Which phosphate treatment scheme achieves the highest efficiency and also removes suspended solids?

• A. Raw
• B. Post precipitation
• C. Co-precipitation
• D. Anaerobic digestion

Answer: (B)

Post-precipitation focuses on removing phosphorus by forming insoluble metal-phosphate compounds after primary treatment, and the added coagulants help particles clump together so suspended solids settle as well. This combination delivers high phosphorus removal while also achieving good solids removal in one step, making it the most efficient option among the choices for both targets.

Raw means no treatment, so neither phosphorus nor solids are effectively removed. Co-precipitation also uses precipitating agents to pull phosphate from solution, but it typically doesn’t provide the same level of removal in a single stage as post-precipitation with concurrent flocculation. Anaerobic digestion is a biological process aimed at stabilizing organics and reducing sludge volume, not primarily a method for removing phosphate or achieving high solids removal.