Ozonation of domestic secondary effluent for recycling and reuse - a pilot plant study

Abstract

In this study, a pilot plant combined ozonation with sand filtration is established. Wastewater from the secondary effluent was taken as the sample for looking into the feasibility of domestic wastewater recovery and recycling. At the beginning, a series of hydraulic analysis and ozone transfer tests was conducted in the bubble column reactor. From these tests, it was found that when the gas flow is controlled to within 0.2 to approximately 1.0 L/min and liquid flow within 0.5 to approximately 2.5 L/min, using series connected mixing tank model for our calculation, the result J (CSTR) is 1 to approximately 2. From the ozone transfer test it is known that the smaller the gas flow, the better the transfer rate, and the same pattern occurs on ozone gas concentration. After sand filtration and ozone treatment, the G/L ratio within the ozone column reactor can be maintained within 0.2 to approximately 0.4 and the ozone dosage within 8 to approximately 12 mg/L. The removal rate for coliform bacillus, BOD, turbidity and color is 99.96%, 62.2%, 89.6% and 67% respectively. After ozonation treatment, coliform bacillus content can be controlled under 10 CFU/mL, BOD under 10 mg/L, turbidity within 2.0 to approximately 2.5 (NTU), and color within 10.3 to approximately 13.7 degree. The recycled water is almost colorless and odorless, and is capable of reaching the reference standard for recycled water.