Influent NO3 Research Articles

Effect of Substrate Ratio on Nitrogen Removal Performance of ANAMMOX in ABR

In order to solve the problem of low nitrogen removal caused by incomplete removal of anaerobic ammonium oxidation (ANAMMOX) substrate, The nitrogen removal performance of the ANAMMOX was investigated by controlling different influent substrate ratios in an anaerobic baffled reactor (ABR). The result showed the optimal influent NO2--N/NH4+-N was 1.34 with which the NH4+-N and NO2--N removal efficiencies were about 99.99% and the total nitrogen removal efficiency reached a peak of 87%. When the influent NO2--N/NH4+-N gradually reduced from 1 to 0.49 and increased from 1.34 to 1.62, the absolute removal of NH4+-N and NO2--N was stable in the reactor and no significant inhibition was observed in the system. Under the condition of different substrate ratios, the removal of NH4+-N and NO2--N was basically consumed in the first compartment of ABR, the change of substrate ratio did not have an obvious impact on the nitrogen removal performance of each compartment in the ABR, thus, the ABR ANAMMOX system had good stability to the change of substrate concentration.

High-rate autotrophic denitrification in a fluidized-bed reactor at psychrophilic temperatures

In this study, high-rate autotrophic denitrification driven by thiosulfate (S2O32−) was maintained under psychrophilic conditions in a lab-scale fluidized-bed reactor (FBR) with a Thiobacillus-dominated biofilm. The temperature effects on the denitrifying performance of the FBR were monitored by gradually decreasing the temperature from 20 to 3°C. The potential of the FBR biofilm to maintain thiosulfate-driven denitrification at 3°C was further investigated at different HRTs (5.4, 3 and 1h) and influent NO3− concentrations (200, 600 and 1078mg/L), resulting in a gradual increase of the nitrogen loading rate (NLR) from 0.20 to 3.3kg N-NO3−/m3d. Complete thiosulfate-driven denitrification could be maintained at all temperatures, HRTs and influent NO3− concentrations tested. PCR-DGGE analysis revealed the dominance of the sulfur-oxidizing chemolithotrophs T. denitrificans and T. thioparus at all temperatures investigated. The FBR operation at a temperature as low as 3°C promoted bed expansion and increased the dissolved organic carbon (DOC) concentration in the effluent, but had no significant effects on the denitrification efficiency. The findings of this study are highly significant for the treatment of cold nitrogen-contaminated waters poor in organics and confirm the FBR as a robust and powerful bioreactor system for autotrophic denitrification.

Pyrosequencing reveals microbial community dynamics in integrated simultaneous desulfurization and denitrification process at different influent nitrate concentrations

Integrated simultaneous desulfurization and denitrification (ISDD) process has proven to be feasible for the coremoval of sulfate, nitrate, and chemical oxygen demand (COD). In this study, we aimed to reveal the microbial community dynamics in the ISDD process with different influent nitrate (NO3−) concentrations. For all tested scenarios, full denitrification was accomplished while sulfate removal efficiency decreased along with increased influent NO3− concentrations. The proportion of S0 to influent SO42− maintained a low level (5.6–17.0%) regardless of the increased influent NO3− concentrations. Microbial community analysis results showed that higher influent NO3− concentrations affected the microbial community structure greatly. Phyla Proteobacteria, Spirochaetae, Firmicutes, Synergistetes, and Chloroflexi dominated in all the community compositions, of which Proteobacteria exhibited a clear difference among eight microbial samples. Members of δ-Proteobacteria, with 16S rRNA gene sequences related to Desulfobulbus, were clearly decreased at influent NO3− = 3000 and 3500 mg/L, suggesting an inhibitory effect of NO3− on sulfate reduction. In contrast, as influent NO3− concentration increased, microbial community was notably enriched in γ-Proteobacteria and ε-Proteobacteria, which revealed the enrichment of 16S rRNA gene sequences related to Pseudomonas (γ-Proteobacteria), and Arcobacteria and Sulfurospirillum (ε-Proteobacteria).

