What are the typical steps in wastewater treatment and their purpose?

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Multiple Choice

What are the typical steps in wastewater treatment and their purpose?

Wastewater treatment works by progressively removing different types of contaminants through stages. Primary treatment uses physical settling to remove larger solids and floatables. Secondary treatment then relies on microorganisms to biologically degrade remaining organic matter, reducing pollutants like BOD and COD. Finally, tertiary treatment provides polishing, including disinfection to kill pathogens and often nutrient removal to limit eutrophication. This sequence and these purposes are why the first option is the best choice. The other options misorder steps or misdescribe the processes: disinfection before solids are removed doesn’t make sense, secondary is not just sedimentation, and discharging without any treatment would be unsafe.

Wastewater treatment works by progressively removing different types of contaminants through stages. Primary treatment uses physical settling to remove larger solids and floatables. Secondary treatment then relies on microorganisms to biologically degrade remaining organic matter, reducing pollutants like BOD and COD. Finally, tertiary treatment provides polishing, including disinfection to kill pathogens and often nutrient removal to limit eutrophication. This sequence and these purposes are why the first option is the best choice. The other options misorder steps or misdescribe the processes: disinfection before solids are removed doesn’t make sense, secondary is not just sedimentation, and discharging without any treatment would be unsafe.

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