The environmental feasibility of low-cost algae-based sewage treatment as a climate change adaption measure in rural areas of SADC countries

Abstract

Employing specific algae treatment to treat municipal domestic wastewater effluent presents an alternative practice to improving water quality effluent of existing rural pond systems in Southern Africa. In the present study, domestic wastewater was treated by using existing infrastructure and inoculated specific selected algae strains in a pond system treatment plant. The objective was to determine through a field pilot study if algae nutrient treatment efficiencies in current traditional water-stabilisation ponds can be optimised by manipulating the existing natural consortium of algae through mass inoculation of specific algae strains of Chlorella spp. The reduction of total phosphorus in the unfiltered water (contain algae) after specific algae treatment was 74.7 and 76.4% for water-stabilisation ponds 5 and 6, while total nitrogen removal was 43.1 and 35.1%, respectively. Chlorella protothecoides was the dominant algal species in ponds 4, 5 and 6 after specific algae treatment. The maximum algae abundance (4.6 × 106 cells mL-1 in pond 4 and 6.1 × 106 cells mL-1 in pond 5) were observed in August 2016, while the maximum chlorophyll-a concentration of 783 µg L-1 was measured in pond 5 after 2 months of specific algae inoculation. Although the present study showed that inoculation of specific algal strains can potentially enhance the treatment efficiencies of existing rural domestic sewage pond systems, it was also evident from the algae-treated effluent analysis that the algae biomass in the upper surface water layer must be harvested for maximum treatment results.