Post-treatment of secondary treated effluent by Electrocoagulation: Nutrients removal and process optimization

¹ Civil and Architectural Engineering Department, College of Engineering and Technology, University of Technology and Applied Sciences, Oman
² Applied Chemistry Department, College of Applied Sciences and Pharmacy, University of Technology and Applied Sciences, Oman
³ Research and Development Department, Oman Water and Wastewater Services Company

^* Corresponding author: arahimalomairi@gmail.com

Abstract

The leve of nutrients in the treated effluent should be maintained at a low level to mitigate the rapid algal bloom and the associated risks in the receiving water bodies. Electrocoagulation (EC) was proven to be an effective method to remove a broad range of impurities in different water matrices. This study evaluated the EC technique as a polishing step for the treated effluent targeting phosphate, nitrate, and dissolved organic matter (DOM). A factorial design was implemented to evaluate the effects of two factors (voltage, and treatment time) at three levels (high, centre, and low) on the EC process. Two electrode types (Fe and Al) performances were compared. The results revealed that both electrodes were capable of high removal of phosphate (100%) from the treated effluent within 10 minutes for both tested voltages 3 and 5 volts. However, the nitrate showed a high persistence for both electrode types and the removal never exceed 10%. Interestingly, aluminum electrodes achieved higher removal (54.5%) of DOC compared to 25.7% by iron electrodes. The main drawback of using the iron electrode was its contribution to the original turbidity which makes it less favourable compared to the Al electrode. The results of this study revealed that the aluminum-based EC process could achieve the target level of nutrient removal without compromising the water quality.