Function of Different Units of Biological Effluent Treatment Plant (ETP)

Textile processing industries produce wastewater containing suspended solids, large amount of dissolved solids, untreated dyestuffs, recalcitrant organics, toxicants, inhibitory compounds, surfactants, chlorinated compounds, and other chemicals that are used in different stages of dyeing, washing and other wet processing. Effluent treatment plant (ETP) is used for this treated waste water. ETP plant in textile industry has some units in which waste water are done treatment. In this article I have given the functions of different units of effluent treatment plant.
ETP plant in textile industry
Fig: ETP plant in textile industry
Different Units of ETP:

Screening unit: 
It works like a filter. By filtering waste water, it removes threads, pieces of fabrics, small metal pieces etc. In this unit a rotating brush is used for clean the pores if screen. The brush rotates periodically.

Storage and Homogenization tank:
Different waste water from varies process is stored and makes a homogeneous mixture by mixing different concentration of waste water.

Neutralization tank:
Neutralization of waste water is performed by dosing 98% H2SO4 as required to control the PH Of waste water. PH range 6.5 to 7.5.

Distribution tank:
It distributes the water to the biological oxidation tank. Continuous aeration is supplied here. Antifoam is dosed here to control the foaming in the oxidation tank.

Biological oxidation tank:
It is the heat of ETP. The entire harmful chemicals are damaged here by breaking their bonds. This is done by bacteria. To ensure the proper function work and growth of bacteria, few conditions must be maintained.
  1. Temperature : 35º to 37º C
  2. pH (Maximum) : 6.5
  3. Dissolved oxygen : 4 PPM
Sedimentation Tank / Biological feeding tank:
Treated water is overflowed here from oxidation tank. Decolourent is used here to destroy the color of waste water.

Settling tank / Sedimentation Basin:
A tank or basin in which waste water is held for a period of time, during which the heavier solids settle to the bottom and the lighter material will floats to the water surface. In this tank sludge is immersed and the harmless water is discharge to ponds, Land, river etc.

Sludge Thickener:
Sludge taken here from clarifier. Polyelectrolyte is dosed coagulate the sludge. After one hour of Polyelectrolyte dosing aeration is stopped and fresh water discharge to drain when sludge is taken. The thickened sludge is transferred to the sludge thickener bed.

Sludge Thickener bed:
Here sludge is dried which is used as good fertilizer as well as fuel of brick field. Sludge is dried under the sunlight.
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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