Comparison of Nanofiltration and Direct Contact Membrane Distillation as an alternative for gold mining effluent reclamation

Abstract

Effluent reuse is becoming an environmentally-economically viable option for industries that have been struggling with environmental/legislative pressure and high costs of water supply and effluents discharge. Mining effluents are promising for reuse, but for this, (hazardous) metals and ions such as sulfate must be removed efficiently. This study aimed to compare the technical-economic performance of Nanofiltration (NF) and Direct Contact Membrane Distillation (DCMD) on gold mining effluent treatment. The results showed that both technologies are promising for mining effluent reclamation as high pollutants removal rates were observed (rejection >73% and >96% for NF and DCMD, respectively). DCMD showed lower flux than NF and was limited to operate up to permeate recovery rate (RR) of 40% due to severe fouling (CaSO4 precipitation), but produced a higher quality permeate with no reuse restriction, low energy requirement and lower associated costs due to use of the effluent residual heat. Capex and Opex (for membrane lifespan of 1–5 years) were estimated at US$ 575,490.30 and 2.00–2.10 US$/m3 for NF and US$ 305,483.85 and 0.13 to 0.27 US$/m3 for DCMD systems. The permeate reuse would reduce water consumption in 490,560 m3 year−1, which represents almost 50% of the industrial water demand.