BOD samples should be evaluated for these two parameters prior to setting up the analysis.

BOD samples should be evaluated for these two parameters prior to setting up the analysis.

• A. Temperature and turbidity
• B. Dissolved oxygen and nitrate
• C. Conductivity and salinity
• D. pH and chlorine residual

Answer: (D)

BOD analysis relies on microbes actively consuming oxygen during incubation, so the setup environment must be non-toxic and within a range that supports microbial activity. The two things to check before starting are pH and chlorine residual because they directly affect the microbes doing the work. If pH is outside a near-neutral range (roughly 6.5 to 7.5), the enzymes the microbes rely on won’t function properly, leading to inaccurate BOD results; adjust the sample to around neutral before setting up the test. Residual chlorine from disinfection can kill or inhibit the seed microbes, causing the BOD to appear lower than it truly is; test for chlorine and dechlorinate using a recommended reagent prior to incubation. Temperature is important and controlled during incubation, but the immediate pre‑setup checks that prevent skewed microbial activity are pH and chlorine residual.

BOD analysis relies on microbes actively consuming oxygen during incubation, so the setup environment must be non-toxic and within a range that supports microbial activity. The two things to check before starting are pH and chlorine residual because they directly affect the microbes doing the work. If pH is outside a near-neutral range (roughly 6.5 to 7.5), the enzymes the microbes rely on won’t function properly, leading to inaccurate BOD results; adjust the sample to around neutral before setting up the test. Residual chlorine from disinfection can kill or inhibit the seed microbes, causing the BOD to appear lower than it truly is; test for chlorine and dechlorinate using a recommended reagent prior to incubation. Temperature is important and controlled during incubation, but the immediate pre‑setup checks that prevent skewed microbial activity are pH and chlorine residual.