Denitrifying Sulfide Removal Research Articles

Nitrogen removal from low C/N wastewater in a novel Sharon&DSR (denitrifying sulfide removal) reactor

Denitrification reactions commonly remove nitrate and other reactive nitrogen (Nr) from wastewater. The C/N ratio indicates the sufficiency of organic carbons to drive heterotrophic denitrification; a low C/N ratio frequently leads to poor denitrification performance in wastewater treatment. This study proposed and tested a novel Sharon&DSR (denitrifying sulfide removal) process, with nitrite generated by the Sharon reactions and sulfide from sulfur-reducing reactions for promoting the following nitrite-based denitrification and denitrifying sulfide removal (DSR) process. The present reactor can remove nitrate at an efficiency of 97.7 %−93.5 % at an influent C/N ratio of 0.646–0.737 over a 96-d continuous-flow test. The microbial community study reveals the functional strains corresponding to individual groups of critical reactions. The stoichiometry analysis reveals the potential to apply the nitrite-based DSR process for Nr removal from ultra-low C/N (<0.64) wastewaters, experimentally demonstrated in the present study with a C/N ratio of 0.16–0.39.

A novel intra- and extracellular distribution pattern of elemental sulfur in Pseudomonas sp. C27-driven denitrifying sulfide removal process

Pseudomonas sp. C27 can achieve the conversion of toxic sulfide to economical elemental sulfur (S0) with various electron acceptors. In this study the distribution pattern of S0 produced by C27 in denitrifying sulfide removal (DSR) process was explored. The SEM observation identified that the particle size of the biogenic S0 was at micron level. Strikingly, a novel distribution pattern of S0 was revealed that the produced S0 was not directly secreted extracellularly, but be stored temporarily in the cell interior. Pyrolysis at 65 °C for 20 min were recommended prior to S0 recovery, which could maximize the separation of extracellular polymeric substances (EPS) from C27. Furthermore, the effects of N/S molar ratio, initial sulfide concentration, and micro-oxygen condition were investigated to improve the production of S0 by C27. The highest S0 production was obtained at S/N of 3 and anaerobic condition seemed to favor the S0 production by C27. This study would provide a theoretical support for highly efficient sulfide removal as well as S0 recovery in sulfide-laden wastewater treatment.

Bio-augmentation of the filler-enhanced denitrifying sulfide removal process in expanded granular sludge bed reactors

Sulfur- and nitrogen-containing organic industrial wastewaters, which primarily result from several processes, including pharmaceutical, slaughter, papermaking, and petrochemical processes, are typical examples of refractory wastewaters. To ensure resource utilization, sulfur compounds at high concentrations in such wastewaters can be converted to elemental sulfur through specific methods. Specifically, the denitrifying sulfide removal (DSR) process can be employed to effectively recover elemental sulfur via biological sulfide oxidation, and reportedly, bio-augmentation presents as an effective strategy by which the challenges that limit the application of the DSR process can be overcome. However, the bacterial loss resulting from microorganism activity inhibition owing to toxic effect of high sulfide concentration as well as the complexity of the organic matter (carbon source) in actual wastewater environments reduce the actual elemental sulfur production rate. In this regard, the bio-augmentation effect of adding fillers under complex carbon source conditions was studied. The structure and function of the microbial community on the surface of the fillers were also analysed to reveal the internal factors that contributed to the increased efficiency of elemental sulfur generation. The results obtained showed that relative to the control, elemental sulfur generation increased 1.5- and 2-fold following the addition of fillers and fillers with microbial inoculants, respectively. Further, in the reactor with the added filler, the dominant bacteria in the biofilm on the filler surface were Pseudomonas and Azoarcus, while in reactor with added fillers plus microbial inoculates, the dominant bacteria in the biofilm on the filler surface were Pseudomonas and Arcobacter. These findings indicated that bio-augmentation promoted the expression of sulfur oxidation functional genes. Furthermore, adding Pseudomonas sp. gs1 for bio-augmentation improved the impact load resistance of the biofilm on the surface of the filler, leading to the rapid restoration of the elemental sulfur generation rate after the impact.

