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Steps of Wastewater Treatment

By wastewater treatment is meant the process of conversion of wastewater (water that is no more needed or is unsuitable for use) into bilge water, which can be discharged again into the environment.

Such wastewater is created by a number of activities like rainwater run-off, use of water in the toilet, washing, bathing, etc. Industrial waste also takes the form of wastewater. Wastewater is full of contaminants such as chemicals, bacteria and other toxins. Wastewater treatment aims to reduce these contaminants so that water can be used again. This is done by wastewater treatment companies.

The following steps help in wastewater treatment:

Collection

Wastewater is collected and directed to a central point. This water is directed to a treatment plant using drainage systems in the underground. Transport of wastewater must be conducted hygienically.

Odour control

This is a vital step at the treatment plant. Wastewater contains much dirt which has a foul odour. To make sure that surrounding areas are free of offensive smell, odour treatment processes are begun at the treatment plant.

Screening

This involves the removal of large objects like plastics, cotton buds, nappies, broken bottles, diapers, face wipes, etc., all of which can damage equipment. Solid wastes removed from the water are transported and disposed of away in landfills.

Primary treatment

The macrobiotic solid matter is separated from wastewater. The solid matter is allowed to settle by storing wastewater in big tanks. The material called as sludge is removed by large scrappers, pushed to the centre of cylindrical tanks and pumped out for further treatment. Remaining water moves towards secondary treatment.

Secondary treatment

In this stage, seed sludge is added to the wastewater for breaking it down further. The wastewater is mixed with the seed sludge, which fuels the growth of bacteria. The small micro-organisms consume the remaining organic matter. This process leads to the production of big particles, which settle down at the bottom of big tanks. This takes 3 to 6 hours.

Handling of bio-solids

The solid material emerging from first and second treatment stages are transferred to digesters. Digesters are heated at room temperature. For one month, solid wastes are treated to undergo anaerobic digestion. Methane and nutrient-rich bio-solids are generated which are used for generating energy and recycled respectively.

Tertiary treatment

This stage has the ability to remove up to 99% of impurities in the wastewater. It creates effluent water which has nearly drinking water quality. But this is an expensive process.

Disinfection

After the treatment processes, there still remain some disease-causing organisms in the treated wastewater. To get rid of them, the water must be disinfected for 20 to 25 minutes in tanks which contain a mix of sodium and chlorine. This stage is crucial as such water will be used by local people. The treated effluent water is released via local waterways.

Sludge treatment

The sludge generated is put into thickening tanks where it settles down and separates from the water. This may take 24 hours. The remaining water is collected and sent to big aeration tanks for additional treatment. The sludge can be used for agricultural purposes.

These are the main steps of wastewater treatment. It ensures that the environment is kept clean and the water is regenerated for useful purposes.

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Written by Keith Wilson

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