Reduction of sludge production from WWTPs using thermal pre-treatment and enhanced anaerobic methanisation

This study investigates the performance of an enhanced two-step anaerobic process for the treatment of WWTP sludge. This process was developed to answer the urgent need currently faced by WWTP operators to reduce the production of biosolids, for which disposal pathways are facing increasing difficulties.

A pilot plant was operated on a full-scale WWTP (2,500 p.e.) over a period of 4 months. It consisted of a thermal pre-treatment of excess sludge at 175 °C for 40 minutes, followed by dewatering and methanisation of the centrate in a fixed-film reactor.

The thermal lysis had a two-fold enhancing effect on sludge reduction efficiency: firstly, it allowed a decrease of the hydraulic retention time (HRT) in the methaniser to 2.9 days. Secondly, it yielded biosolids with a high dewaterability. This contributed to further reductions in the final volume of sludge to be disposed of.

The two-step process achieved a sludge reduction efficiency of 65% total suspended solids (TSS), thus giving an interesting treatment option for WWTP facing sludge disposal problems.

Download or read the full article in Water Science & Technology.