Ozone tertiary treatment for pharmaceuticals and personal care products removal from municipal wastewater

In recent years, the occurrence, fate and effects of emerging contaminants have been increasingly investigated, indicating the growing need for effective technologies to control the spread of these pollutants into the environment. To improve the biological treatment efficiency, tertiary processes are needed. In PerFORMWATER 2030 project, funded by Lombardy Region, an ozone pilot plant was installed at a municipal WWTP in the north of Italy. The filtered secondary effluent flow rate ranged between 1.3÷1.9 m3/h and the plant was operated with an ozone dose of 2-4 mgO3/l, even in combination with H2O2, with a retention time of 10÷30 minutes. Micropollutants (pharmaceuticals, personal care products and transformation products, metals) were monitored beside conventional parameters. Hydrodynamic and process modelling was performed. Experimental results evidenced that removal efficiencies were 80-100% for most of the organic compounds. Lower removal efficiencies, between 20% and 80%, were observed for some substances, e.g. Gabapentin-Lactam, Galaxolidone, Irbesartan, Lamotrigine and Tonalide. Results also indicated that AOP (Advanced Oxidation Process) treatment, O3/H2O2, improved the removal rate of the investigated micropollutants. For example, the removal rate of Galaxolidone reached 70%, with O3/H2O2 = 1:2. Additionally, ozone allowed wastewater disinfection, UV254 absorbance has been found highly correlated with the organic micropollutant content, especially with fragrances, and a GC-MS approach highlighted an overall redistribution of the compounds after ozonation with a significant drop of the chromatographic area. No significant correlation has been obtained with other water quality parameters, such as metals, DOC, TOC and COD.