Dynamic modeling and simulation of the impact of micro-aeration on anaerobic treatment of sulfate-rich wastewater

Abstract

This study investigates the application of microaeration to remove dissolved sulfide produced during the anaerobic treatment of wastewater containing sulfate. A completely mixed batch reactor was used to develop a dynamic model of batch anaerobic digestion with micro-aeration of the liquid phase using BioWin (version 6.2) software to simulate the performance of sulfate reduction and sulfide oxidation in a single reactor unit. When calibrating the micro-aerated model, maximum specific growth rate for sulfur-reducing acetotrophic bacteria was altered to 0.38 d-1, switching function (which determines the minimum DO concentration at which oxidation of hydrogen sulfide to elemental sulfur takes place) was altered to 0.0001 mgO2/L and air was introduced to the system for 12 hours (after half an hour of feeding) at a rate of 0.018 m3/hr and another 12 hours at a rate of 0.015 m3/hr. Although methane production improved over the first half of the micro-aerated time period, a negative impact of the presence of oxygen on methanogens could be evident when the oxygen presents in the system beyond 13 hours. The micro-aerated system shows a significant decrease in dissolved sulfides when compared to the anaerobic system. Moreover, an average of 80% H2S removal could be achieved with micro-aeration.