Performance and microbial community analysis of a novel DEAMOX based on partial-denitrification and anammox treating ammonia and nitrate wastewaters

In this study, a novel DEAMOX (DEnitrifying AMmonium OXidation) process coupling anammox with partial-denitrification generated nitrite (NO2−-N) from nitrate (NO3−-N) was developed for simultaneously treating ammonia (NH4+-N) and NO3−-N containing wastewaters. The performance was evaluated in sequencing batch reactors (SBRs) with different carbon sources for partial-denitrification: acetate (R1) and ethanol (R2). Long-term operation (180 days) suggested that desirable nitrogen removal was achieved in both reactors. The performance maintained stably in R1 despite the seasonal decrease of temperature (29.2 °C–12.7 °C), and high nitrogen removal efficiency (NRE) of 93.6% on average was obtained with influent NO3−-N to NH4+-N ratio (NO3−-N/NH4+-N) of 1.0. The anammox process contributed above 95% to total nitrogen (TN) removal in R1 with the nitrate-to-nitrite transformation ratio (NTR) of 95.8% in partial-denitrification. A little lower NRE was observed in R2 with temperature dropped from 90.0% at 22.7 °C to 85.2% at 16.6 °C due to the reduced NTR (87.0%–67.0%).High-throughput sequencing analysis revealed that Thauera genera were dominant in both SBRs (accounted for 61.53% in R1 and 45.17% in R2) and possibly played a key role for partial-denitrification with high NO2−-N accumulation. The Denitratisoma capable of complete denitrification (NO3−-N→N2) was found in R2 that might lead to lower NTR. Furthermore, different anammox species was detected with Candidatus Brocadia and Candidatus Kuenenia in R1, and only Candidatus Kuenenia in R2.

Treatment of artificial secondary effluent for effective nitrogen removal using a combination of corncob carbon source and bamboo charcoal filter

Nitrogen from secondary effluents has endangered the aquatic environment and human health. A new experimental setup combining a corncob carbon source and bamboo charcoal filter (BCF) was used to effectively purify artificial sewage treatment plant tail water that had high nitrate and nitrogen content, and a low carbon to nitrogen (C/N) ratio. The nitrogen concentration in the reactor's effluent was below the limit of 15 mg/L when the influent COD concentration was 20 mg/L–60 mg/L, the influent NO3−-N concentration was 15 mg/L–30 mg/L, and the hydraulic retention time (HRT) was 1 h–4 h. The reactor's maximum volumetric load of total nitrogen was 0.585 kg/(m3 d). The COD and NO3−-N balances of the reactor indicated that 4.77 g corncob was required to remove 1 g NO3−-N and 2 g corncob was required to release 1 g COD.

Feasibility of Sulfur-based Autotrophic Denitrification of Photovoltaic Wastewater Containing High Fluorine

Effect of different influent F- concentrations on nitrogen removal efficiency of sulfur-based autotrophic denitrification was researched at room temperature(20-25℃) using domesticated biofilm reactor to explore the feasibility of sulfur-based autotrophic denitrification of photovoltaic wastewater containing high fluorine. The results indicated that when the influent F- concentration was in the range of 0-700 mg·L-1, the nitrogen removal efficiency promoted with rising influent F- concentration. The maximum TN removal rate of 1.0 kg·(m3·d)-1 was attained with the influent F- concentration was 700 mg·L-1. When the influent F- concentration increased to 700-900 mg·L-1, the removal rate of TN reached a stable level at 0.81-0.87 kg·(m3·d)-1 after short-term domestication. When the influent F- concentration was above 900 mg·L-1, the removal efficiency of reactor lowered with rising influent F- concentration. The minimum TN removal rate was 0.4-0.5 kg·(m3·d)-1. Photovoltaic wastewater was used as the influent of the reactor. After 50 d operation, the reactor gained steady denitrification efficiency. With the influent NO3--N concentration of 390-420 mg·L-1, F- concentration of 800 mg·L-1, and HRT of 8.8 h, the maximum TN removal rate of 1.1 kg·(m3·d)-1 was attained. The effluent TN concentration was 15-25 mg·L-1, which met the standard of sewage discharge. Costs of treating photovoltaic wastewater by disposing conventional denitrification and sulfur-based autotrophic denitrification were 2.468 Yuan·t-1 and 2.0728 Yuan·t-1, respectively. Compared with conventional denitrification, the sulfur-based autotrophic denitrification could save more costs.

