Enhancement of tribromophenol removal in a sequencing batch reactor via submicron magnetite.

Conductive magnetite (Fe3O4) has been applied into some anaerobic bioprocesses to accelerate direct interspecies electron transfer (DIET), however, Fe3O4 is usually dissolved by iron-reducing bacteria under anaerobic conditions, resulting in the loss of magnetite. Therefore, submicron magnetite particles were added to the sequencing batch reactor (SBR) to build a Fe3O4/SBR system, which could alleviate magnetite dissolution and simultaneously remove tribromophenol (TBP) effectively. The average removal efficiencies of chemical oxygen demand (COD) and TBP in Fe3O4/SBR system were 81% and 91%, respectively, which were 51% and 18% higher than those of the control group without Fe3O4 (SBR system). The enhanced TBP biodegradation was likely related to potential DIET, which was supported by the scanning electron microscopy (SEM) analysis, the increase of dehydrogenase and heme c (fivefold and 1.7-fold), and the enrichment of iron-redoxing bacteria (Geobacter and Thiobacillus). Furthermore, magnetite mainly remained intact in structure as indicated by X-ray diffraction (XRD), which might be ascribed to in situ iron redox cycle and magnetite biosynthesis via Magnetospirillum. Notably, the content of hydrogen peroxide (H2O2) and hydroxyl radical (⋅OH) in Fe3O4/SBR system was 4-5 times higher than that of SBR system. These findings could provide insights into the development of cost-effective strategy for the removal of refractory organic pollutants.

Change in the microbial community of saline geothermal fluids amended with a scaling inhibitor: effects of heat extraction and nitrate dosage.

Geothermal plants are often affected by corrosion caused by microbial metabolites such as H2S. In the Bad Blumau (Austria) geothermal system, an increase in microbially produced H2S was observed in the hot (107 °C) and scaling inhibitor-amended saline fluids and in fluids that had cooled down (45 °C). Genetic fingerprinting and quantification revealed the dominance, increasing abundance and diversity of sulfate reducers such as Desulfotomaculum spp. that accompanied the cooling and processing of the geothermal fluids. In addition, a δ34S isotopic signature showed the microbial origin of the H2S that has been produced either chemolithotrophically or chemoorganotrophically. A nitrate addition test in a test pipe as a countermeasure against the microbial H2S formation caused a shift from a biocenosis dominated by bacteria of the phylum Firmicutes to a community of Firmicutes and Proteobacteria. Nitrate supported the growth of nitrate-reducing sulfur-oxidizing Thiobacillus thioparus, which incompletely reduced nitrate to nitrite. The addition of nitrate led to a change in the composition of the sulfate-reducing community. As a result, representatives of nitrate- and nitrite-reducing SRB, such as Desulfovibrio and Desulfonatronum, emerged as additional community members. The interaction of sulfate-reducing bacteria and nitrate-reducing sulfur-oxidizing bacteria (NR-SOB) led to the removal of H2S, but increased the corrosion rate in the test pipe.

Influence of pH, EDTA/Fe(II) ratio, and microbial culture on Fe(II)-mediated autotrophic denitrification.

Fe(II)-mediated autotrophic denitrification with four different microbial cultures under different pH and EDTA/Fe(II) conditions was investigated in batch bioassays. Initially, the highest nitrate removal (72%) was achieved with an activated sludge inoculum. The use of pure cultures of Pseudogulbenkiania strain 2002 and Thiobacillus denitrificans resulted in a 55 and 52% nitrate removal, respectively. No denitrification was observed for a mixed culture dominated by Thiobacillus thioparus and T. denitrificans. A longer enrichment on Fe(II) and the supplementation of thiosulfate as additional electron donor were needed to stimulate the denitrifying activity of the Thiobacillus-mixed culture. A second subculture on Fe(II) as sole electron donor resulted in higher denitrification efficiencies for all microbial cultures. In particular, nitrate removal reached up to 84% with a specific nitrate removal rate of 1.160 mM·(g VSS·day)-1 in the bioassays seeded with the Thiobacillus-mixed culture. All cultures were favored by decreasing the EDTA/Fe(II) molar ratio from 2.0 to 0.5. The most significant denitrification enhancement was observed for the Pseudogulbenkiania species, indicating a lower tolerance to EDTA. The two pure cultures effectively maintained denitrification at pH 7.0 and were more sensitive to a pH decrease. Conversely, the optimal pH was 6.0 for the Thiobacillus-mixed and activated sludge cultures.

