Hydrogen Sulfide Oxidation by a Microbial Consortium in a Recirculation Reactor System:  Sulfur Formation under Oxygen Limitation and Removal of Phenols

Abstract

Wastewater from petroleum refining may contain a number of undesirable contaminants including sulfides, phenolic compounds, and ammonia. The concentrations of these compounds must be reduced to acceptable levels before discharge. Sulfur formation and the effect of selected phenolic compounds on the sulfide oxidation were studied in autotrophic aerobic cultures. A recirculation reactor system was implemented to improve the elemental sulfur recovery. The relation between oxygen and sulfide was determined calculating the O2/S2- loading rates (Q(O2)/Q(S)2- = Rmt), which adequately defined the operation conditions to control the sulfide oxidation. Sulfur-producing steady states were achieved at Rmt ranging from 0.5 to 1.5. The maximum sulfur formation occurred at Rmt of 0.5 where 85% of the total sulfur added to the reactor as sulfide was transformed to elemental sulfur and 90% of it was recovered from the bottom of the reactor. Sulfide was completely oxidized to sulfate (Rmt of 2) in a stirred tank reactor, even when a mixture of phenolic compounds was present in the medium. Microcosm experiments showed that carbon dioxide production increased in the presence of the phenols, suggesting that these compounds were oxidized and that they may have been used as carbon and energy source by heterotrophic microorganisms present in the consortium.

Mathematical modeling of simultaneous carbon-nitrogen-sulfur removal from industrial wastewater

“…3). ROS 12 determines the end-products of sulfide oxidation [25,26]. At ROS=1.93, complete sulfide oxidation was observed.…”

“…Complicated interactions between different groups of microorganisms can lead to fruitful reactor dynamics [11,13,[25][26][27][28]. Mathematical modeling has been proven to be an effective tool to understand complex biological wastewater treatment processes.…”

Optimization of Oxygen Transfer through Membrane Diffusers for Biological Sweetening of Biogas

“…As such, one possible strategy for obtaining the biological oxygen demand required to oxidize hydrogen sulfide to sulfate is to optimize the airto-water oxygen transfer. (2004) studied the relevance of dissolved oxygen in the liquid phase for a bioscrubber to remove hydrogen sulfide at different oxygen/sulfide ratios [9]. Authors observed that at flowrate ratios below 0.5 the hydrogen sulfide oxidation is incomplete producing mainly elemental sulfur.…”

Recuperação de enxofre elementar a partir de águas residuárias em reatores anaeróbio/microaerado

“…Um processo interessante para o tratamento do sulfeto é sua oxidação parcial a enxofre elementar, um intermediário insolúvel que pode ser separado e retirado do sistema para reúso (Janssen et al, 1995). O processo de oxidação do sulfeto a enxofre elementar pode ser realizado tanto por via química (Chen e Morris, 1972) quanto por via biológica (Buisman e Lettinga, 1990;Janssen et al, 1999;Alcantara et al, 2004;Kleinjan et al, 2005b), e tem sido reportado por trabalhos que utilizam baixas concentrações de oxigênio (Buisman e Lettinga, 1990;Janssen et al, 1999;Alcantara et al, 2004;Kleinjan et al, 2005b). A manutenção de baixas concentrações de oxigênio no meio justifica-se pela estequiometria da reação (Gijs Kuenen, 1975), segundo a qual, com elevada concentração de oxigênio no meio, o sulfeto pode ser reoxidado a sulfato.…”

“…Trabalhos têm sido realizados com aeração em um tanque próprio com controle da concentração e posterior injeção do líquido contendo oxigênio dissolvido no reator (Janssen et al, 1998;Janssen et al, 1999;Alcantara et al, 2004;Kleinjan et al, 2005a). Essa técnica evita a turbulência no meio e permite maior controle sobre a dosagem de oxigênio no meio líquido reacional.…”