Prospect of denitrifying anaerobic methane oxidation (DAMO) application on wastewater treatment and biogas recycling utilization.

Old-fashioned wastewater treatments for nitrogen depend on heterotrophic denitrification process. It would utilize extra organic carbon source as electron donors when the C/N of domestic wastewater was too low to ensure heterotrophic denitrification process. It would lead to non-compliance with carbon reduction targets and impose an economic burden on wastewater treatment. Denitrifying anaerobic methane oxidation (DAMO), which could utilize methane serving as electron donors to replace traditional organic carbon (methanol or sodium acetate), supplies a novel approach for wastewater treatment. As the primary component of biogas, methane is an inexpensive carbon source. With anaerobic digestion becoming increasingly popular for sludge reduction in wastewater treatment plants (WWTPs), efficient biogas utilization through DAMO can offer an environmentally friendly option for in-situ biogas recycling. Here, we reviewed the metabolic principle and relevant research for DAMO and biogas recycling utilization, outlining the prospect of employing DAMO for wastewater treatment and biogas recycling utilization in WWTPs. The application of DAMO provides a new focal point for enhancing efficiency and sustainability in WWTPs.

A novel sulfide-driven denitrification methane oxidation (SDMO) system: Operational performance and metabolic mechanisms.

Microbial denitrification is a crucial biological process for the treatment of nitrogen-polluted water. Traditional denitrification process consumes external organic carbon leading to an increase in treatment costs. We developed a novel sulfide-driven denitrification methane oxidation (SDMO) system that integrates autotrophic denitrification (AD) and denitrification anaerobic methane oxidation (DAMO) for cost-effective denitrification and biogas utilization in situ. Two SDMO systems were operated for 735 days, with nitrate and nitrite serving as electron acceptors, to explore the performance of sewage denitrification and characterize metabolic mechanisms. Results showed SDMO system could reach as high as 100% efficiency of nitrogen removal and biogas desulfurization without an external carbon source when HRT was 10 days and inflow nitrogen concentrations were 50-100 mgN·L-1. Besides, nitrate was a preferable electron acceptor for SDMO system. Biogas not only enhanced nitrogen removal but also intensified the DAMO, nitrogen removed through DAMO contribution doubled as original period from 2.9 mgN·(L·d)-1 to 6.2 mgN·(L·d)-1, and the ratio of nitrate removal through AD to DAMO was 1.2:1 with nitrate as electron acceptor. While nitrogen removed almost all through AD contribution and DAMO was weaken as before, the ratio of nitrate removal through AD to DAMO was 21.2:1 with nitrite as electron acceptor. Biogas introduced into SDMO system with nitrate inspired the growth of DAMO bacteria Candidatus Methylomirabilis from 0.3% to 19.6% and motivated its potentiality to remove nitrate without ANME archaea participation accompanying with gene mfnE upregulating ∼100 times. According to the reconstructed genome from binning analysis, the dramatically upregulated gene mfnE was derived from Candidatus Methylomirabilis, which may represent a novel metabolism pathway for DAMO bacteria to replace the role of archaea for nitrate reduction.

The interaction between Pseudomonas C27 and Thiobacillus denitrificans in the integrated autotrophic and heterotrophic denitrification process.

Compared to autotrophic and heterotrophic denitrification process, the integrated autotrophic and heterotrophic denitrification (IAHD) shows wider foreground of applications in the actual wastewaters with organic carbon, nitrogen and sulfur co-existing. The efficient co-removal of sulfur, nitrogen, and carbon in the IAHD system is guaranteed by the interaction between heterotrophic and autotrophic denitrificans. In order to further explore the interaction between functional bacteria, Pseudomonas C27 and Thiobacillus denitrifcans were selected as typical heterotrophic and autotrophic bacteria, and their characteristics metabolic responses to different sulfide concentrations were studied. Pseudomonas C27 had higher metabolic activity than T. denitrificans in the IAHD medium with sulfide concentration of 3.12-15.62 mmol/L. Moreover, the fastest sulfide removal rate (0.35 mmol/L·h) was achieved with a single inoculation of Pseudomonas C27. Meanwhile, in mixed inoculant conditions, the interaction between Pseudomonas C27 and T. denitrificans (P:T = 3:1, P:T = 1:1 and P:T = 1:3) yielded the highest sulfide removal efficiency (more than 85%) when sulfide concentration was 6.25-12.5 mmol/L. Additionally, the sulfide removal rate increased with the inoculation proportion of Pseudomonas C27. Thus, this apparent interaction provided a theoretical basis for further understanding and guidance on the efficient operation of IAHD system.

