A microelectrode study of redox potential change in biofilms

1999 ◽  
Vol 39 (7) ◽  
pp. 179-185 ◽  
Author(s):  
Paul L. Bishop ◽  
Tong Yu
Keyword(s):  
Redox Potential ◽  
Sulfate Reduction ◽  
Aerobic Oxidation ◽  
Microbial Processes ◽  
Anoxic Zone ◽  
Sulfate Reducing ◽  
Shallow Layer ◽  
Profile Changes ◽  
Stratified Structure ◽  
Microelectrode Techniques

In this study, we examined the stratification of microbial processes and the associated redox potential changes in biofilms using microelectrode techniques. Two types of biofilms, each with a different combination of microbial processes, were examined. The first type carried aerobic oxidation and sulfate reduction, while the second one provided aerobic oxidation and nitrification. The microelectrodes used were oxygen, sulfide, ammonium, pH and redox potential microelectrodes. The results of this study provide the following new experimental evidence: (1) The aerobic/sulfate-reducing biofilm had a clearly stratified structure with depth. In this biofilm, aerobic oxidation took place only in a shallow layer near the surface and sulfate reduction occurred in the deeper anoxic zone. The boundary between these two processes was well defined. (2) The aerobic/nitrifying biofilm also had a stratified structure with depth. In this biofilm, though aerobic oxidation took place throughout the biofilm depth, more nitrification occurred in the deeper section of the biofilm. The boundary between these two processes, however, was less well defined. (3) Redox potential could be an indicator for the existence of certain microbial processes in biofilms. The redox potential profile changes were correlated to shifts of microbial processes in both types of biofilms. The redox potential profiles in these biofilms can be used to elucidate the stratification of microbial processes in the biofilms.

Stratification of microbial metabolic processes and redox potential change in an aerobic biofilm studied using microelectrodes

1998 ◽  
Vol 37 (4-5) ◽  
pp. 195-198 ◽  
Author(s):  
Tong Yu ◽  
Paul L. Bishop
Keyword(s):  
Redox Potential ◽  
Sulfate Reduction ◽  
Aerobic Oxidation ◽  
Sharp Decrease ◽  
Bulk Solution ◽  
Metabolic Processes ◽  
Dissolved Sulfide ◽  
Experimental Findings ◽  
Ph Microelectrodes ◽  
Aerobic Zone

In this study we used oxygen, sulfide, redox potential and pH microelectrodes to examine the stratification of microbial metabolic processes and the change of redox potential within an aerobic biofilm used to treat azo dye containing wastewater. These microelectrodes have tip diameters of 3 to 20 μm and a high spatial resolution. They were used to measure the profiles of oxygen, total dissolved sulfide, redox potential and pH as a function of depth in the biofilm. These profiles demonstrated that oxygen was depleted at 550 μm from the surface and the deeper section of the biofilm was actually anaerobic. While aerobic oxidation took place only in a shallow layer near the surface, sulfate reduction occurred in the deeper anaerobic zone, even with a low concentration of sulfate (6.75 mg/l as SO2−) in the bulk solution. We discovered a sharp decrease of redox potential (271 mV) from a positive potential to a negative potential within a very narrow band of 50 μm near the interface between the aerobic zone and the sulfate reduction zone. The new experimental findings support the concept of stratification of the microbial metabolic processes in biofilms.

Effect of sulfate on anaerobic processes fed with dual substrates

1995 ◽  
Vol 31 (9) ◽  
pp. 101-107 ◽  
Author(s):  
Chongchin Polprasert ◽  
Charles N. Haas
Keyword(s):  
Acetic Acid ◽  
Sulfate Reduction ◽  
Mixed Culture ◽  
Biogas Production ◽  
Cod Removal ◽  
Methane Formation ◽  
Batch Mode ◽  
Sulfate Reducing ◽  
Anaerobic Reactors ◽  
Optimal Feed

Anaerobic reactors were operated in a semi-batch mode and fed with the dual substrates glucose (G) plus acetic acid (Ac) as primary organic sources to study the effect of sulfate on COD oxidation. With glucose, COD removal by methane formation was seriously inhibited, resulting in COD accumulation in the reactor. Although acetic acid can be consumed by some sulfate-reducing species, it was not a major substrate for sulfate reduction, but was largely responsible for methane formation in the anaerobic mixed culture used in this study. With dual substrates, extreme inhibition of methanogenesis did not occur as did with glucose alone. Instead, methanogens were found to work in harmony with acid formers as well as sulfate reducers to oxidise COD. Interestingly, from 12-hour monitoring, increased G/Ac COD ratios decreased COD removal rates as well as biogas production, but resulted in higher sulfate reduction. This suggests that there should be an optimal feed G/Ac COD ratio, for which removal of both organics could be maximised.

