Final answer:
The primary clarification process in wastewater treatment can achieve between 25% and 35% BOD reduction by removing much of the dissolved solids but doesn't make the water potable or remove all harmful biological agents.
Step-by-step explanation:
Without chemical addition, the primary clarification process in wastewater treatment can achieve between 25% and 35% Biological Oxygen Demand (BOD) reduction. If you analyzed wastewater directly after primary treatment, you would notice that much of the dissolved solids have been removed. However, this does not mean that the harmful bacteria and other biological agents have been killed or removed, nor is the water potable at this stage. Wastewater and sewage treatment involves three phases: primary, which is solid removal, secondary, which involves bacterial decomposition, and tertiary, which includes extra filtration. Primary treatment mainly focuses on the physical separation of solid waste from the wastewater, thereby reducing the overall BOD, but it does not comprehensively treat all pollutants.