Elaboration of an algae-to-energy system and recovery of water and nutrients from municipal sewage

Abstract

Increasing pressure is being exerted on the peri-urban space that has elevated the demand for electricity, affects the global water resource, and impacts the potential to produce food, fiber, and commodity products. Algae-based technologies and in particular algae-based sewage treatment provides an opportunity for recovery of water for recycle and re-use, sequestration of greenhouse gases, and generation of biomass. Successful coupling of municipal sewage treatment to an algae-to-energy facility depends largely on location, solar irradiance, and temperature to achieve meaningful value recovery. In this paper, an algae-to-energy sewage treatment system for implementation in southern Africa is elaborated. Using results from the continued operation of an integrated algal pond system (IAPS), it is shown that this 500-person equivalent system generates 75 kL per day water for recycle and re-use and, ∼9 kg per day biomass that can be converted to methane with a net energy yield of ∼150 MJ per day, and ∼0.5 kL per day of high nitrogen-containing liquid effluent (>1 g/L) with potential for use as organic fertilizer. It is this opportunity that IAPS-based algae-to-energy sewage treatment provides for meaningful energy and co-product recovery within the peri-urban space and, which can alleviate pressure on an already strained water–energy–food nexus.