Evaluation of oxygen injection as a means of controlling sulfide production in a sewer system

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bSimultaneous production of sulfide and methane by anaerobic sewer biofilms has recently been observed, suggesting that sulfate-reducing bacteria (SRB) and methanogenic archaea (MA), microorganisms known to compete for the same substrates, can coexist in this environment. This study investigated the community structures and activities of SRB and MA in anaerobic sewer biofilms (average thickness of 800 m) using a combination of microelectrode measurements, molecular techniques, and mathematical modeling. It was seen that sulfide was mainly produced in the outer layer of the biofilm, between the depths of 0 and 300 m, which is in good agreement with the distribution of SRB population as revealed by cryosection-fluorescence in situ hybridization (FISH). SRB had a higher relative abundance of 20% on the surface layer, which decreased gradually to below 3% at a depth of 400 m. In contrast, MA mainly inhabited the inner layer of the biofilm. Their relative abundances increased from 10% to 75% at depths of 200 m and 700 m, respectively, from the biofilm surface layer. High-throughput pyrosequencing of 16S rRNA amplicons showed that SRB in the biofilm were mainly affiliated with five genera, Desulfobulbus, Desulfomicrobium, Desulfovibrio, Desulfatiferula, and Desulforegula, while about 90% of the MA population belonged to the genus Methanosaeta. The spatial organizations of SRB and MA revealed by pyrosequencing were consistent with the FISH results. A biofilm model was constructed to simulate the SRB and MA distributions in the anaerobic sewer biofilm. The good fit between model predictions and the experimental data indicate that the coexistence and spatial structure of SRB and MA in the biofilm resulted from the microbial types and their metabolic transformations and interactions with substrates. Sewer biofilms comprise complex multispecies microflora with a typical thickness of only about 1 mm (1). Depending on the electron donors and electron acceptors present in the wastewater, different carbon transformation processes can occur in close proximity in the sewer biofilms. Domestic wastewater normally contains a significant concentration (ca. 100 to 1,000 M) of sulfate but negligible nitrite and nitrate concentrations (2, 3). Therefore, under anaerobic conditions (which normally occur in pressure sewers fully filled with wastewater), sulfate reduction carried out by sulfate-reducing bacteria (SRB) could be an important terminal electron-accepting process in the sewer biofilms. The sulfate reduction activity in anaerobic sewers is important, as the production of sulfide can be transferred to the gas phase of partially filled gravity sewers and cause extensive corrosion of concrete sewer pipes (4, 5). Also, the emission of sulfide from sewers can cause odor problems for the surrounding area and pose health risks to sewer workers (6, 7). Apart from sulfate reduction, methanogenesis caused by the respiration of methanogenic archaea (MA) could also be a key terminal process in anaerobic sewer biofilms (8, 9). Guisasola and ...

Section: Methodsmentioning

confidence: 99%

Stratified Microbial Structure and Activity in Sulfide- and Methane-Producing Anaerobic Sewer Biofilms

Sun

Sharma

et al. 2014

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“…Various chemical dosing methods are used to lower hydrogen sulfide production in sewers, and four strategies currently used include sulfide oxidation by the injection of chemical oxidants, such as air, oxygen, or nitrate (5,6); sulfide precipitation by addition of iron salts (7); application of magnesium hydroxide or lime to raise the wastewater pH and prevent the release of hydrogen sulfide (8); and inhibition of the activities of SRB to lessen the generation of hydrogen sulfide (9). However, to obtain the required sulfide control, these strategies require continuous chemical consumption and considerable operational costs (10).…”

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confidence: 99%

Antimicrobial Effects of Free Nitrous Acid on Desulfovibrio vulgaris: Implications for Sulfide-Induced Corrosion of Concrete

