An autotrophic nitrogen removal process:Short-cut nitrification combined with ANAMMOX for treating diluted effluent from an UASB reactor fed by landfill leachate

A combined process consisting of a short-cut nitrification （SN） reactor and an anaerobic ammonium oxidation upflow anaerobic sludge bed （ANAMMOX） reactor was developed to treat the diluted effluent from an upflow anaerobic sludge bed （UASB） reactor treating high ammonium municipal landfill leachate.The SN process was performed in an aerated upflow sludge bed （AUSB） reactor （working volume 3.05 L）,treating about 50% of the diluted raw wastewater.The ammonium removal efficiency and the ratio of NO 2 N to NOx-N in the effluent were both higher than 80%,at a maximum nitrogen loading rate of 1.47 kg/（m 3 ·day）.The ANAMMOX process was performed in an UASB reactor （working volume 8.5 L）,using the mix of SN reactor effluent and diluted raw wastewater at a ratio of 1：1.The ammonium and nitrite removal efficiency reached over 93% and 95%,respectively,after 70-day continuous operation,at a maximum total nitrogen loading rate of 0.91 kg/（m 3 ·day）,suggesting a successful operation of the combined process.The average nitrogen loading rate of the combined system was 0.56 kg/（m 3 ·day）,with an average total inorganic nitrogen removal efficiency 87%.The nitrogen in the effluent was mostly nitrate.The results provided important evidence for the possibility of applying SN-ANAMMOX after UASB reactor to treat municipal landfill leachate.

Distribution, residence time, autotrophic production, and heterotrophic removal of DOP in the Mirs Bay, northern South China Sea

The importance of dissolved organic phosphorus(DOP) as a potential nutrient source for primary producers in marine systems has been recognized for up to eight decades, but currently, the understanding of the biogeochemistry of DOP is in its infancy. In the present study, monthly data between 2000 and 2014 were used to analyze the temporal and spatial distributions of DOP in the Mir Bay, the northern South China Sea. The DOP residence time(TDOP) was also investigated using a simple regression analysis in combination with chlorophyll a(Chl a) measurements while excess DOP(ΔDOP), produced by the biogeochemical processes of autotrophic production and heterotrophic removal, was determined using a two-component mixing mass-balance model in combination with salinity measurements. The results showed that the DOP concentration was(0.017±0.010) mg/L higher in the surface-water compared with the bottom-water and higher in the inner Tolo Harbour and waters adjacent to Shatoujiao compared with the main zone of the bay. Although seasonal changes and annual variability in the DOP were small, the surface DOP concentration was higher in the wet season(April–September)than in the dry season(October–March) due to the impacts of seaward discharges and atmospheric deposition into the bay. Measurement and regression results showed that the DOP release rate from phytoplankton production was about 1.83(gP)/(gChl a) and the TDOP was about 7 d, which implied that the DOP cycle in the bay was rapid. The ΔDOP was calculated from the model to be about 0.000 mg/L in the main zone of the bay and about 0.002 mg/L in the inner Tolo Harbour and waters adjacent to Shaotoujiao, suggesting that the autotrophic production of DOP was almost balanced by the heterotrophic removal in the main zone of the bay and dominated in the inner Tolo Harbour and waters adjacent to Shaotoujiao. In conclusion, the Mirs Bay is very productive and fairly heterotrophic.

Rapid Acclimation of Methanogenic Granular Sludge into Autotrophic Partial Denitrification Granules

Rapid formation of autotrophic partial denitrification(APD)granules is of practical interest to start up an expanded granular sludge bed reactor for wastewater treatment.This study demonstrates that methanogenic granules can be easily acclimated into autotrophic partial denitrification granules in one day,with the ability to remove 82%of 2.7 kg-S/(m^3·d)sulfide into S^0 and to convert 97%of 0.9 kg-N/(m^3·d)nitrate into nitrite,which can provide a promising feedstock for anaerobic ammonia oxidation process.Arcobacter sp.is essential for S^0 accumulation.Under high loadings,the abundance of Arcobacter sp.decreased,while on the contrary the abundance of unclassified_p_Firmicutes increased,leading to the deterioration of autotrophic partial denitrification performance.The granules performance could be recovered by adopting the strategies of properly reducing the influent loadings.

