Operation and Performance of The Lab and Pilotscale Greywater Treatment Systems: Biochar and Gravel Use in South Africa

Water security in South Africa depends on natural and artificial water sources such as rivers, lakes, rainwater harvesting, boreholes, dams, desalination, the importation of water from nearby countries, and wastewater treatment plants. The primary input to these water resources is rainfall which is estimated to be around 492 mm per year and is half of the world average (985 mm per year) due to climate change impacts. This study encourages the treatment and reuse of greywater as an additional water source for non-potable purposes such as toilet flushing and irrigation. The performance of the Laboratory (Lab)-scale Gravel Filter Towers (GFTs) was evaluated concurrently with the Pilot-scale system for remediation of the microbiological and physicochemical constituents in greywater which was sampled from separate single-households for both systems. The highest removal efficiency of faecal coliforms by the GTFs was 92.89 ± 93.39 % while the Pilot-scale exhibited a removal efficiency of 21.51 ± 12.47 %. The systems showed partial removal of microbiological, chemical, nutrient, and physical constituents, indicating that further analysis and improvements are required before decentralization. The GFTs could be improved by the addition of a biochar filter while the pilot-scale systems require fresh treatment materials monthly to avoid clogging and leaching of biofilms to the final collection tank. Further analysis could involve the profiling of the microbial communities using metagenomic techniques which may provide insight into the biochemical functioning (bioremediation, quorum sensing, and pathogenicity) of the system.