Chemical oxygen demand analysis of wastewater using trivalent manganese oxidant with chloride removal by sodium bismuthate pretreatment

Current chemical oxygen demand (COD) analyses generate wastes containing he xavalent and trivalent chromium, mercury, and silver. Waste disposal is dif ficult, expensive, and poses environmental hazards. A new COD test is propo sed that eliminates these metals and shortens analysis time, where trivalen t manganese oxidant replaces hexavalent chromium (dichromate). A silver cat alyst is not required. Optional pretreatment removes chloride via oxidation to chlorine using sodium bismuthate, eliminating the need for mercury. Sam ple aqueous and solid components are separated for chloride removal, then r ecombined for total COD measurement. Soluble and nonsoluble COD can be dete rmined separately. Digestion at 150 degreesC is complete in 1 hour. Results are determined by titration or by spectrophotometric reading. Test wastes contain none of the metals regulated for disposal under the Resource Conser vation and Recovery Act. Results are shown for selected organic compounds a nd various wastewaters. Statistical comparisons are made with dichromate CO D and biochemical oxygen demand (BOD5) test values.