Pretreatment followed by anaerobic digestion of secondary sludge for reduction of sewage sludge volume.

The influence of two pretreatment methods, thermal treatment and low-pressure wet oxidation, on the sludge digestion efficiency was examined. Batch thermophilic anaerobic digestion was used to evaluate the effectiveness of the pretreatment methods in terms of volatile suspended solids (VSS) digestion efficiency and gas production. The results showed that the gas production was not proportional to the VSS degradation efficiency of either thermal treatment or low-pressure wet oxidation.

Development of an efficient process for the treatment of residual sludge discharged from an anaerobic digester in a sewage treatment plant.

In order to reduce the discharge of residual sludge from an anaerobic digester, pre-treatment methods including low-pressure wet-oxidation, Fenton oxidation, alkali treatment, ozone oxidation, mechanical destruction and enzymatic treatment were evaluated and compared. VSS removal efficiencies of greater than 50% were achieved in cases of low-pressure wet-oxidation, Fenton oxidation and alkali treatment. Residual sludge from an anaerobic digester was pre-treated and subjected to thermophilic anaerobic digestion.