Polishing of textile wastewater by H2O2/UV: a comparative pilot scale study on tertiary treatment

It was studied the feasibility of a H2O2/UV AOP for tertiary treatment in a WWTP fed with municipal and textile wastewater (the latter about 30% as flow and 60% as COD load). The plant is located near Como (Italy), in a touristic area characterized by the presence of textile industries and by sensitive receiving water bodies. The effluents from the biological treatment is still coloured, with a scarcely biodegradable residual COD and contains surfactants in significant concentration. A pilot scale H2O2/UV advanced oxidation reactor was implemented after the biological treatment for assessing the possibility of substituting the existing tertiary coagulation-flocculation stage and for evaluating the upgrade of the UV disinfection to an H2O2/UV advanced oxidation treatment. Decolorization yields were monitored as a function of H2O2 and UV radiation dosages (H2O2: 0.1-2 g/L, UV radiation: 120-6,400 mJ/cm2). Surfactants, aldehydes and TOC removals were measured. Process parameters were optimized for identifying the best operating conditions. A cost-effective analysis was conducted for comparing the sustainability of the process with the existing tertiary treatment. Elevate decolorization yields (~30-40%) were obtained without production of sludge. H2O2/UV is a simple and compact technology that provides the partial degradation of organic refractory compounds. On the contrary, high operating costs in relation with existing tertiary treatment (about 3 times higher) and inapplicability to the UV disinfection phase without structural changes were highlighted.