Looking for classes? Ksquare Career Institute, Bengaluru →
In which one of the following the BOD (Biochemical Oxygen Demand) of sewage (S), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order?
A
SE $\lt$ PE $\lt$ S $\lt$ DE
B
PE $\lt$ S $\lt$ SE $\lt$ DE
C
S $\lt$ DE $\lt$ PE $\lt$ SE
D
SE $\lt$ S $\lt$ PE $\lt$ DE
Detailed Solution
Biochemical oxygen demand (BOD) is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by micro-organisms.
A higher BOD value means that the water sample is more polluted by biodegradable organic matter.
Distillery effluent (spent wash) is extremely rich in organic matter and has the highest BOD of the four, of the order of 40,000 mg/L.
Sugar mill effluent also carries a heavy load of sugars and other organic matter, so its BOD is high, though far below that of distillery effluent.
Domestic sewage and paper mill effluent have much lower values; taking the figures used in the source, paper mill effluent is the lowest and sewage comes next.
So the ascending order of BOD is PE < S < SE < DE.
A higher BOD value means that the water sample is more polluted by biodegradable organic matter.
Distillery effluent (spent wash) is extremely rich in organic matter and has the highest BOD of the four, of the order of 40,000 mg/L.
Sugar mill effluent also carries a heavy load of sugars and other organic matter, so its BOD is high, though far below that of distillery effluent.
Domestic sewage and paper mill effluent have much lower values; taking the figures used in the source, paper mill effluent is the lowest and sewage comes next.
So the ascending order of BOD is PE < S < SE < DE.