Optimisation of ultrasonic-electrocoagulation process efficiency in the landfill leachate treatment: a novel advanced oxidation process

Landfilling in many countries is the most embraced method for disposal of municipal, agricultural and industrial waste. However, the main issue imposed for landfilling is the landfill leachate (LL) leakage. Leachate with high pollution is threating the soil and water resources. Leachate treatment is known as a challenging and issues due to inherent liable and refractory composition. A hybrid processes sono-electrocoagulation is an efficient and applicable method for LL treatment. In the present study, response surface methodology (RSM) and central composite design (CCD) approach were employed to optimise the important influencing factors (pH, reaction time, direct electrical current) in Sono-electrocoagulation for LL treatment. The results obtained from the present study indicated that the optimum condition is pH = 6 for efficient COD removal. An important quadratic regression model was taken to fit the laboratory data; the influencing factors were statistically significant. The purposed model was considered for the response in permitted error. The fit precision ratio was achieved as 54.36. The COD removal in optimised conditions (pH: 5.7, reaction time: 80 min, direct current: 1.9 A) was found to be 86%. The kinetics of reaction (R-2 = 0.98) followed from first-order kinetic. Electrocoagulation process (45%) and sonolysis mechanism (12%) have a lower performance in COD removal individually. However, the combined Sono-electrocoagulation showed a synergist effect and increased the COD removal in leachate (SF = 1.5). In the optimum condition, the operational cost of the sono-electrocoagulation process is 6.28 US $/m(3). The changes in the sludge the during process indicate the changes in the microscopic structure and elements in the sludge produced after the process.

Automated summary

Landfilling is a common method for waste disposal, but landfill leachate leakage poses a threat to soil and water resources. The sono-electrocoagulation hybrid process is an efficient method for leachate treatment, with optimum COD removal achieved at pH 6.