What is wastewater, textile wastewater treatment, Major Pollutants in textile wastewater, Steps of textile wastewater treatment, Brief overview of textile wastewater in Bangladesh.

1. Textile Wastewater Treatment; Bangladesh Perspective
Presented by
Md. Mahmudul Hasan Chy.
Agricultural Water Management Engineering
University of Debrecen

2. Contents
● Introduction
● Major Pollutants in textile wastewater
● Process involved in Textile industry
● Specific pollutants from textile wet processing
● Stages of treatment: Preliminary, Primary, Secondary, Tertiary
treatment
● An overview of textile wastewater in Bangladesh

3. Introduction
What is Wastewater?
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. Wastewater
can originate from a combination of domestic, industrial, commercial or agricultural activities, surface runoff
or storm water, and from sewer inflow or infiltration
What is Textile wastewater?
Textile Wastewater is any water that has been adversely affected in quality by textile industrial activities. It
includes a large variety of dyes and chemical additions that make the environmental challenge for textile
industry not only as liquid waste but also in its chemical composition.
Main pollution in textile wastewater come from dyeing and finishing processes. These processes require the
input of a wide range of chemicals and dyestuffs, which generally are organic compounds of complex
structure.

4. Why wastewater needs to be treated?
● Out of various activities in textile industry, chemical processing contributes about
70% of pollution.
● Due to the nature of various chemical processing of textiles, large volumes of waste
water with numerous pollutants are discharged.
● These streams of water affect the aquatic Ecosystem in number of ways such as
depleting the dissolved oxygen content or settlement of suspended substances in
anaerobic condition, a special attention needs to be paid

5. Major pollutants in Textile Effluents
● High suspended solids
● Dissolved solids
● Toxic metals
● Low Biodegradable surfactants
● Halogenated organics
● Other organics
● BOD & COD
● Oil & Grease

6. Process involved in Textile industry
● Scouring
● Desizing
● Bleaching
● Mercerizing
● Dyeing
● Printing
● Finishing

7. Specific pollutants from textile wet processing
Process Compounds
Desizing Size, Enzyme, Starch, Ammonia, Waxes
Scouring Disinfectants and insecticide residue, NaOH, Surfactants, Soaps, Fats,
Waxes, Pectin, Oils, Sizes, Anti-Static agents, Spent Solvents,
Enzymes.
Bleaching H2O2, AOX, Sodium silicate or Organic stabilizers, High pH
Mercerizing High pH, NaOH
Dyeing Color, Metals, Salts, Surfactants, Organic processing assistants,
Sulphide, Acidity / Alkalinity, Formaldihyde
Printing Urea, Solvents, Color, Metals.
Finishing Resins, Waxes, Chlorinated compounds, Acetate, Stearate, Spent
solvents, Softeners.

8. Stages of treatment
Preliminary: It involves removal of large solids such as rags, sticks, grit and grease that may result in damage
to equipment or operational problems (Physical treatment)
Primary: It involves removal of floating and settable materials, i.e., suspended solids and organic matter
(Physical and Chemical)
Secondary: It involves removal of biodegradable organic matter and suspended solids (Biological and
Chemically)
Tertiary: It involves removal of residual suspended solids / dissolved solids (Physical, Chemical and Biological)

9. Primary Treatment
● Screening
● Sedimentation
● Equalization
● Neutralization
● Chemical Coagulation
● Mechanical Flocculation

10. Screening:
● Coarse suspended matters such as rags, pieces of fabric,
fibres, yarns and lint are removed.
● Bar screens and mechanically cleaned fine screens remove
most of the fibres
Equalization:
● Effluent streams are collected into ‘sump pit’.
● Sometimes mixed effluents are stirred by
rotating agitators or by blowing compressed air
from below.
● The pit has a conical bottom for enhancing the
settling of solid particles

11. Sedimentation:
● Process is particularly useful for treatment of
wastes containing high %age of settable solids
● The sedimentation tanks are designed to enable
smaller and lighter particles to settle under
gravity.
● The settled sludge is removed from the
sedimentation tanks by mechanical scrapping into
hoppers and pumping it out subsequently.
Neutralization:
Normally, pH values of cotton finishing effluents are on the alkaline side. Hence, pH value of equalized effluent should be
adjusted. By the use of dilute Sulphuric acid.
Chemical Coagulation:
Finely divided suspended solids and colloidal particles cannot be efficiently removed by simple sedimentation by
gravity. In such cases, mechanical flocculation or chemical coagulation is employed.

12. Chemical coagulants cause formation of a sludge phase
that can be separated by density difference. Major
coagulants:
● Al2(SO4)3.14H2O (Alum)
● FeCl3.6H2O
● Fe2SO4
Mechanical flocculation:
In mechanical flocculation, the textile wastewater is
passed through a tank under gentle stirring; the finely
divided suspended solids coalesce into larger particles
and settle out.
Specialized equipment such as clari-flocculator is also
available, wherein flocculation chamber is a part of a
sedimentation tank.

