An unseeded BOD test is conducted on a polluted surface water sample by adding 100ml to a 300-ml BOD bottle and filling with dilution water. The initial DO measured 8.2mg/l, and the final...

An unseeded BOD test is conducted on a polluted surface water sample by adding 100ml to a 300-ml BOD bottle and filling with dilution water. The initial DO measured 8.2mg/l, and the final concentration after 5 days of incubation at 20°C measured 2.9mg/l. Calculate the BOD.