In-situ utilizing the produced electricity to regulate substrate conversion in denitrifying sulfide removal microbial fuel cells

A denitrifying sulfide removal microbial fuel cell, incorporated with a capacitor and run in an alternate charging and discharging mode, was developed to in-situ utilize the produced electricity. The switching interval, external resistance distribution and temperature were used to adjust substrates conversion via regulating electrode potentials. The switching interval of 10 min favored the formation of sulfur and gaseous nitrogen. Adjusting the external resistances via the constant anode potential method was a feasible measure for regulating the cathode potential and promoting nitrate reduction, achieving a total nitrogen removal rate of 16.5 ± 0.8 g N/(m3 d) and a gaseous nitrogen formation percent of 32.2 ± 1.5%. 30 °C favored gaseous nitrogen formation while 10 °C and 40 °C benefited sulfur formation. In-situ utilization of the produced electricity shifted the microbial community structure. This work provided a novel approach to regulate the substrate conversion by in-situ utilizing the produced electricity.

Manipulating denitrifying sulfide removal of Pseudomonas sp. C27 with nitrite as sole nitrogen source: Shotgun proteomics analysis

Pseudomonas sp. C27 can effectively conduct denitrifying sulfide removal (DSR) reactions via autotrophic denitrification, heterotrophic denitrification and coupled-cycle pathway. This study is the first to cultivate strain C27 using nitrite as the sole nitrogen source, and to conduct shotgun proteomics analysis and investigate the characteristics of DSR growth of strain C27 with nitrate or nitrite as sole nitrogen source. Shotgun proteomics analysis identified a total of 42 specially expressed proteins of C27 in the nitrite medium, based on which, together with chemical analysis data, a supplementary pathway of sulfur metabolism for C27 from sulfate to thiosulfate via intermediate adenosine-5′-phosphosulfate and 3′-phosphoadenosine-5′-phosphosulfate was proposed. Based on the newly revised scheme, the use of nitrite as sole nitrogen source expands the assessible regime of DSR reactions by C27 and provides the potential to recover renewable chemicals such as pyruvate and succinate from the coupled-cycle pathway.

Nutrient Removal Process and Cathodic Microbial Community Composition in Integrated Vertical-Flow Constructed Wetland - Microbial Fuel Cells Filled With Different Substrates.

An integrated vertical-flow constructed wetland-microbial fuel cell system (CW-MFC), consisting of an up-flow chamber and a down-flow chamber, was constructed to treat synthetic sewage wastewater. The performance of CW-MFCs filled with different substrates [i.e., ceramsite (CM-A), quartz (CM-B), and zeolite (CM-C) granules] under various hydraulic retention times (HRTs, 7.6, 4.0, and 2.8 d) was evaluated. Efficient and stable nitrogen (N) and phosphorus (P) removals were observed in CM-A under different HRTs, while the voltage outputs of the CW-MFCs was greatly reduced as the HRTs decreased. With an HRT of 2.8 d, the ammonium (NH4+-N) and orthophosphate (PO43–-P) removal efficiencies in CM-A were as high as 93.8 and 99.6%, respectively. Bacterial community analysis indicates that the N removal in the cathode area of CM-A could potentially benefit from the appearance of nitrifying bacteria (e.g., Nitrosomonas and Nitrospira) and relatively high abundance of denitrifiers involved in simultaneous nitrification and denitrification (e.g., Hydrogenophaga, Zoogloea, and Dechloromonas) and denitrifying sulfide removal (e.g., Thauera). Additionally, the difference in N removal efficiency among the CW-MFCs could be partly explained by higher iron (Fe) content in milled ceramsite granules and higher abundance of denitrifiers with nitrate reduction and ferrous ions oxidation capabilities in CM-A compared with that in CM-B and CM-C. Efficient PO43–-P removal in CM-A was mainly ascribed to substrate adsorption and denitrifying phosphorus (P) removal. Concerning the substantial purification performance in CM-A, ceramsite granules could be used to improve the nutrient removal efficiency in integrated vertical-flow CW-MFC.

Performance of a novel IAHD-DSR process with methane and sulfide as co-electron donors

A novel integrated autotrophic and heterotrophic denitrification- denitrifying sulfide removal (IAHD-DSR) process was established in this study for biogas desulfurization to simultaneously remove nitrogen in wastewater. The study demonstrated that the system could utilize methane and sulfide as co-electron donors to replace organic carbon source in IAHD process. Three batch tests (B1, B2 and B3) were set up with IAHD sludge to explore how the novel process works. According to mass balance in B2, methane oxidation and sulfide oxidation contributed 18.75 % and 71.25 % to nitrate removal, respectively; however, the contribution of methane oxidation to total nitrogen (TN) removal reached 84.36 %. Sulfide was mainly responsible for the reduction of nitrate to nitrite, while the methane was for nitrite to nitrogen gas in the presence of insufficient sulfide as electron donors. The TN removal in B2 was almost the same as in normal IAHD-DSR process B3-C. The functional genes mcrA and pmoA responsible for methane oxidation were detected in all three batches, with the abundance of 2.23 ×106 copies/(g dry soil) for mcrA in B1 being the highest in three batches. The sulfide addition in B2 increased the abundance of gene pmoA, indicating the enhancement of nitrite reduction coupled with methane oxidation.