Identify biosorption effects of Thiobacillus towards perfluorooctanoic acid (PFOA): Pilot study from field to laboratory.

The concentration of Perfluoroalkyl acids (PFAAs) and the bacterial community composition along the Xiaoqing River were explored with HPLC-MS/MS and Illumina high-throughput sequencing in present study. The results showed that perfluorooctanoic acid (PFOA) was the predominant PFAAs in all sediment samples, and high level of PFOA could lead to an evident increase in the abundance of Thiobacillus. Thiobacillus was identified with the survival ability in high concentrations of PFOA accordingly. Therefore, Thiobacillus thioparus and Thiobacillus denitrificans were selected as receptors to design indoor biosorption experiment. The growth curves under different PFOA concentrations and residual rates of PFOA in the processes of cultivation were analyzed. The results showed that upwards concentrations of PFOA below 5000 ng/L led to an obvious increase in the growth rate of T. thioparus. Whereas PFOA promoted the growth of T. denitrificans in a relatively limited range of concentration, and the effect was not obvious. The addition of different concentrations of PFOA had no apparent effects on pH values in the media of both T. thioparus and T. denitrificans. The concentrations of PFOA in liquid media reduced after the process of bacteria culturing. The removal rates of T. thioparus and T. denitrificans to PFOA were 21.1-26.8% and 13.5-18.4%, respectively. The current findings indicated that T. thioparus could play a significant role as potential biosorbent with the ability to eliminate PFOA effectively in aquatic environment, which would provide novel information for PFOA ecological decontamination and remediation.

Bioelectrochemical denitrification on biocathode buried in simulated aquifer saturated with nitrate-contaminated groundwater.

Nitrate contamination in aquifers has posed human health under high risk because people still rely on groundwater withdrawn from aquifers as drinking water and running water sources. These days, bioelectrochemical technologies have shown a great number of benefits for nitrate remediation via autotrophic denitrification in groundwater. This study tested the working possibility of a denitrifying biocathode when installed into a simulated aquifer. The reactors were filled with sand and synthetic groundwater at various ratios (10, 50, and 100 %) to clarify the effect of various biocathode states (not-buried, half-buried, and fully buried) on nitrate reduction rate and microbial communities. Decreases in specific nitrate reduction rates were found to be correlated with increases in sand/medium ratios. A specific nitrate reduction rate of 322.6 mg m(-2) day(-1) was obtained when the biocathode was fully buried in an aquifer. Microbial community analysis revealed slight differences in the microbial communities of biocathodes at various sand/medium ratios. Various coccus- and rod-shaped bacteria were found to contribute to bioelectrochemical denitrification including Thiobacillus spp. and Paracoccus spp. This study demonstrated that the denitrifying biocathode could work effectively in a saturated aquifer and confirmed the feasibility of in situ application of microbial electrochemical denitrification technology.

Role of humic substances in promoting autotrophic growth in nitrate-dependent iron-oxidizing bacteria.

Nitrate-dependent iron oxidation was discovered in 1996 and has been reported from various environments ever since. To date, despite the widespread nature of this process, all attempts to cultivate chemolithoautotrophic nitrate-dependent iron oxidizers have been unsuccessful. The present study was focused on understanding the influence of natural chelating agents of iron, like humic substances, on the culturability, activity, and enumeration, of these microorganisms. Pure culture studies conducted with Thiobacillus denitrificans showed a constant increase in cell mass with a corresponding nitrate-dependent iron oxidation activity only when Fe(II) was provided together with humic substances, compared to no growth in control incubations without humic substances. The presence of a relatively strong chelating agent, such as EDTA, inhibited the growth of Thiobacillus denitrificans. It was concluded that complex formation between humic substances and iron was required for chemolithoautotrophic nitrate-dependent iron oxidation. Most probable number enumerations showed that numbers of chemolithoautotrophic nitrate-dependent iron-oxidizing bacteria were one to three orders of magnitude higher in the presence of humic substances compared to media without. Similar results were obtained when potential nitrate-dependent iron oxidation activity was determined in soil samples. In summary, this study showed that humic substances significantly enhanced the growth and activity of autotrophic nitrate-dependent iron-oxidizing microorganisms, probably by chelation of iron.

