Nutrient removal from membrane bioreactor permeate using microalgae and in a microalgae membrane photoreactor

This paper explores the use of a novel microalgae membrane photoreactor (mMR) to polish the effluent from an aerobic membrane bioreactor (MBR) fed with domestic wastewater. Four microalgae species Chlorella (Chlorella sp.), Chlorella vulgaris (C. vulgaris), Scenedesmus quadricauda (S. quadricauda) and Scenedesmus dimorphus (S. dimorphus) were isolated from the environment and tested in batch reactors fed with permeate from the aerobic MBR to evaluate the nutrient removal rates for each species. All four microalgae species were able to completely remove NH4 in the reactor within 3 days. The removal rates of NO3, NO2 and PO4 were between 43–54%, 83–95% and 70–92%, respectively after 3 days in the batch reactor. Subsequently, an MBR–mMR system was operated for 23 days. The mMR was able to remove on average 50% of NH4, 75% of NO2, 35% of NO3 and 60% of PO4 consistently from the MBR effluent under the conditions tested.