Effect of Element Sulfur Particle Size and Type of the Reactor on Start-up of Sulfur-based Autotrophic Denitrification Reactor

The effect of element sulfur particle size and type of the reactor on sulfur autotrophic denitrification reactor start-up was researched at room temperature(19-24℃) by using sulfur autotrophic denitrification bio-membrane reactor and anaerobic sludge bed biofilm reactor and inoculating anaerobic sludge. The research indicated that after 65 d operation, the bio-membrane reactor gained steady denitrification efficiency. With an influent NO3^--N of 150 mg·L^-1, and an HRT of 3.3 h, the removal efficiencies of NO3^--N and TN were 91% and 77%, and the removal rate of TN was 0.67-0.83 kg·(m³·d)^-1. The increase of volumetric loading rate of NO3^--N and production of nitrogen gas led to the floating of sludge in the anaerobic sludge bed biofilm reactor. With an influent NO3^--N of 185 mg·L^-1 and an HRT of 3.3 h, the maximum removal rate of NO3^--N of 1.1 kg·(m³·d)^-1 was attained in anaerobic sludge bed biofilm reactor. But the increase of effluent NO3^--N and NO2^--N lowered the quality of effluent water seriously, and the floating of sludge affected the steady operation of the anaerobic sludge bed biofilm reactor. Sulfur particles with particle size of 0.8 mm and 3.0 mm were used as electron donors for start-up of two batch reactors. The experiment results indicated that the reactor which used sulfur particle size of 0.8 mm attained higher removal efficiency of NO3^--N and TN, and its effluent accumulated less NO2^--N compared with the reactor which used particle size of 3.0 mm.

Simultaneous nitrate and phosphate removal from wastewater lacking organic matter through microbial oxidation of pyrrhotite coupled to nitrate reduction

This study investigated the efficiency of a pyrrhotite autotrophic denitrification biofilter (PADB) technology for simultaneous N and P removal from wastewater lacking organic matter. A PADB was constructed with natural pyrrhotite as the biofilter medium and inoculated with autotrophic denitrifies enriched from anaerobic sludge. Over an operating period of 247 days, PADB efficiently removed NO3− and PO43− simultaneously from wastewater that lacked organic matter. The hydraulic retention time (HRT), and influent NO3− and PO43− concentrations affected the removal of NO3− and PO43−. A longer HRT led to lower concentrations of NO3− and PO43− in the effluent. The PO43− removal was influenced by NO3− removed; the more NO3− removed, the more PO43− removed. As the synthetic wastewater containing NO3−–N of 28 mg L−1 and PO43−–P of 6 mg L−1 in the absence of organic matter was treated by PADB at HRT of 24 h, total oxidized nitrogen (TON; NO2−–N + NO3−–N) and PO43−–P concentrations of effluent were as low as 1.13 and 0.28 mg L−1, respectively. When treatment of municipal wastewater treatment plant (WWTP) secondary effluent with TON of 21.11 mg L−1 and PO43−–P of 2.62 mg L−1 at HRT of 24 h, the effluent TON was 1.89 mg L−1 and PO43−–P was 0.34 mg L−1. PO43− was removed through the formation of secondary minerals with Fe and Ca. These secondary minerals contained elevated phosphorus, which presents a potential for P recovery from wastewater.

Optimization of nitrate removal from wastewater with a low C/N ratio using solid-phase denitrification.