[Study on sulfur-based autotrophic denitrification with different electron donors].

Sulphur-based autotrophic denitrification was applied to treat the low concentration nitrate-contaminated water. Different electron donors, namely, elemental sulfur, sulfide and thiosulfate, were used in three continuous reactors to compare the denitrification performance. When treating the low concentration nitrate-contaminated water (13 mg x L(-1)), the thiosulfate system showed the best performance and the sulfide system was the worst. The thiosulfate system was less sensitive to low temperature than the other two. At temperatures higher than 20 degrees C, the sulfur system was greatly influenced by mass transfer efficiency and HRT. It removed 81% of nitrate and 79% of TN when HRT was no less than 2 h, but could only achieve a low nitrate and TN removal rate of 47% and 51% when HRT was shorter than 2 h. No obvious nitrite accumulation was observed and the average effluent nitrite was 0.53 mg x L(-1). The sulfide system could only remove 47% of nitrate and 41% of TN with 0.29 mg x L(-1) nitrite in the effluent at the HRT of 4 h. Meanwhile, the thiosulfate system had a high removal rate of 99% for nitrate and 90% for TN, with a low content of effluent nitrite of 0.080 mg x L(-1), and the HRT could be shortened to 0.5 h. The molecular biological analysis showed that different bacteria predominated in the three reactors, and that Thiobacillus denitrificans existed abundantly in the sulfur system, while the functional bacteria in the sulfide and thiosulfate systems could not be identified yet. A new species of sulfur-based autotrophic denitrification bacterium may have been found.

Linking TFT-LCD wastewater treatment performance to microbial population abundance of Hyphomicrobium and Thiobacillus spp.

This study investigated the linkage between performance of two full-scale membrane bioreactor (MBR) systems treating thin-film transistor liquid crystal display (TFT-LCD) wastewater and the population dynamics of dimethylsulfoxide (DMSO)/dimethylsulfide (DMS) degrading bacteria. High DMSO degradation efficiencies were achieved in both MBRs, while the levels of nitrification inhibition due to DMS production from DMSO degradation were different in the two MBRs. The results of real-time PCR targeting on DMSO/DMS degrading populations, including Hyphomicrobium and Thiobacillus spp., indicated that a higher DMSO oxidation efficiency occurred at a higher Hyphomicrobium spp. abundance in the systems, suggesting that Hyphomicrobium spp. may be more important for complete DMSO oxidation to sulfate compared with Thiobacillus spp. Furthermore, Thiobacillus spp. was more abundant during poor nitrification, while Hyphomicrobium spp. was more abundant during good nitrification. It is suggested that microbial population of DMSO/DMS degrading bacteria is closely linking to both DMSO/DMS degradation efficiency and nitrification performance.

Effects of sulphur and Thiobacillus thioparus on cow manure aerobic composting.

A simulated aerobic composting experiment was used to explore the effects of sulphur and Thiobacillus thioparus during six manure composting treatments. The addition of sulphur led to a decrease of the pH level within the range 6-6.3, which was lower than the control treatment (CK). The concentration of ammonium nitrogen in T1 (0.25% sulphur), T2 (0.5% sulphur), T3 (0.25% sulphur + T. thioparus) and T4 (0.5% sulphur + T. thioparus) were much higher than the ammonium N in CK. The results indicated that addition of sulphur could increase the concentration of ammonium N and reduce loss of nitrogen. However, excess sulphur had a negative effect on temperature and GI. Addition of T. thioparus could increase concentration of available S, alleviate these negative influences and reduce compost biological toxicity.

Microbial community analysis in the autotrophic denitrification process using spent sulfidic caustic by denaturing gradient gel electrophoresis of PCR-amplified genes.

Spent sulfidic caustic (SSC) produced from petrochemical plants contains a high concentration of hydrogen sulfide and alkalinity, and some almost non-biodegradable organic compounds such as benzene, toluene, ethylbenzene and xylenes (BTEX). SSC is mainly incinerated with auxiliary fuel, leading to secondary pollution problems. The reuse of this waste is becoming increasingly important from economic and environmental viewpoints. To denitrify wastewater with low COD/N ratio, additional carbon sources are required. Thus, autotrophic denitrification has attracted increasing attention. In this study, SSC was injected as an electron donor for sulfur-based autotrophic denitrification in the modified Ludzack-Ettinger (MLE) process. The efficiencies of nitrification, COD, and total nitrogen (TN) removal were evaluated with varying SSC dosage. Adequate SSC injection exhibited stable autotrophic denitrification. No BTEX were detected in the monitored BTEX concentrations of the effluent. To analyse the microbial community of the MLE process, PCR-DGGE based on 16 S rDNA with EUB primers, TD primers and nirK gene with nirK primers was performed in order to elucidate the application of the MLE process to SSC.

