Sulfide Generation Research Articles

Identification and Expression Analysis of an Atypical Alkaline Phosphatase in Emiliania huxleyi.

Emiliania huxleyi, a cosmopolitan coccolithophore in the modern ocean, plays an important role in the carbon cycle and local climate feedback as it can form extensive blooms, calcify, and produce dimethylsulfoniopropionate (DMSP) leading to the generation of dimethyl sulfide (DMS) which affects climate when oxidized in the atmosphere. It is known to be able to utilize dissolved organic phosphorus (DOP) by expressing a specific type of alkaline phosphatase (EHAP1) under phosphorus-limited conditions. In this study, we identified a new alkaline phosphatase (EH-PhoAaty) in this species, which we found belongs to the newly classified PhoAaty family. The expression of this atypical phosphatase was up-regulated under P-depleted conditions at both the transcriptional and translational levels, suggesting that E. huxleyi is able to express this AP to cope with phosphorus limitation. Comparative analysis revealed different transcriptional expression dynamics between eh-PhoAaty and ehap1, although both genes exhibited inducible expression under phosphate deficiency. In addition, after AP activity was eliminated by using EDTA to chelate metal ions, we found that AP activity was recovered with the supplement of Ca2+ and Zn2+, indicative of the adoption of Ca2+ as the cofactor under Zn-P co-limited conditions, likely a result of adaptation to oceanic environments where Zn2+ is often limiting.

Biogeochemical Cycling by a Low-Diversity Microbial Community in Deep Groundwater.

Olkiluoto, an island on the south-west coast of Finland, will host a deep geological repository for the storage of spent nuclear fuel. Microbially induced corrosion from the generation of sulphide is therefore a concern as it could potentially compromise the longevity of the copper waste canisters. Groundwater at Olkiluoto is geochemically stratified with depth and elevated concentrations of sulphide are observed when sulphate-rich and methane-rich groundwaters mix. Particularly high sulphide is observed in methane-rich groundwater from a fracture at 530.6 mbsl, where mixing with sulphate-rich groundwater occurred as the result of an open drill hole connecting two different fractures at different depths. To determine the electron donors fuelling sulphidogenesis, we combined geochemical, isotopic, metagenomic and metaproteomic analyses. This revealed a low diversity microbial community fuelled by hydrogen and organic carbon. Sulphur and carbon isotopes of sulphate and dissolved inorganic carbon, respectively, confirmed that sulphate reduction was ongoing and that CO2 came from the degradation of organic matter. The results demonstrate the impact of introducing sulphate to a methane-rich groundwater with limited electron acceptors and provide insight into extant metabolisms in the terrestrial subsurface.

Eugenol Confers Cadmium Tolerance via Intensifying Endogenous Hydrogen Sulfide Signaling in Brassica rapa

Eugenol, a plant-derived small compound, shows great medicinal potential. However, whether and how eugenol regulates crop physiology remains elusive. Here we reported that eugenol induced Cd (cadmium) tolerance in the root of Brassica rapa. Roots were treated with eugenol and CdCl2 simultaneously (eugenol + Cd) or pretreated with eugenol followed by CdCl2 treatment (eugenol → Cd). Eugenol significantly attenuated Cd-induced growth inhibition, ROS accumulation, oxidative injury, and cell death, which were confirmed by in vivo histochemical analysis. Eugenol remarkably decreased free Cd2+ accumulation in root. Eugenol intensified GSH (glutathione) accumulation in roots upon CdCl2 exposure, which explained the decrease in free Cd2+ and attenuation of oxidative injury. Eugenol stimulated endogenous H2S (hydrogen sulfide) generation by upregulating the expression of BrLCD ( l-cysteine desulfhydrase) and BrDCD ( d-cysteine desulfhydrase) as well as their enzymatic activities in CdCl2-treated root. Application of H2S biosynthesis inhibitor or H2S scavenger led to the decrease in endogenous H2S level in Cd-treated root, which further compromised all the above effects of eugenol. These findings suggested that eugenol triggered H2S → GSH signaling cassette in plants to combat Cd stress, which shed new light on eugenol-modulated plant physiology and the interaction between eugenol and H2S.