Recirculation ratio regulates denitrifying sulfide removal and elemental sulfur recovery by altering sludge characteristics and microbial community composition in an EGSB reactor

Expanded granular sludge blanket (EGSB) is regarded as a promising reactor to carry out denitrifying sulfide removal (DSR) and elemental sulfur (S0) recovery. Although the recirculation ratio is an essential parameter for EGSB reactors, how it impacts the DSR process remains poorly understood. Here, three lab-scale DSR-EGSB reactors were established with the different recirculation ratios (3:1, 6:1 and 9:1) to evaluate the corresponding variations in pollutant removal, S0 recovery, anaerobic granular sludge (AGS) characteristics and microbial community composition. It was found that an intermediate recirculation ratio (6:1) could facilitate long-term reactor stability. Adequate recirculation ratio could enhance S0 recovery, but an excessive recirculation ratio (9:1) was likely to cause AGS fragmentation and biomass loss. The S0 desorbed more from sludge at higher recirculation ratios, probably due to the enhanced hydraulic disturbance caused by the increased recirculation ratios. At the low recirculation ratio (3:1), S0 accumulation as inorganic suspended solids in AGS led to a decrease in VSS/TSS ratio and mass transfer efficiency. Although typical denitrifying and sulfide-oxidizing bacteria (e.g., Azoarcus, Thauera and Arcobacter) were predominant in all conditions, facultative and heterotrophic functional bacteria (e.g., Azoarcus and Thauera) were more adaptable to higher recirculation ratios than autotrophs (e.g., Arcobacter, Thiobacillus and Vulcanibacillus), which was conducive to the formation of bacterial aggregates to response to the increased recirculation ratio. The study revealed recirculation ratio regulation significantly impacted the DSR-EGSB reactor performance by altering AGS characteristics and microbial community composition, which provides a novel strategy to improve DSR performance and S0 recovery.

Nitrogen and sulfur metabolisms of Pseudomonas sp. C27 under mixotrophic growth condition

Pseudomonas sp. C27 is a facultative autotrophic bacterium that can grow mixotrophically to undergo denitrifying sulfide removal (DSR) reactions with both organic matters and sulfide as electron donors. A detailed understanding of how the C27 strain simultaneously removes nitrogen, sulfur and carbon from water is critical for optimal DSR process design and implementation. This study is the first to reveal the pathways of nitrogen and sulfur metabolisms, identifying a total of 47 proteins that are related to the nitrogen metabolism and seven proteins to the sulfur metabolism of strain C27 using iTRAQ and LC-MS/MS techniques. The proposed pathway of nitrogen metabolism for strain C27 from external nitrate to nitrogen gas and phosphate with a coupled ammonia cycle is based on the identified proteins, and suggests that nitrate was not essential for nitrogen metabolism and could be replaced by nitrite as the sole nitrogen source for C27.

Simultaneous sulfide removal, nitrogen removal and electricity generation in a coupled microbial fuel cell system

A coupled microbial fuel cell (MFC) system, consisting of a nitrifying sulfide removal MFC and a denitrifying sulfide removal MFC, was assembled to simultaneously treat ammonium and sulfide in wastewater. It provided a promising approach to recover electricity from wastewater containing sulfide and ammonium. Considering both substrate removal and electricity generation performance, the desirable feeding S/N molar ratio was deemed as 3 and the optimal temperature was found to be 30 °C. Under this condition, the coupled MFC achieved a sum coulomb production of 554.8 C/d, a total nitrogen removal efficiency of 58.7 ± 1.3% and a sulfur production percent of 27.4 ± 0.4–33.3 ± 0.9%. The introduction of nitrifiers and electroactive oxic microbes from the oxic-cathode chamber into the anoxic-cathode chamber favored nitrogen removal.

