Nutrient recycling from the effluent of a decentralized anaerobic membrane bioreactor (AnMBR) treating fresh domestic wastewater by cultivation of the microalgae Acutodesmus obliquus M. Foix-Cablé, R. A. Darmawan, M. Sahnoun, S. Hindersin, M. Kerner and M. Kraume ABSTRACT This study investigates the feasibility of microalgae cultivation with the effluent (permeate) of a decentralized anaerobic membrane bioreactor (AnMBR) treating high strength domestic wastewater. Two experiments, consisting of three and two successive batch experiments with incubation times varying between 5 and 9 days, were conducted. Nutrient removal and growth of the microalgae species Acutodesmus obliquus were studied for the following culture media: (A) permeate, (B) permeate enriched with iron (Fe), magnesium (Mg), manganese (Mn), sulfur (S) and the chelating agent EDTA, (C) commercial fertilizer as control culture. Initial nutrient concentrations in the culture media ranged from 9.3 to 16.6 mg·L 1 total phosphorus (TP) and from 85.1 to 126.2 mg·L 1 total nitrogen (TN). TP reached an average removal of 97%, 98% and 99% in (A), (B) and (C) respectively. An average TN removal of 94% and 96% was achieved in (B) and (C). Starting from the third batch of the first experiment and the second batch of the second experiment, the culture with permeate (A) showed a decrease in TN removal. Further batch experiments showed the need to add iron to ensure an optimal TN removal from the permeate. M. Foix-Cablé (corresponding author) Chair of Chemical and Process Engineering, ACK7, Technical University of Berlin, Ackerstraße 76, 13355 Berlin, Germany E-mail: mathilde.foix-cable@tu-berlin.de R. A. Darmawan University of Hamburg, Biocentre Klein Flottbek, Department of Aquatic Ecophysiology and Phycology, Ohnhorststraße 18, 22609 Hamburg, Germany M. Sahnoun M. Kraume Chair of Chemical and Process Engineering, FH6-1, Technical University of Berlin, Fraunhoferstraße 33-36, 10587 Berlin, Germany S. Hindersin M. Kerner Strategic Science Consult GmbH, Beim Alten Gaswerk 5, 22761 Hamburg, Germany Key words | anaerobic membrane bioreactor, microalgae, nutrient removal, wastewater treatment, water recycling INTRODUCTION Domestic wastewater treatment with efficient nutrient recovery is a worldwide key challenge for the 21st century. While industrialized countries treat 70% of their sewage, between 28% and 38% of the wastewater is treated in the emerging countries and only 8% in the developing countries (Sato et al. ). When the wastewater is treated, nitrogen and phosphorus removal often remains insuffi- cient, leading to eutrophication of the water bodies (Rawat et al. ). At the same time, phosphorus resources are expected to be depleted within the next 100 years (Withers et al. ) and demand could exceed supply start- ing from 2035 (Cordell ). Phosphorus from human feces represents 28% of the phosphorus global demand (Mihelcic et al. ). If this major nutrient was reused, it could lead to an enhancement of the water bodies’ quality and be a long-term solution to phosphorus depletion. For this purpose, microalgae cultivation appears to be well adapted: • Contrary to conventional wastewater treatments, nitro- gen and phosphorus can be entirely and simultaneously removed without the addition of any chemical product. At the same time, these main nutrients are recycled through biomass production. • Microalgae do not need an external organic carbon source. During photosynthesis, they instead use carbon dioxide, one of the main gases responsible for the global warming, as a carbon source. • Numerous high value products are made from microal- gae. They include especially lipids, proteins, pigments and fatty acids (Spolaore et al. ). Nevertheless, the most promising application for microalgae grown on 1556 © IWA Publishing 2018 Water Science & Technology | 78.7 | 2018 doi: 10.2166/wst.2018.428 Downloaded from http://iwaponline.com/wst/article-pdf/78/7/1556/505456/wst078071556.pdf by guest on 15 March 2023