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 m3.d−1, total life cycle costs were £0.095, 0.128 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 m3.d−1, IEX with brine recycle MBR proved the most cost effective option (total life cycle cost £0.044–0.087.m–3, 1500–30000 m3.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 (∼100 g NaCl.L−1), provided an appropriate halo-tolerant community can be established.