromatic amines and otherwise toxic molecules and therefore, it should not be used (Sheng et al., 1997).

Membrane separation process

Membrane separation process is the method that uses the membrane’s micropores to filter and makes use of membrane’s selective permeability to separate certain substances in wastewater. Currently, the membrane separation process is often used for treatment of dyeing wastewater mainly based on membrane, such as reverse osmosis, ultrafiltration, nanofiltration and microfiltration. Membrane separation process is a new separation technology, with high separation efficiency, low energy consumption, easy operation, no pollution and so on. However, this technology is still not large-scale promoted it has the limitation of requiring special equipment, and having high investment and the membrane fouling and so on (Ranganathan et al., 2007).

Reverse osmosis

Reverse osmosis membranes have a retention rate of 90% or more for most types of ionic compounds and produce a high quality of permeate. Decolorization and elimination of chemical auxiliaries in dye house wastewater can be carried in a single step by reverse osmosis. Reverse osmosis permits the removal of all mineral salts, hydrolyzed reactive dyes, and chemical auxiliaries. It must be noted that osmotic pressure becomes; therefore, the greater the energy required for the separation process (Babu et al., 2007).

Nanofiltration

Nagy, 2012 described on nanofiltration. Nanofiltration is a pressure-driven membrane process that lies between ultrafiltration and reverse osmosis in terms of its ability to reject molecular or ionic species. Nanofiltration membranes, organic membranes or ceramic membranes are either dense or porous. The membranes may have a larger free space, small pores or nanovoids. The specific features include the combination of very high rejections for multivalent ions with low to moderate for monovalent ions and high rejection of organic compounds with a molecular weight above that of the membrane. During filtration processes, the uncharged solute particles, their size and the steric effects have significant influence on the separation efficiency. Due to the steric effects, a hindered diffusion and convection can take place in the membrane matrix. The mechanism of the mass transport depends strongly on the membrane structure and interactions between the membrane and transported molecules. The separation efficiency is governed by the sieving effect or by the solution and diffusion properties of the solute molecules. In the case of charged molecules, the electrical field plays an important role in the transport. Three parameters are crucial for operation of a nanofiltration unit: solvent permeability, rejection of solutes and yield or recovery.

Ultrafiltration

Ultrafiltration, whose aperture is only about 1 nm-0.05 µm, enables elimination of macromolecules and particles, but the elimination of polluting substances, such as dyes, is never complete. Even in the bets of cases, the quality of the treated wastewater does not permit its reuse for sensitive processes, such as dyeing of textile. So the retention molecular weight is range from 1000-300000 da. Rott and Minke, 1999 emphasize that 40% of the water treated by ultrafiltration can be recycled to feed processes termed minor in the textile industry (rinsing and washing) in which salinity is not a problem. Ultrafiltration can only be used as a pretreatment for reverse osmosis or in combination with a biological reactor (Babu et al., 2007).

Microfiltration

Microfiltration whose aperture is about 0.1 -1 µm is suitable for treating dye baths containing pigment dyes, as well as for subsequent rinsing baths. The chemicals used in dye bath, which are not filtered by microfiltration, will remain in the bath. Microfiltration can also be used as a pretreatment or reverse osmosis (Babu et al., 2007). Textile wastewater contains large amounts of difficult biodegradable organic matter and inorganic. At present, many factories have adopted physicochemical treatment process (Zeng et al., 2005).

2.5 Biological wastewater treatment method

Biological methods, i.e. degradation of dyes with the biological phenomenon such as bioremediation is a green technique to improve dye from textile effluent with minimum cost and optimum operating time (Ekambaram et al., 2016). Ali et al., 2010 suggested applications of biological material such as algae, fungi and yeasts which have an ability to disintegrate as well as absorb varieties of synthetic dyes. Biological based methods employed for degradation of the effluent from the textile industries have been successfully used. The biological degradation (i.e. bioremediation) is economically feasible, environmental-friendly and degradation of synthetic dyes to a comparatively less toxic inorganic compound because of breakdown of bond (i.e. chromophoric group) and finally helps in removal of color (Babu et al., 2015). The catabolism of the azo dyes takes place in two steps, firstly the dyes underwent through the breaking of the azo bonds forming the amines and secondary the aromatic amines are further catabolized to small non-toxic molecules under aerobic environment (Chequer  et. al., 2011). The techniques are being developed to use the ability of bacteria to survive under the aerobic as well as the anaerobic conditions for the complete degradation of the azo bonds formed within the dyes.

Lewinsky, 2007, Lin and Lo, 1997 gave the insight that biological process is efficient in reducing the COD and turbidity but inefficient in removing the color. Muda et al., 2013 reported success and benefit of the two-phase process in developing biological methods for decolorization in a future where the first phase involves anaerobic processes followed by aerobic process. Normally, selection of ideal treatment system is dependent on the characteristics of the textile waste water generated and the ability of the textile operator to equip their treatment facilities based on economic evaluation and effectiveness of the proposed system. In general, every treatment option has their advantages and drawbacks. Biological treatment for instance is capable to render the concentration of organic compound that presence in the waste water. In addition, the low cost implications and environmentally safe techniques have been seen as the main option for the treatment method (Khelifi et at., 2008, Balamurugan et al., 2011 and Ulson et al., 2008). However, a few biological treatment option namely aerobic processes were inefficient to degrade most of azo dyes (Isik and Sponza 2008). Incomplete destruction of organic compound during biological treatment has caused the transfer of the dye onto biomass via adsorption (Gomaa et al., 2012).

