Availability for denitrification of organic carbon in meat-processing wastestreams

Meat-processing wastewater typically contains high concentrations of nitrogen, which must be removed before discharge of the water to water bodies. Nitrogen can be removed by biological denitrification, and for this, readily metabolisable organic carbon must be present. This study investigated the ability of three meat-processing wastestreams (rendering stickwater, paunch liquor, slaughterfloor effluent) and dilute (1%) blood to supply organic carbon for denitrification. Anoxic batch tests were used, and the maximum specific denitrification rates and anoxic half-saturation constants were estimated for each wastestream. Rendering stickwater and paunch liquor contained large amounts of readily biodegradable GOD, with a maximum of 315-mg l(-1) in paunch liquor and 2145 mg l(-1) in stickwater, and so sustained high initial denitrification rates. Slaughterfloor wastewater and dilute blood contained little or no significant amounts of readily biodegradable COB, resulting in slower denitrification rates. The ultrafiltered COD fraction (< 5000 and < 10000 MW) provided a good indication of the presence of readily biodegradable GOD. (C) 2000 Elsevier Science Ltd. All rights reserved.