Abstract

Recycling of sewage sludge for agricultural purposes is recommended as one of the most adequate forms of final disposal of this waste. This study evaluated the effectiveness of solarization combined with chemical treatments by acid and alkali during different periods of cleaning. The experiment was conducted at the Experimental Farm of the Federal University of Uberlândia (UFU) in Uberlândia-MG. The experimental design used randomized blocks in a 5x3+1 factorial arrangement with four replications. The factor plots consisted of sanitizing products (260 mg L^-1 peracetic acid, 2400 mg L^-1 quaternary ammonium compounds, hydrated lime equivalent to 30% of the dry mass of the sewage sludge, 2500 mg L^-1 sodium hypochlorite, and pure sludge) for different times: T1 = 7 days, T2 = 14 days, and T3 = 21 days. Data were also collected from the pure mud at time zero. The concentration of fecal coliforms, pH, N (Nitrogen), Na (Sodium), Al (Aluminium), Ca (Calcium), Mg (Magnesium), K (Potassium), OM (Organic Matter), C (Carbon), Cr (Chromium), Ni (Nickel), Cd (Cadmium), Pb (Lead), Cu (Copper) and Zn (Zinc) were all evaluated. Lime increased the concentration of Ca and Mg in the biosolids, reduced the level of fecal coliforms below the limits specified by environmental standards from seven days and decreased the levels of available N, Al, OM, C, Na, Cr, Ni , Cd, Cu and Zn in the biosolids.

Key words: Environment, heavy metal, mineral nutrient, micro-organism.