Biological treatment of wastewater using microbes has been one of the active fields of research (Drogui et al., 2005, Cheung and Gu 2007). Microbes are nature’s original recyclers, converting toxic organic compounds into simpler non-toxic products, often carbon dioxide and water. The presence of a large number of diverse bacteria, fungi and other microbes in nature expands the variety of chemical pollutants that can be degraded and the extent to which polluted sites can be decontaminated by indigenous microbes. There are several reports dealing with the decolorization of dyestuffs using pure bacteria strains and combination of selected strains (Oturkar et al., 2013). Natural bacteria and fungi, isolated from effluents sites, i.e.,  Aeromonas sp., Pseudomonas sp., Flavobacterium sp., Rhodococcus sp. and fungal strains. Myrothecium sp. and Phanerochaete chrysosporium may have potential to absorb and degrade the dye component from textile effluent (Hu et al., 1992, Mou et al., 1991, Heiss et al., 1992, Glenn and Gold 1981). Pure bacterial strains, such as Pseudomonas luteola, Aeromonas hydrophila, Bacillus subtilis, Pseudomonas sp. and Proteus mirabilbis decolorizex dye under anoxic conditions while in some cases they need additional carbon sources to decolorize as they are unable to utilize the dyes due to their toxicity (Chang et al., 2001). Bacillus strains are ubiquitous in activated sludge and have been found to degrade different dye groups (R.G et al., 2011).

Florence et at., 2019 studied on innovation for new anaerobic domestic wastewater treatment recycling system in developing countries. Over the years, the spate of water pollution has assumed an alarming dimension globally because of rapid urbanization, aggressive economic development and geometric population growth. This has given rise to acute shortage of freshwater resources. The need for appropriate and efficient treatment technologies to achieve effluent quality that complies with acceptable standard has become imperative. Conventional wastewater treatment technologies are not only costly to build, but also have combined functional and maintenance problem. As a result, forward-looking innovative technologies which are cost effective such as domestic multi recycler (DMR) is desperately needed to restore poor water pollution that poses serious health threat to most people in developing countries and to improve the soundness of water and wastewater recycling system. Also enhance the quality of treated water discharged from the source to the municipal in a wastewater treatment method anaerobically without requiring electricity and the sludge generated is utilize as fertilizer. Since functional wastewater collection and treatment are of vital importance from the perspective of both environmental and public health. In this paper, the technology application is aimed at contributing immensely to attain goal 6 of sustainable development goals (SDGs), “Ensuring availability and sustainable management of clean water and sanitation for all”.

Karim et al., 2017 studied a preliminary comparative analysis of MBR and CAS Wastewater Treatment Systems. A preliminary analytical study was conducted to compare the cost effectiveness and performance of a membrane bio-reactor (MBR) versus conventional activated sludge (CAS) systems for the treating of wastewater. The design and construction cost, Operation and Maintenance (O&M) cost and foot-print of different MBR and CAS wastewater treatment plants were collected from various states. The performance data for several parameters were collected from local MBR and CAS wastewater treatment plants. It was found from this study that based on the capital cost considerations; CAS system appears to be a better option compared to the MBR system. However, for long-term operation, foot-print requirements and treatment effectiveness to meet more stringent effluent characteristics, the MBR system appears to be a better option over the CAS system. Based on the long-term normalized cumulative cost analysis, the MBR system is a better option for a plant operating longer than 67 years, whereas the CAS system is a better option for a plant operating less than 67 years. Therefore, for a long-term operational goal and for performance considerations, the MBR system seems to be the best option.

Mark et al., 2013 published on activated sludge and aeration process. Activated sludge systems are constructed for secondary treatment of wastewater. The aeration basin is a long rectangular tank with air diffusers along the bottom for oxygenation and mixing. Air diffusers are set on the bottom of the tank or attached to pipe headers along one side at a depth of 8 feet or more to provide deep mixing and adequate oxygen transfer. Fine-bubble diffusers, in the form of aeration domes or plates mounted over channels in the floor, are distributed over the entire bottom of the tank to provide uniform vertical mixing. The smaller bubble size and increased floor coverage improve oxygen transfer and decrease air requirements and blower size. In spiral flow aeration, a large number of diffuser tubes or nozzles are attached to air headers along one side of the tank. A number of different kinds are manufactured, including perforated tubes with or without removable sleeves, jet nozzles and a variety of air sparger. These produce coarser bubbles than a ceramic diffuser. The air headers are connected to a jointed arm so that the diffusers can be swung out of the tank for cleaning and maintenance. The plug-flow pattern of long rectangular tanks produces an oscillating biological growth pattern. The relatively high food to microorganism ratio at the head of the tank decreases as mixed liquor flows through the aeration basin. The aeration period is 5 to 8 hour can be considerably greater during low flow, the microorganisms move into the endogenous growth during low flow, the microorganism move into the endogenous growth phase before their return to the head of the aeration basin. This starving microbial population must quickly adapt to a renewed supply of waste organics. This process wastewater flow should maintain greater than 0.5 mgd.

