This study analyzed the levels of cadmium, lead, copper, chromium, manganese, mercury, and zinc in leachate from the Ribeirão Preto landfill site in São Paulo State, Brazil. Samples were taken from runoff tanks in Module I (operating from 1989 to 2000) and Module II (operating since November 2000). Metal levels were measured by atomic absorption spectrophotometry at the University of São Paulo in Ribeirão Preto (University Hospital). Results were compared to the maximum limits for metal concentration in liquid effluents set by Ruling 357/2005 of the National Environmental Council (CONAMA). The study also investigated whether there was any attenuation in metal concentrations in the leachate, considering differences in the life spans of the various Ribeirão Preto landfill site modules. Metal levels in the samples were within the maximum limits for cadmium, chromium, copper, mercury, and manganese, but lead and zinc were above the limits set by the above-mentioned ruling.

According to the current metal levels, RP-BWTP sludge might be used for agriculture purposes. However, for an environmentally safe use of sewage sludge, further studies including systematic monitoring are recommended. Annual metal concentrations and predicted variations of those elements in the sludge should be monitored.

Abstract