Sulfide Formation as a Result of Sulfate Subduction into Silicate Mantle (Experimental Modeling under High P,T-Parameters)

Ca,Mg-sulfates are subduction-related sources of oxidized S-rich fluid under lithospheric mantle P,T-parameters. Experimental study, aimed at the modeling of scenarios of S-rich fluid generation as a result of desulfation and subsequent sulfide formation, was performed using a multi-anvil high-pressure apparatus. Experiments were carried out in the Fe,Ni-olivine–anhydrite–C and Fe,Ni-olivine–Mg-sulfate–C systems (P = 6.3 GPa, T of 1050 and 1450 °C, t = 23–60 h). At 1050 °C, the interaction in the olivine–anhydrite–C system leads to the formation of olivine + diopside + pyrrhotite assemblage and at 1450 °C leads to the generation of immiscible silicate-oxide and sulfide melts. Desulfation of this system results in the formation of S-rich reduced fluid via the reaction olivine + anhydrite + C → diopside + S + CO2. This fluid is found to be a medium for the recrystallization of olivine, extraction of Fe and Ni, and subsequent crystallization of Fe,Ni-sulfides (i.e., olivine sulfidation). At 1450 °C in the Ca-free system, the generation of carbonate-silicate and Fe,Ni-sulfide melts occurs. Formation of the carbonate component of the melt occurs via the reaction Mg-sulfate + C → magnesite + S. It is experimentally shown that the olivine-sulfate interaction can result in mantle sulfide formation and generation of potential mantle metasomatic agents—S- and CO2-dominated fluids, silicate-oxide melt, or carbonate-silicate melt.

In situ Pb-Pb isotopic dating of sulfides from hydrothermal deposits: a case study of the Lala Fe-Cu deposit, SW China

Precisely dating different generations of mineralization is important for understanding the origin and tectonic environment of ore formation. In this study, we have dated two generations of sulfides from the Lala Fe-Cu deposit, SW China, using in situ Pb-Pb isotopic data obtained by the LA-MC-ICPMS technique. The Lala deposit is composed of Fe-Cu ore bodies hosted in sedimentary-volcanic rocks of the Paleoproterozoic Hekou Group. It has a paragenetic sequence of pre-ore banded pyrite (Stage I) and Na alteration (Stage II), followed by early Fe (Stage III) and late Cu (Stage IV) mineralization. The sulfides in the deposit have dominantly formed in two stages, including pyrite from stratiform pyrite bands in the host rocks (i.e., Stage I) and epigenetic pyrite-chalcopyrite in Fe-Cu ore (i.e., Stage IV). The sulfides of both stages have highly radiogenic Pb isotopic ratios which form linear trends in the 207Pb/204Pb versus 206Pb/204Pb diagram. The regression trend for Stage I pyrite grains defines an errorchron age of 1669 ± 110 Ma (MSWD = 32), undistinguishable from zircon LA-ICPMS U-Pb ages of volcanic rocks in the Hekou Group (i.e., ~ 1700 Ma). The regressions for Stage IV pyrite and chalcopyrite yield younger errorchron ages of 1088 ± 88 Ma (MSWD = 93) and 1053 ± 220 Ma (MSWD = 15), respectively. Taking pyrite and chalcopyrite together, an errorchron age of 1053 ± 75 Ma (MSWD = 108) is obtained. These errorchron ages agree well with the molybdenite Re-Os age of the Fe-Cu ore (1086 ± 8 Ma). Despite the large error and MSWD values that are interpreted to be related to the small variation of initial ratios, or post-ore open system behavior, the good agreement with the precise zircon U-Pb and molybdenite Re-Os ages indicates that the Pb-Pb errorchron ages for Stage I and IV sulfides are geologically meaningful. Therefore, this study shows that the in situ Pb isotopic analyses can yield geologically meaningful Pb-Pb ages for radiogenic Pb-rich sulfide minerals. We also propose that in situ Pb-Pb isotopic dating may be more promising for Precambrian deposits containing sulfides with ingrown Pb, particularly for those involving multiple mineralization/hydrothermal events but without relevant minerals for precise Re-Os or U-Pb dating.

