Quality of public water supply of Ribeirão Preto in the Guarani aquifer area: metals and nitrate analyses

Abstract

The city of Ribeirão Preto, SP, is fully supplied by groundwater from the Guarani aquifer. The city has a total of 102 public supply wells registered in the Ribeirão Preto Water and Sewage Department, approximately 13,400 m³/h of water are uptaken from them. Some wells are located in the recharge area of the Guarani Aquifer, a region susceptible to anthropogenic pollution. This study aimed to evaluate the quality of water of public supply wells in Ribeirão Preto considering specific chemical parameters including pH, metals and nitrate. Three sampling collections were performed in 33 wells for water supply in Ribeirão Preto, in May and November 2008, and in July 2009, as well. Analyses of the metals Fe, Zn, Mn, Cr, Pb, Cu and Cd were performed using the Induced Plasma Spectroscopy technique (ICP-OES). The analyses of nitrate concentration were performed using spectrophotometric method. Regarding the metals and nitrate parameters, all samples were within the values established by the ordinance of the Ministry of Health No. 518 of 2004. Regarding pH, a small number of wells had pH below the limit of drinkable water, but values were very close to the lower limit established by the ordinance. Water of public supply wells in Ribeirão Preto are, in general, of good quality, showing no restrictions for use. Nevertheless, continuous monitoring of all public supply wells is necessary, especially regarding the presence of nitrate and chromium, second report of Company of Technology and Environmental Sanitation – Cetesb.