Process Flowchart Of Effluent Treatment Plant (ETP)
Effluent can be defined as the excess chemical liquor which is discharged after using original operation.
Effluent is defined by the United States Environmental Protection Agency as "wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters". The Compact Oxford English Dictionary defines effluent as "liquid waste or sewage discharged into a river or the sea".
Effluent Treatment Plant is a plant which is used to treat the effluent and make it environment friendly. The process flow chart of ETP is shown in the following fig:
Now I’ll briefly discuss the steps of ETP plant –
Steps
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Description
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Screening
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Screening is the first unit operation in ETP plant. Screen is a perforated device which is used to retain the coarser materials found in waste water. When the solid materials come in contact of the screen they stack and are removed manually or mechanically. This process is called screening.
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Flow Equalization
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Flow equalization is a system which is used to reduce the operational problems created by flow variations, to accelerate the downstream process. In case of any process failure in the treatment process, it is also used as an emergency tank to equalize the effluent. It ensures the constant or nearly constant flow rate of the effluent.
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Coagulation
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It takes place in rapid mix basins which is very rapid. The key function of rapid mix basin is to disperse the coagulant so that it contacts all of the effluent.
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Flocculation
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It is done to form aggregates from the finely divided matter. The flocculation of effluent is done in two ways. One is mechanical and another is agitation. In both mechanical and air agitation systems, it is common practice to taper the energy input so that the aggregates initially formed will not be broken as they leave the flocculation facilities.
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Neutralization
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Generally, industrial wastewater contains acidic or alkaline components which should be neutralize before discharge or treatment. Especially sulphuric acid, lime etc. are used to neutral the waste water.
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Primary Clarifier
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Primary clarification is a physical treatment process. In this process, solids are removed before biological process. After basic screening, it is the most cost effective way to remove these solids. When the process water enters the clarifier tank, floatable solids are removed from the surface by skimmers while settleable solids are collected at the bottom by a rack and are removed via a sludge removal system.
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Biological Treatment
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There are many biological processes that are used for wastewater treatment. The processes can be divided into five major groups: aerobic process, anoxic process, anaerobic process, combined aerobic anoxic and anaerobic process.
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