The carbonate-hosted MVT Morro Agudo Zn-Pb deposit, central Brazil

Morro Agudo is the largest known Mississippi-Valley Type deposit (MVT) in Brazil with original estimated reserves of 18.3 Mt @ 5.08% Zn and 1.75% Pb of which 3.92 Mt@ 4% Zn and 1.45% Pb remained in 2017. In spite of having been mined for more than 30 years, a comprehensive study of Morro Agudo metallogenic features was still lacking in the international literature. This deposit is hosted within the 250 km long Vazante Sequence, a N-S-trending Mesoproterozoic-Neoproterozoic carbonate-dominant sedimentary sequence thrusted over Neoproterozoic rocks during the Brasiliano Orogeny. Sulfide bodies in Morro Agudo are restricted to the Morro do Calcário Formation as a 1300 m long ore envelope averaging 9 m thick, comprising stacked up stratabound orebodies that thin out down dip and are limited to the NE by the Main Fault. Five orebodies are described: (a) Breccia-hosted orebody “GHI”, (b) Sphalerite-rich doloarenite orebody “JK”, (c) Galena-rich doloarenite orebody “L”; (d) Lower replaced stratiform orebody “M”; (e) Upper replaced stratiform orebody “N”. Comparison of these orebodies reveals mineral zonation patterns and variations in Zn-Pb grade consistent with sulfide textural relationships. These relationships indicate five mineralization styles that provide spatial and timing constraints for Morro Agudo; (a) Stratiform sulfides, (b) Massive Ore, (c) Laminated Ore, (d) Breccia-hosted Ore, (e) Late stage fracture-filling Ore. Carbon and oxygen stable isotope data for each mineralization style shows a pattern of mixing of signatures of mineralizing fluids and barren host rocks and supports our interpretation that these mineralization styles occurred in more than one stage of ore formation. The ore was later offset by a set of strike slip normal faults associated with compression related to the Brasiliano Orogeny, of which the Main Fault (Falha Principal) is the most important because it limits the deposit to the NE. Previous interpretation of upper orebodies as part of a SEDEX system is revisited in the present work. In our model, data used to support a syngenetic origin for Morro Agudo, such as synsedimentary structures, Pb isotopes in sulfides and fluid inclusion data indicate a younger, barren generation of sulfides deposited long before Zn-Pb mineralization, during sedimentation of the Morro do Calcário Formation in the Mesoproterozoic. These early sulfides were preserved in cherts and as massive pyrite beds that were later overprinted by sphalerite and galena. Overprinting thus mixed Meso and Neoproterozoic Pb isotopic sources and led to a long standing argument over whether the Morro Agudo ores were syngenetic or epigenetic. This interpretation is also in agreement with the current classification of the Vazante Sequence as containing imbricated Neoproterozoic and Mesoproterozoic sedimentary rocks. Based on our work of sulfide textural relationships, stable isotopes, whole-rock geochemistry and previously published data, we argue that Morro Agudo ores formed by at least two stages of percolation of mildly hot hydrothermal fluid in the Neoproterozoic. The primary reason for sulfide precipitation is interpreted to be mixing of mildly-hot, metal-bearing basinal brines and seawater/connate waters.

Coronary artery hypoxic vasorelaxation is augmented by perivascular adipose tissue through a mechanism involving hydrogen sulphide and cystathionine-β-synthase.

