Produção de biogás de resíduo de lodo ativado proveniente do tratamento de esgoto sanitário

Abstract

The looking for greater efficiency in the treatment of effluents allows to create alternatives for the recovery of water resources, however the systems used in Brazil such as anaerobic reactors and activated sludge do not allow final destination. The waste activated sludge keep a large amount of organic matter still passive of digestion, this substrate can feed anaerobic reactors, favoring the reduction of pollutants, generating alternative for biogas production. This work aims to evaluate the biogas generation potential of the sludge residue of an activated sludge reactor treating sewage. The methodology used is to compare reactor performance with the use of Unisinos sewage treatment plant (WWTP) sludge as inoculum, combined with activated sludge residue from the São João Navegantes WWTP. Three different inoculum / substrate volume ratios were adopted. , (I / S 1: 1, 2: 1 and 3: 1) equalized directly by the mass of total volatile solids (SVT). The study found the best ratio for production with the highest methane rate in biogas. The temperature used was mesophilic at 35 ° C. Volumes produced, solids retention time, SVT removal, pH, alkalinity and volatile fatty acids (VFA) were monitored. The digestion process remained stable, performing in the first hours, the tests took between 216h and 312h, with pH maintenance in the methanogenic range. The generated biogas showed a methane rate of over 70%, reaching 69.72mL / mg.SVT in the first ratio (I / S 1: 1) 128.96 mL / mg.SVT in the second (I / S 2: 1 ) and 130.52 mL.CH4 / mg.SVT in the third (3: 1 I / O). The ratio with the best performance was 3: 1, allowing the highest CH4 production for each mg of SVT ingested in the reactor. For comparison, the generation capacity of 130.52m³/t.lodo can be estimated. None of the ratios presented phytotoxic characteristics for seeds in a germination test.