Diverting electron fluxes towards sulfate reduction using linoleic acid in a mixed anaerobic culturePaper submitted to the Journal of Environmental Engineering and Science.

2010 ◽  
Vol 37 (11) ◽  
pp. 1492-1504
Author(s):  
Mamata Sharma ◽  
Nihar Biswas
Keyword(s):  
Linoleic Acid ◽  
Sulfate Reduction ◽  
Degradation Rate ◽  
Volatile Fatty Acids ◽  
Removal Rate ◽  
Electron Flow ◽  
Methane Formation ◽  
Sulfate Removal ◽  
Degradation Rates ◽  
High Concentrations

Sulfate (1500 mg/L) reduction and glucose (1870 mg/L) degradation was examined in the presence of five varying linoleic acid (LA) levels (100–1000 mg/L) at 37 ± 2 °C and pH 7.0–7.2. The sulfate reduction and methane formation data suggest that LA selectively inhibited methane producing bacteria (MPB). The quantity of sulfate removed increased with increasing LA dosage. Approximately 1375 mg/L (92%) sulfate was removed in cultures fed with high concentrations of LA (1000 mg/L), which was 68% more than that removed in glucose and sulfate controls. The quantity of sulfate removed in cultures fed with 100, 300, 500 and 700 mg/L LA were 62%, 66%, 77%, and 84%, respectively. Initial sulfate degradation rates increased with increasing LA levels in the cultures. High LA levels (1000 mg/L) attributed to approximately a sevenfold increase in the initial sulfate degradation rates compared to cultures containing sulfate plus glucose. The highest initial sulfate removal rate (0.19 µg/(mgVSS min)) was observed in cultures receiving 1000 mg/L LA. Initial glucose degradation rates decreased with increasing LA concentrations. The rates for the cultures receiving 1000 mg/L LA were 2.53 µg/(mgVSS min) while the degradation rate for cultures containing 100 mg/L LA was 5.40 µg/(mgVSS min). Methane formation decreased when sulfate and LA were added. Methane formation was lowest in cultures receiving elevated LA concentrations. The percent electron flow fluxes increased towards sulfidogenesis and decreased towards methanogenesis with increasing LA levels. Less than 0.6% electron flow was diverted to methanogenesis in cultures containing high levels of LA (≥700 mg/L) while ≤ 45% was diverted to sulfidogenesis. Acetate and propionate were the major volatile fatty acids (VFAs) detected during glucose degradation. The amount of sulfate reduced in the cultures receiving only LA or sulfate and no other carbon source was comparable (approximately 10%), which suggests that LA did not contribute to electrons during the course of experiment for sulfate reduction.

Biological sulfate removal in an acidogenic bioreactor with an ultrafiltration membrane system

1998 ◽  
Vol 38 (4-5) ◽  
pp. 513-520 ◽  
Author(s):  
O. Mizuno ◽  
H. Takagi ◽  
T. Noike
Keyword(s):  
Sulfate Reduction ◽  
Membrane Filtration ◽  
Membrane Bioreactor ◽  
Volatile Fatty Acids ◽  
Membrane System ◽  
Organic Substrate ◽  
Ultrafiltration Membrane ◽  
Sulfate Concentration ◽  
Sulfate Removal ◽  
Chemostat Reactor

The biological sulfate removal in the acidogenic bioreactor with an ultrafiltration membrane system was investigated at 35°C. Sucrose was used as the sole organic substrate. The sulfate concentration in the substrate ranged from 0 to 600mgS·1−1. The chemostat reactor was operated to compare with the membrane bioreactor. The fouling phenomenon caused by FeS precipitate was observed at higher concentration of sulfate. However, it was possible to continuously operate the membrane bioreactor by cleaning the membrane. The efficiency of sulfate removal by sulfate reduction reached about 100% in the membrane bioreactor, and 55 to 87% of sulfide was removed from the permeate by the membrane filtration. The composition of the metabolite was remarkably changed by the change in sulfate concentration. When the sulfate concentration increased, acetate and 2-proponol significantly increased while n-butyrate and 3-pentanol decreased. The sulfate-reducing bacteria play the role as acetogenic bacteria consuming volatile fatty acids and alcohols as electron donors under sulfate-rich conditions. The results show that the acidogenesis and sulfate reduction simultaneously proceed in the membrane bioreactor.

