Wastewater Treatment – Wastewater should undergo three types of treatments to purify it.
Primary Treatment of Wastewater
- In primary treatment of water, screens, grit chambers and sedimentation tanks are arranged in a serial order.
- Water which passes through them is treated with chlorine gas which kills the harmful bacteria in water. However, dissolved organic matter like salts cannot be treated in this method.
Secondary Treatment of Wastewater
- In this method, the organic matter which is present in water is biologically degraded by microorganisms. When water enters a tank, it comes into contact with microorganisms.
- Air is introduced into the tank through diffusers. Microorganisms in the presence of oxygen break the organic matter and the impurities then settle to the bottom of the tank which is later removed.
- Water is then treated with chlorine gas which then kills the rest of the harmful organisms.
Tertiary Treatment of Wastewater
In this method, nutrients such as nitrogen or phosphorus are removed. This water can be reused for industrial, agricultural, and domestic purposes.
Sources of water pollution which cause an inflow of pollutants over a large area are known as non-point sources. Example: Runoff from agricultural fields. The following steps should be taken to reduce water pollution from non-point sources:
- Two separate drainages should be built for sewage and rainwater so that both rainwater and sewage do not overflow together.
- Nitrogen-fixing plants should be planted to reduce the use of chemical fertilisers.
- Agrochemicals and pesticides should be used judiciously to prevent them from draining into a water body.
- Efforts should be made to prevent runoff of manures.
- Biofertilisers and biopesticides should be used.
Sources that discharge pollutants to only one specific site are known as point sources. Example: Discharge of effluents from the factory into a river. To prevent pollution from point sources, it is essential to first treat wastewater before it is discharged. Laws should be made carrying strict punishment for discharging untreated wastewater into any water body.
Also, Read What is Water Pollution?