Maulin et al., 2016 shows the pros and cons of using the combination of various technologies for industrial waste water treatment plant. Rapid industrialization, intensive agriculture and other human activities cause soil degradation, pollution and lowers the productivity and sustainability of the crops that further increase the pressure on natural resources and contribute to their degradation. Environmental bio remediation is an effective management tool for managing the polluted environment and in restoring the contaminated soil. The use of microbial sources, coupled with advanced technology is one of the most promising and economic strategies for the removal of environmental pollutants. There is a strong scientific growth with both the in situ and ex situ ways of bio remediation, in part due increased use of natural damping as most of the natural attenuation is due to bio degradation. The degradation of pollutants by environmental bio remediation technology can be a lucrative and environmentally friendly alternative. This article provides an overview of the important environmental bioremediation technologies and their application in treating the industrial waste water.

Sharma, 2004 written on method of treatment, objectives of wastewater treatment and studied on different industry takes different types of water and discharges different types of wastewater to the water bodies. Water is essential for each industry by follows:

a) Raw materials b) Power supply c) Water d) Transport facilities

Each industry has its own water requirements and sometimes adequate supply of water may be very suitable for one industry but the same may be dangerous for other. It is therefore, extremely important to take into account the uses of water to be carried out, it’s suitably based on the results of chemical analysis and bacteriological examinations. For example, boiler feed water should be as soft as possible and should contain least amount of nitrate and organic matter. Water used for alcoholic distilleries should be as pure as possible and should contain few microorganisms along with traces of NaCl and MgCl₂. Water used for paper mills should not contain iron and excess of lime and magnesia. In sugar industries, the crystallization becomes more difficult if water contains sulphates and alkaline carbonates and also the nitrates. If water is rich in microorganisms, they may decompose the sugar. Water used for alcoholic breweries must contain and lime and magnesia in much lesser amounts. In dye industry, water used should be free iron and should possess little hardness only. Water used for cooking purposes should contain little hardness otherwise the vegetables do not cook easily. Water used for laundries should be as soft as possible.

Industrial activities generate a large number and variety of waste products which are generally discharged into water streams. The nature of waste water treatment depends upon the industrial process in which, waste treatment depend the industrial process in which they originate. Such as lime sludges may be lagooned and settled or they may be dewatered and calcined for reuse. Brine used in regenerating ion exchange plants. Activated sludge process is used to treat the wastes, when the industry uses raw materials of complicated organic matter. This process can be successfully employed to wastes from tanneries, meat packing plants, milk processing plants, rendering plants, etc. Tannery wastes may be treated flocculation and sedimentation or filtration. Brewery wastes are subjected to trickling filters.

The method of treatment of an industrial waste depends on various factors-

• Nature of industrial waste
• BOD and COD of the effluent
• pH
• Suspended solids
• Total solids present
• Pollutants present
• Toxic chemical substances present, etc.

Objectives of the treatment of wastewater are:

• To remove colour, objectionable odour and taste
• To remove dissolved gases, dissolved and suspended impurities and harmful minerals
• To remove suspended as well as dissolved organic impurities
• To remove pathogenic bacteria
• To make water safe for drinking and domestic purposes.

Khopkar, 2012 written on method for quantitative analysis. There are some methods of quantitative analysis of pollutants. These methods are applicable when the pollutant is present at milligram (10^-3) to femtogram concentration (10^-15). The classical gravimetric and volumetric methods can alalyse a pollutant up to 10^-4 g concentration, while analytical absorption or emission spectroscopic method can analyse pollutants to the level of nanogram (i.e. 10^-9 g) concentration. Other methods involving light scattering or molecular luminescence spectroscopy operate up to microgram levels. The radio analytical or electroanalytical methods can work in the range 10^-7 to 10^-9 concentration. At this stage, methods used for pollution analysis shall be reviewed. No attempt is made to provide details of these instruments methods of analysis. In fact it is assumed that reader is quite conversant with this modern method of analysis. Only endeavor is made to pinpoint the specific method for analysis of particular pollutant with due emphasis on the basic principles involved in such analysis.

Amin et al., 2017 studied on feasibility study of the wastewater using electrocoagulation treatment technique. Electrocoagulation (EC) is becoming a popular process to be used for wastewater treatment. In this study, the application of EC technique in the treatment of dyeing effluent has been investigated. The experiments were carried out in an electrochemical reactor using iron electrode. Different operating time and electrode spacing has been studied in an attempt to achieve a higher removal capacity. Majority of the textile industries of Bangladesh are located in the Savar, Ashulia, Tongi and Gazipur around of Dhaka city. Wastewater samples were collected from Noman Dyeing industry. At present, wastewater from the industries is discharged through open drains in to the stagnant ponds that exist in Tongi area and finally fall in to the river Turag. In the samples, the parameters DO, pH, Color, Turbidity, TSS, TDS, EC, COD, BOD₅ were measured. The values of pH didn’t satisfy the limit of Bangladesh standard values for drinking water.

