Social Science (087) — AI-generated practice question

Primary phase involves mechanical treatment — processes like screening, grinding, flocculation, and sedimentation. These physically remove large solids, suspended particles, and settle out heavier impurities from the effluent.

Secondary phase involves biological treatment — microorganisms break down organic matter dissolved in the wastewater. This removes contaminants that mechanical processes cannot separate.

Essential difference: Primary treatment removes physical/solid impurities through mechanical means, while secondary treatment removes dissolved organic impurities through biological processes.

Source: Control of Environmental Degradation, Chapter 6

---

• The examiner expects you to name the method used in each phase (mechanical vs. biological) and what it removes/achieves — these are the two sides of the "essential difference."
• Give examples of primary treatment processes (screening, sedimentation, etc.) to show you know the content.
• Do not just say "physical vs. chemical" — the textbook specifically says secondary = biological process, so use that word.
• 3 marks → roughly 3 points: name primary method, name secondary method, state the key contrast.