Anaerobic digestion of ozonized biosolids

The effect of an oxidative pretreatment on the anaerobic digestion of sewag e sludge was investigated. Sewage sludge from a domestic wastewater treatme nt plant was partially oxidized by ozone. The pretreatment could alter up t o 67% of the organic matter: 29 +/- 3% was solubilized, 38 +/- 9% was remov ed. Anaerobic degradability tests indicated that the pretreatment step enha nced the subsequent anaerobic sludge digestion. The methane production was increased by a factor of 1.8 after an ozone treatment at a dose of 0.1 g O- 3/g chemical oxygen demand (COD), while the methane production rate was 2.2 times higher compared to the untreated sludge. Higher ozone doses, althoug h still positive, were found to have a less pronounced effect. Limited ozon e treatment appears compatible with subsequent digestion of biosolids and e conomically feasible. (C) 2000 Elsevier Science Ltd. All rights reserved.