Reclaiming Biologically Stable Water from Treated Secondary Effluent Using a Dual-Membrane System

The effectiveness of a lab-scale multibarrier membrane system, comprised of microfiltration (MF) and reverse osmosis (RO) modules, for reclaiming biologically stable water from treated secondary effluent was evaluated under various operating and environmental conditions. The biological stability of reclaimed water was quantified by using assimilable organic carbon (AOC). The results obtained from this study revealed that the RO process was able to reduce AOC more efficiently under either a high operating pressure (>50 psi) or under the condition of a medium recovery ratio (∼20%) with a slightly alkaline (pH ∼ 7.5) operating environment. Generally, the MF could reduce the turbidity of its feed water from 4.1–5.3 NTU to only around 0.3 NTU, which helped to enhance RO operation by slowing down the fouling development rate. The removal efficiencies of the RO, under optimal conditions, was 98.1–98.9% for total organic carbon (TOC) and 96.1–98.7% for AOC, respectively. The observations were compared with the co...