Dynamic Modeling and Simulation of the Impact of Micro-Aeration on Anaerobic Treatment of Sulfate-Rich Wastewater

This study investigates the application of micro-aeration 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 $0.38 \mathrm{~d}^{-1}$, switching function (which determines the minimum DO concentration at which oxidation of hydrogen sulfide to elemental sulfur takes place) was altered to $0.0001 \mathrm{mgO}_{2} / \mathrm{L}$ and air was introduced to the system for 12 hours (after half an hour of feeding) at a rate of $0.018 \mathrm{~m}^{3} / \mathrm{hr}$ and another 12 hours at a rate of $0.015 \mathrm{~m}^{3} / \mathrm{hr}$. 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 $80\% \mathbf{H}_{2} \mathrm{~S}$ removal could be achieved with micro-aeration.