Study of La Candelaria streams water photocatalysis treatment over Lactuca sativa L seeds

Natural waters surface contain, among other compounds, humic and fulvic acids refractory to standard treatments, which are the main contributions to chemical oxygen demand (COD). To mineralize this organic matter heterogeneous photocatalysis (HP) has been used for the treatment of La Candelaria stream in Santa Fe (Argentina) close to wastewater treatment plant of the city, with a 9W low-pressure mercury lamp and TiO 2 as photocatalyst. Aromaticity elimination has been followed by UV intensity at 254nm, and mineralization by analysis of COD. Effect of pH (7 − 5), TiO 2 catalyst loading (500–1000 mg/L) and COD (17–120 mg/L) was studied in the treatment of these natural waters. The results reported optimal treatment conditions at pH 5 and TiO 2 loading of 1000 mg/L. Biotoxicity tests were performed using Lactuca sativa L. seeds with the samples of natural waters containing 20, 48 and 76 mg/L COD, and the respective sample treated by photocatalysis in order to explore the effect of the photocatalytic treatment and over COD in media. While collected natural waters and the mineralized waters, after treatment, have non biotoxic behavior, the incomplete treated waters evidence a significant negative effect over germination rate (GR) and the elongation rate (ER), as consequence of concentration of compounds formed during the water photocatalytic treatment process. These results suggest as toxicology tests in outcome effluents to check efficiency of the water treatment plants should be necessary.