Immersed membrane bioreactors for nitrate removal from drinking water: Cost and feasibility

Brine disposal remains a key consideration when employing ion exchange (IEX) for nitrate removal. To circumvent this issue, research was conducted into developing an immersed membrane bioreactor (MBR) as a replacement for ion exchange. This paper compares the economics of the two process options whilst also considering MBR for brine treatment. At a blend flow rate of 3000 m(3).d(-1), total life cycle costs were 0.095,0.128 pound and 0.064.m(-3) for IEX, MBR and IEX with brine recycle MBR respectively. Capital and O&M costs associated with MBR were extremely sensitive to membrane price variation. For blend flows >700 m(3).d(-1), IEX with brine recycle MBR proved the most cost effective option (total life cycle cost 0.044-0.087 pound.m(-3), 1500-30000 m(3).d(-1)) when assuming similar hydrodynamic efficiencies to the IEX replacement MBR. Further cost reductions (<= 17%) can be found by operating Brine recycle MBR at higher salinity (similar to 100 g NaCl.L(-1)), provided an appropriate halo-tolerant community can be established.