Electrocoagulation treatment of shale gas drilling wastewater: Performance and statistical optimization

Shale gas drilling wastewater is a challenging waste stream generated in gas industries. It is a mixture of different organic and inorganic compounds. Treatment of this complex wastewater relies on a suitable technology for the removal of small suspended particles and dissolved elements. This study employed electrocoagulation (EC) as an efficient method for shale gas drilling wastewater pretreatment. The optimum operating conditions for turbidity, TOC, and Ca2+ removal were determined using a response surface methodology (RSM). The chloride (Cl-) removal and residual iron of effluent in the EC process were also tested and evaluated. Based on the analysis of variance (ANOVA), the coefficient of determination (R-2) was calculated and found to be above 0.86 for all the responses. The maximum removal efficiencies were found to be around 98.3%, 78.5%, and 56.5% for turbidity, TOC, and Ca2+ removal under the optimum conditions, respectively. In order to treat drilling wastewater by EC process both efficiently and economically, the following operating parameters are recommended: 318 A/m(2) for current density, 20 min for reaction time and 4.4 for initial pH. A total operation cost of 0.80 US$/m(3) was estimated under these conditions. (C) 2021 Published by Elsevier B.V.

Automated summary

The study employed electrocoagulation (EC) as an efficient method for pretreatment of shale gas drilling wastewater, determining the optimum operating conditions for turbidity, TOC, and Ca2+ removal using response surface methodology. The maximum removal efficiencies were found to be around 98.3%, 78.5%, and 56.5% for turbidity, TOC, and Ca2+ removal, respectively, under the recommended operating parameters.