Necrotizing Fasciitis Associated with Hailey-Hailey Disease: A Rare Case.

Necrotizing fasciitis (NF) is a rare and life-threatening infection of soft tissue characterised by rapid and extensive destruction of the skin, subcutaneous fat, and fascia. Early diagnosis of NF is challenging, and it can be very difficult to distinguish NF from other infectious diseases of skin and subcutaneous tissue. Imaging studies and laboratory investigations are crucial diagnostic means for NF. We diagnosed a case of NF with multiple organ dysfunction and septic shock, and this is the first case of NF associated with Hailey-Hailey disease (HHD) to our knowledge. Clinicians should be alert to signs and symptoms of NF in HHD and other skin diseases with damaged skin barrier function such as pemphigus, pemphigoid, and all kinds of ulcers, especially in diabetic and immunosuppressed patients. Key Words: Necrotizing fasciitis, Genodermatosis, Hailey-Hailey disease.

A land-use decision approach integrating thermal regulation, stormwater management, and economic benefits based on urbanization stage identification.

Driven by global climate change and urbanization, urban heat island (UHI) and urban storm flood (USF) have become the most frequent and influential hazards in recent decades. Land-use optimization can effectively cope with these hazards. However, the trade-offs between multi-hazard mitigation and economic development impose many limitations in practice. Furthermore, current region-based optimization methods no longer meet the precise management demand, and both subdivision and spatial heterogeneity identification have the potential for wider applicability. Hence, a systematic integration of climate adaptation and urban construction through land-use planning is urgently required. This paper proposes a new land-use decision approach for improving climate adaptability of urbanization. This approach involves multi-objective optimization, spatial subdivision, and urbanization stage identification, which enable the simultaneous achievement of environmental and economic benefits. Taking Xiamen as case study, the results showed that excessive pursuit of land economic output (LEO) limits the chance of mitigating UHI and USF. Improving the LEO per unit area of construction land could disrupt the link between land exploitation and the increasing side effects of climate hazards. Future urbanization hotspots in Xiamen will likely emerge at the urban fringe in Tong'an District and Xiang'an District. Within each developing unit, the upper limit of construction land was 81.06 hm2 and the green space was recommended to be 7.29-21.94 hm2. Construction land and bare land contributed most to UHI and USF, while forest and grassland were highly efficient in heat and runoff mitigation. The developed approach proved to be effective and practicable, especially for reducing the impacts of extreme UHI and USF.

The Diagnostic and Prognostic Value of Plasma Galectin 3 in HFrEF Related to the Etiology of Heart Failure.

Aim: The aim of present study is to evaluate the diagnostic and prognostic value of plasma galectin 3 (Gal-3) for HF originating from different causes. Methods: We investigated the plasma levels and expression of Gal-3 in cardiac tissues in two transgenic (TG) strains of mice with cardiomyocyte-restricted overexpression of either ß2- adrenergic receptor (ß2- AR TG) or Mammalian sterile 20-like kinase 1 (Mst1-TG) in the present study. Additionally, 166 patients suffering from heart failure with reduced ejection fraction (HFrEF) in two hospitals within the Shaanxi province were examined in this study. All these patients were treated according to the Chinese HF guidelines of 2014; subsequently, they were followed up for 50 months, and we analyzed the prediction value of baseline Gal-3 to endpoints in these patients. Results: Gal-3 was localized in the cytoplasm and nucleus of cardiomyocytes, often formed aggregates in Mst1-TG mice. Extracellular Gal-3 staining was uncommon in Mst1-TG hearts. However, in ß2-AR TG mice, although Gal-3 was also expressed in myocardial cells, it was more highly expressed in interstitial cells (e.g., fibroblasts and macrophages). Plasma Gal-3 was comparable between nTG and Mst1-TG mice. However, plasma Gal-3 was higher in ß2-AR TG mice than in nTG mice. In the cohort of HFrEF patients, the median plasma Gal-3 concentration was 158.42 pg/mL. All participants were divided into two groups according to Gal-3 levels. Patients with Gal-3 concentrations above the median were older, and had lower plasma hemoglobin, but higher plasma creatinine, tissue inhibitor of metalloproteinases 1 (TIMP-1), left ventricular end systolic diameter (LVESD), left ventricular end-systolic volumes (LVESV) and end-diastolic, as well as left ventricular end-diastolic volumes (LVEDV). Spearman correlation analysis revealed that Gal-3 was positively correlated with TIMP-1 (r = 0.396, P < 0.001), LVESV (r = 0.181, P = 0.020) and LVEDV (r = 0.190, P = 0.015). The 50-month clinical follow-up revealed 43 deaths, 97 unplanned re-hospitalizations, and 111 composite endpoint events. Cox analysis demonstrated that although Gal-3 did not provide any prognostic value in either total-HF subjects or coronary-heart-disease (CHD) patients, it did provide prognostic value in non-CHD patients. Conclusion: Although plasma Gal-3 is associated with TIMP-1 and echocardiographic parameters, the diagnostic and prognostic value of Gal-3 in HFrEF is determined by the etiology of HF.

