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
This results in an effluent of poor quality, which is high in
BOD and COD load.
WHY WASTE WATER NEEDS TO BE
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
DIFFERENT TYPE OF WASTE
Total Dissolved Solid
Chemical Oxygen Demand (COD)
Bio Chemical Oxygen Demand (BOD)
Oil & Grease
NATURE OF WASTE GENERATED AT
LEVEL OF 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)
It involves removal of floating and settable
materials, i.e. suspended solids and organic
matter (Physical and Chemical);
It involves removal of biodegradable organic
matter and suspended solids (Biological and
It involves removal of residual suspended
solids / dissolved solids (Physical, Chemical
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
Sometimes mixed effluents are
stirred by rotating agitators or by
blowing compressed air from
The pit has a conical bottom for
enhancing the settling of solid
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
The settled sludge is removed
from the sedimentation tanks by
mechanical scrapping into
hoppers and pumping it out
Normally, pH values of cotton finishing effluents are
on the alkaline side. Hence, pH value of equalized
effluent should be adjusted.
Use of dilute sulphuric acid and boiler flue gas rich in
carbon dioxide are not uncommon.
Since most of the secondary biological treatments are
effective in the pH 5 to 9, neutralization step is an
important process to facilitate.
Chemical coagulation and
Finely divided suspended solids and colloidal
particles cannot be efficiently removed by simple
sedimentation by gravity. In such cases,
mechanical flocculation or 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
Most commonly used chemicals for
chemical coagulation are alum,
ferric chloride, ferric sulphate,
ferrous sulphate and lime.
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