Toriqul et al., 2018 studied on exploring option for sustainable faecal sludge management system in Mymensingh city. The study was undertaken to analyze and explore a sustainable fecal sludge management option for Mymensingh city. In order to achieve the objective, the specific issues such as containment, emptying, transport and disposal systems were assessed. The average faecal sludge generation rate in Mymensingh municipality was 0.97 liter/person/day. The estimated total volume of faecal sludge was 112 cubic meter in 2018. When pit or septic tank is full, the emptying was conducted manually (95%) and mechanically (5%). The deposition pattern of the emptied sludge followed as drain>canal>pond water bodies. The implication of this study suggests an innovative sustainable sanitation service chain which improves current faecal sludge management practice in municipality.

Siddik et al., 2016 shows on determination of health risk assessment of heavy metal concentration in food wastes of waste management plant at Jahangirnagar University, Dhaka, Bangladesh. Around the year to determine the minimum, maximum and mean concentration of seven heavy metals (Cadmium, lead, chromium, nickel, copper, iron and zinc) in commonly consumed vegetables at Jahangirnagar University waste management plant. Estimated daily intake (EDI), target hazards quotient (THQ) and total carcinogenic risk (TCR) were determined.

Islam et al., 2018 studied on feasibility study of the wastewater using electrocoagulation treatment technique. Water crisis is increasing day by day to fulfill the demand of huge population of world and deteriorated the water quality as well. Most of the water treatment processes are expensive and also challenging. Among all the water treatment processes, anaerobic baffled reactor (ABR) process is rather economical viable and environmental friendly one. Over the last decade, anaerobic digestion has proven to be a better alternative than aerobic processes, especially in the treatment of high-strength wastewaters. Compared to aerobic processes, anaerobic treatment processes consume less energy and produce less sludge, which lead to lower operational costs of water treatment by ABR process.

Eddy et al., 2014 published and written on wastewater biological characteristics and described how they found in wastewater. The biological characteristics of wastewater are of fundamental importance of disease caused by pathogens organisms of human origin and because of the extensive and fundamental role played by bacteria and other microorganisms in the decomposition and stabilization of organic matter, both in nature and in wastewater treatment plants. Organism found in surface water and wastewater includes bacteria, fungi, algae, protozoa, plants, animals and viruses. Bacteria, fungi, algae, protozoa and viruses can only be observed microscopically. Living single-cell microorganisms that can be only seen with a microscope are responsible for the activity in biological wastewater treatment. The basic functional and structural unit of all living matter is the cell. Living organisms are divided into either prokaryote or eukaryote cells as a function of their genetic information and cell complexity. The prokaryotes have the simplest cell structure and include bacteria, blue-green algae (cyanobacter) and archaea. The archaea are separated from bacteria due to their DNA composition and unique cellular chemistry, such as differences in the cell wall and ribosome structure. Many archaea are bacteria that can grow under extreme conditions of temperature and salinity, and also include methanogenic methane-producing bacteria, important in anaerobic treatment processes.  In contrast to the prokaryotes, the eukaryotes are much more complex and contain plants and animals and single-celled organisms in wastewater treatment including protozoa, fungi and green algae.

2.6 Feasibility study for ETP in sweater factories

Saha et al., 2018 studied on sweater factories in Bangladesh play a very important role in our economy. Almost all the sweater factories in Bangladesh normally have small washing unit for cleaning, softening etc. purpose. Now-a-days, discharged water from these washing units has become a matter of concern for environmental degradation. It also put one in a dilemma whether to build an effluent treatment plant (ETP) or not. This decision should come from the business pattern of the entrepreneur, customers’ requirements, legal and international requirements etc. Indeed, for sweater factory, there is no legal requirement to build ETP as long as the discharged wastewater meets tolerance limit of environmental conservation rules, schedule-10 (ECR- 1997). From this project, it has been identified that without ETP, discharge wastewater in sweater factories in 86% of cases are able to meet the requirements ECR-1997, in 43% of cases meet ZDHC foundational requirements. But none of these factories was able to meet ZDHC progressive and aspirational requirements. We can say wastewater of a sweater factory sometimes can meet legal requirement which is subjected to waste water test report. If does not meet, ETP should be build. On the other hand, to meet ZDHC requirements properly and to have a sustainable business with ZDHC signatory brands, entrepreneurs must install ETP in their sweater factories.