Effect of Hydraulic Retention Time on Pretreatment of Sulfate-Laden Wastewater for Desulfurization-Denitrification Process

2010 ◽  
Vol 113-116 ◽  
pp. 536-539
Author(s):  
Wei Li ◽  
Xiao Liang ◽  
Jian Guo Lin
Keyword(s):  
Organic Carbon ◽  
Sulfate Reduction ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Removal Rate ◽  
Reduction Stage ◽  
Sulfate Removal ◽  
Carbon Sulfide ◽  
Set Up ◽  
Denitrification Process

In order to treat wastewater rich in sulfate and organic carbon, an anaerobic attached-growth bioreactor was set up. It was the pretreatment of desulfurization-denitrification process. At hydraulic retention time of 128h-6.2h, sulfate removal rate and sulfide generating rate took on initial increasing and subsequent decreasing. At hydraulic retention time of 7.7h-10.2h, the removals of sulfate and organic carbon, sulfide generating rate reached 95.79%, 80% and 58.82%, respectively. The results showed that the suitable hydraulic retention time in sulfate reduction stage for the pretreatment of desulfurization-denitrification process was 7.7h-10.2h.

Vacuum Operation for Overloaded Anaerobic Treatment Systems

1989 ◽  
Vol 21 (4-5) ◽  
pp. 87-95
Author(s):  
J. De Santis ◽  
A. A. Friedman
Keyword(s):  
Volatile Fatty Acids ◽  
Loading Rate ◽  
Anaerobic Treatment ◽  
Optimum Operating ◽  
Operating Pressure ◽  
Simple Modification ◽  
Anaerobic Reactors ◽  
Fixed Film ◽  
Solids Retention ◽  
High Concentrations

Overloaded anaerobic treatment systems are characterized by high concentrations of volatile fatty acids and molecular hydrogen and poor conversion of primary substrates to methane. Previous experiments with fixed–film reactors indicated that operation with reduced headspace pressures enhanced anaerobic treatment. For these studies, four suspended culture, anaerobic reactors were operated with headspace pressures maintained between 0.5 and 1.0 atm and a solids retention time of 15 days. For lightly loaded systems (0.4 g SCOD/g VSS-day) vacuum operation provided minor treatment improvements. For shock organic loads, vacuum operation proved to be more stable and to support quicker recovery from upset conditions. Based on these studies and a companion set of bioassay tests, it was concluded that: (a) a loading rate of about 1.0 g SCOD/g VSS-day represents a practical loading limit for successful anaerobic treatment, (b) a headspace pressure of approximately 0.75 atm appears to be an optimum operating pressure for anaerobic systems and (c) simple modification to existing systems may provide relief for organically overloaded systems.

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.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

Use of a sequencing batch biofilter for degradation of azo dyes (acids and bases)

2000 ◽  
Vol 42 (5-6) ◽  
pp. 329-336 ◽  
Author(s):  
M. Quezada ◽  
I. Linares ◽  
G. Buitrón
Keyword(s):  
Azo Dyes ◽  
Azo Dye ◽  
Degradation Rate ◽  
Removal Rate ◽  
Textile Effluent ◽  
Colour Removal ◽  
Substrate Degradation ◽  
Acids And Bases ◽  
Removal Efficiencies ◽  
Basic Red 46

The degradation of azo dyes in an aerobic biofilter operated in an SBR system was studied. The azo dyes studied were Acid Red 151 and a textile effluent containing basic dyes (Basic Blue 41, Basic Red 46 and 16 and Basic Yellow 28 and 19). In the case of Acid Red 151 a maximal substrate degradation rate of 288 mg AR 151/lliquid·d was obtained and degradation efficiencies were between 60 and 99%. Mineralization studies showed that 73% (as carbon) of the initial azo dye was transformed to CO2 by the consortia. The textile effluent was efficiently biodegraded by the reactor. A maximal removal rate of 2.3 kg COD/lliquid·d was obtained with removal efficiencies (as COD) varying from 76 to 97%. In all the cycles the system presented 80% of colour removal.

