EFFLUENT TREATMENT PLANTS

-BY

B.NIKHIL KUMAR

DEFINITION

• Industrial effluent are materials generally discarded from industrial operations or derived from manufacturing processes.

• “Wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters”

• Waste water treatment is a series of steps. Each of the steps can be accomplished using one or more treatment processes.

FACTORS OF CETP

Factors, which influence the proper planning and operation of the CETPs include following:

• Categories of effluent generating member industries• Qualitative/quantitative fluctuations of effluent

(equalization/ homogenization /modules)• Pre-treatment requirements• Segregation of effluent streams at individual member

industry• Collection and monitoring mechanism• Mode of disposal and• Charging system

List of waste-water treatment technologies

• Activated sludge systems• Diffuser (sewage)• Reverse osmosis• Adsorption• Filtration• Ultra filtration• Ion exchange, etc.

Advantages of CETP

• Facilitates ‘economy of scale’ in waste treatment, thereby reducing the cost of pollution abatement.

• Addresses the ‘lack of space’ issue – CETP can be planned in advance to ensure that adequate space is available including plans for expansion in future.

• Homogenization of wastewater.• Relatively better hydraulic stability.• Professional control over treatment can be

affordable.

• Facilitates small scale units, which often can not internalize the externalities due to control of pollution.

• Eliminates multiple discharges in the area, provides opportunity for better enforcement i.e., proper treatment and disposal.

• Provides opportunity to improve the recycling and reuse possibilities.

• Facilitates better organization of treated effluent and sludge disposal etc.

Problems and constraints

• Operating on ‘one-size-fits-all-basis’.• Lack of access to capital investments, working

capitals, specialized technical skills, inconsistent effluent quality from member industries.

• Improper management of treatment units at common facility.

• Varied nature and scale of the industries, along with the addition of industries in a lack of proper planning

Categories of effluent generating industries

CETPs can be classified based on the combination of industries that it serves:

• Those serving homogenous industries (textiles, tanneries, etc.).

• Those serving heterogeneous industries including chemical industries.

• Therefore CETP inlet standards shall be based on the designed inlet concentrations.

Different Effluent Treatments

Steps in treatment of waste water treatment are

• 1) Segregation• 2) Preliminary treatment• 3) Primary treatment• 4) Secondary treatment• 5) Tertiary treatment

Conveyance system

Prevailing modes of collection of effluents from individual industries to CETP are as follows:

• Tankers• Pipes• Open channels• Combination of the above

Methods of disposal

• There are three methods by which final disposal of wastewater can be accomplished.

• The general problem areas that are of concern in final disposal are:

1) Pathogenic microorganisms (viruses, etc.). 2) Heavy metals. 3) The presence of biologically resistant

organic compounds, such as pesticides.

• Surface Disposal: Generally this is disposal by irrigation. This involves spreading the wastewater over the surface of the ground, generally by irrigation ditches.

• Subsurface Disposal: By this method wastewater is introduced into the ground below its surface through pits or tile fields. It is commonly used for disposal of settled wastewater from residences or institutions where there is only a limited volume of wastewater.

• Disposal by Dilution: Disposal by dilution is the simple method of discharging wastewater into a surface water such as a river, lake, ocean, estuaries or wetlands. The dissolved oxygen in the receiving water is the determining factor.

Modes of disposal

Disposal of treated effluents from a CETP can be done in the following modes:

• Surface water bodies• On land for irrigation• Marine outfall• Public sewers

Treated Effluent Quality of Common Effluent Treatment PlantConcentration in mg/l

S.NO Parameter Into inlandsurface waters

On land forIrrigation

Into Marine Coastalareas

1 BOD5 68F 30 100 100

2 Oil & Grease 10 10 20

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