Which of the following is NOT a typical preliminary treatment process?

• A. Chlorination
• B. Screening
• C. Grit Removal
• D. Flow Equalization

Answer: (A)

In wastewater treatment, preliminary treatment is all about removing large solids and preparing the flow for downstream processes. This means physical steps like screening to catch big debris that could clog pumps, and grit removal to pull out heavy inorganic particles like sand. Flow equalization helps even out the incoming flow so the plant isn’t overwhelmed by peaks and can run more smoothly.

Chlorination, by contrast, is a disinfection step. It uses chlorine to kill remaining pathogens and is typically applied after primary and secondary treatment (and sometimes as part of tertiary treatment). It’s not used to remove solids or balance flow, so it isn’t a typical preliminary treatment.