Chemical composition of sewage sludge organic matter

Abstract

Sewage sludge can be recycled in agricultural soil as a source of plant nutrients and in order to increase the organic matter content. The objective of this study was to characterize the organic fraction of sewage sludge (contents of carbon, nitrogen and total organic and inorganic phosphorus; concentrations of protein, fat, fiber, phenol and tannin) in order to assist in planning their use in agriculture. Five types of sewage sludge with differences were used for the later stages of chemical conditioning and / or complementary treatment for dehydration, three from anaerobic process: lime and ferric chloride, mechanically dehydrated (LAC); synthetic polymer and dehydrated mechanically (LAP); synthetic polymer and thermally dehydrated (LAS), and two aerobic digestion process: etching synthetic polymers with drying beds (LLP); LLP after the composting process in aerated piles mixed with bagasse from sugar and urban pruning debris, sludge compost (CL). The conditioning polymer and heat drying the organic matter retained in the residue, which was evidenced by the presence of higher concentrations of readily degradable organic compounds and carbon (337.24 g kg-1), nitrogen (39.02 g kg-1) and phosphorus (2.93 g kg-1) in the organic compartment. In all sludge was significant participation of the protein content in organic matter, which was approximately 43, 42, 28 and 25% for sewage sludge LAC, LAP, LAS, LLP and CL, respectively.