Experimental study on colour removal from textile wastewaters using the H₂O₂/UV process with low- and medium-pressure lamps

In this paper we present the results of an experimental study aimed at estimating the efficiency and comparing the operating costs of a low pressure lamp and a medium pressure lamp in the H₂O₂/UV process for colour removal. Trials have been carried out on the secondary effluent of a wastewater treatment plant which treats part of the effluents of one of the largest textile industries district in Italy. Because of the great irregularity of the effluent composition it is very difficult to monitor all the variables and assess their influence on the decolorization process. For this reason the H₂O₂/UV efficiency in colour removal has been also evaluated using synthetic solutions: demineralized water or groundwater added with five different dyes. In this latter case we determined the single effect of the control parameters on the process. From the experimental results we can assess that the H₂O₂/UV process guarantees a very high colour removal efficiency (up to 90%), which mainly depends on H₂O₂ dosages, dye concentration and characteristics, water quality (above all water hardness) and UV intensity. In our experimental conditions, the low pressure lamp showed to be more cost-effective both to remove colour and to reduce TOC and COD.