2.7 Analysis of pharmaceutical wastewater quality: comparison of inlet and outlet water

Akter et al., 2019 studied on characterization of pharmaceutical wastewater quality: comparison of inlet and outlet water. In Bangladesh, pharmaceutical industries are responsible for 15.9% water pollution and 12.6% toxic chemical emission to the environment (World Bank). Pharmaceutical wastewater contains a lot of organic and inorganic constituents and many of them has been classified as hazardous pollutants because of their potential harm to human health and ecosystem. The long term exposure of lower concentration of complex pharmaceutical mixtures on stream biota may result in active and chronic damages, accumulation in tissues, reproductive damages and inhibition of cell proliferation. They identified the physicochemical parameter and the concentration of heavy metals of the wastewater are within the standard of DoE in Bangladesh. In case of Cr, the effluent is not suitable for irrigated land but it is suitable for inland surface water as it is within the standard of DoE. Total coliform count is much higher than the permissible limit.

2.8 Pollution of Buriganga river

Chowdhury et al., 2019 researched on pollution of Buriganga river. Buriganga river is one of the most polluted rivers in Bangladesh, as this river receives huge amount of waste from various types of industries, households etc. This study framed the water quality of Buriganga river and analyzed the presence and concentration of poly chlorinated biphenyls (PCBs), one of the notorious persistent organic pollutants (POPs). The distribution and concentrations of 7 polychlorinated biphenyl (PCB) congeners, numbers, 1, 11, 29, 47, 116, 136 and 185 were determined in the surface water from five sampling points of the Buriganga river. The five sampling points were Mitford ghat, Switz gate ghat, Babubazar ghat, Badamtoli Masjid ghat and Lalkuthi kheya ghat. The analysis of PCB congeners were achieved by gas chromatography-mass spectrometry (GC/MS) using modified SW-846 Method 8082. The total PCB concentrations in the samples ranged between 0.211 to 8.114 ppb. The concentrations of the congener profiles showed significant differences. This study provided a snapshot of the water quality and PCB contamination status in the Buriganga river and allowed for a clear idea for further investigation. The measured parameters for the detection of water quality showed variation among the sampling points. All parameters were not within the standards of ECR, 97 and DoE, except pH.

Chapter Three

MATERIALS AND METHODS

3.1 Study area

The effluent sample was collected from The Civil Engineers Ltd., Unit-2 ETP inlet and outlet. Activated sludge treatment process is applied on the existing ETP outlet water. Reason is that existing ETP outlet treated water does not meet the standard ECR. Factory is located at Plot No. 8, 9, 159 & 160, Bagbari, Horindhora, Hemayetpur, Savar, Dhaka, Bangladesh. It is mainly a washing factory which washes the fabrics and garments.  The main source of wastewater of this industry is the washing of fabrics and garments. The existing ETP outlet water is again will be treated by activated sludge i.e., biological process.

3.2 Working laboratories

1.      Water Research Center, department of Environmental Sciences, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

2.      ETP laboratory, The Civil Engineers Ltd., Unit-2, Plot No. 8, 9, 159 & 160, Bagbari, Horindhora, Hemayetpur, Savar, Dhaka, Bangladesh

3.3 Materials

3.3.1 Apparatus and glassware

To conduct this study various apparatus and glassware were used. They are as follows-

o   Glass box

o   Diffuser

o   Air blower

o   Air line from air blower

o   Plastic sample bottles

o   Beakers

o   Glass rod

o   Pipette

o   Burette

o   Pipette pumper

o   Measuring cylinder

o   Conical flask

o   300 ml BOD bottles

3.3.2 Laboratory equipments

To carry this study following instruments were used-

o   Electrical balance ( Radwag, AS220/C/2)

o   pH meter ( EuTech pH 700)

o   TDS meter ( Hanna EC/TDS)

o   COD reactor ( HACH DRB 200)

o   COD digestion reagent high range (HACH COD vial HR)

o   Spectrophotometer ( HACH DR3900)

o   Incubator ( VELP FOC120E)

o   BOD measurement system ( Aqua lytic BD600)

3.3.3 Chemicals and Reagents

Different chemicals and reagents were used in laboratory analysis. They are following:

o   Ferrous sulphate (FeSO₄)

o   Sulphuric acid (H₂SO₄)

o   Mercuric sulphate (HgSO₄)

o   Potassium dichromate (K₂Cr₂O₇)

o   Hydrochloric acid (HCl)

o   Ferrous Ammonium Sulphate (NH₄Fe(SO₄)₂)

o   De-ionized water

3.4 Sample collection

Samples were collected from existing ETP inlet and outlet. These were collected following the sampling techniques as outlined by APHA, 1995 and Sincero and Sincero, 2004. To prevent the loss, the samples were collected carefully and transported to the ETP laboratory as quickly as possible in a preserved condition. Before sampling, the bottles were cleaned with detergent and then washed with copious of distilled water. After sampling, the bottles containing samples were sealed immediately to avoid exposure to air and marked with necessary information. The capacity of sample bottle was 1000 ml. Lab serial number, sample collection date, time, location and address written on the sample bottles. In the laboratory, the bottles were kept in a clean, cool and dry place to avoid contamination.

3.4.1 Selection of appropriate method

In ETP lab waste water was measured. Then individual tests performed by given direction.

