Membrane Bioreactor (MBR) Treated Domestic Wastewater for Reuse in a Recirculating Aquaculture System (RAS)

Membrane bioreactor (MBR) technology has attracted great attention over the last 3 decades and achieved rapid growth in an increasing number of practical small- and large-scale applications worldwide. However, its application in Sub-Saharan Africa as well as in aquaculture was so far limited. The installation and operation of a pilot membrane bioreactor (MBR) in Kisumu, Kenya, adopts an integrated approach by providing an integral, sustainable, cost-effective, and robust solution for water sanitation, which also meets the demand for clean water in the fish processing industry, aquaculture, and irrigation. The innovative system comprises a pilot MBR coupled with a recirculating aquaculture system (RAS) which is linked to a 14.3 kW photovoltaic (PV) system, including a 30 kWh Li battery storage to supply sustainable energy. The RAS is able to recirculate 90-95% of its water volume; only the water loss through evaporation and drum filter back flushing has to be replaced. To compensate for this water deficit, the MBR treats domestic wastewater for further reuse. Additionally, excess MBR treated water was used for irrigating a variety of local vegetables and could be also used in fish processing plants. The pilot-scale MBR plant with around 6 m2 submerged commercial UF polyethersulfone (PES) membranes provides treated water in basic agreement with Food and Agriculture Organization (FAO) standards for irrigation and aquaculture, showing no adverse effects on tilapia fingerlings production. A novel membrane module with a low-fouling coating technology is operating stably but has not yet shown improved performance compared to the commercial one.