Characteristics of nitrogen removal and microbial distribution by application of spent sulfidic caustic in pilot scale wastewater treatment plant.

Since spent sulfidic caustic (SSC) produced from petrochemical industry contains a high concentration of alkalinity and sulfide, it was expected that SSC could be used as an electron donor for autotrophic denitrification. To investigate the nitrogen removal performance, a pilot scale Bardenpho process was operated. The total nitrogen removal efficiency increased as SSC dosage increased, and the highest efficiency was observed as 77.5% when SSC was injected into both anoxic tank (1) and (2). FISH analysis was also performed to shed light on the effect of SSC dosage on the distribution ratio of nitrifying bacteria and Thiobacillus denitrificans. FISH results indicated that the relative distribution ratio of ammonia-oxidizing bacteria, Nitrobacter spp., Nitrospira genus and Thiobacillus denitrificans to eubacteria varied little with the pH of the tanks, and SSC injection did not give harmful effect on nitrification efficiency. These results show that SSC can be applied as an electron donor of autotrophic denitrification to biological nitrogen removal process effectively, without any inhibitory effects to nitrifying bacteria and sulfur-utilizing denitrifying bacteria.

[Biofilm on a metal surface as a factor of microbial corrosion].

Main attention was given in the present review to the research methods, phases of biofilm's forming, exopolymer compounds of bacteria as main biofilm forming factor. A microbial corrosion as a result of interaction between the biofilm and metal surface was considered. The interaction was displayed in biomineralization. The future trends of biofilms study were bound with research of their architecture. That architecture was determined by the structure and function of biofilms compounds: biopolymers and biominerals.

[Domestication study about desulfuration microorganism from oxidation ditch by low concentration SO2].

An excellent desulfuration microorganism with a quick growth and propagation, high activation, high efficiency of removing SO2 is obtained from oxidation ditch of a city sewage treatment plant by inductive acclimatization over 6 d with low concentration SO2 gas (100-2 000 mg/m3). The desulfurition microorganism get their energy sources for growth from transforming SO2 (SO3(2-)) to SO4(2-). The predominant bacterium of the desulfuration microorganism has the same characteristic with Thiobacillus ferrooxidans (T. ferrooxidans), which showed that it was Gram negative, short rod bacteria with a single polar flagellum under a microscopic examination, and obtained its nourishment through the oxidation of inorganic compounds. The technology process condition of domestication and desulfuration of microorganism are particular studied, and the results showed that aerating time, SO2 flux and time to provide nutriment contained N, P, K to microorganism were very important. They have an ability with degradation rate of 160g/ (m3 x h) and degradation efficiency over 50% to transform sulfite to sulfate in liquid phase. The bacteria have a 98% of removing efficiency and over 80% of biodegradation efficiency for the 5 500 mg/m3 SO2 gas and the outlet concentration of SO2 is lower than 100 mg/m3, and also have a 95% of removing efficiency for 15 000 mg/m3 SO2 gas in the packed tower reactor with Raschig ring at 3s contact time.

[Characteristic of autotrophic denitrification in bioaugmented anaerobic system].