A simulated mucus layer protects Lactobacillus reuteri from the inhibitory effects of linoleic acid

2013 ◽  
Vol 4 (4) ◽  
pp. 299-312 ◽  
Author(s):  
R. De Weirdt ◽  
E. Coenen ◽  
B. Vlaeminck ◽  
V. Fievez ◽  
P. Van den Abbeele ◽  
...  
Keyword(s):  
Linoleic Acid ◽  
Lactobacillus Reuteri ◽  
Close Contact ◽  
Mucus Layer ◽  
Inhibitory Effects ◽  
Intestinal Mucus ◽  
Gut Microbe ◽  
Protective Environment ◽  
Bacterial Cell Membrane ◽  
High Concentrations

Lactobacillus reuteri is a commensal, beneficial gut microbe that colonises the intestinal mucus layer, where it makes close contact with the human host and may significantly affect human health. Here, we investigated the capacity of linoleic acid (LA), the most common polyunsaturated fatty acid (PUFA) in a Western-style diet, to affect L. reuteri ATCC PTA 6475 prevalence and survival in a simulated mucus layer. Short-term (1 h) survival and mucin-agar adhesion assays of a log-phase L. reuteri suspension in intestinal water demonstrated that the simulated mucus layer protected L. reuteri against the inhibitory effects of LA by lowering its contact with the bacterial cell membrane. The protective effect of the simulated mucus layer was further evaluated using a more complex and dynamic model of the colon microbiota (SHIME®), in which L. reuteri survival was monitored during 6 days of daily exposure to LA in the absence (L-SHIME) and presence (M-SHIME) of a simulated mucus layer. After 6 days, luminal L- and M-SHIME L. reuteri plate counts had decreased by 3.1±0.5 and 2.6±0.9 log cfu/ml, respectively. Upon supplementation of 1.0 g/l LA, the decline in the luminal L. reuteri population started earlier than was observed for the control. In contrast, mucin-agar levels of L. reuteri (in the M-SHIME) remained unaffected throughout the experiment even in the presence of high concentrations of LA. Overall, the results of this study indicate the importance of the mucus layer as a protective environment for beneficial gut microbes to escape from stress by high loads of the antimicrobial PUFA LA to the colon, i.e. due to a Western-style diet.

Effects of sulfate concentration and sludge retention time on the interaction between methane production and sulfate reduction for butyrate

1994 ◽  
Vol 30 (8) ◽  
pp. 45-54 ◽  
Author(s):  
O. Mizuno ◽  
Y. Y. Li ◽  
T. Noike
Keyword(s):  
Sulfate Reduction ◽  
Retention Time ◽  
Methane Production ◽  
Electron Flow ◽  
Degradation Pathway ◽  
Sulfate Concentration ◽  
High Concentration ◽  
Total Electron ◽  
Sludge Retention Time ◽  
Wide Range

The effects of sulfate concentration and COD/S ratio on the anaerobic degradation of butyrate were investigated by using 2.0 L anaerobic chemostat-type reactor at 35°C. The study was conducted over a wide range of the COD/S ratio (1.5 to 148) by varying COD concentrations (2500–10000 mg/L) and sulfate concentrations (68–1667 mg-S/L) in the substrate. The sludge retention time at each COD/S ratio was changed from 5 to 20 days. The interaction between methane producing bacteria (MPB) and sulfate-reducing bacteria (SRB) was evidently influenced by COD/S ratio in the substrate. When COD/S ratio was 6.0 or more, methane production was the predominate reaction and over 80% of the total electron flow was used by MPB. At the COD/S ratio of 1.5, SRB utilzed over 50% of the total electron flow. A large amount of sulfate reduction resulted in not only the decrease of methane production, but also the rapid increase of the bacterial growth. The degradation pathway of butyrate and the composition of bacterial populations in the reactor were also dominated by COD/S ratio. In sulfate depleted condition, butyrate was degraded to methane via acetate and hydrogen by MPB. On the other hand, butyrate was firstly degraded into sulfide and acetate in sulfate rich conditions by SRB, and the produced acetate was then degraded by acetate consuming MPB and SRB. The methanogenesis from acetate was inhibited by the high concentration of sulfide.

scholarly journals Enhancing the Lubricity of Gas-to-Liquid (GTL) Paraffinic Kerosene: Impact of the Additives on the Physicochemical Properties

