Textile effulent treatment, Waste water treatment

REASONS OF TEXTILE EFFLUENT Wet processing of textiles involves, in addition to extensive amounts of water and dyes, a number of inorganic and organic chemicals aid in the dyeing proces

REASONS OF TEXTILE EFFLUENT

 Wet processing of textiles involves, in addition to extensive amounts of water and dyes, a number of inorganic and organic chemicals aid in the dyeing process to impart the desired properties to dyed textile products

 Natural impurities such as waxes, proteins and pigment

 Other impurities used in processing such as spinning oils, sizing

chemicals and oil stains present in cotton textiles, are removed during desizing, scouring and bleaching operations

 This results in an effluent of poor quality, which is high in BOD and

COD load

WHY WASTE WATER 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 eco-system 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.

DIFFERENT TYPE OF WASTE GENERATED

 Total Dissolved Solid

 Chemical Oxygen Demand (COD)

 Bio Chemical Oxygen Demand (BOD)

 Oil & Grease

 Surfactant

NATURE OF WASTE GENERATED AT EACH STEP

High COD

Preliminary PRIMARY SECONDARY TERTIARY

LEVEL OF TREATMENT

Preliminary Treatment

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 TREATMENT

It involves removal of floating and settable materials, i.e suspended solids and organic matter (Physical and Chemical);

SECONDARY TREATMENT

It involves removal of biodegradable organic matter and suspended solids (Biological and Chemically)

TERTIARY TREATMENT

It involves removal of residual suspended

solids / dissolved solids (Physical, Chemical and Biological)

PRIMARY-TREATMENT

 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

 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

EQUALIZATION TANK

 This process is particularly useful for treatment of

wastes containing high percentage of settable

solids or when the waste is subjected to combined

treatment with sewage

 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.

SEDIMENTATION TANK

on the alkaline side Hence, pH value of equalized

effluent should be adjusted.

carbon dioxide are not uncommon

effective in the pH 5 to 9, neutralization step is an

important process to facilitate.

Chemical coagulation and Mechanical

flocculation

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.

Chemical coagulation

 It is a controlled process, which forms a floc

(flocculent precipitate) and results in

obtaining a clear effluent free from matter in

suspension or in the colloidal state.

 The degree of clarification obtained also

depends on the quantity of chemicals used In

this method,

 80-90% of the TSS

 40-70% of BOD, 5days ,

 30-60% of the COD and

 80-90% of the bacteria can be removed

 Most commonly used chemicals for chemical

coagulation are alum, ferric chloride, ferric

sulphate, ferrous sulphate and lime.

Mechanical flocculation

 In mechanical flocculation, the

textile waste water 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

Result After Primary Treatment

INLET EFFULENT PARAMETER AFTER PRIMARY TREATMENT

PH

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