Automatic monitoring of denitrification rates and capacities in activated sludge processes using fluorescence or redox potential

1998 ◽  
Vol 37 (12) ◽  
pp. 121-129 ◽  
Author(s):  
S. Isaacs ◽  
Terry Mah ◽  
S. K. Maneshin
Keyword(s):  
Biological Activity ◽  
Activated Sludge ◽  
Redox Potential ◽  
Treatment Plant ◽  
Automatic Monitoring ◽  
Organic Substrate ◽  
Anoxic Zone ◽  
Optimal Dosing ◽  
Denitrifying Microorganisms ◽  
Activated Sludge Processes

A novel method is described to automatically estimate several key parameters affecting denitrification in activated sludge processes: the nitrate concentration, the denitrification capacity, and the maximum (substrate unlimited) and actual denitrification rates. From these, the concentration of active denitrifying microorganisms and the quality of available organic substrate pool can be estimated. Additionally, a modification of the method allows the determination of the efficacy of various carbon substrates to enhance denitrification, and this can be used to determine optimal dosing rates of an external carbon source. The method is based on measurements of either fluorescence or redox potential (ORP) in an isolated mini-reactor, the Biological Activity Meter (BAM), situated in the anoxic zone of the wastewater treatment plant. Advantages of the method are that it is in situ, operating at the same temperature as in the measured anoxic zone, requires no pumps or pipes for mixed liquor sampling, consumes little or no reagents, and uses measurement signals which are instantaneous and low maintenance, one of which provides a direct measure of biological activity.

Trialing wetlands to treat coal mining wastewaters in a low rainfall, high evaporation environment

1997 ◽  
Vol 35 (5) ◽  
pp. 293-299 ◽  
Author(s):  
Wendy R. Tyrrell ◽  
David R. Mulligan ◽  
Lindsay I. Sly ◽  
L. Clive Bell
Keyword(s):  
Sulfate Reduction ◽  
Coal Mining ◽  
Pilot Scale ◽  
Cattle Manure ◽  
Annual Rainfall ◽  
Sulfate Reducing ◽  
Black Precipitate ◽  
Final Treatment ◽  
Reducing Bacteria ◽  
Initial Results

The large number of wetlands treating mining wastewaters around the world have mostly been constructed in temperate environments. Wetlands have yet to be proven in low rainfall, high evaporation environments and such conditions are common in many parts of Australia. BHP Australia Coal is researching whether wetlands have potential in central Queensland to treat coal mining wastewaters. In this region, mean annual rainfall is < 650 mm and evaporation > 2 000 mm. A pilot-scale wetland system has been constructed at an open-cut coal mine. The system comprises six treatment cells, each 125 m long and 10 m wide. The system is described in the paper and some initial results presented. Results over the first fourteen months of operation have shown that although pH has not increased enough to enable reuse or release of the water, sulfate reduction has been observed in parts of the system, as shown by the characteristic black precipitate and smell of hydrogen sulfide emanating from the wetlands. These encouraging signs have led to experiments aimed at identifying the factors limiting sulfate reduction. The first experiment, described herein, included four treatments where straw was overlain by soil and the water level varied, being either at the top of the straw, at the top of the soil, or about 5 cm above the soil. The effect of inoculating with sulfate-reducing bacteria was investigated. Two controls were included, one covered and one open, to enable the effect of evaporation to be determined. The final treatment consisted of combined straw/cattle manure overlain with soil. Results showed that sulfate reduction did occur, as demonstrated by pH increases and lowering of sulfate levels. Mean pH of the water was significantly higher after 19 days; in the controls, pH was < 3.3, whereas in the treatments, pH ranged from 5.4 to 6.7. The best improvement in sulfate levels occurred in the straw/cattle manure treatment.