Effect of C/N Ratio,Temperature,pH on Autotrophic Denitrification Rate with Hydrogen Gas,Iron(Ⅱ) and Sodium Sulfide as Electron Donors

Nitrate is considered to be one of the most widely present pollutants leading to eutrophication of environment. The purpose of this work was to isolate and identify new anaerobic denitrifying bacteria from reservoir sediments and utilize different electron donors for isolates to improve nitrate removal efficiency. Using traditional enrichment approach,one purified anaerobic bacterium( Y12) capable of NO-3-N removal from sediments was obtained. The species identity of Y12 was determined via 16 S rRNA gene sequence analysis to be Acinetobacter. In this work,the fastest denitrification rates were observed with ferrous iron as electron donor.And,slightly slower rates were observed with hydrogen and sodium sulfide as electron donors. However,when used hydrogen gas, ferrous iron and sodium sulfide as electron donors, C / N ratios had little effect on autotrophic denitrification rate at the initial C / N ratio from 1.5 to 9.0. Meanwhile,when made use of hydrogen gas,ferrous iron and sodium sulfide as electron donors,a maximum nitrate removal ratio of 100.00%,91.43%and 87.99% at the temperature of 30 ℃,respectively. Moreover,maximum denitrification activity was observed at p H 6.0-7.0.

Characterization of the start-up period of single-step autotrophic nitrogen removal in a sequencing batch reactor

The characteristics of the start-up period of single-step autotrophic nitrogen removal process were investigated. The autotrophic nitrogen removal process used a sequencing batch reactor to treat wastewater of medium to low ammonia-nitrogen concentration, with dissolved oxygen （DO）, hydraulic retention time （HRT） and temperature controlled. The experimental conditions were temperature at （30±2） ℃, ammonia concentration of （60 to 120） mg/L, DO of （0.8 to 1.0） mg/L, pH from 7.8 to 8.5 and HRT of 24 h. The rates of nitrification and nitrogen removal turn out to be 77% and 40%, respectively, after a start up period going through three stages divided according to nitrite accumulation： sludge domestication, nitrifying bacteria selection and sludge adaptation, It is demonstrated that dissolved oxygen is critical to nitrite accumulation and elastic YJZH soft compound packing is superior to polyhedral hollow balls in helping the bacteria adhere to the membrane.

Heterotrophic and Autotrophic Soil Respiration under Simulated Dormancy Conditions

Carbon cycling research has increased over the past 20 years, but less is known about the primary contributors to soil respiration (i.e. heterotrophic and autotrophic) under dormant conditions. It is understood that soil CO2 effluxes are significantly lower during the winter of temperate ecosystems and assumed microorganisms dominate efflux origination. We hypothesized that heterotrophic contributions would be greater than autotrophic under simulated dormancy conditions. To test this hypothesis, we designed an experiment with the following treatments: combined autotrophic heterotrophic respiration, heterotrophic respiration, autotrophic respiration, no respiration, autotrophic respiration in vermiculite, and no respiration in vermiculite. Engelmann spruce seedlings and soil substrates were placed in specially designed respiration chambers and soil CO2 efflux measurements were taken four times over the course of a month. Soil microbial densities and root volumes were measured for each chamber after day thirty-three. Seedling presence resulted in significantly higher soil CO2 efflux rates for all soil substrates. Autotrophic respiration treatments were not representative of solely autotrophic soil CO2 efflux due to soil microbial contamination of autoclaved soil substrates;however, the mean autotrophic contributions averaged less than 25% of the total soil CO2 efflux. Soil microorganism communities were likely the primary contributor to soil CO2 efflux in simulated dormant conditions, as treatments with the greatest proportions of microbial densities had the highest soil CO2 efflux rates. Although this study is not directly comparable to field dormant season soil CO2 effluxes of Engelmann spruce forest, as snowpack is not maintained throughout this experiment, relationships, and metrics from such small-scale ecosystem component processes may yield more accurate carbon budget models.