In this study, the optimization of nitrate removal from wastewater with a low C/N ratio using solid-phase denitrification was investigated. Biodegradable polymer, an attractive alternative to liquid carbon sources for biological denitrification, was used as a carbon source and biofilm support for nitrate removal. An experiment was conducted based on a central composite design (CCD) with response surface methodology (RSM). A secondary polynomial regression with nitrate removal efficiency as response value was developed. Based on statistical analysis, the nitrate removal model was highly significant with very low probability values (<0.0001). At the optimal conditions for nitrate removal (hydraulic retention time (HRT), 3.5h; influent NO3 (-)-N concentration, 14.73mg/L; and influent CODCr concentration, 15.00mg/L), the nitrate removal efficiency was 99.23%. The results of an ANOVA and response surface analysis showed that HRT, influent NO3 (-)-N concentration, influent CODCr concentration, and the interaction between the HRT and influent CODCr concentration significantly affected the nitrate removal efficiency (P < 0.05). In solid-phase denitrification process, electron donor for denitrification could be obtained by biological degradation of biodegradable polymer. Therefore, the influent CODCr concentration has no major effect on nitrate removal efficiency compared with that of HRT and influent NO3 (-)-N concentration.

Development of the combined nitritation–anammox process in an upflow anaerobic sludge blanket (UASB) reactor with anammox granules

The combined nitritation–anaerobic ammonium oxidation (anammox) process represents a promising innovative technology for biological nitrogen removal, especially for treating wastewater with low chemical oxygen demand (COD) to ammonium ratios. In the present study, a laboratory-scale upflow anaerobic sludge blanket (UASB) reactor, which has been operated under low oxygen levels (⩽0.5mgL−1) for over 280days, was shown to remove about 88% of the supplied total nitrogen loads without nitrite/nitrate accumulation. During the start-up period, the reactor was initially inoculated with enriched anammox granules and fed with synthetic wastewater, where the ammonium concentration was fixed but nitrite concentration was gradually decreased to zero. As the influent NO2−-N/NH4+-N ratio decreased, O2 supply was increased gradually to facilitate the conversion of ammonium to nitrite by ammonium oxidation bacteria (AOB). Our results showed that the nitritation–anammox granules with porous structures were enriched and featured good settling ability. Microbial community composition was investigated by fluorescence in situ hybridization (FISH), which demonstrated the coexistence of AOB and anammox bacteria in the granules. The two groups of bacteria exhibited an overlapping growth style, which can improve ammonium availability to anammox bacteria and facilitate the immediate consumption of nitrite (produced by AOB) by anammox bacteria.

Nitrate Shaped the Selenate-Reducing Microbial Community in a Hydrogen-Based Biofilm Reactor

To study the effect of nitrate (NO3(-)) on selenate (SeO4(2-)) reduction, we tested a H2-based biofilm with a range of influent NO3(-) loadings. When SeO4(2-) was the only electron acceptor (stage 1), 40% of the influent SeO4(2-) was reduced to insoluble elemental selenium (Se(0)). SeO4(2-) reduction was dramatically inhibited when NO3(-) was added at a surface loading larger than 1.14 g of N m(-2) day(-1), when H2 delivery became limiting and only 80% of the input NO3(-) was reduced (stage 2). In stage 3, when NO3(-) was again removed from the influent, SeO4(2-) reduction was re-established and increased to 60% conversion to Se(0). SeO4(2-) reduction remained stable at 60% in stages 4 and 5, when the NO3(-) surface loading was re-introduced at ≤ 0.53 g of N m(-2) day(-1), allowing for complete NO3(-) reduction. The selenate-reducing microbial community was significantly reshaped by the high NO3(-) surface loading in stage 2, and it remained stable through stages 3-5. In particular, the abundance of α-Proteobacteria decreased from 30% in stage 1 to less than 10% of total bacteria in stage 2. β-Proteobacteria, which represented about 55% of total bacteria in the biofilm in stage 1, increased to more than 90% of phylotypes in stage 2. Hydrogenophaga, an autotrophic denitrifier, was positively correlated with NO3(-) flux. Thus, introducing a NO3(-) loading high enough to cause H2 limitation and suppress SeO4(2-) reduction had a long-lasting effect on the microbial community structure, which was confirmed by principal coordinate analysis, although SeO4(2-) reduction remained intact.

