Simultaneous removal of dissolved sulphide and dissolved methane from anaerobic effluents with hollow fibre membrane contactors.

Dissolved gases in the effluent of anaerobic reactors, specifically dissolved methane (D-CH 4 ) and sulphide (S 2- ), are a drawback for anaerobic-based sewage treatment plants (STPs). This article studied the simultaneous desorption/removal of both gases from anaerobic effluents with hollow fibre membrane contactors (HFMCs), evaluating two types of membrane materials (e.g. microporous and dense) at different operating conditions (atmospheric air as sweeping gas or vacuum, and different gas/liquid flows and vacuum pressures). The transfer of other gases, such as O 2 and CO 2 , was studied as well. Desorption/removal efficiencies up to 99% for D-CH 4 and 100% for S 2- were obtained, with the higher efficiencies reported for the dense HFMC and with air as sweeping gas. It was found that the removal mechanism for S 2- was oxidation with O 2 from the air. In addition, the use of air as sweeping gas allowed the obtention of a nearly O 2 saturated effluent, with more elevated dissolved oxygen concentrations in the microporous HFMC. Finally, it was found that the higher mass-transfer resistance in the dense membrane was compensated by a better performance in the liquid phase (lower mass-transfer resistance) in this unit, which allowed better D-CH 4 desorption efficiencies.