Coupling ozonation with hydrogen peroxide and chemically enhanced primary treatment for advanced treatment of grey water

Grey water is a valuable water source due to its high-volume generation. This study was conducted with grey water that was obtained from a hotel with 1000 inhabitants and average flowrate of 40 m³/day. The main objective of the study was to determine the optimum operational conditions for ozonation process in terms of micropollutant removal along with conventional parameters and to enhance the removal efficiency of ozonation process by coupling with hydrogen peroxide or chemically enhanced primary treatment (CEPT) process. The results indicated that the COD removal efficiencies were around 37% by both sole ozonation and peroxone processes. However, CEPT+ozonation process increased the COD removal efficiency to 71%. On the other hand, TSS removal efficiency by peroxone and CEPT+ozonation processes were 57% and 89%, while TP removal efficiencies were 26% and 74%, respectively. All micropollutants that were detected in grey water, were removed until the limit of detection (LOQ) with all treatment processes. Overall evaluation of the results indicated that CEPT combined with the ozonation process was more effective in terms of removal of conventional parameters compared to sole ozonation and peroxone processes. Therefore, CEPT+ozonation process with the optimum ozone dosage and contact time is recommended to increase the possibility to reuse the treated grey water. A feasibility analysis was conducted for optimum ozonation mode and CEPT+ozonation, and the results revealed that unit total cost and unit operational cost for ozonation system was 0.027 $/m³ and 0.01 $/m³, respectively. The unit operational cost for CEPT+ozonation system was 0.124 $/m³.