Nitrate and COD removal in an upflow biofilter under an aerobic atmosphere

A continuous-upflow submerged biofilter packed with ceramsite was constructed for nitrate removal under an aerobic atmosphere. Pseudomonas stutzeri X31, an aerobic denitrifier isolate, was added to the bioreactor as an inoculum. The influent NO3(-)-N concentrations were 63.0-73.8 mg L(-1). The best results were achieved when dissolved oxygen level was 4.6 mg L(-1) and C/N ratio was 4.5. The maximum removal efficiencies of carbon oxygen demand (COD) and NO3(-)-N were 94.04% and 98.48%, respectively at 30°C, when the hydraulic load was 0.75 m h(-1). The top section of the bioreactor possessed less biofilm but higher COD and NO3(-)-N removal rates than the bottom section. Polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) technique combined with electron microscopic examination indicated P. stutzeri X31 and Paracoccus versutus were the most dominant bacteria. Amoeba sp., Vorticella sp., Philodina sp., and Stephanodiscus sp. were also found in the bioreactor.

Effect of C/N ratio and aeration rate on performance of internal cycle MBR with synthetic wastewater

Effect of C/N ratio and aeration rate on performance of continuously operated internal circulation membrane bioreactor (ICMBR) was investigated thoroughly using synthetic domestic wastewater. The results show that COD and total nitrogen (TN) removal efficiencies were improved with the increase of C/N ratio under certain conditions (T = 25 °C, MLSS = 10 g/L, aeration rate was 0.15 m3/h, influent NH3-N concentration was 20 mg/L, influent NO3--N concentration was 100 mg/L, and HRT = 12 h). Meanwhile, a steady ammonia nitrogen (AN) removal rate (~80%) was obtained when C/N ratio increased from 2:1 to 6:1. Furthermore, when C/N ratio was 6:1 and aeration rate was 0.15 m3/h, average removal rates of COD, AN, and TN reached 98.5, 97.4, and 52.6%, respectively. Additionally, the improvement in activity of denitrifying bacteria could increase TN removal rate at a lower aeration rate. Under the optimal operation parameters (C/N ratio of 6:1 and aeration rate of 0.05 m3/h), the high average removal efficiencies of COD (96.0%), AN (96.4%), and TN (81.0%) were obtained by ICMBR. Finally, the membrane fouling was unobvious during this experiment process.

Enrichment of a High-Current Density Denitrifying Microbial Biocathode

The pairing of a nitrate reducing microbial biocathode with an organic matter oxidizing microbial bioanode represents a potential high value wastewater treatment methodology. While such bioanodes are relatively optimized, such biocathodes suffer from relatively low current densities and low operating potentials. Here we present enrichment and characterization of a denitrifying microbial biocathode that generates more than 10-fold greater current density per unit geometric surface area and operates at nearly 0.2 V higher than those previously reported. A mixture of aquatic sediments and denitrifying biomass was first enriched for microbes that reduce nitrate with electrons supplied by oxidation of Fe(II), then enriched for microbes that reduce nitrate with electrons supplied by a graphite electrode. The resulting biocathode exhibited a Nernstian current-potential dependency (onset of current at = −0.125 V vs. Ag/AgCl, limiting current density = −3.2 A/m2). Non-turnover voltammetry exhibited current peaks that scale with the square root of scan rate, consistent with diffusive electron hopping to microbes acting as nitrate reduction catalysts from the electrode surface via endogenous redox cofactors. In non-optimized electrochemical reactors, the biocathode removed 14–40% of influent NO3− without significant production of ammonia-nitrogen (NH3-N), suggesting that reduction of nitrate to nitric or nitrous oxide gas is occurring and that reduction of NO3− to NH3 is not a metabolic pathway. Results of 16S rDNA sequencing revealed a predominance of Betaproteobacteria, including Rhodocyclales and Burkholderiales, known environmental nitrogen cyclers, as the potential microbial cathode catalysts.