Hypoxia causes vasodilatation of coronary arteries which protects the heart from ischaemic damage through mechanisms including the generation of hydrogen sulphide (H2 S), but the influence of the perivascular adipose tissue (PVAT) and myocardium is incompletely understood. This study aimed to determine whether PVAT and the myocardium modulate the coronary artery hypoxic response and whether this involves hydrogen sulphide. Porcine left circumflex coronary arteries were prepared as cleaned segments and with PVAT intact, myocardium intact or both PVAT and myocardium intact, and contractility investigated using isometric tension recording. Immunoblotting was used to measure levels of H2 S-synthesizing enzymes: cystathionine-β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulphurtransferase (MPST). All three H2 S-synthesizing enzymes were detected in the artery and myocardium, but only CBS and MPST were detected in PVAT. Hypoxia elicited a biphasic response in cleaned artery segments consisting of transient contraction followed by prolonged relaxation. In arteries with PVAT intact, hypoxic contraction was attenuated and relaxation augmented. In arteries with myocardium intact, hypoxic contraction was attenuated, but relaxation was unaffected. In replacement experiments, replacement of dissected PVAT and myocardium attenuated artery contraction and augmented relaxation to hypoxia, mimicking the effect of insitu PVAT and indicating involvement of a diffusible factor(s). In arteries with intact PVAT, augmentation of hypoxic relaxation was reversed by amino-oxyacetate (CBS inhibitor), but not DL-propargylglycine (CSE inhibitor) or aspartate (inhibits MPST pathway). PVAT augments hypoxic relaxation of coronary arteries through a mechanism involving H2 S and CBS, pointing to an important role in regulation of coronary blood flow during hypoxia.

Modulation of NLRP3 inflammasome activation in human monocytes by mitochondria-targeted superoxide and hydrogen sulphide

Background: Anti-inflammatory targeting of IL-1β in people with previous MI is beneficial in terms of recurrent cardiovascular events. Mechanisms for modulation of IL-1β synthesis by macrophages is therefore also of potential value. The NLRP3 inflammasome complex plays a crucial role in IL-1β synthesis and is activated in a two-step process – “Signal 1” and “Signal 2”. This study investigated the possible role of mitochondrial and cytosolic superoxide and slow-release hydrogen sulfide generation in activation of the NLRP3 inflammasome in human THP-1 monocytes.

Cysteine allows ovarian cancer cells to adapt to hypoxia and to escape from carboplatin cytotoxicity

Ovarian cancer is the second most common gynaecologic malignancy and the main cause of death from gynaecologic cancer, due to late diagnosis and chemoresistance. Studies have reported the role of cysteine in cancer, by contributing for hydrogen sulphide (H2S) generation and as a precursor of glutathione (GSH). However, the role of cysteine in the adaptation to hypoxia and therapy response remains unclear. We used several ovarian cancer cell lines, ES2, OVCAR3, OVCAR8, A2780 and A2780cisR, to clarify cysteine relevance in ovarian cancer cells survival upon hypoxia and carboplatin. Results show that ES2 and OVCAR8 cells presented a stronger dependence on cysteine availability upon hypoxia and carboplatin exposure than OVCAR3 cells. Interestingly, the A2780 cisR, but not A2780 parental cells, benefits from cysteine upon carboplatin exposure, showing that cysteine is crucial for chemoresistance. Moreover, GSH degradation and subsequent cysteine recycling pathway is associated with ovarian cancer as seen in peripheral blood serum from patients. Higher levels of total free cysteine (Cys) and homocysteine (HCys) were found in ovarian cancer patients in comparison with benign tumours and lower levels of GSH were found in ovarian neoplasms patients in comparison with healthy individuals. Importantly, the total and S-Homocysteinylated levels distinguished blood donors from patients with neoplasms as well as patients with benign from patients with malignant tumours. The levels of S-cysteinylated proteins distinguish blood donors from patients with neoplasms and the free levels of Cys in serum distinguish blood from patients with benign tumours from patients with malignant tumours. Herein we disclosed that cysteine contributes for a worse disease prognosis, allowing faster adaptation to hypoxia and protecting cells from carboplatin. The measurement of serum cysteine levels can be an effective tool for early diagnosis, for outcome prediction and follow up of disease progression.