An autotrophic denitrification process using reduced sulfide as electron donor in anaerobic system is proposed as an efficient and cost effective alternative to conventional heterotrophic denitrification for low C/N ratio wastewaters and for simultaneous removal of sulfide and nitrate. A suspended culture of Thiobacillus denitrificans bacteria was fast and efficiently established in anaerobic system. 5 series bioaugmented anaerobic systems with different N/S ratio synthetic influent were set up. Sulfide, nitrate, sulfate, and nitrite concentration in the effluent at every 3 hours were measured after 15 day. The primary objective was to investigate the characteristic of autotrophic denitrification and sulfide oxidation, and to reveal the mechanism of autotrophic denitrification process using reduced sulfide as electron donor in bioaugmented anaerobic system. 90% removal efficiency of sulfide was observed after 3 hours and removal efficiency of sulfide had no reference to N/S ratio. The rate of sulfide oxidation was 20-24 g x (m3 x h)(-1), which was 10 times higher than that have been reported in the literatures. Maximum removal efficiency of nitrate was 65% after 6 hours, which enhanced with increasing N/S ration of influent. The result showed bacteria reduced nitrate to nitrite at first step, and resulted in accumulation of nitrite to 93 mg x L(-1) to the large extent. Accumulated nitrite was disappear on low influent N/S ratio condition after 6 hours, and need 21 hours on high influent N/S ratio condition. So, complete sulfide and nitrate removal was achieved during 6 hours. The results revealed that the sharp decreasing of sulfide concentration attributed to the reaction between sulfide and biosulfur particles to form polysulfide anions. In addition, biosulfur produced in 3 hours was the main source of electron donor for reducing nitrate.

Growth kinetics of Hyphomicrobium and Thiobacillus spp. in mixed cultures degrading dimethyl sulfide and methanol.

The growth kinetics of Hyphomicrobium spp. and Thiobacillus spp. on dimethyl sulfide (DMS) and methanol (in the case of Hyphomicrobium spp.) in an enrichment culture created from a biofilter cotreating DMS and methanol were studied. Specific growth rates of 0.099 h(-1) and 0.11 h(-1) were determined for Hyphomicrobium spp. and Thiobacillus spp., respectively, growing on DMS at pH 7. These specific growth rates are double the highest maximum specific growth rate for bacterial growth on DMS reported to date in the literature. When the pH of the medium was decreased from pH 7 to pH 5, the specific growth rate of Hyphomicrobium spp. decreased by 85%, with a near 100-fold decline in the yield of Hyphomicrobium 16S rRNA gene copies in the mixed culture. Through the same pH shift, the specific growth rate and 16S rRNA gene yield of Thiobacillus spp. remained similar. When methanol was used as a substrate, the specific growth rate of Hyphomicrobium spp. declined much less over the same pH range (up to 30%) while the yield of 16S rRNA gene copies declined by only 50%. Switching from an NH(4)(+)-N-based source to a NO(3)(-)-N-based source resulted in the same trends for the specific growth rate of these microorganisms with respect to pH. This suggests that pH has far more impact on the growth kinetics of these microorganisms than the nitrogen source. The results of these mixed-culture batch experiments indicate that the increased DMS removal rates observed in previous studies of biofilters cotreating DMS and methanol are due to the proliferation of DMS-degrading Hyphomicrobium spp. on methanol at pH levels not conducive to high growth rates on DMS alone.

Treatment of leather industry wastewater by aerobic biological and Fenton oxidation process.

Degradation of leather industry wastewater by sole aerobic treatment incorporating Thiobacillus ferrooxidans, Fenton's reagents, and combined treatment was investigated in this study. The sole treatment by Fenton's oxidation involving the introduction of 6g FeSO(4) and 266 g H(2)O(2) in a liter of wastewater at pH of 3.5 and 30 degrees C for 30 min at batch conditions reduced COD, BOD(5), sulfide, total chromium and color up to 69%, 72%, 88%, 5%, 100% and T. ferrooxidans alone showed maximum reduction to an extent of 77, 80, 85, 52, 89, respectively, in 21 d treatment at pH 2.5, FeSO(4) 16 g/L and temperature of 30 degrees C. The combined treatment at batch conditions involving 30 min chemical treatment by Fenton's oxidation followed by 72 h biochemical treatment by T. ferrooxidans at batch conditions gave rise up to 93%, 98%, 72%, 62% and 100% removal efficiencies of COD, BOD, sulfide, chromium and color at pH of 2.5 and 30 degrees C. Decrease in photo absorption of the Fenton's reagent treated samples, as compared to the banks, at 280, 350 and 470 nm wave lengths was observed. This may be the key factor for stimulating the biodegradation by T. ferrooxidans.

[Regulation of hydrogen sulfide level by acidophobic bacteria of Thiobacillus genus in technogenic reservoirs of sulfur mining regions].

