Grit removal is typically included in which stage of wastewater treatment?

• A. Preliminary treatment
• B. Secondary treatment
• C. Tertiary treatment
• D. Disinfection

Answer: (A)

Grit removal is done early because it targets heavy inorganic particles, like sand and gravel, that can cause wear and clogging in pumps, pipes, and downstream equipment. In preliminary treatment, water first encounters screening to remove large solids, and then grit chambers slow the flow so these heavy particles settle by gravity and can be removed. This keeps the subsequent biological and polishing steps from being contaminated or damaged by abrasive material, allowing the secondary treatment to operate smoothly.

Secondary treatment focuses on biological degradation of organic matter, so grit removal would not occur there and could even hinder the process due to unnecessary solids in biological reactors. Tertiary treatment and disinfection are about polishing the effluent and killing pathogens, respectively, not about removing grit.