This exercise presents one possible procedure to calculate COD fractions from the wastewater. Following tests have been performed with an industrial wastewater (pulp and paper processing plant):

Total COD = 2000 mg/l Soluble COD = 1825 mg/l Influent (filtered after flocculation with zinc sulfate) ffCOD = 1595 mg/l Effluent (filtered after flocculation with zinc sulfate) ffCOD = 149 mg/l

Zinc sulfate flocculates colloids from the water. Thus, after filtration only soluble COD remains in the water.

In order to estimate the biodegradable organic matter in the sample, a mixture of activated sludge from the plant (V=4l) and influent water (V=4l) was aerated during 24 hours. Total and soluble COD were measured before and after the aeration.

Following results were obtained: Total COD beginning = 4704 mg/l Soluble COD beginning = 939 mg/l Total COD end = 4658 mg/l Soluble COD end = 216 mg/l

Calculate the concentrations and fractions (%) in the influent water of readily (RBCOD) and slowly biodegradable (SBCOD) COD and soluble and particulate unbiodegradable COD.