3.4.2 Sample collection for testing

The samples were collected in 1000 ml plastic water bottles. The plastic sample bottles were washed 20% HNO₃ solution and then rinsed thoroughly with distilled water. During sampling the sample bottles were tightly screwed and marked with respective identification number.

3.4.3 Description of the collected sample

The sample were collected during June 2019 – July 2019 from existing ETP inlet and outlet of The Civil Engineers Ltd., Unit-2, Plot No. 8, 9, 159 & 160, Bagbari, Horindhora, Hemayetpur, Savar, Dhaka, Bangladesh. Water sample was collected five liter from the respective processing in clean dry plastic bottles on different days at different time as per required. The samples were quickly brought into the laboratory. After initial physicochemical test the sample were preserved in refrigeration at 4°C for further test.

3.4.4 Sampling record and precaution

Properly checked writings on the sample collection bottles during sampling, such as-

o   The sample number was marked on the bottles by the permanent marker.

o   Laboratory serial number was written on the bottles.

o   Location of sample collection was written on the bottles.

o   Time of sample collection was written on the bottles.

o   Date of the sample collection was written on the bottles.

o   Address of factory was written on the bottles.

The following precautions were taken during sample time since all the data analysis is based on the proper sampling-

o   To avoid contamination and the adsorption of trace metals within the bottles.

o   The bottles were sealed tightly.

o   The bottles and plastic cap were cleaned before each sampling.

o   The collected samples were stored in 4°C in the refrigerator.

3.5 Wastewater treatment by activated sludge

Clean the glass box and placed on the plane table in the ETP laboratory. The size of the glass box is 18” × 18” × 24”. A diffuser is set of bottom of the glass box. Diffuser size was 10” diameter and it was fine bubble diffusing capacity. Air line from the air blower is connected with the diffuser. Wastewater collected from the existing ETP Outlet and placed in the glass box. Then activated sludge is added to the waste water in the glass box. Activated sludge is collected from another ETP.  Activated sludge is collected from the holding tank. Airline is run and air diffusing is started. After every hour water collected from the glass box and tested. Test result is recorded.

3.6 Physicochemical analysis of the water sample

pH

The pH was measured by using pH meter (EuTech pH 700).

Test Procedure of pH

The pH meter is calibrated with three known buffer solution pH 4.0, 7.0 and 10.0. Then the probe was rinsed thoroughly with distilled water and wiped by tissue paper. The probe was kept in solution until stable was measured.

Total Dissolved Solids (TDS) (mg/L)

TDS was determined by using total dissolved solid (TDS) meter (Hanna EC/TDS). The electrode was rinsed thoroughly by using distilled water and wiped by fresh tissue paper. The electrode was dipped into sample water and kept there stable reading with beep was observed. TDS value of all the samples were measured in triplicate and value was recorded.

Chemical Oxygen Demand (COD) (mg/L)

COD vial preparation

To determine COD value of wastewater first COD vial need to be prepared. To prepare COD vial 3.0644 g of K₂Cr₂O₇ (analytical grade) was dissolved in 250 ml water and 0.25 N solution was prepared. From this solution by taking 2 ml of K₂Cr₂O₇ solution with 3 ml of H₂SO₄ (analytical grade) and small amount of HgSO₄ (analytical grade) and Ag₂SO₄ (analytical grade), COD vial was prepared.

Determination

Then 2 ml of water sample was added to this vial. Then COD vial was placed in COD reactor at 150°C temperature for 2 hours. After digestion it will be cooled to normal temperature. After cooling it will be titrated with 0.125 N ferrous ammonium sulphate solution. For preparation 0.125 N ferrous ammonium sulphate solution (FAS), dissolving 4.902 g of (NH₄)₄Fe(SO₄)₂ (analytical grade) chemical in 100 ml of distilled water. After digestion, the chemical should be taken in 50 ml conical flask and 5-7 drops ferroin indicator should be added to the conical flask. Then 0.125N FAS solution should be taken into a burette. During titration color change was observing very carefully. The color change of conical flask solution will be from Dark green to brownish color. Finally color change will be observed and burette reading was recorder.

 

                                

                                Scheme 3.1: Titration procedure of the COD testing

Calculation

                                                      (A-B) × M × 8000

COD as mg O₂/l =

                                                        ml sample

Where, A= ml FAS (Ferrous ammonium sulphate) used for blank

            B= ml FAS used for sample

            M= molarity of FAS

           8000 = milli-equivalent weight of oxygen × 1000 ml/l

Biological Oxygen Demand (BOD) (mg/L)

The biochemical oxygen demand (BOD) in water (e.g. waste water, surface water) is the amount of oxygen that is consumed during the degradation of organic substances through biochemical processes.