Estimation of water quality dynamics under long-term anoxic state in organically polluted reservoir by field observations and improved ecosystem model

In closed water bodies with significant organic pollution, anoxification due to thermal stratification leads to the elution of nitrogen and phosphorus from the bottom sediment and the generation of sulfide, resulting in further degradation of the water environment. This study focuses on the water quality dynamics in an organically polluted reservoir exhibiting long-term anoxification using two approaches: (1) field observations of seasonal changes in vertical profiles of dissolved oxygen, nitrogen, phosphorus, and sulfide and (2) construction of a water quality prediction model based on an ecosystem model incorporated with anaerobic biochemical processes. Iron and sulfate reduction occurred simultaneously because nitrate–nitrogen was reduced by denitrifying bacteria after the anoxification, and iron reduction became the main factor of the increase in ammonium–nitrogen and phosphate–phosphorus. The redox state of the bottom sediment surface, when anoxification began to occur, greatly affected the water quality dynamics caused by gradual reductive reactions under anaerobic conditions. Furthermore, the calculation accuracy of ammonium–nitrogen, phosphate–phosphorus, and sulfide was highly improved by modifying the conventional model based on the field observations. The characteristics of water quality under anaerobic conditions were sufficiently reflected in the upgraded ecosystem model. The proposed water quality prediction model could be used to quantitatively estimate the water environment dynamics in organically polluted water bodies. The model could be developed further in the future to solve the problems caused by long-term anoxification.

Taste and Flavor Perceptions of Glucosinolates, Isothiocyanates, and Related Compounds.

Brassicaceae plants are renowned for their taste, aroma and trigeminal characteristics; predominantly bitter taste, sulfurous aroma, and pungency. Compounds responsible for these sensations include the glucosinolates (GSLs) and their hydrolysis products, particularly isothiocyanates (ITCs), but also sulfur-containing volatile compounds. This article reviews the relative importance of taste and flavor perceptions resulting from such compounds; collating evidence from papers where findings are based on sensory analytical correlations, and those that have extracted specific compounds prior to sensory evaluation. Where specific GSLs impart bitterness and many ITCs impart pungency, this is clearly not true for all GSLs and ITCs. Designing crop improvement strategies for sensory traits based on total GSL content would be flawed, as it does not consider the relative differences in sensory characteristics of different GSLs and ITCs, nor the contribution from other GSL hydrolysis products. In addition, some Brassicaceae plants are consumed raw, whilst others are cooked; this affects not only the hydrolysis of GSLs, but also the generation and release of sulfides. Therefore, in breeding new plant varieties, it is prudent to consider the individual GSLs, the typical cooking conditions the plant is subjected to, enzyme stability, and resultant composition of both GSL hydrolysis products (including ITCs) and sulfides.

Role of Minerals in Hydrogen Sulfide Generation during Steam-Assisted Recovery of Heavy Oil

Heavy oil is recovered from reservoirs using steam-assisted technology, which can lead to H2S generation if the oil is relatively sulfur-rich. We have used laboratory aquathermolysis to simulate the steam-assisted gravity drainage process and have compared free heavy oil to that contained within the mineral matrix. The presence of a mineral matrix was found to affect the amount of H2S produced and the chemical properties of the oil generated. Our findings show that H2S production is initiated by the presence of naturally occurring minerals at specific temperatures and pressures and production techniques that avoid these conditions will minimize H2S production.

Simultaneous removal of nitrate and hydrogen sulfide by autotrophic denitrification in nitrate-contaminated water treatment

ABSTRACTNitrate contamination is a risk to human health and may cause eutrophication, whereas H2S is an undesirable constituent in biogas. In order to better understand denitrification using gaseous H2S as electron donor, this study investigated denitrification at different molar ratios of sulfur and nitrogen (S/N ratios) and H2S dosages. Although nitrate continued to decrease, a lag in sulfate generation was observed, implying the generation of sulfide oxidizing intermediates, which accumulated even though nitrate was in excess at lower S/N ratios of 0.19 and 0.38. More addition of H2S could result in a longer lag of sulfate generation. Before depletion of dissolved sulfide, denitrification could proceed with little nitrite accumulation. High throughout sequencing analysis identified two major genera, Thiobacillus and Sulfurimonas, that were responsible for autotrophic denitrification. The simultaneous removal of nitrate and H2S using a wide range of concentrations could be achieved.