scholarly journals Pseudodesulfovibrio cashew sp. Nov., a Novel Deep-Sea Sulfate-Reducing Bacterium, Linking Heavy Metal Resistance and Sulfur Cycle

2021 ◽  
Vol 9 (2) ◽  
pp. 429
Author(s):  
Rikuan Zheng ◽  
Shimei Wu ◽  
Chaomin Sun
Keyword(s):  
Heavy Metal ◽  
Sulfate Reduction ◽  
Marine Sediments ◽  
Deep Sea ◽  
Sulfur Cycle ◽  
Metal Sulfides ◽  
Phenotypic Traits ◽  
Dissimilatory Sulfate Reduction ◽  
Metabolic Potential ◽  
Sulfate Reducing

Sulfur cycling is primarily driven by sulfate reduction mediated by sulfate-reducing bacteria (SRB) in marine sediments. The dissimilatory sulfate reduction drives the production of enormous quantities of reduced sulfide and thereby the formation of highly insoluble metal sulfides in marine sediments. Here, a novel sulfate-reducing bacterium designated Pseudodesulfovibrio cashew SRB007 was isolated and purified from the deep-sea cold seep and proposed to represent a novel species in the genus of Pseudodesulfovibrio. A detailed description of the phenotypic traits, phylogenetic status and central metabolisms of strain SRB007 allowed the reconstruction of the metabolic potential and lifestyle of a novel member of deep-sea SRB. Notably, P. cashew SRB007 showed a strong ability to resist and remove different heavy metal ions including Co2+, Ni2+, Cd2+ and Hg2+. The dissimilatory sulfate reduction was demonstrated to contribute to the prominent removal capability of P. cashew SRB007 against different heavy metals via the formation of insoluble metal sulfides.

Precipitation of heavy metals from coal ash leachate using biogenic hydrogen sulfide generated from FGD gypsum

2013 ◽  
Vol 67 (2) ◽  
pp. 311-318 ◽  
Author(s):  
Madawala Liyanage Duminda Jayaranjan ◽  
Ajit P. Annachhatre
Keyword(s):  
Heavy Metals ◽  
Hydrogen Sulfide ◽  
Sulfate Reduction ◽  
Bottom Ash ◽  
Coal Ash ◽  
Reduction Process ◽  
Fgd Gypsum ◽  
Sulfate Reducing ◽  
Sulfate Reduction Process ◽  
Biological Sulfate Reduction

Investigations were undertaken to utilize flue gas desulfurization (FGD) gypsum for the treatment of leachate from the coal ash (CA) dump sites. Bench-scale investigations consisted of three main steps namely hydrogen sulfide (H2S) production by sulfate reducing bacteria (SRB) using sulfate from solubilized FGD gypsum as the electron acceptor, followed by leaching of heavy metals (HMs) from coal bottom ash (CBA) and subsequent precipitation of HMs using biologically produced sulfide. Leaching tests of CBA carried out at acidic pH revealed the existence of several HMs such as Cd, Cr, Hg, Pb, Mn, Cu, Ni and Zn. Molasses was used as the electron donor for the biological sulfate reduction (BSR) process which produced sulfide rich effluent with concentration up to 150 mg/L. Sulfide rich effluent from the sulfate reduction process was used to precipitate HMs as metal sulfides from CBA leachate. HM removal in the range from 40 to 100% was obtained through sulfide precipitation.

Microbial ecology of sulfate-reducing bacteria in wastewater biofilms analyzed by microelectrodes and fish (fluorescent in situ hybridization) technique

1999 ◽  
Vol 39 (7) ◽  
pp. 41-47 ◽  
Author(s):  
Satoshi Okabe ◽  
Hisashi Satoh ◽  
Tsukasa Itoh ◽  
Yoshimasa Watanabe
Keyword(s):  
In Situ Hybridization ◽  
Sulfate Reduction ◽  
Sulfate Reducing Bacteria ◽  
Hybridization Technique ◽  
Concentration Profiles ◽  
Reduction Zone ◽  
Sulfate Reducing ◽  
Reducing Bacteria ◽  
Culture Dependent

