SUPERVIVENCIA DE BACTERIAS FECALES EN LODOS RESIDUALES DESHIDRATADOS TRATADOS CON AMONIACO FECAL BACTERIA SURVIVAL IN AMMONIA-TREATED WASTEWATER DEWATERED SLUDGES

One of most important pollution problems in sludge from municipal and agro industrial wastewater treatment plants of Mexico is the high level of pathogens microorganisms. Ammonia is known as an important disinfectant capable to significantly inactivate high microbial populations in sludge. In this study, the effect of ammonia was evaluated in agro industrial physicochemical sludge and kinetic parameters of the Hom model were used to describe the inactivation of bacteria at different total solids concentrations. Raw physicochemical sludge with 2.0 ± 0.5% TS were sampled from a bird slaughterhouse wastewater treatment plant. Ammonia in doses from 1 to 40% w/w was directly applied to dehydrated sludge (4, 8 and 12% TS). After 2h, samples were taken for microbial analyses. Results showed that the ammonia removed 9 and 6.5 logs of fecal coliforms and Salmonella spp., respectively, making possible to meet the US EPA limits for Class A biosolids. The analysis of parameters k, n and m of the Hom model, indicates higher resistance to inactivation of bacteria when lower is the total solids concentration, due mainly to the ammonia dilution in the water. Also, 75% less ammonia was needed to meet the US EPA standard when sludge was dewatered.