Mitigating adverse impacts of varying sulfide/nitrate ratios on denitrifying sulfide removal process performance

Complete removal of nitrogen, sulfur and carbon in wastewaters by denitrifying sulfide removal (DSR) process can be achieved at stoichiometry sulfide to nitrate ratio (S/N) of 1:1 in expanded granular sludge bed reactor. Wastewaters with varying S/N ratios can adversely impact the DSR performances with deterioration of synergetic cooperation between autotrophic and heterotrophic denitrifiers. DO (dissolved oxygen) serves effectively as supplementary electron receiver for sulfide oxidation, leaving more nitrate for heterotrophic denitrifiers to utilize acetate. The optimal oxygen to sulfide molar ratio (DO/S) is 0.5:1 for complete removal of sulfide, nitrate and acetate at different S/N ratios. The heterotrophic denitrification rate was decreased to 0.03 ± 0.002, 0.24 ± 0.011 and 0.35 ± 0.027 NO3−-N·h−1·gVSS−1 at S/N ratio of 5:2, 5:5 and 5:8, respectively, when DO/S of 3:1 was performed. This optimal condition was proposed as an easy-to-implement control criterion for subsiding the adverse impact by varying S/N ratios in handling real wastewaters.

Interactions of functional bacteria and their contributions to the performance in integrated autotrophic and heterotrophic denitrification

Compared to autotrophic and heterotrophic denitrification process, the Integrated autotrophic and heterotrophic denitrification (IAHD) has wider foreground of applications in the condition where the organic carbon, nitrate and inorganic sulfur compounds usually co-exist in the actual wastewaters. As the most well-known IAHD process, the denitrifying sulfide removal (DSR) could simultaneously convert sulfide, nitrate and organic carbon into sulfur, dinitrogen gas and carbon dioxide, respectively. Thus, systematical metabolic functions and contributions of autotrophic and heterotrophic denitrifiers to the IAHD-DSR performance became an problem demanding to be promptly studied. In this work, three upflow anaerobic sludge bioreactors (UASBs) were individually started up in autotrophic (a-DSR), heterotrophic (h-DSR) and mixotrophic conditions (m-DSR). Then, the operating conditions of each bioreactor were switched to different trophic conditions with low and high sulfide concentrations in the influent (200 and 400 mg/L). The removal efficiencies of sulfide, nitrate and acetate all reached 100% in all three bioreactors throughout the operational stages. However, the sulfur transformation ratio ranged from 34.5% to 39.9% at the low sulfide concentration and from 76.8% to 86.7% at the high sulfide concentration in the mixotrophic conditions. Microbial community structure analyzed by the Illumina sequencing indicated that Thiobacillus, which are autotrophic sulfide-oxidizing, nitrate-reducing bacteria (a-soNRB), was the dominant genus (81.3%) in the a-DSR bioreactor. With respect to the mixotrophic conditions, at low sulfide concentration in the m-DSR bioreactor, Thiobacillus (a-soNRB) and Thauera, which are heterotrophic nitrate-reducing bacteria (hNRB), were the dominant genera, with percentages of 48.8% and 14.9%, respectively. When the sulfide concentration in the influent was doubled, the percentage of Thiobacillus decreased by approximately 9-fold (from 48.8% to 5.4%), and the total percentage of Azoarcus and Pseudomonas, which are heterotrophic sulfide-oxidizing, nitrate-reducing bacteria (h-soNRB), increased by approximately 6-fold (from 10.1% to 59.4%). Therefore, the following interactions between functional groups and their functional mechanisms in the DSR process were proposed: (1) a-soNRB (Thiobacillus) and hNRB (Thauera) worked together to maintain the performance under the low sulfide concentration; (2) h-soNRB (Azoarcus and Pseudomonas) took the place of a-soNRB and worked together with hNRB (Thauera and Allidiomarina) under the high sulfide concentration; and (3) a-soNRB (such as Thiobacillus) were possibly the key bacteria and may have contributed to the low sulfur transformation, and h-soNRB may be responsible for the high sulfur transformation in the DSR process.