Cystathionine β-Synthase Is Necessary for Axis Development in Vivo.

The cystathionine ß-synthase (CBS) is a critical enzyme in the transsulfuration pathway and is responsible for the synthesis of cystathionine from serine and homocysteine. Cystathionine is a precursor to amino acid cysteine. CBS is also responsible for generation of hydrogen sulfide (H2S) from cysteine. Mutation in CBS enzyme causes homocysteine levels to rise, and gives rise to a condition called hyperhomocysteinuria. To date, numerous mouse knockout models for CBS enzyme has been generated, which show panoply of defects, reflecting the importance of this enzyme in development. In zebrafish, we and others have identified two orthologs of cbs, which we call cbsa and cbsb. Previous gene knockdown studies in zebrafish have reported a function for cbsb ortholog in maintaining ion homeostasis in developing embryos. However, its role in maintaining H2S homeostasis in embryos is unknown. Here, we have performed RNA analysis in whole zebrafish embryos that showed a wide expression pattern for cbsa and cbsb primarily along the embryonic axis of the developing embryo. Loss-of-function analysis using a combination of approaches which include splice morpholinos and CRISPR/Cas9 genomic engineering show evidence that cbsb ortholog is responsible for anterior-posterior axis development, and cbsa function is redundant. Cbsb loss of function fish embryos show shortened and bent axis, along with less H2S and more homocysteine, effects resulting from loss of Cbsb. Using a chemical biology approach, we rescued the axis defects with betaine, a compound known to reduce homocysteine levels in plasma, and GYY4137, a long term H2S donor. These results collectively argue that cells along the axis of a developing embryo are sensitive to changes in homocysteine and H2S levels, pathways that are controlled by Cbsb, and thus is essential for development.

An Optical Microbial Biosensor Based on Whole Cell of Acidithiobacillus thiooxidans for Hydrogen Sulfide Determination

Due to its corrosive and highly toxic character, the generation of hydrogen sulfide is a serious problem for the environment, human health, and the industry. This paper reported a new and simple methodology for aqueous hydrogen sulfide determination through the development of an optical microbial biosensor. The principle of detection was based on the aerobic and chemolithotrophic metabolism of Acidithiobacillus thiooxidans bacterial cells. Under low oxygen concentration and acidic conditions A. thiooxidans can rapidly oxidize H2S to elemental sulfur. The biochemical formation of elemental sulfur can be spectrophotometrically detected and the increase in absorbance at 620 nm exhibited a linear relationship to an H2S concentration up to 100 mg.L-1. The parameters concerning the analytical performance of the biosensor such as cell harvesting time and pH influence were measured and optimized through the optical absorption value. The biosensor was selective to H2S with no important disturbance by tested species except thiosulfate ion (11.5% error). Biosensor response expressed good repeatability (RSD = 4.46 %) and reproducibility (RSD = 4.66 %). The low cost of cell cultivation and the absence of the immobilization step make feasible the optic biosensor application.

A triangle study of human, instrument and bioelectronic nose for non-destructive sensing of seafood freshness

