Treating Sewage water

What is the first step in treating sewage at a treatment plant?

• Screening to remove large solid objects

• Secondary treatment with bacteria

• Anaerobic digestion of sludge

• Final treatment and discharge

During primary treatment, what happens to solid sediments?

• They are aerated

• They settle out from the mixture

• They are treated with chlorine

• They are immediately recycled

What is the role of large paddles in the first circular tank?

• To push solids towards the centre

• To aerate the waste water

• To sterilize the water with UV light

• To filter out harmful microorganisms

What is the effluent?

• The sludge piped out for further treatment

• The biogas produced from sludge

• The watery liquid above the sludge

• The solid sediments settled at the bottom

What is the purpose of secondary treatment?

• To remove large solid objects

• To allow solid sediments to settle

• To break down organic matter aerobically

• To filter the water through sand

How is the tank aerated during secondary treatment?

• By bubbling air through the waste water

• By rotating large paddles

• By exposing it to ultraviolet light

• By adding chlorine

What happens to the useful bacteria after the final treatment?

• They are removed by metal grids

• They are sterilized by ultraviolet light

• They settle out to the bottom of the tank

• They are discharged into rivers

How can treated waste water be further purified before discharging into sensitive ecosystems?

• By screening for large solids

• By secondary treatment

• By filtering through a bed of sand

• By aeration

What is the primary use of the sludge separated during primary treatment?

• Both as fertilizer and a source of renewable energy

• To improve soil as fertilizer

• As a source of renewable energy

• To be discharged into rivers

How is biogas produced from sludge?

• By filtering through sand

• By anaerobic digestion

• By aerobic digestion

• By exposure to ultraviolet light