Which factor is cited as interference in BOD measurements due to biological variability?

Which factor is cited as interference in BOD measurements due to biological variability?

• A. Temperature changes
• B. Dissolved Oxygen
• C. Algae
• D. pH fluctuations

Answer: (C)

Biological variability in BOD measurements can be introduced by living organisms that are present in the sample. Algae are a common source of this interference because they are alive and metabolically active, which can alter the oxygen balance inside the BOD bottle beyond what the microbial degradation of the wastewater would cause. Algae can respire and consume oxygen, and in some conditions may photosynthesize, releasing oxygen, both of which can shift DO readings unpredictably during the incubation. This makes the measured DO drop (and thus the calculated BOD) less representative of just the organic matter being measured. Temperature, dissolved oxygen, and pH are important factors that influence BOD readings, but they are abiotic or the measurement itself, not biological variability caused by living organisms. Algae specifically introduce biological variability, which is why they are the factor cited as interference in this context.

Biological variability in BOD measurements can be introduced by living organisms that are present in the sample. Algae are a common source of this interference because they are alive and metabolically active, which can alter the oxygen balance inside the BOD bottle beyond what the microbial degradation of the wastewater would cause. Algae can respire and consume oxygen, and in some conditions may photosynthesize, releasing oxygen, both of which can shift DO readings unpredictably during the incubation. This makes the measured DO drop (and thus the calculated BOD) less representative of just the organic matter being measured.

Temperature, dissolved oxygen, and pH are important factors that influence BOD readings, but they are abiotic or the measurement itself, not biological variability caused by living organisms. Algae specifically introduce biological variability, which is why they are the factor cited as interference in this context.