What does primary sewage treatment involve?

What does primary sewage treatment involve?

• A. Physical removal of large solids through screening and settling
• B. Aeration and nutrient removal
• C. Biological digestion
• D. Chemical disinfection

Answer: (A)

Primary sewage treatment is about removing solids using physical processes. In this stage, wastewater first passes through screens that catch large debris to prevent damage to pumps and downstream equipment. It then moves to a settling tank where gravity causes suspended solids to settle to the bottom as sludge, while the clearer liquid rises to the top. This combination of screening and settling significantly reduces suspended solids and some organic load, producing a clarified effluent that proceeds to the next treatment steps. It does not effectively remove dissolved substances, nutrients, or pathogens, which is why subsequent secondary and tertiary treatments are needed. Aeration and nutrient removal involve biological processes that break down organic matter and remove nutrients, characteristic of secondary treatment. Biological digestion refers to microbial breakdown in sludge or wastewater, typically part of later treatment stages rather than the initial primary step. Chemical disinfection is used after primary and secondary stages to kill remaining pathogens, not during primary treatment.

Primary sewage treatment is about removing solids using physical processes. In this stage, wastewater first passes through screens that catch large debris to prevent damage to pumps and downstream equipment. It then moves to a settling tank where gravity causes suspended solids to settle to the bottom as sludge, while the clearer liquid rises to the top. This combination of screening and settling significantly reduces suspended solids and some organic load, producing a clarified effluent that proceeds to the next treatment steps. It does not effectively remove dissolved substances, nutrients, or pathogens, which is why subsequent secondary and tertiary treatments are needed.

Aeration and nutrient removal involve biological processes that break down organic matter and remove nutrients, characteristic of secondary treatment. Biological digestion refers to microbial breakdown in sludge or wastewater, typically part of later treatment stages rather than the initial primary step. Chemical disinfection is used after primary and secondary stages to kill remaining pathogens, not during primary treatment.