This study demonstrates that microalgae can effectively recover all P and N from anaerobically treated black water (toilet wastewater). Thus, enabling the removal of nutrients from the black water and the generation of a valuable algae product in one step. Screening experiments with green microalgae and cyanobacteria showed that all tested green microalgae species successfully grew on anaerobically treated black water. In a subsequent controlled experiment in flat-panel photobioreactors, Chlorella sorokiniana was able to remove 100% of the phosphorus and nitrogen from the medium. Phosphorus was depleted within 4 days while nitrogen took 12 days to reach depletion. The phosphorus and nitrogen removal rates during the initial linear growth phase were 17 and 122 mg·L(-1)·d(-1), respectively. After this initial phase, the phosphorus was depleted. The nitrogen removal rate continued to decrease in the second phase, resulting in an overall removal rate of 80 mg·L(-1)·d(-1). The biomass concentration at the end of the experiment was 11.5 g·L(-1), with a P content of approximately 1% and a N content of 7.6%. This high algal biomass concentration, together with a relatively short P recovery time, is a promising finding for future post-treatment of black water while gaining valuable algal biomass for further application.
Funding InformationThe authors would like to kindly acknowledge (i) the MIP i-Cleantech Flanders (Milieu-innovatieplatform; Environment innovation platform) project Microbial Nutrients on Demand (MicroNOD) for financial support, (ii) the DOCPRO4 project 'PurpleTech', funded by the BOF (Bijzonder onderzoeksfonds; Special research fund) from the University of Antwerp for financially supporting J.S., (iii) all MicroNOD partners, including the University of Antwerp, Ghent University, AgrAqua, Greenyard Horticulture and Avecom; and (iv) all steering committee members, including Greenyard Frozen, Agristo, AVBS,
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