Ultrasonic-electrochemical treatment for effluents of concrete plants

Abstract

Huge quantities of water are consumed by the construction industry, and consequently huge amount of polluted wastewater is discharged from this industry to the surrounding environment. For example, it was reported that a single 8000 L capacity concrete mixer requires 1,500 litters of water per each shift for washing process and 1,600 litters for concrete preparation. This huge consumption of water results in substantial production of wastewater, which is generally highly contaminated with various contaminates and high pH (≥ 11). Consequently, it exerts serious influence on quality of freshwater and marine lives. Therefore, this research was devoted to examine the efficiency of a new method of wastewater treatment, which combines and applies electrocoagulation and ultra-sonication systems (UL-EC) for remediation of concrete plants' effluents from chemical oxygen demand (COD) from. The electrocoagulation cell was based on four aluminum electrodes, while ultrasonic treatment was applied using ultrasonic bath. The effect of other major parameters, including initial pH of wastewater (IPHW) (4, 7 and 10), current densities (CDS) (1, 3 and 5 mAcm-2), and electrodes spacing (ES) (5, 10 and 15 mm) on the efficiency of UL-EC were optimized using Box-Behnken Design (B-BD). The results of the present experiments confirmed that 68.14% COD removal was gotten by the electrocoagulation unit, while, the UL-EC removed 87.8% of COD. The optimum removal of COD was achieved at IPHW of 7, CDS of 5 mA.cm-2 and ES of 5mm.