Heterotrophic sulfide-oxidizing nitrate-reducing bacteria enables the high performance of integrated autotrophic-heterotrophic denitrification (IAHD) process under high sulfide loading.

Micro-aerobic enhancement technology has been developed as an effective tool to enhance simultaneous removal of sulfide, nitrate and organic carbon during the integrated autotrophic-heterotrophic denitrification (IAHD) process under high loading; however, its mechanism of enhancement for functional bacteria remains ambiguous. In this study, we discovered that heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) are responsible for enhancing IAHD performance under micro-aerobic conditions with high sulfide loading. In a continuous IAHD bioreactor, aeration rate of 2.6 mL min-1·L-1 promoted 2 to 4 times higher removal efficiencies of sulfide, nitrate and acetate with an influent sulfide concentration of 18.75 mmol/L. Metagenomic analysis revealed that trace oxygen stimulated the abundance of genes responsible for sulfide oxidation (sqr, glpE, pdo, sox and cysK), which were upregulated by 15.2%-129.9%, and the genes encoding nitrate reductase were up-regulated by 67.4%. The increased acetate removal efficiency was attributed to upregulation of ack, pta and TCA cycle related genes. The h-NRB Pseudomonas, Azoarcus, Thauera and Halomonas were detected and regarded as h-soNRB in our bioreactor. According to Illumina MiSeq sequencing, these genera were absolutely dominant in the micro-aerobic microbial community at relative abundances ranging from 82.72% to 90.84%. The sulfide, nitrate and acetate removal rates of Pseudomonas C27, a typical h-soNRB, were at least 10 times higher under micro-aerobic conditions than under anaerobic conditions. Besides, the sulfur, nitrogen and carbon metabolic network was constructed based on the Pseudomonas C27 genome. The pdo and cysK genes found in this strain may be the most advantageous for autotrophic sulfide oxidizing nitrate reducing bacteria (a-soNRB), which are closely related to the high-efficiency sulfide, nitrate and acetate removal performance under high sulfide concentrations and a limited oxygen supply. In addition, after micro-aerobic cultivation, the anaerobic sulfide loading tolerance of the IAHD bioreactor increased from 18.75 to 37.5 mmol/L with sulfide, nitrate and acetate removal efficiencies increasing 1.5 to 3 times, which suggests that intermittent micro-aeration might be a more economical and efficient regime for high-sulfide IAHD regulation.

The stimulating metabolic mechanisms response to sulfide and oxygen in typical heterotrophic sulfide-oxidizing nitrate-reducing bacteria Pseudomonas C27.

Micro-aeration is an effective tool that helps integrated autotrophic and heterotrophic denitrification process to withstand high sulfide concentration by making heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) prevail. For further understanding of the dominance of h-soNRB, Pseudomonas C27 was selected as the typical bacterium and its metabolic characteristics responding to sulfide and oxygen stimulation were studied. Under high sulfide concentration condition, addition of trace oxygen led to a two-stage sulfide oxidation process, and sulfide oxidation rate in the first stage was 1.4 times more than that under anaerobic condition. According to transcriptome analysis, the pdo gene significantly up-regulated 2.36 and 2.57 times with and without oxygen under stimulation of high sulfide concentration. Additionally, two possible enhanced sulfide removal pathways coping with high sulfide concentration, namely sqr-cysI-gpx-gor-glpE and cysK-gshA-gshB-pdo-glpE, caused by oxygen were proposed in Pseudomonas C27. These findings provide a theoretical basis for locating high-efficiency sulfur oxidase in h-soNRB.

Detection of Prostate Cancer Antigen 3 and Prostate Cancer Susceptibility Candidate in Non-DRE Urine Improves Diagnosis of Prostate Cancer in Chinese Population.