Combined biologic aerated filter and sulfur/ceramisite autotrophic denitrification for advanced wastewater nitrogen removal at low temperatures

An innovative advanced wastewater treatment process combining biologic aerated filter （BAF） and sulfur/ ceramisite-based autotrophic denitrification （SCAD） for reliable removal of nitrogen was proposed in this paper. In SCAD reactor, ceramisite was used as filter and Ca （HCO3）2 was used for supplying alkalinity and carbon source. The BAF-SCAD was used to treat the secondary treatment effluent. The performance of this process was investigated, and the impact of temperature on nitrogen removal was studied. Results showed that the combined system was effective in nitrogen removal even at low temperatures （8℃）. Removal of total nitrogen （TN）, NH4＋ -N, NO3-N reached above 90% at room temperature. Nitrification was affected by the temperature and nitrification at low temperature （8℃） was a limiting factor for TN removal. However, denitrification was not impacted by the temperature and the removal of NO3 -N maintained 98% during the experimental period. The reason of effective denitrification at low temperature might be the use of easily dissolved Ca（HCO3）2 and high-flux ceramisite, which solved the problem of low mass transfer efficiency at low temperatures. Besides, vast surface area of sulfur with diameter of 2-6 mm enhanced the rate of microbial utilization. The removal of nitrate companied with the production of SO42-, and the average concentration of SO27 was about 240mg.L^-1. These findings would be beneficial for the application of this process to nitrogen removal especially in the winter and cold regions.

Autotrophic denitrification for nitrate and nitrite removal using sulfur-limestone

Sulfur-limestone was used in the autotrophic denitrification process to remove the nitrate and nitrite in a lab scale upflow biofilter.Synthetic water with four levels of nitrate and nitrite concentrations of 10,40,70 and 100 mg N/L was tested.When treating the low concentration of nitrate-or nitrite-contaminated water（10,40 mg N/L）,a high removal rate of about 90% was achieved at the hydraulic retention time（HRT） of 3 hr and temperature of 20-25°C.At the same HRT,50% of the nitrate or nitrite could be removed even at the low temperature of 5-10°C.For the higher concentration nitrate and nitrite（70,100 mg N/L）,longer HRT was required.The batch test indicated that influent concentration,HRT and temperature are important factors afiecting the denitrification eficiency.Molecular analysis implied that nitrate and nitrite were denitrified into nitrogen by the same microorganisms.The sequential two-step-reactions from nitrate to nitrite and from nitrite to the next-step product might have taken place in the same cell during the autotrophic denitrification process.

An efficient way to enhance the total nitrogen removal efficiency of the Anammox process by S^0-based short-cut autotrophic denitrification

In order to reduce the amount of NO_3^-–N generated by the Anammox process, and alleviate the competition between denitrification and Anammox for NO_2^-–N in a single reactor, the preference of S^0 for reacting with coexisting NO_2^-–N and NO_3^-–N in the sulfur autotrophic denitrifying(SADN) process and the coupling effect of short-cut SADN and the Anammox process were studied. The results showed that S^0 preferentially reacted with NO_3^-to produce NO_2^-–N, and then reacted with NO_2^-–N when NO_3^-–N was insufficient, which could effectively alleviate the competition between SADN bacteria(SADNB) and Anammox bacteria(An AOB) for NO_2^-–N. After 170 days of operation, coupling between short-cut S^0-SADN and the Anammox process was first successfully achieved. SADNB converted the NO_3^-–N generated by the Anammox process into NO_2^-–N, which was once again available to An AOB. The total nitrogen removal efficiency eventually stabilized at over 95%, and the effluent NO_3^-–N was controlled within 10 mg/L, when high NH_4^+–N wastewater was treated by the Anammox process. Microbial community analysis further showed that Candidatus Brocadia and Thiobacillus were the functional microorganisms for An AOB and SADNB.

Advances and challenges of sulfur-driven autotrophic denitrification(SDAD)for nitrogen removal

Sulfur-driven autotrophic denitrification(SDAD),a process suited for the treatment of nitrogen and sulfur-polluted wastewater without extra supplement of organic carbon,is a promising biological nitrogen removal process.However,the SDAD process was affected by many factors such as various electron donors,organic carbon and exogenous substances(e.g.,antibiotics and heavy metal),which prevent further application.Thus,we conducted a detailed review of previous studies on such influence factors and its current application.Besides,a comparative analysis was adopted to recognize the current challenges and future needs for feasible application,so as to ultimately perfect the SDAD process and extend its application scope.