The vertical distribution of sulfate-reducing bacteria (SRB) in microaerophilic wastewater biofilms grown on fully submerged rotating disk reactors (RDR) was determined by the conventional culture-dependent MPN method and in situ hybridization of fluorescently-labelled 16S rRNA-targeted oligonucleotide probes for SRB in parallel. Chemical concentration profiles within the biofilm were also measured using microelectrodes for O2, S2-, NO3- and pH. In situ hybridization revealed that the SRB probe-stained cells were distributed throughout the biofilm even in the oxic surface zone in all states from single scattered cells to clustered cells. The higher fluorescence intensity and abundance of SRB probe-stained cells were found in the middle part of the biofilm. This result corresponded well with O2 and H2S concentration profiles measured by microelectrodes, showing sulfate reduction was restricted to a narrow anaerobic zone located about 500 μm below the biofilm surface. Results of the MPN and potential sulfate reducing activity (culture-dependent approaches) indicated a similar distribution of cultivable SRB in the biofilm. The majority of the general SRB probe-stained cells were hybridized with SRB 660 probe, suggesting that one important member of the SRB in the wastewater biofilm could be the genus Desulfobulbus. An addition of nitrate forced the sulfate reduction zone deeper in the biofilm and reduced the specific sulfate reduction rate as well. The sulfate reduction zone was consequently separated from O2 and NO3- respiration zones. Anaerobic H2S oxidation with NO3- was also induced by addition of nitrate to the medium.

Control of sulfate reduction by molybdate in anaerobic digestion

1997 ◽  
Vol 36 (12) ◽  
pp. 143-150 ◽  
Author(s):  
Shuzo Tanaka ◽  
Young-Ho Lee
Keyword(s):  
Anaerobic Digestion ◽  
Sulfate Reduction ◽  
Methane Production ◽  
Phase 1 ◽  
Continuous Operation ◽  
Phase 2 ◽  
Sulfate Reducing ◽  
Start Up ◽  
Reducing Bacteria ◽  
Control Batch

Control of sulfate reduction by adding molybdate was investigated to enhance the methane production under batch and continuous operation in the anaerobic digestion of a sulfate-rich lysine wastewater. In phase 1 of the continuous operation, four anaerobic filters were fed with the lysine wastewater and then added with molybdate at 1,3,5 and 10 mM just after methane producing bacteria (MPB) were completely inhited by H2S produced by sulfate reducing bacteria (SRB). In phase 2, three anaerobic filters were operated with continuous or intermittent addition of 3 mM molybdate from the beginning of operation, including one with no molybdate as a control. Batch experiments revealed that the sulfate reduction was strongly inhibited and finally ceased by adding 3 mM or more of molybdate, resulting in great enhancement of the methane production. In phase 1 of the continuous experiments, all reactors showed the cessation of the methane production when the content of H2S reached 9–10 % in biogas, but the MPB activity was gradually recovered after initiating the molybdate addition at 3 or 5 mM. The 10 mM dosage of molybdate, however, had an inhibiting effect to MPB as well as SRB, resulting in the accumulation of acetate within the reactor. In phase 2, the control reactor continued to decrease the methane production, and a methane conversion rate was only 3 % in the control, while 35 and 10 % in continuously-added and intermittently-added reactors, respectively. Thus, it was confirmed that the MPB activity was greatly enhanced under control of the SRB activity by the continuous addition of molybdate. Comparing phase 2 with phase 1, addition from the start-up of the process is considered more effective than addition after the methane production dropped in the control of the sulfate reduction by molybdate.

scholarly journals Occurrence of benthic microbial nitrogen fixation coupled to sulfate reduction in the seasonally hypoxic Eckernförde Bay, Baltic Sea

2012 ◽  
Vol 9 (6) ◽  
pp. 6489-6533 ◽  
Author(s):  
V. J. Bertics ◽  
C. R. Löscher ◽  
I. Salonen ◽  
A. W. Dale ◽  
R. A. Schmitz ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sulfate Reduction ◽  
N2 Fixation ◽  
Bottom Water ◽  
N Cycling ◽  
Microbial Processes ◽  
Desulfovibrio Vulgaris ◽  
N Loss ◽  
Column Temperature ◽  
Oxygen Concentrations

