Minimisation of excess sludge production in a WWTP by coupling thermal hydrolysis and rapid anaerobic digestion

Chauzy, J, Graja, S, Gerardin, F, Cretenot, D, Patria, L, Fernandes, P

Water Science and Technology, 2005


In many cases, reducing sludge production could be the solution for wastewater treatment plants (WWTP) struggling to manage their sludge. The aim of this study was to test the possibility of minimising the excess sludge production by coupling a thermal hydrolysis stage and anaerobic digestion with a very short hydraulic retention time (HRT).

The tests were carried out on a 2,500 p.e. pilot plant installed on a recycling loop between the clarifier and the activated sludge basin. The line equipped with the full scale pilot plant produced 38% total suspended solids (TSS) less than the control line during a 10 week period. Moreover, the rapid anaerobic digestion removed, on average, more than 50% of the total COD load with an HRT of 3 days. Lastly, the dryness of the remaining excess sludge, sanitised by thermal hydrolysis, was more than 35% with an industrial centrifuge.

This combination of thermal hydrolysis and rapid anaerobic digestion equally permits a significant gain of compactness compared to traditional anaerobic digesters.

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