Performance of a completely autotrophic nitrogen removal over nitrite process for treating wastewater with different substrates at ambient temperature

The stability and parameters of a bio-ceramic filter for completely autotrophic nitrogen removal were investigated. The completely autotrophic nitrogen removal over nitrite （CANON） reactor was fed with different concentrations of ammonia （400, 300, and 200 mg N/L） but constant influent ammonia load. The results showed that the CANON system can achieve good treatment performance at ambient temperature （15-23℃）. The average removal rate and removal loading of NH4＋-N and TN was 83.90%, 1.26 kg N/（m3.day）, and 70.14%, 1.09 kg N/（m3.day）, respectively. Among the influencing factors like pH, dissolved oxygen and alkalinity, it was indicated that the pH was the key parameter of the performance of the CANON system. Observing the variation of pH would contribute to better control of the CANON system in an intuitive and fast way. Denaturing gradient gel electrophoresis analysis of microorganisms further revealed that there were some significant changes in the community structure of ammonium oxidizing bacteria, which had low diversity in different stages, while the species of anaerobic ammonium oxidizing （anammox） bacteria were fewer and the community composition was relatively stable. These observations showed that anaerobic ammonia oxidation was more stable than the aerobic ammonia oxidation, which could explain that why the CANON system maintained a good removal efficiency under the changing substrate conditions.

Sulfur-based autotrophic denitrification from the micro-polluted water

Eutrophication caused by high concentrations of nutrients is a huge problem for many natural lakes and reservoirs. Removing the nitrogen contamination from the low C/N water body has become an urgent need. Autotrophic denitrification with the sulfur compound as electron donor was investigated in the biofilter reactors. Through the lab-scale experiment,it was found that different sulfur compounds and different carriers caused very different treatment performances. Thiosulfate was selected to be the best electron donor and ceramsite was chosen as the suitable carrier due to the good denitrification efficiency, low cost and the good resistibility against the high hydraulic loads. Later the optimum running parameters of the process were determined. Then the pilot-scale experiment was carried out with the real micro-polluted water from the West Lake, China. The results indicated that the autotrophic denitrification with thiosulfate as electron donor was feasible and applicable for the micro-polluted lake water.

Performance of completely autotrophic nitrogen removal over nitrite process under different aeration modes and dissolved oxygen

In this study,three sequential batch biofilm reactors(SBBRs)were operated for 155 days to evaluate the performance of completely autotrophic nitrogen removal over nitrite(CANON)process under different aeration modes and dissolved oxygen(DO).Synthetic wastewater with 160-mg NH_(4)^(+)-N/L was fed into the reactors.In the continuously-aerated reactor,the efficiency of the ammonium nitrogen conversion and total nitrogen(TN)removal reached 80% and 70%,respectively,with DO between 0.8–1.0 mg/L.Whereas in the intermittently-aerated reactor,at the aeration/non-aeration ratio of 1.0,ammonium was always under the detection limit and 86% of TN was removed with DO between 2.0–2.5 mg/L during the aeration time.Results show that CANON could be achieved in both continuous and intermittent aeration pattern.However,to achieve the same nitrogen removal efficiency,the DO needed in the intermittently-aerated sequential batch biofilm reactor(SBBR)during the aeration period was higher than that in the continuously-aerated SBBR.In addition,the DO in the CANON system should be adjusted to the aeration mode,and low DO was not a prerequisite to CANON process.

Control of hydrogen sulfide emissions using autotrophic denitrification landfill biocovers:engineering applications

Hydrogen sulfide(H_(2)S)emitted from construction and demolition waste landfills has received increasing attention.Besides its unpleasant odor,longterm exposure to a very low concentration of H_(2)S can cause a public health issue.In the case of construction and demolition(C&D)waste landfills,where gas collection systems are not normally required,the generated H_(2)S is typically not controlled and the number of treatment processes to control H_(2)S emissions in situ is limited.An attractive alternative may be to use chemically or biologically active landfill covers.A few studies using various types of cover materials to attenuate H_(2)S emissions demonstrated that H_(2)S emissions can be effectively reduced.In this study,therefore,the costs and benefits of H_(2)S-control cover systems including compost,soil amended with lime,fine concrete,and autotrophic denitrification were evaluated.Based on a case-study landfill area of 0.04 km^(2),the estimated H_(2)S emissions of 80900 kg over the 15-year period and costs of active cover system components(ammonium nitrate fertilizer for autotrophic denitrification cover,lime,fine concrete,and compost),ammonium nitrate fertilizer is the most cost effective,followed by hydrated lime,fine concrete,and yard waste compost.Fine concrete and yard waste compost covers are expensive measures to control H_(2)S emissions because of the large amount of materials needed to create a cover.Controlling H_(2)S emissions using fine concrete and compost is less expensive at landfills that provide on-site concrete recovery and composting facilities;however,ammonium nitrate fertilizer or hydrated lime would still be more cost effective applications.

