Combined microbubble ozonation-BAC system for reverse osmosis concentrate treatment

Microbubble ozonation was used to increase ozone utilization rate and to enhance ozone oxidation of reverse osmosis concentrate (ROC) followed by biodegradation using a BAC system. The average influent COD and BOD5/COD of ROC to microbubble ozonation system were 240 mg/L and 0.01, respectively. With the continuous operation of a lab-scale microbubble ozonation system under an optimum condition with 40mg/L O3 dosage and 30 mins HRT, the average COD removal obtained was 55% with an increase in BOD5/COD ratio from 0.01 to 0.25. Under the optimum operating condition, the average ratio between COD removed and O3 consumed was 1:2.5. Microbubble ozone treated ROC was then fed in to a biological activated carbon (BAC) column for further biodegradation of ROC. Combining the BAC column at 120 mins EBCT with microbubble ozonation was able to increase the COD removal efficiency 2-3 times higher as compared without pre-ozonation. With the lab-scale combined microbubble ozonation and BAC system, the average effluent COD of 35 mg/L was achieved that can meet the COD discharge limit standard.