Estudo da atividade metanogênica específica e microbiota de iodo proveniente de um reator UASB instalado na ETE-UFLA tratando esgoto sanitário

Abstract

The specific methanogenic activity (SMA) is the determination of the maximum potential of methane production by the microbial community contained within a system. Through a laboratory test, optimum conditions are provided, such as substrate addition and temperature control, in order to favor the metabolism of methanogenic archaeas to produce methane. Since it allows quantification of the biological activity, the test can be used periodically as a monitoring parameter of the sludge activity, determining the minimum sludge mass required to be maintained in the reactor for the removal of the applied organic load, thus contributing with the operational control of the treatment system. Considering that the wastewater treated at UFLA’s WWTP shows distinct characteristics if compared with typical sanitary sewage, as well as issues regarding collection and utilization of the generated biogas in the system, the present study aimed to evaluate the maximum potential of methane generation by the anaerobic sludge from a UASB reactor in the wastewater treatment plant of the Federal University of Lavras using the SMA test, through biogas washing in alkaline solution and direct measurement of methane. In addition, the microbial community within the UASB sludge, as well as after 70 days of cultivation in Zinder basal medium for enrichment of methanogenic archaea, was also evaluated, through Illumina MiSeq Next-Generation Sequencing Platform for identification of microorganisms. An SMA value of 0.055 gCODCH4/gTVS.day was obtained, at least two times lower than the values usually found for anaerobic sludge treating domestic wastewater, while a significant change in the result was observed in the case of an operational disturbance in the STP, demonstrating the potential of this test as a monitoring parameter in anaerobic systems. It was further estimated that each UASB reactor in the STP would be able to convert 117 kgCOD day-1 to CH4, producing almost 46 m3 day-1 of methane. The evaluation of the microbial community showed that the UASB sludge 3.89% in abundance of the hydrogenotrophic methanogen Methanobacterium, and only 0.12% of the acetoclastic Methanosaeta. After cultivation, Methanosaeta increased in abundance from 0.12% to 1.37%, indicating that the method was effective for cultivating acetoclastic methanogenic archaea.