Anaerobic Membrane Reactors

In the last decade anaerobic membrane reactors (AnMBRs) have evolved from aerobic MBRs, with the membrane either external or submerged within the reactor. These reactors can achieve high chemical oxygen demand (COD) removals (∼98%) at low hydraulic retention times (HRTs) of 3 hours. In addition, since the membrane stops biomass being washed out of the reactor, they are capable of enhancing performance with inhibitory substrates, and at psychrophilic and thermophilic temperatures, and enable nitrogen removal via Anammox. As with MBRs, fouling is an issue, but addition of activated carbon or resins/precipitants can remove soluble organic products (SMPs) and enhance flux. Due to their low energy use and solids production, and a solids-free effluent, they also have considerable potential to enhance nutrient and water recycling. Nevertheless, more work is needed to compare fouling in aerobic and anaerobic systems, to determine how much knowledge in aerobic systems can be transferred, to determine how reactor operation influences fouling, to evaluate the effect of different additives to the reactor on membrane fouling, to determine whether nitrogen removal can be incorporated into AnMBRs, to determine methane solubility at low temperatures and recover it from the effluent, and to establish sound mass and energy balances on pilot scale plants to evaluate the economics of AnMBRs.