Tertiary treatment with ferrate and ozone

Based on the results of a batch study, a bench-scale pilot plant study was conducted to determine the improvements in effluent quality of secondary treated wastewater using ferrate (VI) and ozone with primary objective of achieving coliform level of 2.2 MPN/100 ml for reuse purposes. The batch study showed that a ferrate dose of 15 mg/L gave effective removal of turbidity, COD, and coliform. Therefore, in a continuous flow study a mixture of ferrate stock solution and secondary effluent at a flow rate of 250 ml/min, was subjected to ferrate (15 mg/L) coagulation and flocculation for 45 min followed by sedimentation, filtration, and ozonation. Ozone gas was allowed to react for 5 min in a contactor for an ozone utilization of 1-5.8 mg per liter of the effluent with resulting ozone residual (peroxide) of 0.4-1.9 mg/L. This treatment has shown a significant improvement with respect to removal of suspended solids (70.8%), turbidity (78%), besides achieving the desired level of disinfection (total coliform 99.99941% and total plate count 99.99%).