Experiments on the Benthal Oxygen Demands and Leaching Rates of Raw, Digested and Wet Oxidized Sludges

Raw and digested sludge from the New York Metropolitan area is presently barged out to sea for ultimate disposal. This report presents the results of laboratory studies to determine the effects of various types of sludge treatment - digestion, wet oxidation and heat treatment - on the benthal oxygen demands and leaching rates of sludge deposits. Two types of laboratory studies were conducted: ( 1 ) Warburg studies to determine the oxygen demand of the sludges when in an aerobic condition and (2) continuous flow reactor studies with the sludge layered on the bottom of reactors to simulate actual sludge deposits. The results of the studies indicated that treatment of the sludge prior to disposal at sea would significantly reduce the benthal oxygen demands and leaching rates of the bottom deposits. An oxygen diffusion analysis indicated that anaerobic decomposition in the raw, digested, heat-treated and low wet oxidized sludge layers markedly increased the benthal oxygen demands. In contrast the bottom layers of the intermediate and h i g h wet oxidized sludges were relatively dormant with negligible anaerobic decomposition occurring