Combined electrocoagulation/electrooxidation process for the COD removal and recovery of tannery industry wastewater

The efficiencies of electrooxidation (EO), electrocoagulation (EC) and combined EC/EO processes for the treatment and recovery of tannery wastewater were investigated. In this way, not only the effect of retention time and current density on the COD and color removal was investigated, but also, the recovery of effluent was investigated to provide a standard quality for effluent disposal and supply for agricultural and industrial uses. The results showed that the EO process was able to eliminate COD and color by 98.9 and 99.0%, respectively. The EC process at optimum conditions had the removal efficiencies of 82.2 and 68.3% for COD and color, respectively, which could not treat the effluent completely. While the EC process produces a wastewater with COD of 1620 mg/L that needs extra treatment for agriculture and reuse, the process of EO produces a wastewater with COD of about 92 mg/L, whose its organic loading is suitable for agricultural purposes but not appropriate for industrial uses. The combined EC/EO process can produce an effluent with COD5 mg/L that has standard quality for disposal and use for agricultural needs as well as for reuse in tannery process. Moreover, the EC/EO process has low energy consumption of 18.2 kWh/m(3) as compared with EO process with energy consumption of 60 kWh/m(3). The combined EC/EO process is useful for the treatment of tannery wastewater so that the effluent can be used for industrial purposes. (c) 2017 American Institute of Chemical Engineers Environ Prog, 37: 637-644, 2018