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EVALUATION OF THE COMPOSTING PROCESS IN DIGESTED SEWAGE SLUDGE FROM A MUNICIPAL WASTEWATER TREATMENT PLANT IN THE CITY OF SAN MIGUEL DE ALLENDE, CENTRAL MEXICO

2013; National Autonomous University of Mexico; Volume: 29; Issue: 3 Linguagem: Inglês

0188-4999

Katarzyna Wróbel, Kazimierz Wróbel, Ricardo Navarro, Luis A. Godı́nez, Margarita Teutli-León, Francisco J. Rodríguez‐Valadez,

Plant and soil sciences

The purpose of this work was to examine the feasibility of using municipal sewage sludge from San Miguel de Allende city WWTP, located at central Mexico, for compost production. Experimental piles were prepared with an aerobic digested activated sludge from a municipal WWTP dewatered in a filter press, grass was added as a nitrogen source and bulking was increased by mixing with either crushed porous volcanic material called tezontle (SGT) or wooden sticks wastes collected from municipal gardening of green areas (SGW). The specific composition of the compost piles was as follows: 30 % municipal sewage sludge, 60 % grass clippings and 10 % small wooden sticks (compost SGW); 30 % municipal sewage sludge, 60 % grass clippings and 10 % tezontle (compost SGT); 100 % sewage sludge (control). The efficient reduction of fecal bacteria was achieved in both piles yielding the USEPA class A compost, yet better process performance was obtained in SGW. In this pile the thermophilic phase lasted seven days longer and higher temperatures were reached, for which the desired removal of coliforms was achieved at two weeks of composting versus three weeks required in SGT. The analysis of typical spectrophotometric assays used in the compost characterization, confirmed the decomposition of organic matter and generation of humic substances. The fractionation of humic extracts by size exclusion chromatography with spectrophotometric detection indicated the increase of humic substances amount, and also the increase of molecular mass with the time of composting process. Overall, this work demonstrates the feasibility of municipal sewage sludge compost production for soil fertilization and provides new data about the changes of the molecular mass in humic fraction during composting.