Ingeniería ambiental

 

Supervivencia de bacterias fecales en lodos residuales deshidratados tratados con amoniaco

 

Fecal bacteria survival in ammonia–treated wastewater dewareted sludges

 

J.M. Méndez ¹*, C. González ¹, A. Alvarado–Lassman¹, G. Alvarado–Kinnell¹ y S. Martínez–Delgadillo²

 

¹ Instituto Tecnológico de Orizaba (lTO), 852 Tecnológico, Zapata 94320, Orizaba, Ver. México. * Autor para la correspondencia. E–mail: jmmendez@itorizaba.edu.mx

² Departamento de Energía, Universidad Autónoma Metropolitana —Azcapotzalco. Av. San Pablo 180. Azcapotzalco. CP.02200. México D.F.

 

Recibido 14 de Enero 2008
Aceptado 26 de Agosto 2008

 

Resumen

Uno de los problemas más importantes de contaminación en lodos provenientes de plantas de tratamiento de aguas residuales municipales y agroindustriales de México es el alto nivel de microorganismos patógenos. El amoniaco es conocido como un desinfectante importante capaz de inactivar significativamente las altas concentraciones microbianas presentes en el lodo. En este estudio, se evaluó el efecto del amoniaco en lodo fisicoquímico agroindustrial y se utilizaron los parámetros cinéticos del modelo de Hom para describir la inactivación de bacterias a diversas concentraciones de sólidos totales. El lodo fisicoquímico crudo con 2.0 ± 0.5% de ST se obtuvo de una planta de tratamiento de aguas residuales de un rastro avícola. El amoniaco se aplicó en dosis de 1 hasta 40% p/p directamente al lodo deshidratado (4%, 8% y 12% de ST). Después de 2h, las muestras fueron analizadas microbiológicamente. Los resultados mostraron que el amoniaco removió 9 y 6.5 logs de coliformes fecales y de Salmonella spp., respectivamente, cumpliendo con los límites de la US EPA para biosólidos clase A. El análisis de los parámetros k, n y m del modelo de Hom, indican mayor resistencia de inactivación de bacterias cuando la concentración de sólidos totales es baja, debido principalmente a dilución del amoníaco en el agua. También, se requirió 75% menos amoníaco para cumplir con el estándar de la US EPA cuando el lodo fue deshidratado.

Palabras clave: amoniaco, bacterias fecales, biosólidos, lodo fisicoquímico, estabilización.

 

Abstract

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.

Keywords: ammonia, biosolids, faecal bacteria, physicochemical sludge, stabilization.

 

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