Question

ml of river water with BODs of 1000 ppm is diluted to 1 L, aerated and seeded. The If 2 disolved oxygen content was 7.8 mg/L initially. After 20 days, the dissolved oxygen ssolv content had dropped to 5.3 mg/L. What is the ultimate BOD, and remaining BOD? Which of the two BODs give better prediction of BODL, and why?

Answer 1

BOD ( Biochemical Oxygen Demand) is a measure of the organic matter present in the water, or BOD refers to the amount of oxygen that is consumed infall organic matter in one litre of water oxidised by bacteria.

If greater the BOD, more is its polluting potential& Low BOD less polluting potential.

A BOD levels of 1000 ppm indicates that water is very much polluted with organic wastes.

BOD(20) = 7.8-5.3/(0.001/1) here BOD= D1-D2/P D1= initial concentration

=2500 D2 =final concentration

P= decimal volumetric fraction of sample used

Here, final BOD concentration (5.8 mg/l) is better because it indicates that water is less polluted.