Treatment of Wastewater from rinsing of herbicide containers. Optimization of UV/H2O2 Process

S. NEDER; A. NEGRO; A. CASSANO; C. ZALAZAR

Praga

Encuentro; 7th European Meeting on Solar Chemistry and Photocatalysis: Environmental Applications - SPEA6; 2010

Institute of Chemical Technology Prague

The disposal of pesticide wastewaters including equipment rinsates and unusable product such as empty plastic pesticide containers remains an unsoved problem in many countries. Pesticide contamination is common at farm, landfills and incineration processes receiving unregulated pesticide waste. In some cases, disposal legislation is not accomplished with the pretext that there is a lack of availability of on-site, small scale, simple remediation technologies. The result is that only a small amount of this waste is currently treated. Glyphosate (N-phosphonomethyl glycine) is a non-selective, post-emergence, broad-spectrum organophosphate herbicide. Glyphosate is the active ingredient in herbicides and it is the most widely used in the world. The combination of hydrogen peroxide and UV radiation (H2O2/UV) could be a simple and convenient process for the treatment of this type of pollutants. However, the degradation of glyphosate by this method has been seldom investigated2.. In this work the potential of the H2O2/UV process for treating the wastewater from rinsing commercial containers of glyphosate was studied. In addition to this, the effects of hydrogen peroxide initial concentration and the toxicity of the resulting by-products were studied. The employed experimental device was a cylinder, with two parallel, flat windows made of quartz. Each window was irradiated with a tubular, germicidal lamp (253.7 nm) placed at the focal axis of a parabolic reflector. The small reactor was part of a recycle that includes a pump, a heat exchanger (for temperature control) and a large volume, well stirred tank with provisions for sampling and temperature measurements. It must be noted that due to the type of equipment used in this work (a recycle with a tank) the time shown in the plots does not represent the one effectively corresponding to the irradiation time of the reactor volume. Further details on the experimental device can be found in Zalazar et al. Glyphosate was analyzed by ion chromatography with a suppressed conductivity detector employing an Ion Pac AS4A-SC analytical column and a solution of Na2CO3 (9 mM) and NaOH (4 mM) as eluent. Hydrogen peroxide was analyzed with spectrophotometric methods at 350 nm employing a Cary Bio UV visible instrument. Total organic carbon (TOC) was also analyzed (Shimadzu TOC-5000A). Additionaly, a Vibrio fischeri bioassay determined the toxicity of glyphosate and photoproducts generated during UV/H2O2 process.