Estudo da remoção dos gases metano e sulfeto de hidrogênio dissolvidos em efluentes de reatores UASB tratando esgoto doméstico

Abstract

One of the problems associated with anaerobic domestic sewage treatment relates to the presence of dissolved gases, hydrogen sulphide and methane in the effluent from anaerobic reactors, which can potentially be emitted into the atmosphere. The escape of these gases can cause problems of bad odors and contribute to the greenhouse effect. The objective of this research was to investigate alternative techniques to minimize the disadvantages of anaerobic technology, by using techniques such as: stripping inside the sedimentation compartment, desorption chamber installed immediately after the reactor effluent exit, microaeration and biogas recirculation with microaeration. Two UASB-type reactors, one on a demonstration scale and another on a pilot scale, were installed at the UFMG/COPASA Sanitation Research and Training Center (CePTS). The results obtained with the stripping technique showed low methane removal efficiency, about 30%, and removal in the range of 40 to 60% of hydrogen sulphide, indicating the need for further studies and a better theoretical understanding of the removal mechanisms which could lead to improved technique. On the other hand, the removal efficiencies obtained with the desorption chamber technique were much higher, depending on the operating condition, reaching 60% or more for both dissolved compounds, methane and sulfide under the most efficient conditions. For the best tested operational condition, removal efficiencies of 73 and 97% for methane and sulfide were observed, respectively, which shows that the desorption chamber technique has great potential to be used in larger scale. The technique of microaeration and microaeration with recirculation did not have an effect on the removal of the liquid phase, for the dissolved sulfide and methane, for the conditions of 30 and 40 ml/min for microaeration and 30 and 70 ml/min for microaeration with recirculation of biogas. However, it has been shown to be promising in terms of improving the quality of biogas formed in the UASB reactor, with a focus on energy utilization.