Reduction of nitrogen dioxide from etching vent gases by scrubbing with caustic sodium sulfide solution

BACKGROUND Acids and nitrogen dioxide (NO2) in gases that are vented from Al-etching operations for the production of thin-film transistor-liquid crystal displays (TFT-LCD) are harmful to the environment. Scrubbing the gases using traditional caustic liquids with high salinities is ineffective in removing NO2. This work develops practices for improving the removal of NO2 by adding reducing agents to the scrubbing liquids. RESULTS Field results reveal that Na2SO3 is a less effective agent for reducing NO2 than is Na2S, because it has a stronger reduction ability. In this work, when the scrubber parameters were a packing height of 1.0–2.0 m, a liquid-to-gas ratio L/G of 0.48–2.64 L m−3 and a superficial gas velocity U of 0.66–2.08 m s−1, and for influent NO2 concentrations of several tenths of ppm, the NO2 removal depended more on the sulfide dose than on the mass-transfer rate of NO2 to the liquid. CONCLUSIONS A sodium sulfide dose of 1.53±0.22 kg/(kg NO2 removed) over influent NO2 at a concentration 30–50 ppm was obtained. This value was much higher than the stoichiometric value for the reduction of NO2 to nitrite. Sulfide addition using an ORP-controlled mode with an ORP of −400 ± 10 mV and a pH of 12.5 ± 0.1 in the scrubbing liquid is suggested for reducing chemical costs and obtaining the desired NO2 concentration of exhaust gas. © 2013 Society of Chemical Industry

Effect of nitrate concentration on performance of pre-denitrification moving bed biofilm reactor system in treating coal gasification wastewater

An anoxic moving bed biofilm reactor (ANMBBR) followed by an aerobic moving bed biofilm reactor (AEMBBR) operated as pre-denitrification system was used to investigate the effect of different influent NO3--N concentrations on performance of the pre-denitrification system in treating real coal gasification wastewater. Influent NO3--N concentration was controlled at 50, 100, 200, and 400 mg/L during the experiments. Evolution of COD and phenols in the effluent of the ANMBBR and AEMBBR, and performance of nitrification in the AEMBBR with different influent NO3--N concentrations were studied. Almost complete denitrification was achieved when influent NO3--N concentration was 100 mg/L. NO3--N and NO2--N accumulated in the effluent of the ANMBBR with influent NO3--N concentrations of 200 and 400 mg/L. NO3--N concentration of 400 mg/L facilitated high NH4+-N removal efficiency in the AEMBBR when influent NH4+-N concentration was around 165 mg/L. The ratio of CODconsumed/NO3--Nconsumed along with phenols removal of the ANMBBR under different influent NO3--N concentrations was discussed.

Nitrate removal from tail water by integrated vertical-flow constructed wetlands at a high hydraulic loading rate

Nitrate removal rates of two pilot-scale integrated vertical-flow constructed wetlands (IVCWs) treating tail water, under a hydraulic loading rate (HLR) of 250 mm/d with a mean influent NO3--N concentration of 24.4 mg.L-1, were evaluated. Mean NO3--N removal efficiencies of 15.5 and 18.5% with mass removal rates of 1.01 g.m(-2).d(-1) and 1.16 g.m(-2).d(-1) for IVCW 1 (planted with Canna indica and Pontederia cordata) and 2 (planted with Typha orientalis and Arundo donax var. versicolor), respectively, were achieved. The removal rate constants as fitted by the first-order area-based model averaged 0.046 and 0.055 m.d(-1), respectively. Since NO3--N was the dominant nitrogen form in the effluent, denitrification was the limiting step in nitrogen removal despite of favorable pH and anaerobic conditions in the wetland beds. Low availability of carbon source, high HLR, and low temperature could be the probable influencing factors for the observed low NO3--N removal efficiencies. However, IVCW could be used to treat tail water for nitrate removal at a comparable high loading rate.

