Question

For how long and at what temperature an experiment is run to determine the value of BOD of a water body?
(A) ${10^{^0}}C$ for 10 days
(B) ${20^0}C$ for 5 days
(C) ${20^0}C$ for 2 days
(D) ${5^0}C$ for 20 days

Answer 1

BOD stands for Biochemical oxygen demand which tells about the amount of oxygen consumed by the microorganisms or bacteria. Highly polluted water has a high BOD value.

Complete step by step answer:
BOD is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic materials present in a given water sample at a certain temperature over a specific time period. BOD reduction is used as a gauge of the effectiveness of wastewater treatment plants. BOD of wastewater effluents is used to indicate the short term impact on the oxygen levels of the receiving water. The BOD is used in measuring waste loadings to treatment plants and in evaluating the BOD-removal efficiency of such treatment systems. The amount of oxygen needed to completely oxidize the organic compounds to carbon dioxide and water through generations of microbial growth, death, decay, and cannibalism is ‘Total biochemical oxygen demand(BOD). Before and after 5 days of incubation, the sample is tested at ${20^0}C$. The value shows the amount of organic material present in the waste or contaminated water.
Hence, the correct answer is option (B), i.e., ${10^0}C$ for 5 days

Note: According to WHO for drinking water, the BOD limit is less than < 5.0mg/l at this limit BOD will not cause any harmful impacts on the human body. Wastewater sewage must be BOD around 80ppm and COD 200ppm for discharge in the sea.