Analysis of Membrane Fouling Reported in Membrane Photobioreactors (MPBRs) for Treatment of Secondary Effluents

Abstract

AbstractMembrane photobioreactors (MPBRs) can be applied as promising advanced treatment of effluents from conventional activated-sludge plants, focused on the recovery of nutrients present in wastewater instead of using energy for their removal. A lab MPBR equipped with a submerged hollow fiber ultrafiltration membrane has been operated with a secondary effluent and without microalgae inoculation. The first phase was focused on promoting spontaneous microorganisms growth and rising a stable suspended solid concentration, while the second phase was dedicated to studying the reactor performance and membrane fouling at a stationary state. The microorganisms that spontaneously developed in the systems were identified as Scenedesmus sp. and diatoms. In addition, suspension filterability tests were carried out following the step flux methodology varying the imposed flux from 8 to 30 l/h·m2. Stable MLSS content of around 1200–1400 mg/L in the MPBR was achieved after the acclimation phase of 45 days operating at a hydraulic retention time of 18 h and solids retention time of 40 days. In both phases, membrane fouling behavior was similar, with around 80% of reversible nature and easy removal by physical cleaning and completely independent of the suspended solids content. Regarding the reclamation efficiency, dissolved organic carbon was not significantly removed while the nitrogen load was reduced by 20%. The nitrification process was mainly due to nitrifying bacteria.KeywordsAdvanced treatmentSubmerged membraneHollow fiberPolymeric bioclustersNutrients recovery