A new concept for heavy metal removal by forming hydroxide precipitation using alkalinity produced by microbial desalination cell (MDC) was proposed. Four five-chamber MDCs were hydraulically connected to concurrently produce alkalinity to treat synthetic copper-containing wastewater and salt removal. There was nearly complete removal of copper, with a maximum removal rate of 5.07kg/(m3d) under the initial copper concentration of 5000mg/L (final pH of 7). The final copper concentration met the emission standard for electroplating of China (0.5mg/L, GB 21900-2008). XRD analysis indicated copper was precipitated as Cu2Cl(OH)3. The best performance of MDCs in terms of average power density, salt removal and COD removal rate achieved in stage 3 were 737.3±201.1mW/m2, 53.6±0.8kg/(m3d), and 1.84±0.05 kgCOD/(m3d) respectively. For purposes of water recovery, an electrodialysis (ED) system was presented based on in-situ utilization of generated electricity by MDCs as post-desalination treatment for salt effluent after sedimentation. The maximum discharging voltage of 12.75±1.26V at switching time (Ts) of 15min using a capacitor-based circuit produced a maximum desalination efficiency of 30.4±2.6%. These results indicated that this combined system holds great promise for real-world treatment of copper-containing wastewater and deep desalination of high-salinity-water.
Keywords: Alkalinity production; Copper-containing wastewater treatment; High-salinity-water desalination; Microbial desalination cell.
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