Abstract. Despite the worldwide occurrence of marine hypoxic regions, benthic nitrogen (N) cycling within these areas is poorly understood and it is generally assumed that these areas represent zones of intense fixed N loss from the marine system. Sulfate reduction can be an important process for organic matter degradation in sediments beneath hypoxic waters and many sulfate-reducing bacteria (SRB) have the genetic potential to fix molecular N (N2). Therefore, SRB may supply fixed N to these systems, countering some of the N lost via microbial processes such as denitrification and anaerobic ammonium oxidation. The objective of this study was to evaluate if N2-fixation, possibly by SRB, plays a role in N cycling within the seasonally hypoxic sediments from Eckernförde Bay, Baltic Sea. Monthly samplings were performed over the course of one year to measure N2-fixation and sulfate reduction rates, to determine the seasonal variations in bioturbation (bioirrigation) activity and important benthic geochemical profiles, such as sulfur and N compounds, and to monitor changes in water column temperature and oxygen concentrations. Additionally, at several time points, rates of benthic denitrification were also measured and the active N-fixing community was examined via molecular tools. Integrated rates of N2-fixation and sulfate reduction showed a similar seasonality pattern, with highest rates occurring in August (approx. 22 and 880 nmol cm−3 d−1 of N and SO42−, respectively) and October (approx. 22 and 1300 nmol cm−3 d−1 of N and SO42−, respectively), and lowest rates occurring in February (approx. 8 and 32 nmol cm−3 d−1 of N and SO42−, respectively). These rate changes were positively correlated with bottom water temperatures and previous reported plankton bloom activities, and negatively correlated with bottom water oxygen concentrations. Other variables that also appeared to play a role in rate determination were bioturbation, bubble irrigation and winter storm events. Molecular analysis demonstrated the presence of nifH sequences related to two known N2-fixing SRB, namely Desulfovibrio vulgaris and Desulfonema limicola, supporting the hypothesis that some of the nitrogenase activity detected may be attributed to SRB. Denitrification appeared to follow a similar trend as the other microbial processes and the ratio of denitrification to N2-fixation ranged from 6.8 in August to 1.1 in February, indicating that in February, the two processes are close to being in balance in terms of N loss and N gain. Overall, our data show that Eckernförde Bay represents a complex ecosystem where numerous environmental variables combine to influence benthic microbial activities involving N and sulfur cycling.

Interactions between filamentous sulfur bacteria, sulfate reducing bacteria and poly-P accumulating bacteria in anaerobic-oxic activated sludge from a municipal plant

1998 ◽  
Vol 37 (4-5) ◽  
pp. 599-603 ◽  
Author(s):  
Ryoko Yamamoto-Ikemoto ◽  
Saburo Matsui ◽  
Tomoaki Komori ◽  
Edja. Kofi. Bosque-Hamilton
Keyword(s):  
Activated Sludge ◽  
Sulfate Reduction ◽  
Reduction Rate ◽  
Sulfate Reducing Bacteria ◽  
Sulfate Reduction Rate ◽  
Filamentous Bulking ◽  
Sulfate Reducing ◽  
Sulfur Bacteria ◽  
Sulfate Reduction Rates ◽  
Reducing Bacteria

The interactions between filamentous sulfur bacteria (FSB), sulfate reducing bacteria (SRB) and poly-P accumulating bacteria (PAB) in the activated sludge of a municipal plant operated under anaerobic-oxic conditions were examined in batch experiments using return sludge (RAS) and settled sewage. Phosphate release and sulfate reduction occurred simultaneously under anaerobic conditions. SRB were more sensitive to temperature changes than PAB. SRB played an important role in the decomposition of propionate to acetate. When the sulfate reduction rates were high, there was a tendency for the maximum release of phosphate also to be high. This was explained by the fact that PAB utilized the acetate produced by SRB. Sulfur oxidizing bacteria were sensitive to temperature change. When the sulfate reduction rate was high, the sulfide oxidizing rate was also high and filamentous bulking occurred. The results showed that sulfate reduction was a cause of filamentous bulking due to Type 021N that could utilize reduced sulfur.

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