Sustainable treatment of nitrate-containing wastewater by an autotrophic hydrogen-oxidizing bacterium

Bacteria are key denitrifiers in the reduction of nitrate(NO_(3)^(-)N),which is a contaminant in wastewater treatment plants(WWTPs).They can also produce carbon dioxide(CO_(2))and nitrous oxide(N2O).In this study,the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp.TH_(2)0 was isolated for sustainable treatment of NO_(3)^(-)N in wastewater.Efficient removal of NO_(3)^(-)N and recovery of biomass nitrogen were achieved.Up to 99%of NO_(3)^(-)N was removed without accumulation of nitrite and N2O,consuming CO_(2)of 3.25 mol for each mole of NO_(3)^(-)N removed.The overall removal rate of NO_(3)^(-)N reached 1.1 mg L^(-1)h^(-1)with a biomass content of approximately 0.71 g L^(-1)within 72 h.TH20 participated in NO_(3)^(-)N assimilation and aerobic denitrification.Results from 15N-labeled-nitrate test indicated that removed NO_(3)^(-)N was assimilated into organic nitrogen,showing an assimilation efficiency of 58%.Seventeen amino acids were detected,accounting for 43%of the biomass.Nitrogen loss through aerobic denitrification was only approximately 42%of total nitrogen.This study suggests that TH_(2)0 can be applied in WWTP facilities for water purification and production of valuable biomass to mitigate CO_(2)and N_(2)O emissions。

Unraveling pharmaceuticals removal in a sulfur-driven autotrophic denitrification process:Performance,kinetics and mechanisms

The removal of eight typical pharmaceuticals(Ph ACs)(i.e.,ibuprofen(IBU),ketoprofen(KET),diclofenac(DIC),sulfadiazine(SD),sulfamethoxazole(SMX),trimethoprim(TMP),ciprofloxacin(CIP)and enoxacin(ENO))in sulfur-driven autotrophic denitrification(Sd AD)process were firstly investigated via long-term operation of bioreactor coupled with batch tests.The results indicated that IBU and KET can be effectively removed(removal efficiency>50%)compared to other six Ph ACs in Sd AD bioreactor.Biodegradation was the primary removal route for IBU and KET with the specific biodegradation rates of 5.3±0.718.1±1.8μg g ^(-1)-VSS d ^(-1)at initial concentrations of 25-200μg/L.The biotransformation intermediates of IBU and KET were examined,and the results indicated that IBU was biotransformed to three intermediates via hydroxylation and carboxylation.KET biotransformation could be initiated from the reduction of the keto group following with a series of oxidation/reduction reactions,and five intermediates of KET were observed in this study.The microbial community composition in the system was markedly shifted when long-term exposure to Ph ACs.However,the functional microbes(e.g.,genus Thiobacillus)showed high tolerance to Ph ACs,resulting in the high efficiency for Ph ACs,N and S removal during long-term Sd AD reactor operation.The findings provide better insight into Ph ACs removal in Sd AD process,especially IBU and KET,and open up an innovative opportunity for the treatment of Ph ACs-laden wastewater using sulfur-mediated biological process.

Influence of agriculture and aquaculture activities on the response of autotrophic picoplankton in Laguna Macapule, Gulf of California (Mexico)

