The eect of an oxidative pretreatment on the anaerobic digestion of sewage sludge was
investigated. Sewage sludge from a domestic wastewater treatment plant was partially oxidized by
ozone. The pretreatment could alter up to 67% of the organic matter: 2923% was solubilized, 382
9% was removed. Anaerobic degradability tests indicated that the pretreatment step enhanced 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 O3/g chemical oxygen demand (COD), while the methane
production rate was 2.2 times higher compared to the untreated sludge. Higher ozone doses, although
still positive, were found to have a less pronounced eect. Limited ozone treatment appears compatible
with subsequent digestion of biosolids and economically feasible. 7 2000 Elsevier Science Ltd. All
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