Use of spray nozzles to recover dissolved methane from an Upflow Anaerobic Sludge Blanket (UASB) reactor effluent

Methane is a powerful greenhouse gas and a source of energy. Recovering this gas means lower greenhouse gas emission and potential reduction of energetic costs. The lack of full-scale results, the use of different methodologies to detect dissolved methane (d-CH₄) and the fact that no process to remove d-CH₄ from anaerobic effluents is energetically or economically viable at full-scale urged a different approach to the problem. To avoid methodological interference and facilitate comparison of results the Standard Test Method number D8028-17 published by ASTM International can be used to determine d-CH₄. The use of real anaerobic reactor effluent also helps results to be compared. In this study, 80 samples from a full-scale anaerobic reactor showed an average concentration of dissolved methane of 14.9 mg·L^-1, meaning an emission of 229 kg of CO₂ eq·h^-1 and an average of 113.5 kW wasted. Using spray nozzles, an alternative to the methods being researched, the average methane recovery was 11.5 mg·L^-1 of CH₄, an efficiency of 81.6%, meaning 177 kg of CO₂ eq·h^-1 emissions avoided and 87.9 kW of recoverable energy.