Water reuse options for decentralised MBR effluents: a case study in South Africa

ABSTRACT Treated wastewater is emerging as a promising alternative water solution. This study evaluated the feasibility of reusing effluents from three decentralised membrane bioreactor (MBR) wastewater treatment facilities in Western Cape, South Africa. Using water quality results from each facility, the technical feasibility of irrigation and both indirect potable and direct potable reuse (DPR) options for MBR effluents was evaluated. Effluents from all facilities typically meet national irrigation standards, with only one site requiring pH correction. Partially recharged groundwater with 25% of its water demand using MBR effluents requires additional treatment for organic matter, faecal coliform, nitrates, colour, saturation index, iron, and manganese parameters to meet drinking water quality upon abstraction. For DPR, MBR effluent must undergo pre-treatment to remove excess organic matter, turbidity, and suspended solids before advanced treatment with reverse osmosis. However, only one facility has economic feasibility for potable reuse with payback periods of 7 and 8 years for DPR and indirect potable reuse, respectively. Potable reuse may not be economical for small-scale MBR plants unless the necessity for drinking water reuse outweighs the financial implications. The study highlights the need for evaluating alternative low-cost technologies for MBR effluent treatment and integrated managed aquifer recharge modelling to assess various groundwater recharge scenarios.