An approach to resources recovery from domestic wastewater applying membrane photobioreactors

The effluent produced by traditional wastewater treatment plants (WWTPs) is often insufficient to meet the quality standards required by the European legislation for water reuse; consequently, additional treatment steps are commonly necessary. The integration of anaerobic processes, such as the Up-flow Anaerobic Sludge Blanket (UASB) reactor, with membrane photobioreactors (MPBRs) represents a promising advancement in wastewater treatment. In this final project, domestic wastewater that had already undergone primary treatment was treated using an UASB reactor as secondary treatment, followed by a MPBR as tertiary treatment, the latter employing in parallel ceramic (microfiltration) and organic (ultrafiltration) membranes. The system consisted of an outdoor pilot-scale plant operated continuously for three months at the Northeast Tenerife Wastewater Treatment Plant (EDAR Noreste), in Canary Islands, Spain. The study aimed to evaluate the quality of the produced permeate, analyze membranes’ performance, concentrate the harvested biomass in order to obtain a valuable by-product, better understand membrane fouling mechanisms through filtration and cleaning procedures, investigate the impact of multiple solids retention times (SRTs) on system performance. The outcome consisted of four experiments: three performed with the organic membrane (at infinite SRT, SRT=60 d and SRT=40 d), and one with the ceramic membrane (at infinite SRT). The system produced particle free permeate with up to 90% chemical oxygen demand (COD) and up to 88% dissolved organic carbon (DOC) removal, while nitrogen and phosphorus removals were lower. TMP monitoring showed stable membrane performance. Fouling behavior varied with SRT, suggesting a nonlinear relationship between biomass growth dynamics and resistance development. Biomass harvesting generated a concentrated, valuable by product, confirming the UASB–MPBR system as a promising solution for advanced wastewater treatment.