Simultaneous bioreduction of nitrate and chromate using sulfur-based mixotrophic denitrification process

This study aims at evaluating simultaneous chromate and nitrate reduction using sulfur-based mixotrophic denitrification process in a column reactor packed with elemental sulfur and activated carbon. The reactor was supplemented with methanol at C/N ratio of 1.33 or 2. Almost complete denitrification was achieved at influent NO3−–N and Cr(VI) concentrations of 75mg/L and 10mg/L, respectively, and 3.7h HRT. Maximum denitrification rate was 0.5g NO3−–N/(L.d) when the bioreactor was fed with 75mg/L NO3−–N, 150mg/L methanol and 10mg/L Cr(VI). The share of autotrophic denitrification was between 12% and 50% depending on HRT, C/N ratio and Cr(VI) concentration. Effluent total chromium was below 50μg/L provided that influent Cr(VI) concentration was equal or below 5mg/L. DGGE results showed stable microbial community throughout the operation and the presence of sulfur oxidizing denitrifying bacteria (Thiobacillus denitrificans) and Cr(VI) reducing bacteria (Exiguobacterium spp.) in the column bed.

Anammox Bacteria Enrichment and Phylogenic Analysis in Moving Bed Biofilm Reactors

Start-up of autotrophic ammonia oxidation process for removal of nitrogen from low C:ANN ratio (<1) wastewaters is complicated due to needs of specific inoculation material and strict process control. Anaerobic ammonium oxidation (Anammox) process was started up from zero at 26°C in moving bed biofilm reactor by using the reject water as a feed medium and source of anammox bacteria. Efficient nitrogen removal process was observed for 270 days (average total nitrogen [TN] removal rate 0.5 kgN/(m3d); TN removal efficiency 80%). The highest TN removal rate of 1 kgN/(m3d) was obtained with a hydraulic retention time of 0.75 days and the influent NO2−:NH4+ molar ratio of 1.2. Polymerase chain reaction detected uncultured Planctomycetales bacterium clone P4 from the biofilm. Scanning electron microscopy observations indicated that the biofilm was dominated by cocci-like and spherical bacteria while filamentous bacteria were lacking. The start-up method studied could be used in wastewater treatment system for removal of ammonia from anaerobic digester effluent.

Anammox bacteria enrichment and characterization from municipal activated sludge

A sustainable option for nitrogen removal is the anaerobic ammonium-oxidizing (anammox) process in which ammonium is oxidized to nitrogen gas with nitrite as electron acceptor. Application of this process, however, is limited by the availability of anammox biomass. In this study, two Brocadia-like anammox phylotypes were successfully enriched, detected and identified from an activated sludge taken from a domestic wastewater treatment plant (Minas Gerais, Brazil) employing a Sequencing Batch Reactor (SBR). The dominant phylotype was closely related to 'Candidatus Brocadia sinica', but one clone seemed to represent a novel species for which we propose the name 'Candidatus Brocadia brasiliensis'. Based on Fluorescence in situ hybridization (FISH) analysis, this enrichment led to a relative population size of 52.7% (±15.6) anammox bacteria after 6 months of cultivation. The cultivation process can be divided into three phases: phase 1 (approximately 25 days) was characterized by heterotrophic denitrification metabolism, phase 2 was the propagation phase and phase 3 (from the 87th day onwards), in which significant anammox activity was detected. A long-term performance of the SBR showed a near perfect removal of nitrite based on the influent NO(2)(-)-N concentration of 61-95 mg L(-1). The average ammonia removal efficiency was 90% with the influent NH(4)(+)-N concentration of 55-82 mg L(-1). Therefore, anammox cultivation and enrichment from activated sludge was possible under a controlled environment within 3 months.