Thermophilic (55 °C) and hyper-thermophilic (70 °C) anaerobic digestion as novel treatment technologies for concentrated black water

Thermophilic and hyper-thermophilic anaerobic digestion (AD) are promising techniques for the treatment of concentrated black water (toilet fraction of domestic wastewater collected by low flush volume toilets; BW), recovery of nutrients and simultaneous pathogen removal for safe recovery and reuse of those nutrients. This study showed that thermophilic AD (55 degrees C) of concentrated BW reaches the same methanisation and COD removal as mesophilic anaerobic treatment of BW (conventional vacuum toilets) and kitchen waste while applying a higher loading rate (OLR) (2.5-4.0 kgCOD/m(3)/day). With a retention time of 8.7 days, and an OLR of >3 kgCOD/m(3)/day, COD removal of 70% and a methanisation of 62% (based on CODt) was achieved during thermophilic AD. Hyper-thermophilic (70 degrees C) reached lower levels of methanisation (38%). Start-up time of thermophilic AD was 12 days. And during thermophilic AD, a shift from acetoclastic methanogenesis towards syntrophic acetate oxidation was observed.

Automated summary

Thermophilic and hyper-thermophilic anaerobic digestion are effective methods for treating concentrated black water, achieving efficient COD removal and methane production with a shorter start-up time, but may result in lower methane production rates at high temperatures.