Reducing the environmental footprint of wastewater screenings through anaerobic digestion with resource recovery

Abstract

Screenings produced as the first stage of wastewater treatment and currently disposed of to landfill, are rich in volatile organic solids, nitrogen and phosphorus which could be recovered through anaerobic digestion. Biochemical methane potential (BMP) tests on screenings demonstrated a methane yield of 0.33m 3 methane/kg volatile solids (VS) and a VS destruction of 50%. Consequently, the effect of a range of hydraulic retention time (HRT) and organic loading rates (OLRs) was evaluated in lab-scale continuously fed mesophilic digesters. The highest methane yield of 0.416Nm 3 methane/kg VS added was observed with an HRT of 15 days and an OLR of 2.5kg VS/m 3/day, when up to 65% of the VS were destroyed. If treated by anaerobic digestion, every dry tonne of screenings digested would divert 466kg from landfill, save 4.6 tonne equivalent carbon dioxide (CO 2eq) and deliver 3.4MWh of renewable energy. © 2011 The Authors. Water and Environment Journal © 2011 CIWEM.