Advanced Non-Sewered sanitation system for onsite water recycling in a South African informal settlement

Abstract

Non-sewered sanitation systems (NSSS) are treatment solutions for complex, high-density urban environments in developing countries. Through advanced treatment, NSSS can provide onsite water recycling to enable water-based sanitation in regions with limited water supply. This study presents the outcomes of a three-month field trial of the NEWgenerator (NG) in a South African informal settlement. During the field trial, the NG treated high-strength blackwater from a community facility and recycled the product water for toilet flushing. Throughout the trial, the NG consistently met local recycled water standards for pH, COD, TSS, turbidity, residual chlorine, and Escherichia coli. Additionally, total nitrogen levels were reduced by 97 %, surpassing the recently developed ISO 30500 standard. Through water recycling, the NG offset municipal water demand for toilet flushing. However, a high leakage rate resulted in elevated toilet flush water demand. Approximately 78 % of the flush water demand was wasted due to leaks, which also reduced the NG's ability to offset the total flush water demand. If demand reduction measures were conducted, such as leak repairs and the installation of water-efficient toilets, the NG could meet the entire flush water demand, thus achieving a closed-loop water system. No significant ion accumulation was observed during this water recycling trial. However, a simulation of ion accumulation indicates that in a closed-loop system, periodic water replacement is necessary to maintain the nutrient removal efficiency of the NG. Overall, the NG successfully treated high-strength blackwater in an informal settlement for recycling and contributed to reducing potable water usage for sanitation.