Application of Box–Behnken design for circulating flow sono-electrocoagulation for oily wastewater treatment

Abstract

The increasing production of oily wastewater as a by-product of industry has become a major environmental problem. Therefore, this article investigates the removal of mineral oil from oily wastewater by a circulating flow sono-electrocoagulation. The Box–Behnken design was used to study the effects of characteristic electrocoagulation and ultrasonic parameters on mineral oil removal efficiency. A total of 34 different experimental setups were performed at a laboratory scale. A reduced cubic regression model with derived coefficients was developed to describe the mineral oil removal rate. The experimental results show that circulating flow sono-electrocoagulation with iron electrodes can effectively reduce mineral oil by 93.3% under the optimum conditions of 10.948 cycles, a current density of 107.12 A m⁻² and a flow rate of 0.468 L s⁻¹. The experimental observations agreed well with the modeled values, and the model was verified experimentally. Under the optimal conditions, the average operating cost was 0.77 EUR/m³.

Keywords:

• Sono-electrocoagulation
• Box–Behnken design
• mineral oil
• flow rate
• iron electrodes

Acknowledgements

This work has been fully supported by Croatian Science Foundation under the project “IP-2019-04-1169—use of treated oily wastewater and sewage sludge in brick industry—production of innovative brick products in the scope of circular economy.”

Disclosure statement

The authors report there are no competing interests to declare. The authors confirm that the data supporting the findings of this study are available within the article.