Keywords: ozone, wastewater treatment, biofiltration, organic matter, micropollutants, COD, chemical oxygen demand, BOD, biological oxygen demand, suspended solids, disinfection, acute toxicity, chronic toxicity, domestic wastewater, industrial wastewater, pulp mills, bubble column, molecular diffusion, eddy diffusion
Applications of ozone for modern wastewater treatment
Modern Wastewater Treatment Plants (WWTPs) efficiently eliminate organic pollution down to Biological Oxygen Demand (BOD) and Suspended Solids (SS) values of less than 30 mg/l. However, these treated effluents still contain biologically Persistent Organic Matter (POM), characterised by a Chemical Oxygen Demand (COD) of between 50 and more than 100 mg/l. Industrial WWTP effluents have COD concentrations of several hundred mg/l. Under certain conditions of discharge imposed to the effluent, POM abatement is necessary. Elimination of pathogenic micro–organisms, i.e., disinfection and inhibition of acute toxicity, is also required. Another class of toxic compounds, Micro–Pollutants (MPs), present in WWTP effluents in much lower concentrations, µg/l even ng/l, has become a serious matter of concern. Ozonation, as a complementary stage in the treatment sequence of a WWTP, alone or in combination with biofiltration, has been demonstrated by multiple laboratory–pilot tests and existing operating plants to be an efficient and economically sound technology for the abatement of and POM and MPs and for disinfection. The purpose of this essay is to present ozone with its state–of–the–art features, from a qualitative as well as a quantitative aspect, with examples of modern applications for improved wastewater treatment.