Recovery of reusable water from sewage using aerated flat-sheet membranes.

Continuous developments and advances in membrane technology allow recovering to large extent reusable water from untraditional water sources, such as municipal effluents. In this paper, operational results and preliminary cost-analysis of a microfiltration (MF) process used for raw sewage and secondary effluent polishing are given. The research was conducted with a 22 sandwich-type flat-sheet membrane module (0.45 µm and 4.5 m(2)) employing aeration for fouling control. During raw sewage filtration the majority of the organics were retained (effluent COD < 90 mg/L and SS ~ 0 mg/L). However, the fluxes were significantly lower [~7 L/(m(2) h)] compared to those achieved during secondary effluent filtration [~29 L/(m(2) h)] (at TMP 0.14 bar). In the second case, aeration was found to be suitable mean for fouling control. The total costs (capital and operational) for water recovery from raw sewage and secondary effluent were estimated to be in the order of 2 and 0.75 €/m(3) respectively.

Upflow anaerobic clarification tank (UACT) to upgrade existing anaerobic effluents.

The Upflow Anaerobic Clarification Tank (UACT) is of interest as a post-treatment step for high-rate anaerobic wastewater treatment systems. The UACT contributes to extra capture of methane from the raw wastewater. It also significantly facilitates the reuse of the treated water. The efficiency of the UACT process is demonstrated in this study using laboratory-scale reactors. The water produced by the UACT had a low total COD, in most cases below 145 mg/L and a soluble COD below 60 mg/L at surface loading rates between 0.1-0.4 m(3)/(m(2) h) and hydraulic retention times between 5-6 h. The sludge bed of the UACT was characterised by 6-10 times higher substrate affinity (for ethanol, acetate and propionate) compared to the parent UASB and similar specific activity. The results suggest that a UASB followed by the UACT can, upon subsequent application of a rapid filtration, qualify as a total COD removal, no longer necessitating aerobic treatment.