Gao

Lü

et al. 2016

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Hydrogen sulfide produced by sulfate-reducing bacteria (SRB) in sewers causes odor problems and asset deterioration due to the sulfide-induced concrete corrosion. Free nitrous acid (FNA) was recently demonstrated as a promising antimicrobial agent to alleviate hydrogen sulfide production in sewers. However, details of the antimicrobial mechanisms of FNA are largely unknown. Here, we report the multiple-targeted antimicrobial effects of FNA on the SRB Desulfovibrio vulgaris Hildenborough by determining the growth, physiological, and gene expression responses to FNA exposure. The activities of growth, respiration, and ATP generation were inhibited when exposed to FNA. These changes were reflected in the transcript levels detected during exposure. The removal of FNA was evident by nitrite reduction that likely involved nitrite reductase and the poorly characterized hybrid cluster protein, and the genes coding for these proteins were highly expressed. During FNA exposure, lowered ribosome activity and protein production were detected. Additionally, conditions within the cells were more oxidizing, and there was evidence of oxidative stress. Based on an interpretation of the measured responses, we present a model depicting the antimicrobial effects of FNA on D. vulgaris. These findings provide new insight for understanding the responses of D. vulgaris to FNA and will provide a foundation for optimal application of this antimicrobial agent for improved control of sewer corrosion and odor management. S ulfate-reducing bacteria (SRB) are anaerobic chemoorganotrophic microorganisms that typically use sulfate as the terminal electron acceptor for respiration and generate energy with the production of hydrogen sulfide (2). In confined spaces, the production of hydrogen sulfide can cause odor and corrosion problems. This is particularly the case in sewers and inlet structures of wastewater treatment plants, where the oxidation of sulfide produces sulfuric acid, which corrodes the concrete surfaces of the sewer. This results in serious deterioration of sewer assets that requires very costly and demanding rehabilitation efforts (3, 4). Consequently, there is great interest in the efficient control of SRB and thereby minimizing hydrogen sulfide production in sewers.Various chemical dosing methods are used to lower hydrogen sulfide production in sewers, and four strategies currently used include sulfide oxidation by the injection of chemical oxidants, such as air, oxygen, or nitrate (5, 6); sulfide precipitation by addition of iron salts (7); application of magnesium hydroxide or lime to raise the wastewater pH and prevent the release of hydrogen sulfide (8); and inhibition of the activities of SRB to lessen the generation of hydrogen sulfide (9). However, to obtain the required sulfide control, these strategies require continuous chemical consumption and considerable operational costs (10).Free nitrous acid (FNA), the protonated form of nitrite, was recently demonstrated to be the true metabolic inhibitor behind the usu...

“…Recent reports suggest that CH 4 emissions from sewers contribute significantly to the total greenhouse gas footprint of wastewater systems (12, 13). Accordingly, different mitigation strategies have been used to reduce H 2 S and CH 4 production in sewers (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24).…”

mentioning

confidence: 99%

Changes in Microbial Biofilm Communities during Colonization of Sewer Systems

Auguet

Pijuan

Batista

et al. 2015

bThe coexistence of sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) in anaerobic biofilms developed in sewer inner pipe surfaces favors the accumulation of sulfide (H 2 S) and methane (CH 4 ) as metabolic end products, causing severe impacts on sewerage systems. In this study, we investigated the time course of H 2 S and CH 4 production and emission rates during different stages of biofilm development in relation to changes in the composition of microbial biofilm communities. The study was carried out in a laboratory sewer pilot plant that mimics a full-scale anaerobic rising sewer using a combination of process data and ). This contrasting trend coincided with a stable SRB community and an archaeal community composed solely of methanogens derived from the human gut (i.e., Methanobrevibacter and Methanosphaera). In turn, CH 4 emissions increased after 1 year of biofilm growth (327.6 ؎ 16.6 mg COD-CH 4 liter ؊1 day ؊1 ), coinciding with the replacement of methanogenic colonizers by species more adapted to sewer conditions (i.e., Methanosaeta spp.). Our study provides data that confirm the capacity of our laboratory experimental system to mimic the functioning of full-scale sewers both microbiologically and operationally in terms of sulfide and methane production, gaining insight into the complex dynamics of key microbial groups during biofilm development. W astewater collection systems, or sewers, consist of an underground network of physical structures-installations composed of pipelines, pumping stations, manholes, and channels that convey wastewaters from their source to the discharge point, usually a wastewater treatment plant (WWTP). Sewer systems thus prevent the direct contact of urban populations to fecal material and potential microbial pathogens, greatly reducing the spread of infectious diseases. Sewers have traditionally been considered only hydraulic transport systems for sewage, although they are in fact "reactors" where complex physicochemical and microbial processes take place. Wastewater microorganisms are diverse and abundant, and they are exposed to a wide range of both inorganic and organic substrates as well as changing conditions along their transport through sewers (1). In this regard, wastewater transport through the pipes facilitates the formation of microbial biofilms that grow attached to the inner surface of sewer pipes (2). Different factors, such as large surface area, low flow velocity near pipe walls, and nutrient availability, may favor microbial colonization of pipe surfaces and biofilm growth. Formation of fully functional biofilms occurs in different steps, from surface conditioning, adhesion of microbial "colonizers," initial growth, and glycocalyx formation, followed by secondary colonization and growth (3).Anaerobic conditions in sewer pipes favor the accumulation of both sulfide (H 2 S) and methane (CH 4 ) as end products of different microbial metabolisms, i.e., anaerobic respiration of organic matter by sulfate-reducing bacteria (SRB) and methanogenic archae...