Although prostate biopsy is the gold standard for the diagnosis of prostate cancer, it also leads to high incidence of negative biopsies and the diagnosis of clinically low-risk prostate cancer and the subsequent overtreatment. It remains an unmet need to discover new biomarkers in order to defer the unnecessary biopsies in clinical practice. In this study, we described a new method, LBXexo score, to measure the urine exosomal PCA3/PRAC expression from non-DRE urine as a noninvasive diagnosis to improve the detection rate in Chinese population with a low serum PSA level. First-voided urine samples were collected to isolate exosomes, and exosomal RNAs of PCA3 and PRAC were measured by quantitative reverse transcription PCR. A significant increase in exoPCA3/PRAC was observed in both any-grade and high-grade prostate cancer groups when compared with the biopsy-negative group. Receiver-operating characteristic curve analyses showed that the LBXexo score significantly improved diagnostic performance in predicting biopsy results, with AUCs of 0.723 (p=0.017) and 0.736 (p=0.038) for any-grade and high-grade (GS ≥ 7) prostate cancer, respectively. For high-grade cancer, LBXexo had the negative and positive predictive values of 100% and 27.59%, respectively, and could potentially avoid unnecessary biopsy. This is the first report in Chinese population that demonstrates the predictive value of the exosomal expression of PCA3 and PRAC derived from non-DRE urine in predicting prostate biopsy outcomes. It could be used in clinical practice to make a better informed biopsy decision and avoid unnecessary biopsies in Chinese population.

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.

[Electron Equilibrium Analysis of Integrated Autotrophic and Heterotrophic Denitrification Process Under Micro-aerobic Conditions].

The integrated autotrophic and heterotrophic denitrification (IAHD) process, which can simultaneously degrade sulfide, nitrate, and organic carbon with nitrate as a solo electron acceptor, has gained increasing attention as a key unit in industrial wastewater treatment. Micro-aerobic technology, which introduces trace oxygen as an additional electron acceptor, has been demonstrated as an effective strategy for enhancing the IAHD performance. This study focus on the electronic balance calculation of the IAHD process and reveals for the first time that the IAHD process can efficient proceed with an insufficient supply of electron acceptors (nitrate) under micro-aerobic conditions. In the IAHD batch tests, the highest sulfide, nitrate, and acetate removal efficiencies and rates were obtained with an electronic deletion rate peak at 55.1%. Further sulfide oxidizing batch tests demonstrated that the electronic deletion rates were 18.7% and 38.2% under oxygen contents of 5 mL and 10 mL, respectively, in the biological sulfide oxidizing process. Illumina sequencing was used to analyze the microbial community structure in the sulfide oxidation process and indicated Thiobacillus, Thauera, Mangroviflexus, and Erysipelothrix dominated in all community compositions, in which the relative abundance of Thiobacillus increased with an increase in the electronic deletion rate. This study reveals a potential linkage between the electronic gap and the enhanced IAHD performance, which proves new insights into the simultaneous sulfur, nitrogen, and organic carbon removal process.

Association of rs3783641 single-nucleotide polymorphism in GTP cyclohydrolase 1 gene with post-herpetic neuralgia.

Post-herpetic neuralgia (PHN) is a well-established clinical problem with potential severe personal and socioeconomic implications. GTP cyclohydrolase 1 (GCH1) gene, which encodes the rate-limiting enzyme in tetrahydrobiopterin synthesis, has been strongly implicated to be associated with neuropathic pain in previous animal and human studies. The rs3783641 (T > A) single-nucleotide polymorphism (SNP) in the GCH1 gene is functional. Here we examine the association between rs3783641 and PHN. A total of 292 subjects including 103 PHN patients, 87 herpes zoster (HZ) patients and 102 healthy controls were enrolled in this study. The rs3783641 polymorphisms were detected via the high-resolution melting curve (HRM) method. There were statistical differences between PHN group and the other two groups in genotype distribution (P = 0.029 and 0.017, respectively) and allele frequency (P = 0.032 and 0.005, respectively) of rs3783641. The proportion of subjects with AA genotype in the PHN group was significantly lower compared to HZ group and control group (P = 0.026 and 0.016, respectively). The frequency of A allele was lower in the PHN group than in control group (P = 0.005), and the frequency of T allele in the PHN group was higher than in HZ group and control group (P = 0.001 and 0.003, respectively). The results of this study suggest that the rs3783641 SNP in the GCH1 gene is associated with PHN, and the AA genotype showed a protective effect in PHN.

The microbial zonation of SRB and soNRB enhanced the performance of SR-DSR process under the micro-aerobic condition.