Because the freshness of seafood determines its consumer preference and food safety, the rapid monitoring of seafood deterioration is considered essential. However, the conventional analysis of seafood deterioration using chromatography instruments and bacterial colony counting depends on time-consuming and food-destructive treatments. In this study, we demonstrate a non-destructive and rapid food freshness monitoring system by a triangular study of sensory evaluation, gas chromatography-mass spectroscopy (GC-MS), and a bioelectronic nose. The sensory evaluation indicated that the acceptability and flavor deteriorated gradually during post-harvest storage (4 °C) for 6 days. The GC-MS analysis recognized the reduction of freshness by detecting a generation of dimethyl sulfide (DMS) from the headspace of oyster in a refrigerator (4 °C) at 4 days post-harvest. However, the bioelectronic nose incorporating human olfactory receptor peptides with the carbon nanotube field-effect transistor sensed trimethylamine (TMA) from the oyster at 2 days post-harvest with suggesting early recognition of oysters’ quality and freshness deterioration. Given that the bacterial species producing DMS or TMA along with toxins were found in the oyster, the bacterial contamination-driven food deterioration is rapidly monitored using the bioelectronic nose with a targeted non-destructive freshness marker.

Assessment of sulfide production in a full scale wastewater sludge rising main

Production and build-up of sulfide in wastewater systems, especially downstream of rising mains, may lead to severe odour nuisance, toxic environments and high risk of corrosion. Due to increased population migration towards cities and lower area availability for treatment facilities, rising mains for the conveyance of wastewater sludge are becoming more frequent, and research on sulfide build-up in such cases is needed. In this paper the findings of the work carried out in a full scale wastewater sludge rising main, operated during different seasons and under distinct conditions are presented (comprising both the start-up and normal operation stages of the facility). Results showed a sulfide build-up rate of 3.24 g S−2 m−2 d−1 in the summer and of 2.30 g S−2 m−2 d−1 during the winter. The ratio of sulfate reduction to sulfide production (SO4−2/S−2) was of roughly 3 to 1, as expected. Furthermore, obtained results allowed adjusting a second order polynomial empirical equation for the forecasting of sulfide build-up within the sludge rising main. The obtained equation for sludge significantly differs from existing equations obtained for wastewater. Moreover, this work also allowed obtaining new insight into the positive influence of biofilm and hydraulic retention time in the biological sulfide generation, as well as into its variation along the length of the rising main.

Influence of pressure main pumping frequency on sulfide formation rates in sanitary sewers

Controlling pumping frequency at sanitary pressure mains is an effective tool for reducing overall sulfide generation.

Sulfide removal from petrochemical wastewater using catalytic wet air oxidation (CWAO) method

The presence of sulfide in wastewater is by the result of biological, physical and chemical processes which mostly takes place in the submerged portion of the sewage collection networks. The rate of sulfide generation depends on several factors including pH, temperature, concentration of organic materials and nutrients, sulfate concentrations, collection system parameters and performance, and the oxidation reduction potential (ORP). Dissolved sulfide could affect biological processes in wastewater treatment plants. Other problems by hydrogen sulfide emission were corrosion of sewer concrete pipes, release of obnoxious odors to the atmosphere, toxicity to sewer workers or human health, water supply and environment pollution, and economic effects. In this research, the main objective was to remove the sulfide content that present in the petrochemical process plant using Catalytic Wet Air Oxidation (CWAO) method.This research was done initially by collecting the wastewater form petrochemical plant. It was followed by the developement of the experimental system in the laboratory to run the preliminary study and the data obtained was use in screening study to detemine the best condition of sulfide removal. The best condition suggested then was optimized using Central Composite Design (CCD) method as a response surface methodology. Three independent factors such as temperature, residence time and catalyst loading that affect the degradation of sulfide are investigated using the 23 factorial analysis. Some of the independent factors were shown to have significant effect on sulfide removals (%). After removing the nonsignificant variables from the model, response surface method was used to obtain the optimum conditions and optimized using central composite design. 13 experiments with 2 factors were designed. These factors (or variables) were: the temperature and the residence time. A full-quadratic polynomial equation between the percentage of sulfide removal (as the response) and the studied parameters are established. The optimum ranges of variables were: 42.5°C for the temperature and 12.5 minutes for the residence time

Hydrogen Sulfide Generation Inhibited by Sulfate-reducing Bacteria using Hydrotalcite as a Sulfate Ion Adsorbent

Hydrogen Sulfide Generation Inhibited by Sulfate-reducing Bacteria using Hydrotalcite as a Sulfate Ion Adsorbent