Solar photocatalytic decontamination of wastewater from the rinsing of pesticide containers

Abstract
One of the sources of high-pesticide-content polluted waters is the rinsing of used pesticide spray containers and their disposal. The main characteristics of this wastewater are its extreme toxicity, low volume and well-defined location. Suitable treatment is therefore required to prevent this pollution, which is easier than cleaning up the environment afterwards. In this paper, a pre-industrial solar TiO₂-photocatalytic treatment is used for this purpose. Commercial pesticides (Lufenuron and Propamocarb) are used to demonstrate the practical application of the treatment. The photocatalytic pilot plant used for these tests has 6 CPC modules (collector surface 8.9 m², photoreactor volume 108 L, total plant volume 247 L) connected in series and mounted on a platform inclined 37°. The results are compared with phenol degradation under the same experimental conditions, and relative photonic efficiency (ξr) is calculated to facilitate comparison with other expimental devices. Total Organic Carbon (TOC) analysis is employed to confirm the mineralization of the contaminants. Relative photonic efficiency related to TOC is also introduced (ξr_TOC). The pesticides were completely photodegraded, but mineralization is slow with only illuminated TiO₂. The use of an additional oxidant (peroxydisulphate) enhances the degradation rate by 5 (propamocarb) and 9 (lufenuron), compared to TiO₂ alone.