Biogás de digestão anaeróbia dos resíduos orgânicos de restaurante universitário com efluente sanitário

Abstract

This work has as its scope the production of biogas from the anaerobic digestion of organic waste from university restaurant associated with sanitary and synthetic sewage. The main advantages of this study are to reduce costs with transportation and final disposal of the organic fraction of municipal solid waste and the implementation of anaerobic treatment with decentralized power generation systems. Thus we evaluated the biogas production over time with simplified reactors associated in gasometers in laboratory scale. Different concentrations of organic solid waste with different sewages were used. A control indicator used was the volume of biogas produced parameterized with the mass of volatile solids. Three different tests were performed: i) use of only organic residue; ii) combination of food waste and synthetic wastewater; iii) combination of food waste and raw sewage from the STP Ibiporã-PR. The food waste were collected on different days of operation of University Restaurant. These composite samples were characterized qualitatively and previously grounded to be obtained a pasty and visually homogeneous material. The dilution rate used in tests ii) and iii) was 100 grams of triturated organic residue in 1 liter of sewage in a proportion of 10%. The samples were inoculated in PVC reactors with a working volume of 0.982 Liter and the biogas was accumulated and measured in free dome gasometers of PVC with total volume of 2,209 Liters. The parameters analyzed during the experiment were: pH, electrical conductivity, volatile suspended solids, fixed solids, total solids, volatile solids, alkalinity and qualitative and quantitative analysis of the biogas produced. The main results obtained were a yield of biogas 5.22mL.g -1 of volatile solids for test i), 32.5mL.g -1 of volatile solids for testing ii) and 16.965 5mL.g -1 of volatile solids to test iii). The qualitative analysis of the biogas by the method of bubbling in NaOH solution with 50 g L-1, resulted in the concentration of 73.61% for CH4 biogas produced in trial 2 and 76.2% CH4 for test 3. Among the analyzed parameters, pH and alkalinity proved essential to the smooth operation of the reactors, crucial to implementation and monitoring of these parameters throughout the experiment in order to achieve the optimum biogas productivity. Time analysis of return on investment in a unit in real time to the production of biogas in working conditions performed in this work resulted in the scale return time of 11 years to the literature data and the turnaround time of 23 to 24 years for experimental data.