Use of ozonation process for the oxidation of liming float wastewater stream

This paper describes the application of ozone treatment for liming float wastewater. Oxidation of both sulphide and organic compounds is investigated and applied on a highly concentrated alkali effluent. The ozonation proves to be efficient for the total oxidation of sulphides (S^2-, HS ^-....) present in this effluent. The present study shows that 3.5 g of ozone are necessary to oxidize 1 g of sulphide. COD removal effectiveness by ozone alone is evaluated to 16% when the effluent is treated at its initial pH (pH = 12.9) and biochemical oxygen demand (BOD₅/COD) ratio of effluent, ozonated for 2 h, increases from 0.22 to 0.36 indicating that the effluent becomes biodegradable. Ozonation effectiveness strongly depends on pH. A high COD reduction (55%) is reached at optimal pH = 8. The addition of hydrogen peroxide, as an oxidant, enhances the efficiency of the ozone treatment. The COD removal increases from 16% with O₃ alone to 64%, after 1 h of ozonation with hydrogen peroxide dose of 8 mL per liter of liming float wastewater.