The micro-aerobic condition has proven to effectively enhance the COD removal and elemental sulfur (S0) transformation rate in the sulfate reduction-denitrifying sulfide removal (SR-DSR) process. However, the mechanisms of how micro-aerobic condition enhances S0 transformation remain largely unknown. Therefore in this work an integrated investigation was performed to document the mechanisms and the effect of different startup modes (micro-aerobic startup (termed as mSR-DSR) and anaerobic startup (termed as aSR-DSR)) on bioreactor performance and microbial community dynamics. The results showed that micro-aerobic startup achieved a shorter period to reach a stable performance for SR-DSR, which could be one of the factors affecting the choice of the bioreactor startup mode considering engineering application. For all the tested conditions, removal of nitrate, sulfate and lactate were 100%, >80% and 100%, respectively. The maximum transformation rate of elemental sulfur in mSR-DSR was 57%, which was higher than that in aSR-DSR. The mechanism explorations revealed that micro-aerobic condition not only particularly enriched the sulfide-oxidizing, nitrate-reducing bacteria (soNRB) but also promoted the microbial zonation of sulfate-reducing bacteria (SRB) and soNRB, thereby achieving more S0 transformation in the effluent. Under micro-aerobic condition, SRB were mainly distributed in the bottom and middle part of the reactor, while soNRB were assembled in the top. The relative abundance of soNRB in both aSR-DSR and mSR-DSR notably increased to 41.5% and 23.7% at the top when 5 mL air min-1 Lreactor-1 was applied. Furthermore, the degradation of organic carbon was also accelerated under micro-aerobic condition, possibly due to the enrichment of organic compounds degrading bacteria Bacteroidetes_vadin HA17.

Bioreactor performance and microbial community analysis of autotrophic denitrification under micro-aerobic condition.

Autotrophic denitrification process is an effective strategy for treating sulfide and nitrate-enriched wastewater with low organic carbon. This study determined the sulfide oxidation and nitrate reduction rates and characterized the dominant bacteria and microbial community structure stimulated by micro-aerobic conditions in autotrophic denitrification system. With gradually increased sulfide concentration, the sulfide removal rate decreased to 37.8% at S2- = 600 mg/L, while the peak sulfide and nitrate removal rates (100% and 53.8%) were achieved at S2- = 800 mg/L with the air aeration rate of 20 mL/min. The Illumina sequencing results indicated that Thiobacillus accounted for 63% of total operational taxonomic units at generic level with sulfide concentration of 200 mg/L under anaerobic condition. However, Azoarcus, Thauera and Aliidiomorina became the dominant genera under micro-aerobic condition and their abundance significantly and positively related to the sulfide concentration and aeration rate (p < 0.05). According to the 16S metaproteomics functional composition prediction, one potential mechanism for autotrophic denitrifying under micro-aerobic condition was deduced that the oxidation of sulfide to thiosulfate further to sulfite was reinforced by trace oxygen, while the sulfite reductase activity was restrained. The decreased sulfide concentration weakened the toxicity inhibition on denitrifiers and accordingly the performance of autotrophic denitrification process was enhanced by micro-aerobic condition.

Response of the reactor performance and microbial community to a shift of ISDD process from micro-aerobic to anoxic condition.

Micro-aerobic condition has proven to be effective in enhancing sulfide oxidation to elemental sulfur (S0) during integrated simultaneous desulfurization and denitrification process (ISDD). In this study we investigated and compared the performance and microbial community of ISDD process operating under initially anoxic, then micro-aerobic and finally switch back to anoxic condition. For all the three tested scenarios, comparable bioreactor performance in terms of sulfate (95.0 ±â€¯4.4%, 90.6 ±â€¯3.8%, 89.8 ±â€¯3.5%) and nitrate (∼100%) removal was achieved. However, a shift of ISDD bioreactor from micro-aerobic to anoxic environment clearly increased the S0 production (30.6%), relative to that at initial anoxic condition (14.2%). Further anoxic bioreactor operation with different influent nitrate concentrations also obtained satisfactory performance particularly in terms of S0 production. Microbial community analysis results showed that functional microorganisms selectively enriched at micro-aerobic condition, particularly sulfide-oxidizing bacteria (SOB), could also function well and enhance S0 production when bioreactor switching from micro-aerobic to anoxic environment. We proposed that micro-aerobic strategy could function as a bio-selector and provide a new idea in functional microorganisms selectively enrichment for wastewater treatment.

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.

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 ±â€¯0.002, 0.24 ±â€¯0.011 and 0.35 ±â€¯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.