Introduction:The lagoon is a component of coastal zones,whose populations of autotrophic picoplankton(APP)remain largely unstudied.These lagoons display high-nutrient productivity and additionally may also be subjected to anthropogenic activities.This study selected Laguna Macapule,located on the eastern shore in the mid-region of the Gulf of California,due to the fact that a drainage network servicing the surrounding agricultural region(>230,000 hectares under cultivation)directs irrigation runoff,shrimp farm effluents,and urban wastewater containing large quantities of nutrients to be discharged into this lagoon.We propose to identify the APP’s response to various types of environmental and anthropogenic influence in this highly impacted coastal lagoon.Methods:Two sites(separated by 2.7 km)were monitored from December 2007 to December 2008.One,located at the entrance to Laguna Macapule(oceanic influence)and the other a discharge canal(eutrophic conditions)inside the lagoon at El Tortugón.Results:APP was the numerically dominant phytoplankton fraction(15×106 to 620×106 cells L−1)with coccoidal cyanobacteria as the dominant fraction throughout the year.Peak levels were reached in spring-early autumn and they were the second largest contributor to biomass.Abundance of APP cells corresponds to the lagoon’s eutrophic status.Maximum numbers and a higher average of APP were recorded at the El Tortugón channel during the warm season(months with SST higher than 24°C).The general positive relationship of the APP’s annual cycle at both sites as well as a negative relationship with heterotrophic nanoflagellates(HNF)abundance,supports the idea that natural forcing,in particular sea surface temperature(SST)is the predominant influences on APP’s seasonal variability.Conclusions:Distinguishable significant differences in APP abundances and nutrients were recognizable between the two sites.The interplay of these variables contributed to lower densities of APP in winter and high densities in springearly autumn.N:P=~4 suggests that spring-early autumn abundance of the APP autotrophic component was sustained by urea from shrimp farm discharge water.Thus,a total nutrient-based approach is likely the most suitable tool for establishing nitrogen limitation of biological production in Laguna Macapule and similarly impacted ecosystems around the world.

Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations

Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.

Thiosulfate oxidation and autotrophy potential by marine prevalent heterotrophic bacteria of genus Marinobacter

The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph.In this study,six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity.These strains,namely Marinobacter guineae M3B^(T),Marinobacter aromaticivorans D15-8PT,Marinobacter vulgaris F01^(T),Marinobacter profundi PWS21^(T),Marinobacter denitrificans JB02H27T,and Marinobacter sp.ST-1M(with a 99.93%similarity to the 16S rDNA sequences of Marinobacter salsuginis SD-14B^(T)),were screened out of 32 Marinobacter strains by autotrophic thiosulfate oxidization medium.The population of cells grew in a chemolithotrophic medium,increasing from 105 cells/mL to 10^(7) cells/mL within 5 d.This growth was accompanied by the consumption of thiosulfate 3.59 mmol/L to 9.64 mmol/L and the accumulation of sulfate up to 0.96 mmol/L,and occasionally produced sulfur containing complex particles.Among these Marinobacter strains,it was also found their capability of oxidizing thiosulfate to sulfate in a heterotrophic medium.Notably,M.vulgaris F01^(T)and M.antarcticus ZS2-30^(T)showed highly significant production of sulfate at 9.45 mmol/L and 3.10 mmol/L.Genome annotation indicated that these Marinobacter strains possess a complete Sox cluster for thiosulfate oxidation.Further phylogenetic analysis of the soxB gene revealed that six Marinobacter strains formed a separate lineage within Gammaproteobacteria and close to obligate chemolithoautotroph Thiomicrorhabdus arctica.The results indicated that thiosulfate oxidizing and chemolithoautotrophic potential in Marinobacter genus,which may contribute to the widespread of Marinobacter in the global ocean.

Bio-reduction of nitrate from groundwater using a hydrogen-based membrane biofilm reactor

A hydrogen-based membrane biofilm reactor （MBfR） using H2 as electron donor was investigated to remove nitrate from groundwater. When nitrate was first introduced to the MBfR, denitrification took place on the shell side of the membranes immediately, and the effluent concentration of nitrate continuously decreased with 100% removal rate on day 45 under the influent nitrate concentration of 5 mg NO3^--N/L, which described the acclimating and enriching process of autohydrogenotrophic denitrification bacteria. A series of short-term experiments were applied to investigate the effects of hydrogen pressures and nitrate loadings on deniWification. The results showed that nitrate reduction rate improved as H2 pressure increasing, and over 97% of total nitrogen removal rate was achieved when the nitrate loading increased from 0.17 to 0.34 g NO3^--N/（m^2.day） without nitrite accumulation. The maximum deniwification rate was 384 g N/（m^3.day）. Partial sulfate reduction, which occurred in parallel to nitrate reduction, was inhibited by denitrififcation due to the competition for H2. This research showed that MBfR is effective for removing nitrate from the contaminated groundwater.