Studying interactive effects of operational parameters on continuous bipolar electrocoagulation–flotation process for treatment of high-load compost leachate

In this research, performance of continuous electrocoagulation/flotation (ECF) process in treating compost leachate, a complex structure and high pollutant load, has been investigated. The effects of initial chemical oxygen demand (COD) concentration, voltage, hydraulic retention time (HRT), and electrode distance (ED) on COD and total suspended solid (TSS) removals were surveyed. The comparison results among some initial batch experiments for various configurations (Al–Al, Al–Fe, Fe–Fe, and Fe–Al) showed that Al–Al bears higher COD and TSS removals. The variables’ interactive effects on COD and TSS removal efficiency in continuous runs for Al–Al configuration were analyzed and correlated by response surface methodology (RSM). Ultimately, experimental results analysis showed that continuous ECF could effectively reduce COD and TSS by 96 and 99 %, respectively, at the optimum conditions of influent COD 13,600 mg/L, voltage 19 V, HRT 75 min, and ED 3 cm. Confirmation tests showed 95 % confidence interval for reasonable agreement of the predicted values from fitted correlations and experimental results. Also, according to outcomes analysis, COD concentration and HRT were, respectively, the most effective items for both COD and TSS removals. Observations showed that applied continuous ECF could efficiently satisfy direct discharge standards at optimal and controlled conditions.

Keywords
Municipal wastewater; COD removal; Physicochemical process; Al–Al electrode; Response surface methodology (RSM)