Waste water treatment

What is wastewater?

Water that has been contaminated by human activity, including sewage, industrial waste, and agricultural run-off.

Why must wastewater be treated before being released into the environment?

To remove harmful bacteria and pollutants that could damage ecosystems or harm human health.

What are the main stages of wastewater treatment?

• Screening – removes large objects (e.g., leaves, plastic).

• Sedimentation – separates sewage sludge (solid waste) from effluent (liquid). Water sits at the top and heavier solids sink to the bottom creating sewage sludge, separating it from the effluence

• Aerobic digestion – bacteria break down organic matter in effluent.

• Anaerobic digestion – bacteria break down sludge, producing methane (used as biogas).

• Disinfection – treated water is sterilised before being released, often with UV light

How is sewage sludge used sustainably?

Anaerobic digestion produces biogas (used as fuel). The remaining solid waste can be used as fertiliser.

How does industrial wastewater differ from domestic wastewater?

It may contain harmful chemicals or heavy metals, requiring additional treatment.

compare how easy it is to obtain potable water from waste water, ground water and salt water.

wastewater requires an extensive process and so is quite complex to remove all the harmful microbes and cchemicals, however it can be used sustainably.

ground water from resevoirs and lakes requires minimal treatement, most it needs is sterilisation using chlrine or UV light which is cheap

salt water is difficult as it requires a lot of energy as it uses desalination or reverse osmosis and distillation which are all expensive due to the equipment and energy required

where is sewage treatment used most

in areas where there’s little freshwater