CHEMICAL OXYGEN DEMAND (DICHROMATE VALUE) AND THE SWEDISH BAN ON MERCURY, OPPORTUNITIES AND PITFALLS
The Chemical Oxygen Demand (COD) test is a key parameter for process control and the routine monitoring of effluent quality in wastewater. However, the present procedure for determination has ro be replaced becausethe scale of COD test chemicals containing Hg will probably not be permitted after the year 2000 in Sweden. Mercury-free procedures are reviewed here with the aim to provide a COD method which is both close to the theoretical Oxygen Demand (ThOD) and which removes chloride interference. We have now developed a method which gives excellent performance and can be used in the closed rube equipment which most sewage treatmenr plant laboratories have invested in. We are now commencing an inrerlaboratory comparison of COD and TOC (Total Organic Carbon) alternarives.