Interactive effect of electrode potential on pollutants conversion in denitrifying sulfide removal microbial fuel cells

The denitrifying sulfide removal microbial fuel cell (MFC) provided an approach for treatment of wastewater containing both sulfide and nitrogenous compounds, but the production of sulfate and nitrite need to be prevented. The interactive effect of electrode potential on sulfide and nitrate conversion was investigated using potentiostatic three-chamber MFC. Both abiotic and biotic processes involved in anodic sulfate formation. Rising anode potential led to an increase of sulfide removal rate and a decrease of sulfur formation percent. The suitable anode potential favoring both sulfide removal and sulfur recovery ranged from −188 mV to −146 mV. The nitrate removal rate and gaseous nitrogen formation percent showed an increase followed by a decrease along with the rise of cathode potential. The suitable cathode potential favoring both nitrate removal and gaseous nitrogen formation ranged from −181 mV to −125 mV. Regulating cathode potential through varying the external resistance was feasible, achieving the optimal sulfur formation percent (32.4 ± 1.9%) and gaseous nitrogen formation percent (92.5 ± 0.3%) at a cathode potential of −139 ± 37 mV. The potentiostatic three-chamber MFC is a suitable configuration for investigating the effect of electrode potential on pollutant conversion because its uncontrolled electrode could simulate the electron driving force situation occurring in a MFC.

Regulation of influent sulfide concentration on anaerobic denitrifying sulfide removal

ABSTRACTThe objective of this study is to find a comprehensive regulation for sulfide removal and elemental sulfur transformation based on the denitrifying sulfide removal process. The experiment was performed based on several influent sulfide concentrations (150–600 mg/L) and nitrate-to-sulfur (N/S) molar ratios (0.5–2.0) at reaction times of 24 and 48 h. Sulfide and nitrate removals were mainly dependent on the influent sulfide concentration at sulfide concentrations of 150–200 and 400–600 mg/L, but on the N/S ratio at sulfide concentrations of 250–350 mg/L. Up to 99.7% and 93.8% of sulfide and nitrate were removed, respectively, with 26.5% of elemental sulfur formed at sulfide concentrations of 250–350 mg/L (N/S of 1.0). Only 4–9.4% of elemental sulfur was formed, with sulfide and nitrate removals of 99.9% and 98.7%, respectively, at sulfide concentrations of 150–200 mg/L. Meanwhile, 46.9–94.7% of sulfate was formed with a nitrogen gas conversion rate of 18.2–57.1%. Fewer microorganisms were detected by fluorescence in situ hybridization (FISH) at high sulfide concentrations of 400–600 mg/L, suggesting that the processes of anaerobic denitrification and desulfurization were inhibited.

Power recovery coupled with sulfide and nitrate removal in separate chambers using a microbial fuel cell

A novel denitrifying sulfide removal microbial fuel cell (MFC), using sulfide and nitrate separately as the anodic electron donor and the cathodic electron acceptor, was explored to recover power coupled with pollutants removal. Power recovery coupled with sulfide and nitrate removal in this MFC was achieved under different buffers, hydraulic retention times (HRTs) and temperatures. Bicarbonate was deemed as a suitable alternative buffer to phosphate in this MFC, obtaining comparable power recovery and pollutant removal loadings but without potential secondary pollution. Shortening HRT from 5.54h to 2.27h or increasing temperature from 20°C to 30°C favored both power recovery and pollutants removal. The suitable HRT and temperature for this MFC were found to be 2.77h and 30°C, achieving a power density of 2.80±0.05W/m3 NC, a sulfide removal loading of 1.07±0.03kg S/(m3NCd), and a nitrate removal loading of 14.4±0.3gN/(m3NCd). Shortening HRT and lowering temperature would be beneficial to suppress sulfate formation, but more than 71.9% of sulfide was oxidized to sulfate in current study.

Enhanced performance of denitrifying sulfide removal process at high carbon to nitrogen ratios under micro-aerobic condition

The success of denitrifying sulfide removal (DSR) processes, which simultaneously degrade sulfide, nitrate and organic carbon in the same reactor, counts on synergetic growths of autotrophic and heterotrophic denitrifiers. Feeding wastewaters at high C/N ratio would stimulate overgrowth of heterotrophic bacteria in the DSR reactor so deteriorating the growth of autotrophic denitrifiers. The DSR tests at C/N=1.26:1, 2:1 or 3:1 and S/N =5:6 or 5:8 under anaerobic (control) or micro-aerobic conditions were conducted. Anaerobic DSR process has <50% sulfide removal with no elemental sulfur transformation. Under micro-aerobic condition to remove <5% sulfide by chemical oxidation pathway, 100% sulfide removal is achieved by the DSR consortia. Continuous-flow tests under micro-aerobic condition have 70% sulfide removal and 55% elemental sulfur recovery. Trace oxygen enhances activity of sulfide-oxidizing, nitrate-reducing bacteria to accommodate properly the wastewater with high C/N ratios.

