Question

The type of wastewater treatment that would be used to reduce the BOD (biological oxygen demand) of liquid waste would be __________.

advanced tertiary treatment

aerobic activated sludge

anaerobic digestion

primary treatment

Answer 1

Answer:Aerobic activated sludge

Explanation: Sewage treatment is a multistep biochemical process where the sewage is treated in different ways so that its BOD(biological oxygen demand ) comes down and it can be safely discharged into the water bodies.

(Note: BOD is the amount of oxygen needed by aerobic microorganisms to break down organic matter into a sewage sample.If sewage with high organic matter is discharged into water bodies then because of action of microorganisms,organic content in sewage will fast deplete the oxygen level of the water body, harming the ecosystem of the particular water body)

Primary treatment of sewage consists of filteration and sedimentation, so that heavy solids or insoluble material are taken out of the sewage.Liquid part of this treatment is subjected to Aerobic activated sludge treatment

Aerobic activated sludge treatment : In this process a bacterial biomass (activated sludge) is used to remove the organic content of the sewage. It is a secondary sewage water treatment where a dense microbial culture degrades the organic substances under aerobic(aerated by supplying oxygen from outside) conditions. In this process the BOD of the liquid is significantly reduced. This process generates almost a clear liquid with microbial biomass settling as flocs which can be easily removed and used again.

Anaerobic digestion is carried out with the help of anaerobic microorganisms to reduce the sludge and treat biodegradable waste. It is a comparatively slow process also used to generate energy source in the form of methane.

Advanced tertiary treatment is used as the final process for sewage treatment where the impurities such as nitrogen and phosphorus and suspended particles which are not removed by primary or secondary treatment are removed