13. Inlet effluent parameter After primary treatment
pH 9.0-10.0 0 8.0-9.0
TSS 500-1500 mg/lit 250-750 mg/lit (50%) decrease
COD 1500-3000 mg/lit 600-1200 mg/lit (60%) decrease
BOD 200-400 mg/lit 50-100 mg/lit (25%) decrease
Result after primary treatment

14. Secondary Treatment:
● Aerated lagoon
● Trickling filter
● Activated sludge process
● Oxidation pond

15. Aerated Lagoon:
● Aerated Lagoon Holding and/or treatment pond
● Provided with artificial aeration
● To Promote the biological oxidation of wastewaters
Trickling Filter:
● Consists of a bed of a highly permeable medium to which microorganisms are attached and through which
wastewater is percolated or trickled
● This easiest step of biological treatment is reducing the BOD5 between 50 and 70%.
Activated sludge:
● The activated sludge process is a process for treating sewage and industrial wastewaters using air and a biological
floc composed of bacteria and protozoa.
● Oxidizing carbonaceous biological matter, oxidizing nitrogenous matter: mainly ammonium and nitrogen in
biological matter, removing nutrients (Nitrogen and Phosphorus).
Oxidation Ditch process:
● The Oxidation Ditch is a highly efficient aeration system using very low speed surface aerators.
● Aerators are mounted at watercourse channels in a racetrack configuration to provide complex mixing in the
aeration zones.
● Plug flow exists in the channels between the aerators.

16. Tertiary Treatment:
Oxidative techniques, Ion exchange, Membrane Techniques
Oxidative Techniques:
Fenton reaction, Ozonation, Adsorption, Ultrafiltration, Nano Filtration
Fenton reaction
Fenton's reagent is a solution of hydrogen peroxide and an iron catalyst that is used to oxidize
contaminants or waste waters. Fenton's reagent can be used to destroy organic compounds.
Fe2+ + H2O2 → Fe3+ + HO• + OH−
Fe3+ + H2O2 → Fe2+ + HOO• + H+

17. Ozonation:
● Very effective and fast decolorizing treatment.
● Can easily break the double bonds present in most of the dyes.
● Inhibit or destroy the foaming properties of residual surfactants.
● It can oxidize a significant portion of COD.
Adsorption:
● Used to removes color and other soluble organic pollutants from effluent
● The process also removes toxic chemicals such as pesticides, phenols, cyanides and organic.
● Most commonly used adsorbent for treatment is activated carbon

18. Ion Exchange:
● Ion exchange process is normally used for the removal of inorganic salts.
● Salts are composed of a +ve ion of a base and a -ve ion of an acid.
● IE materials are capable of exchanging soluble ions and cations with electrolyte solutions.
● e,g a cation exchanger in the Na form when contacted with a sol of CaCl2 will scavenge the Ca ions from the
solution and replace them with Na ions.
● This is a convenient method for removing the hardness from water or effluent.
Membrane Technology
Ultra-filtration (UF)
Membranes retain only macro molecules and suspended solids. Thus salts, solvents and low molecular weight organic
solutes pass through UF membrane with the permeate water.
Nano-filtration (NF)
Capable of removing hardness elements such as calcium or magnesium together with bacteria, viruses, and color.

19. Results of tertiary treatment:
● Suspended solids and organic substances will reduce in absorption.
● Remove about 97% of color, 76% of turbidity, 84% of COD, 77% of BOD and 94% of PO-4
● Ultrafiltration-color removal, chemical oxygen demand (COD) reduction.
● Ozonation-for color removal and remove COD of basics dyes by 64.96%

20. Textile waste in Bangladesh: Overview
● The textile sector has contributed 82% of the country’s total export revenue—about 28 billion USD per year.
● Wastewater from textile industries in Bangladesh was estimated to be about 217 million m3 in 2016,
containing a wide range of pollutants, and will reach 349 million m3 by 2021 if the textile industries continue
using conventional dyeing practices
● Untreated effluent has been discharged into rivers from nearby textile factories, with several major sources of
contaminants being outside the city areas, Gazipur, Tongi, Savar, and Ashulia
● A wide variety of synthetic dyes like azo dye, vat, reactive dye, disperse dye, etc. widely used in the textile
sector.
● Industrial wastes and effluents containing heavy metals such as Vanadium, Molybdenum, Zinc, Nickel,
Mercury, Lead, Copper, Chromium, Cadmium, and Arsenic .
● These metals are being released in the vicinity of the industrial areas and this polluted river water is being used
for irrigation purposes in paddy and vegetable (spinach, tomato, and cauliflower) cultivation fields near
industrial areas.
● Vegetable and fruit samples collected from around Savar, Dhamrai, and Tongi show the presence of textile
dyes.

22. Impacts of Textile Effluent:
Through the food chain, this affects the health of people who live along the polluted rivers.
Short-term problem: Diseases such as painful skin disease, diarrhea, food poisoning, and gastrointestinal
problems.
Long-term problem: Serious health implications such as respiratory problems when toxic materials accumulate
in the body.
Causes for Problems in Bangladesh:
● Insufficient resources (knowledge, human resources, and funds)
● Economic corruption
● Weak political will
● Inadequate coordination among concerned agencies
Solution:
The only way to solve the environmental pollution due to industrial effluents is to restrict the polluted
discharge at the source.

23. Köszönöm!

24. Any Question?