Field solar photocatalytic purification of pesticides-containing rinse waters from tractor cisterns used for grapevine treatment

Abstract

The objective was to assess in a vineyard the effect of purifying by solar photocatalysis the title rinse waters (presently rejected or, extremely rarely, cleaned in specific installations) in terms of efficacy and on-site ease-of-use for the wine grower. The on-site, self-functioning, solar purifying unit included a corrugated-steel inclined plate of area S=1 m 2 onto which a TiO 2-coated thin material had been stuck, a 100-l tank, and an aquarium-type pump powered by a photovoltaic panel. For a vineyard of area A=0.15 km 2, the rinse water (about 80 l) corresponding to each of four typical vine treatments was analysed (major pesticides for each treatment, TOC, Microtox test and, in one case, BOD 5) by independent laboratories, before and after purification for 8 days. These analyses showed that the S/ A ratio tested was insufficient. From the relatively low final organic content reached in one case, it is calculated that a three-time higher S/ A ratio might suffice, but new trials are necessary to determine whether it is valid for the other typical cases. Inferred contribution of inorganic ions to the post-photocatalytic treatment toxicity points out to the need for an additional detoxification. However, even with a too small S, the photocatalytic treatment markedly improved the quality of the rinse waters. These field experiments have also demonstrated that the purifying prototype is robust, and easy to install and use on site by the wine grower.