Toward energy-neutral wastewater treatment : a high-rate contact stabilization process to maximally recover sewage organicsToward energy-neutral wastewater treatment : a high-rate contact stabilization process to maximally recover sewage organics
Faculty of Sciences. Bioscience Engineering
Sustainable Energy, Air and Water Technology
Engineering sciences. Technology
Bioresource technology. - Barking
179(2015), p. 373-381
The conventional activated sludge process is widely used for wastewater treatment, but to progress toward energy self-sufficiency, the wastewater treatment scheme needs to radically improve energy balances. We developed a high-rate contact stabilization (HiCS) reactor system at high sludge-specific loading rates (>2 kg bCOD kg−1 TSS d−1) and low sludge retention times (<1.2 d) and demonstrate that it is able to recover more chemical energy from wastewater organics than high-rate conventional activated sludge (HiCAS) and the low-rate variants of HiCS and HiCAS. The best HiCS system recovered 36% of the influent chemical energy as methane, due to the combined effects of low production of CO2, high sludge yield, and high methane yield of the produced sludge. The HiCS system imposed a feast-famine cycle and a putative selection pressure on the sludge micro-organisms toward substrate adsorption and storage. Given further optimization, it is a promising process for energy recovery from wastewater.