Measuring principle

The BOD measuring unit, comprising test bottle and BOD sensor, is a closed system. With the filled sample quantity, there is a gas compartment with a defined quantity of air in the test bottle. The bacteria in the waste water filled in the bottle (the sample can be used diluted or undiluted) consume the oxygen dissolved in the sample over the course of the BOD measurement. It is replaced by air oxygen from the gas compartment of the test bottle. The simultaneously developing carbon dioxide is chemically bound by the potassium hydroxide in the seal cup of the test bottle. As a result, a pressure drop occurs in the system, which is measured by the BOD sensor and shown in the directly in the display as a BOD value in mg/L O₂. Incubate the sample according to specifications (e.g. BOD₅ at 20 °C).

Measuring ranges and sample volumes

The BOD level of a sample depends on the quantity of organic matter present, which can vary considerably. The BOD measuring system BD600 is therefore calibrated for the various listed in the table below. The overall measuring range of the system is 0 – 4000 mg/L. For all measuring ranges, BOD is shown directly in mg/L. Range and sample volume is given in the table 3.1.

                         Table 3.1: BOD range and taken of sample volume

Range mg/L BOD	Sample volume ml
0 - 40	428
0 - 80	360
0 - 200	244
0 - 400	157
0 - 800	94
0 - 2000	56
0 - 4000	21.7

Testing procedure

o   Estimate the measurement range of the sample to be tested and the sample volume as indicated.

o   Measure the sample volume precisely with the volumetric flask and pour into the BOD bottle.

o   If necessary, add the nitrification inhibitor.

o   Place the magnetic stir bar in the BOD bottle.

o   Fill the seal cup with 3 - 4 drops of KOH solution and place the seal cup in the test bottle.

o   Screw the BOD sensors on the test bottles.

o   Hang the sample in the bottle rack.

o   Start the test.

o   Incubate the sample 5 days at 20°C temperature according to specifications (e.g. BOD₅ at 20 °C).

Identification the result

The BOD measurement system kept in the incubator 5 days at 20 °C. Test result was showing every moment on the digital display. After 5 days the test result shows on the digital display of the BOD measurement system the test result is BOD₅. This test result is recorded.

Chapter Four

RESULTS AND DISCUSSION

4.1 Results of the analyses

The washing factory wastewater contains various kinds of pollution load in terms of pH, temperature, Biological oxygen demand (BOD), Chemical oxygen demand (COD), Total dissolved solids (TDS), etc. Characterization of effluent it is one of the major goals of the present work. The data tables are presented and analysed to design the physicochemical parameter of pH, TDS, COD and BOD. Here especially wastewater of ETP outlet which is treated by activated sludge, i.e., biological process to reduce and control of COD and BOD parameter.

4.2 Analysis of existing ETP inlet and outlet water

Water sample was analysed for different physicochemical parameters. The sample collected from existing ETP inlet and outlet location at different times and different days. Total water collection was 10 times on different days at different times. Existing ETP outlet water sample was slight color and odor was slightly pungent.

4.2.1 pH

pH parameter was tested at 10 times at different times and different days in the ETP inlet and outlet. Test 1 – test 10 is performed and data is recorded properly. It is shown that average pH of the water sample of existing ETP inlet was 8.3 and average pH of the water sample of existing ETP outlet was 7.4. It is observed that existing ETP outlet/treated water pH parameter meets with the standard ECR1997. pH test result shown in the Table 4.1.

                 Table 4.1: pH test result of existing ETP

Serial no.	ETP Inlet water	ETP Outlet water
	pH	pH
Test 1	8.3	7.3
Test 2	8.2	7.1
Test 3	7.9	7.5
Test 4	8.1	7.6
Test 5	8.6	7.7
Test 6	8.3	7.8
Test 7	8.2	7.4
Test 8	8.9	7.1
Test 9	8.7	7.4
Test 10	8.1	7.5
Average result	8.3	7.4

4.2.2 Total Dissolved Solids (TDS)

TDS parameter was tested at 10 times at different times and different days in the ETP inlet and outlet. Test 1 – test 10 is performed and data is recorded properly. It is shown that average TDS of the water sample of existing ETP inlet was 1138.6 mg/L and average TDS of the water sample of existing ETP outlet was 867 mg/L. It is observed that existing ETP outlet/treated water TDS parameter meets with the standard ECR1997. TDS test result is shown in the Table 4.2.

               Table 4.2: TDS test result of existing ETP

Serial no.	ETP Inlet water	ETP Outlet water
	TDS (mg/L)	TDS (mg/L)
Test 1	1083	960
Test 2	1129	823
Test 3	1208	798
Test 4	1087	839
Test 5	1158	825
Test 6	1139	936
Test 7	1127	933
Test 8	1284	847
Test 9	1105	802
Test 10	1066	907
Average result	1138.6	867

4.2.3 Chemical Oxygen Demand (COD)

COD parameter was tested at 10 times at different times and different days in the ETP inlet and outlet. Test 1 – test 10 is performed and data is recorded properly. It is shown that average COD of the water sample of existing ETP inlet was 414 mg/L and average COD of the water sample of existing ETP outlet was 223 mg/L. It is observed that existing ETP outlet/treated water COD parameter does not meet with the standard ECR1997. COD test result is shown in the Table 4.3.

