For the same wastewater sample, the chemical oxygen demand is generally higher than the biochemical oxygen demand because COD includes oxygen needed to oxidize:
Correct answer: B. Biodegradable and many non-biodegradable oxidizable substances
- A. Only settleable mineral particles
- B. Biodegradable and many non-biodegradable oxidizable substances
- C. Only pathogenic microorganisms in the sample
- D. Only dissolved oxygen already present in the sample
Explanation
COD uses a strong chemical oxidant and accounts for many substances that can be chemically oxidized, including some compounds not readily biodegraded. Therefore, COD is normally greater than BOD for the same wastewater.
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About Environmental Engineering
Environmental engineering examines water supply, water quality, treatment processes, wastewater collection and treatment, solid waste management, air pollution and public health protection. It covers sedimentation, coagulation, filtration, disinfection, biological treatment and disposal methods, while distinguishing drinking-water treatment from sewage treatment and BOD from COD.
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