Degradation rate of limed sewage sludge in an agricultural soil
1 Department of Agricultural Engineering, Federal University of Vi osa, Vi osa, MG, CEP-36570-000, Brazil
2 Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Av. Ant nio Carlos, 6627, Belo Horizonte, MG, CEP-31270-901, Brazil
3 Department of Engineering, Federal University of Lavras, Lavras, MG, CEP-37200-000, Brazil
4 Department of Environmental Science and Technology, Federal Center of Technological Education, Belo Horizonte, MG, CEP-30.421-145, Brazil
2 Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Av. Ant nio Carlos, 6627, Belo Horizonte, MG, CEP-31270-901, Brazil
3 Department of Engineering, Federal University of Lavras, Lavras, MG, CEP-37200-000, Brazil
4 Department of Environmental Science and Technology, Federal Center of Technological Education, Belo Horizonte, MG, CEP-30.421-145, Brazil
Abstract
Little is known about the degradation kinetics of sewage sludge, sanitized with Ca(OH)2, in soil. Thus, this work aimed to monitor the degradation of limed sludge, under field conditions, when applied on soil surface or incorporated into the soil. The limed sludge was applied in dystrophic Inceptisol at a dose of 500 kg ha-1 yr-1 of total nitrogen. The mineralization process in the soil was monitored for 131 days. Samples of organic material were collected for analysis of total and easily oxidizable organic carbon; total, ammonium, nitric and organic nitrogen; volatile solids; and water contents. The undigested secondary sewage sludge generated in wastewater aerobic treatment mineralizes faster when limed and incorporated, compared to being arranged on soil surface. The estimated annual mineralization fraction of the limed sludge was 100% and greater than 95%, when incorporated or arranged on soil surface, respectively. Such values are higher than those established in the Brazilian environmental legislation for undigested sewage sludge disposal on soil.
Keywords
organic fertilizer; organic matter; solid wastes