Unit 10: Environmental Engineering

raw sewage

untreated wastewater that contains human waste, household and industrial wastewater, and other pollutants that enter the sewer system

screen

mechanical devices used to remove large solid materials such as plastics, sticks, rags, and other debris from the raw sewage

disinfectant

a chemical or physical process used to kill or remove harmful microorganisms from the effluent before it is discharged into a receiving water body or used for other purposes. Chlorine is a common disinfectant used in sewage treatment

air compressor

a device used to inject air into the aeration tank

sludges

the solid material that settles to the bottom of the primary clarifier. It contains organic matter that can be further treated for disposal

comminutor

a mechanical device that grinds and shreds the screened sewage to break down any larger solid materials into smaller pieces

grit chamber

a tank that allows the flow of sewage to slow down so that heavier materials such as sand, gravel, and other grit can settle to the bottom for removal

primary clarifier

a large tank where the flow of sewage is slowed down so that solid materials can settle to the bottom and oils and grease can rise to the top, creating a sludge layer and a scum layer

primary effluent

the partially treated wastewater that flows out of the primary clarifier

aeration tank

a tank where air is injected into the effluent to encourage the growth of aerobic bacteria that will consume the remaining organic matter in the water

secondary clarifier

a large tank where the flow of water is slowed down again so that the bacteria cam settle to the bottom, creating another sludge layer