What is the main objective of primary treatment in wastewater treatment?
- ARemoval of dissolved solids
- BRemoval of suspended solidsCorrect
- CReduction of biochemical oxygen demand
- DDisinfection of water
Solution
Concept
Primary treatment
Step-by-step solution
1. Primary treatment uses physical processes: screening, grit removal and primary sedimentation. 2. It removes settleable and floating suspended solids.
Explanation
Primary treatment removes suspended solids (and about 30 to 35% of the BOD attached to them). Dissolved solids and most of the BOD are reduced by secondary (biological) treatment, and disinfection is a tertiary step.
Shortcut
Primary = physical = suspended solids. Secondary = biological = BOD.
Common mistake
Choosing BOD reduction.
Correct answer: B) Removal of suspended solids