2020 ◽  
Author(s):  
Hani Ababnah ◽  
Nasr Mohamed ◽  
Hanif Choudhury ◽  
Lei Lei Zhang ◽  
Rafiqul Gani ◽  
...  
Keyword(s):  
Linoleic Acid ◽  
Physicochemical Properties ◽  
Negative Impact ◽  
Freezing Point ◽  
Ethyl Oleate ◽  
Heat Content ◽  
Wear Scar Diameter ◽  
Dual Nature ◽  
Fuel Jet ◽  
High Concentrations

Abstract Synthetic paraffinic kerosene (SPK) is an ultra-clean fuel with low aromatic content and negligible quantities of sulfur compounds . Although, SPK has a good potential to replace the conventional fuel Jet A-1 , it also has some deficiencies. One of them is the low lubricity compared to its conventional counterpart Jet A-1. To improve the lubricity of SPK, three selected additives have been mixed with SPK at different concentrations. The lubricity of the samples was determined experimentally and the samples that meet the industry specifications have been studied further. The effect of the additives on the physicochemical properties, such as, density, flash point, freezing point, viscosity, and heat content, were investigated. Linoleic acid was found to be an excellent lubricity improver even at a very low concentration and its negative impact on the other physicochemical properties was found to be insignificant. Ethyl oleate also demonstrated significant improvement in lubricity at low concentrations but had a negative impact on the fuel’s freezing point at high concentrations. Quinoline, at high concentrations, elevated the blend’s freezing point above the acceptable limits. In parallel to the experimental campaign, a pre-existing mathematical modelling tool was utilized to predict the properties of interest. The lubricity model was successfully introduced into the mathematical model in order to improve the capabilities of the model. Linoleic acid sample showed the best improvement in lubricity of SPK with wear scar diameter of 4 17 μm; well below the ASTM D7566 maximum limit of 850µm. The dual nature of this study facilitated the optimization of the physicochemical properties of the fuel samples.

scholarly journals Partitioning Effects during Terminal Carbon and Electron Flow in Sediments of a Low-Salinity Meltwater Pond near Bratina Island, McMurdo Ice Shelf, Antarctica

1999 ◽  
Vol 65 (12) ◽  
pp. 5493-5499 ◽  
Author(s):  
Douglas O. Mountfort ◽  
Heinrich F. Kaspar ◽  
Malcolm Downes ◽  
Rodney A. Asher
Keyword(s):  
Sulfate Reduction ◽  
Methane Production ◽  
Electron Flow ◽  
Fold Increase ◽  
Cyanobacterial Mats ◽  
Ice Shelf ◽  
Physiological Conditions ◽  
Low Salinity ◽  
Methane Production Rate

ABSTRACT A study of anaerobic sediments below cyanobacterial mats of a low-salinity meltwater pond called Orange Pond on the McMurdo Ice Shelf at temperatures simulating those in the summer season (<5°C) revealed that both sulfate reduction and methane production were important terminal anaerobic processes. Addition of [2-14C]acetate to sediment samples resulted in the passage of label mainly to CO2. Acetate addition (0 to 27 mM) had little effect on methanogenesis (a 1.1-fold increase), and while the rate of acetate dissimilation was greater than the rate of methane production (6.4 nmol cm−3 h−1compared to 2.5 to 6 nmol cm−3 h−1), the portion of methane production attributed to acetate cleavage was <2%. Substantial increases in the methane production rate were observed with H2 (2.4-fold), and H2 uptake was totally accounted for by methane production under physiological conditions. Formate also stimulated methane production (twofold), presumably through H2 release mediated through hydrogen lyase. Addition of sulfate up to 50-fold the natural levels in the sediment (interstitial concentration, ∼0.3 mM) did not substantially inhibit methanogenesis, but the process was inhibited by 50-fold chloride (36 mM). No net rate of methane oxidation was observed when sediments were incubated anaerobically, and denitrification rates were substantially lower than rates for sulfate reduction and methanogenesis. The results indicate that carbon flow from acetate is coupled mainly to sulfate reduction and that methane is largely generated from H2 and CO2 where chloride, but not sulfate, has a modulating role. Rates of methanogenesis at in situ temperatures were four- to fivefold less than maximal rates found at 20°C.

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