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

A mathematical model of carbon, nitrogen and sulfur removal (C-N-S) from industrial wastewater was constructed considering the interactions of sulfate-reducing bacteria (SRB), sulfide-oxidizing bacteria (SOB), nitrate-reducing bacteria (NRB), facultative bacteria (FB), and methane producing archaea (MPA). For the kinetic network, the bioconversion of C-N by heterotrophic denitrifiers (NO3−→NO2−→N2), and that of C-S by SRB (SO42−→S2−) and SOB (S2−→S0) was proposed and calibrated based on batch experimental data. The model closely predicted the profiles of nitrate, nitrite, sulfate, sulfide, lactate, acetate, methane and oxygen under both anaerobic and micro-aerobic conditions. The best-fit kinetic parameters had small 95% confidence regions with mean values approximately at the center. The model was further validated using independent data sets generated under different operating conditions. This work was the first successful mathematical modeling of simultaneous C-N-S removal from industrial wastewater and more importantly, the proposed model was proven feasible to simulate other relevant processes, such as sulfate-reducing, sulfide-oxidizing process (SR-SO) and denitrifying sulfide removal (DSR) process. The model developed is expected to enhance our ability to predict the treatment of carbon-nitrogen-sulfur contaminated industrial wastewater.

Denitrifying sulfide removal process on high-tetracycline wastewater

Antibiotics wastewater from tetracycline (TC) production unit can have high levels of chemical oxygen demand, ammonium and sulfate and up to a few hundreds of milligrams per liter of TC. Denitrifying sulfide removal (DSR) process is set up for simultaneously removal of sulfur, carbon and nitrogen from waters. The DSR process was for the first time studied for treating TC wastewaters. The TC stress has no adverse effects on removal rates of nitrate and acetate; however, it moderately deteriorated sulfide removal rates and S0 accumulation rates when the concentration is higher than 100mgL−1 TC. The Thauera sp., and Pseudomonas sp. present the heterotrophs and Sulfurovum sp. presented the autotroph for the present DSR reactions. The high tolerance of TC stress by the tested consortium was explained by the excess production of extracellular polymeric substances at high TC concentration, which can bind with TC for minimizing its inhibition effects.

Efficient regulation of elemental sulfur recovery through optimizing working height of upflow anaerobic sludge blanket reactor during denitrifying sulfide removal process

In this study, two lab-scale UASB reactors were established to testify S0 recovery efficiency, and one of which (M-UASB) was improved from the previous T-UASB by shortening reactor height once S2− over oxidation was observed. After the height was shortened from 60 to 30cm, S0 recovery rate was improved from 7.4% to 78.8%, and while, complete removal of acetate, nitrate and S2− was simultaneously maintained. Meanwhile, bacterial community distribution was homogenous throughout the reactor, with denitrifying sulfide oxidization bacteria predominant, such as Thauera and Azoarcus spp., indicating the optimized condition for S0 recovery. The effective control of working height/volume in reactors plays important roles for the efficient regulation of S0 recovery during DSR process.

Microbial community structure and function in response to the shift of sulfide/nitrate loading ratio during the denitrifying sulfide removal process

Influence of acetate-C/NO3−-N/S2− ratio to the functional microbial community during the denitrifying sulfide removal process is poorly understood. Here, phylogenetic and functional bacterial community for elemental sulfur (S0) recovery and nitrate (NO3−) removal were investigated with the switched S2−/NO3− molar ratio ranged from 5/2 to 5/9. Optimized S2−/NO3− ratio was evaluated as 5/6, with the bacterial genera predominated with Thauera, Enterobacter, Thiobacillus and Stappia, and the sqr gene highly expressed. However, insufficient or high loading of acetate and NO3− resulted in the low S0 recovery, and also significantly modified the bacterial community and genetic activity. With S2−/NO3− ratio of 5/2, autotrophic S2− oxidization genera were dominated and NO3− reduction activity was low, confirmed by the low expressed nirK gene. In contrast, S2−/NO3− ratio switched to 5/8 and 5/9 introduced diverse heterotrophic nitrate reduction and S0 over oxidization genera in accompanied with the highly expressed nirK and sox genes.