Analysis of trace metals in domestic and industrial sewage sludges

Abstract

The adequate disposal of sewage sludges containing toxic metals still is a challenge. Its application on agriculture has been the most common method around the world and is being considered one of the cheapest ways for disposing this sludge. In that sense, the goal of the current research was to characterize three types of sludge, two coming from industry and one, from domestic sources, through chemical characterizations and determination of the trace metals: lead, chrome, copper, nickel and zinc. These metals were determined by Flame Atomic Absorption Spectrometry. The analyses showed a considerable value of organic matter and humidity, presenting also micro and macronutrients as carbon, nitrogen, phophorus, potassium, calcium and magnesium, which are indispensable to agriculture. The levels of these metals varied from: lead 8,8 to 4,3 mg kg^-1, chrome 65 to 41,6 mg kg^-1, copper 138,5 to 22 mg kg^-1, nickel 25,1 to 4,8 mg kg^-1and zinc 236,1 to 146,3 mg kg^-1being all these values lower than the limits determined by brazilian legislation for agricultural disposal. The results suggest the applicability of these sludges as a nutrient source on agricultural crops, since, beyond from presenting adequate organic matter and chemical properties, these sludges also present low levels of trace metals.