Among the following wastewater characteristics, the one that most strongly supports consideration of Advanced Oxidation Process is
- Ahigh settleable solids and coarse suspended matter
- Blow BOD/COD ratio and persistent dissolved colour after biological treatmentCorrect
- Chigh dissolved oxygen and low COD
- Dlow pH and high grit content
Solution
Concept
Application of Advanced Oxidation Processes in wastewater treatment
Formula
Generation of hydroxyl radicals: H2O2 + UV / Fenton's reagent -> *OH
Step-by-step solution
1. Settleable solids and grit are removed via physical sedimentation and screening. 2. Recalcitrant dyes and toxic organics exhibit low BOD/COD ratios and resist biological oxidation. 3. Advanced Oxidation Processes (AOPs) generate non-selective hydroxyl radicals to break down these persistent compounds. 4. Therefore, persistent dissolved color and low BOD/COD ratio strongly justify AOP. Answer: B
Explanation
Advanced Oxidation Processes (AOPs) generate highly reactive hydroxyl free radicals (•OH) to oxidize recalcitrant, bio-refractory organic pollutants and degrade complex synthetic dyes that cause persistent dissolved color. AOPs are specifically applied when biological treatment fails to eliminate non-biodegradable organics and residual color.
Why the other options are wrong
A) Settleable solids are removed by primary sedimentation or filtration. C) High DO and low COD indicate clean water requiring no advanced treatment. D) Low pH requires neutralization and grit requires physical grit chambers.
Shortcut
AOP = Recalcitrant organics + Non-biodegradable persistent color / low BOD/COD.
Common mistake
Selecting solids or grit removal options, which are physical treatment processes.
Correct answer: B) low BOD/COD ratio and persistent dissolved colour after biological treatment