Rapid single-parameter assessment of river water pollution: which test provides a quick indication of the oxidisable load without waiting for 5-day incubation?

Introduction / Context:
Regulators and operators often need a rapid measure of organic pollution in rivers and effluents. While BOD5 is biologically meaningful, it requires a 5-day incubation. COD offers a fast, laboratory-based oxidation of organics using a strong chemical oxidant, giving a same-day proxy for oxygen demand.

Given Data / Assumptions:

• Sampling is from a river where prompt decisions are needed.
• COD test uses dichromate (or equivalent) under acidic conditions with a catalyst.
• Results approximate the total chemically oxidisable load (often ≥ BOD).

Concept / Approach:
COD correlates with BOD for many wastewaters and is favored for process control due to speed. DO alone indicates current oxygen level, not the oxidisable load; total organic solids lack specificity to oxygen demand; MPN indicates fecal contamination, not organic load magnitude.

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