Three different combinations of treatment techniques, i.e. electrocoagulation combined with microfiltration (EMR), membrane bioreactor (MBR) and electrocoagulation integrated with membrane bioreactor (hybrid MBR, (HMBR)), were analysed and compared for the treatment of tannery wastewater operated for 7 days under the constant trans-membrane pressure of 5 kPa. HMBR was found to be most suitable in performance as well as fouling reduction, with 94 % of chemical oxygen demand (COD) removal, 100 % chromium removal and 8 % improvement in percentage reduction in permeate flux compared to MBR with only 90 % COD removal and 67 % chromium removal. The effect of mixed liquor suspended solids on fouling was also investigated and was found to be insignificant. EMR was capable of elevating the flux but was not as efficient as HMBR and MBR in COD removal. Fouling reduction by HMBR was further confirmed by SEM-EDX and particle size analysis.
This study is based on the investigation of the performance of electrocoagulation (EC), followed by the microfiltration process for heavy metal removal in synthetic model waste water containing Zn2+, Ni2+ and Cd2+ ions. Effects of initial concentration, current density and pH on metal removal were analysed to optimize the EC process. The optimized EC process was then integrated with dead-end microfiltration (MF) and was found that the hybrid process was capable of 99% removal of heavy metals. The cake layer formed over the membrane by the hybrid process was analysed through scanning electron microscope-energy-dispersive X-ray spectroscopy. The particle size analysis of the sludge formed during EC was done to investigate the fouling caused during the process.
This study investigates the performance of electrocoagulation integrated membrane bioreactor (EMBR) in treating synthetic wastewater enriched with heavy metals (Cu, Cr, and Zn). This hybrid system was compared with a conventional membrane bioreactor (MBR). The results suggest that it is superior to conventional MBR in terms to chemical oxygen demand removal, flux improvement, fouling reduction, and metal removal. The metal removal efficiencies in both MBR and EMBR followed the sequence Cr > Cu > Zn. The average removal efficiencies in MBR were 60.90, 53.24, and 48.22% for Cr, Cu, and Zn, respectively, while for the EMBR 98.60, 97.53, and 93.52% could be achieved, respectively. The mixed liquor suspended solids (MLSS) concentration was also found to affect the metal removal potential of the MBR. In MBR, metal removal and MLSS concentration showed significant relationship, while in EMBR, this correlation was found to be less. The specific energy consumption for removing each metal by EMBR was calculated and found to be 6.62, 6.94, and 6.69 kWh/kg removed for Cr, Zn, and Cu, respectively.
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