Evaluating and modeling biological sulfur production in the treatment of sulfide-laden streams containing ammonium

BACKGROUND Biological treatment of effluents containing H2S and ammonium are of great interest as both can trigger serious environmental problems when disposed of. The aim of this study was to optimize the production of biosulfur from the partial oxidation of sulfide in sulfide- and ammonium-containing streams. Biological performance was evaluated under various aerating conditions and key kinetic parameters were adjusted based on an existing mathematical model adapted to this system. RESULTS An optimal conversion of sulfide to S(0)of 86% (w/w) was found at an oxidation-reduction potential (ORP) of -380 +/- 10 mV and at an O-2/S(2-)molar ratio of 0.44. Partial nitrification was observed at ORP higher than -200 mV and in excess of oxygen supply. Sulfide-oxidizing bacteria (SOB) outcompeted ammonium-oxidizing bacteria (AOB) in the competition for dissolved oxygen. In a modeling effort, the maximum specific growth rate for SOB, the sulfur shrinking kinetic constant, the maximum specific growth rate for AOB and the AOB oxygen half-saturation constant were adjusted to 10.1 day(-1), 0.3 mg(2/3)VSS mg(-2/3)S, 1.75 day(-1)and 1.5 mg L-1, respectively, during model calibration. CONCLUSIONS Optimal S(0)production was found under limiting O(2)conditions in which AOB were not able to outcompete SOB. The mathematical model described satisfactorily the experimental profiles for ammonium, nitrite, sulfide and sulfate as a function of the aeration flow rate. (c) 2020 Society of Chemical Industry (SCI)

Automated summary

Optimal production of biosulfur was achieved under limiting oxygen conditions where ammonium-oxidizing bacteria were not able to outcompete sulfide-oxidizing bacteria. The mathematical model accurately described the experimental profiles for ammonium, nitrite, sulfide, and sulfate as a function of the aeration flow rate.