An increase of acidophobic thione bacteria quantity in Rozdil and Yavoriv reservoirs of sulfur mining regions during 2005-2009 years, which correlates with a decrease of hydrogen sulfide content in water surface layers, was shown. The ability of acidophobic bacteria of Thiobacillus genus, isolated from "Yavorivske" lake, to oxidize effectively hydrogen sulfide added into Beijerinck medium instead of thiosulfate, was discovered. It was established, that hydrogen sulfide oxidizing efficiency by Thiobacillus sp. Yav-8, Yav-11 and Yav-14 strains is the highest (78.48-84.56%) when its content in cultivation medium was increased twice: to 2584 mg/l. An increase of sulfur quantity in sodium sulfide form from to six times as compared with its standard content in sodium thiosulfate form in the Beijerinck medium does not lead to the increase of hydrogen sulfide oxidizing efficiency by cells.

Ferrous iron production mediated by tetrathionate hydrolase in tetrathionate-, sulfur-, and iron-grown Acidithiobacillus ferrooxidans ATCC 23270 cells.

When tetrathionate-grown Acidithiobacillus ferrooxidans ATCC 23270 cells were incubated with ferric ions and tetrathionate at pH 3.0, ferrous ions were produced enzymatically. Fe(3+)-reductase, which catalyzes Fe(3+) reduction with tetrathionate, was purified to homogeneity not only from tetrathionate-grown, but also from sulfur- and iron-grown A. ferrooxidans ATCC 23270 cells. The results for apparent molecular weight measured by SDS-PAGE (52.3 kD) and the N-terminal amino acid sequences of the purified enzymes from iron-, sulfur, and tetrathionate-grown cells (AVAVPMDSTG) indicate that Fe(3+)-reductase corresponds to tetrathionate hydrolase. The evidence that tetrathionate-grown A. ferrooxidans ATCC 23270 cells have high iron-oxidizing activity at the early log phase, comparable to that of iron-grown ATCC 23270 cells, is supported by our finding that tetrathionate hydrolase produces Fe(2+) from tetrathionate during growth on tetrathionate. This is the first report on ferric reductase activity associated with tetrathionate hydrolase.

Removal of hydrogen sulfide by immobilized Thiobacillus thioparus in a biotrickling filter packed with polyurethane foam.

In the work described here, a biotrickling filter with Thiobacillus thioparus (ATCC 23645) immobilized on polyurethane foam is proposed for the removal of hydrogen sulfide contained in air. The effect of surface velocity of the recirculation medium (5.9-1.2 m/h), sulfate concentration inhibition (3.0-10.7 g/L), pH (6.0-8.2), empty bed residence time (EBRT) (150-11 s) for constant loads of 11.5 and 2.9 g S/m(3)/h, and pressure drop of the system were investigated. The total amount of biomass immobilized on the carrier was 8.2+/-1.3x10(10) cells/g. The optimal values of the operating variables were: pH between 7.0 and 7.5, surface velocity of 5.9 m/h and sulfate concentration below 5 g/L. The critical EC value was 14.9 g S/m(3)/h (removal efficiency of 99.8%) and the EC(max) was 55.0 g S/m(3)/h (removal efficiency of 79.8%) for an EBRT of 150 s. For loads of 2.89+/-0.05 and 11.5+/-0.1 g S/m(3)/h, the removal efficiency was higher than 99% for an EBRT over 90 s.

Assessment of the addition of Thiobacillus denitrificans and Thiomicrospira denitrificans to chemolithoautotrophic denitrifying bioreactors.

The aim of the present study was to assess the impact of adding cultures of Thiobacillus denitrificans and Thiomicrospira denitrificans to two upflow anaerobic sludge bed (UASB) reactors: one inoculated with granular sludge and the other filled only with activated carbon (AC). The performances of the bioreactors and the changes in biomass were compared with a non-bioaugmented control UASB reactor inoculated with granular sludge. The reactors inoculated with granular sludge achieved efficiencies close to 90% in nitrate and thiosulfate removal for loading rates as high as 107 mmol-NO3 -/l per day and 68 mmol-S2O3 2-/l per day. Bioaugmentation with Tb. denitrificans and Tm. denitrificans did not enhance the efficiency compared to that achieved with non-bioaugmented granular sludge. The loading rates and efficiencies were 30-40% lower in the AC reactor. In all the reactors tested, Tb. denitrificans became the predominant species. The results strongly suggest that this bacterium was responsible for denitrification and sulfoxidation within the reactors. We additionally observed that granules partially lost their integrity during operation under chemolithoautotrophic conditions, suggesting limitations for long-term operation if bioaugmentation is applied in practice.