                   Table 4.3: COD test report of existing ETP

Serial no.	ETP Inlet water	ETP Outlet water
	TDS (mg/L)	TDS (mg/L)
Test 1	493	241
Test 2	455	236
Test 3	397	212
Test 4	286	190
Test 5	379	205
Test 6	451	273
Test 7	463	228
Test 8	438	234
Test 9	372	176
Test 10	406	235
Average result	414	223

4.2.4 Biological Oxygen Demand (BOD)

BOD parameter was tested at 10 times at different times and different days in the ETP inlet and outlet. Test 1 – test 10 is performed and data is recorded properly. It is shown that average BOD of the water sample of existing ETP inlet was 147 mg/L and average BOD of the water sample of existing ETP outlet was 61 mg/L. It is observed that existing ETP outlet/treated water BOD parameter does not meet with the standard ECR1997. BOD test result is shown in the Table 4.4.

                  Table 4.4: BOD test result of existing ETP

Serial no.	ETP Inlet water	ETP Outlet water
	BOD (mg/L)	BOD (mg/L)
Test 1	168	58
Test 2	153	67
Test 3	178	65
Test 4	136	57
Test 5	145	63
Test 6	135	58
Test 7	183	75
Test 8	96	66
Test 9	147	56
Test 10	129	45
Average result	147	61

4.3 Analysis of existing ETP outlet water after treatment by activated sludge

4.3.1 Chemical Oxygen Demand (COD)

To reduce and control properly of existing ETP outlet water COD parameter, here used activated sludge process. COD parameter was tested at 10 times at different times and different days. Test 1 – test 10 is performed and data is recorded properly. It is shown that average COD of the water sample of existing ETP outlet was 223 mg/L and average COD of the water sample treated by activated sludge of existing ETP outlet was 143 mg/L. It is observed that after treatment by activated sludge of existing ETP outlet water COD parameter meets with the standard ECR1997. COD test result shown in the Table 4.5.

                   Table 4.5: COD test result after treated by activated sludge

Serial no.	Before treatment	After treatment
	COD (mg/L)	COD (mg/L)
Test 1	245	125
Test 2	236	153
Test 3	212	168
Test 4	186	142
Test 5	205	130
Test 6	273	152
Test 7	228	173
Test 8	234	128
Test 9	176	132
Test 10	235	127
Average result	223	143

4.3.2 Biological Oxygen Demand (BOD)

To reduce and control properly of existing ETP outlet water BOD parameter, here used activated sludge process. BOD parameter was tested at 10 times at different times and different days. Test 1 – test 10 is performed and data is recorded properly. It is shown that average BOD of the water sample of existing ETP outlet was 61 mg/L and average BOD of the water sample of treated by activated sludge of existing ETP outlet was 26 mg/L. It is observed that after treatment by activated sludge of existing ETP outlet water BOD parameter meets with the standard ECR1997. BOD test result is shown in the Table 4.6.

                   Table 4.6: BOD test result after treated by activated sludge

Serial no.	Before treatment	After treatment
	BOD (mg/L)	BOD (mg/L)
Test 1	58	23
Test 2	67	29
Test 3	65	36
Test 4	57	25
Test 5	63	21
Test 6	58	19
Test 7	75	35
Test 8	66	23
Test 9	56	27
Test 10	45	22
Average result	61	26

4.4 Discussion

Activated sludge containing aerobic bacteria had been used in this experiment to degrade the effluent concentration for the control of wastewater parameters. Activated sludge was used because different literature and experiment shows that it would be a great source of active microbes which may be used for textile wastewater treatment. Another reason for using activated sludge was, as this research is to treat wastewater, it would be good to use environmental microbes rather than using the microbes present in food or in other consortium. The bacteria present in other consortium may not get their proper nutrition by degrading the effluent present in wastewater but as the activated sludge was used; the possibility of degrading effluents to get the microbes nutrition is highest as they both are the environmental constituent. The COD and BOD removal was satisfactory. Wastewater sample were analysed every hour interval. The COD and BOD removal efficiency was satisfactory at 3 hours for both parameters, which can be discharged in open water body. The data was satisfactory enough. The value of pH and TDS were within limit recommended by DoE standard ECR 1997.  This study provides evidence that microbial species carrying effluents degradation traits can be used for bioremediation of textile pollutants. The present study demonstrated that such an approach is indeed possible, because bacterial isolates from sludge possessed the ability to degrade synthetic wastes in water. This biological treatment method of textile wastewater also can reduce the cost of chemicals.

Chapter Five

CONCLUSION

Conclusion

The present study was carried out to characterize the physicochemical parameters of effluents like pH, TDS, COD and BOD of existing ETP inlet and outlet water. It has developed a remediation method of effluent treatment of existing ETP outlet. For the removal of COD and BOD from existing ETP outlet, here I have used and treatment existing ETP outlet water by activated sludge i.e., biological treatment process.  Biological treatment method is the most cost effective method than any other chemical methods. The parameters COD and BOD are changed and achieved to a significant level by the activated sludge process treatment of existing ETP outlet water. The present treated wastewater quality has improved and meets with the standard ECR1997.

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