Autotrophic Nitrogen Removal Research Articles

Autotrophic nitrogen removal in combined nitritation and Anammox systems through intermittent aeration and possible microbial interactions by quorum sensing analysis

Nitrogen removal and microbial interactions in two combined nitritation and Anammox systems with or without the addition of organics were examined. Two systems were successfully started up by adopting intermittent aeration. Organics addition deteriorated nitrogen removal, and total inorganic nitrogen and ammonium removal percentages decreased by 16.4% and 26.3%, respectively. Organics addition promoted the growth of Chloroflexi and Proteobacteria while suppressed the growth of Candidatus Kuenenia. Organics addition decreased activities of fatty acid biosynthesis and metabolism, amino acid metabolism and biofilm formation, while increased activities of steroid metabolism and glycosaminoglycan biosynthesis. Heterotrophs and Candidatus Kuenenia might interact with other organisms by using diverse quorum sensing systems. Chloroflexi and Proteobacteria interacted with Candidatus Kuenenia in nitrogen metabolism and biofilm formation. Proteobacteria played a key role in building a nitrite loop with Candidatus Kuenenia and nitrifiers. These results clarified microbial interactions in the autotrophic nitrogen removal process and advance its application.

Autotrophic nitrogen conversion process and microbial population distribution in biofilter that simultaneously removes Fe, Mn and ammonia from groundwater

One lab-scale biofilter that simultaneously removal of Fe, Mn and ammonia from groundwater was established to investigate autotrophic nitrogen conversion process and microbial population distribution. The results showed that 56 d were needed to achieve the required values of standards for Fe, Mn and ammonia under designing filtration rate. Fe, Mn, and ammonia was mainly removed at 0.2 m, 1.2 m, and 1.0 m in steady phase, respectively. Both nitrification and ANAMMOX contributed to nitrogen conversion. The calculation results demonstrated that autotrophic nitrogen removal proportion was about 48.3% in the steady operation period. Meanwhile, 11 putative Mn oxidizing bacteria (MnOB) were detected and putative MnOB was dominant in all the samples; Candidatus Kuenenia was the only detected Anaerobic Ammonium Oxidation (ANAMMOX) genus. The relationship between removal efficiency along the height and the taxonomic results was also concluded.

Coupling of partial nitritation and anammox in two- and one-stage systems: Process operation, N2O emission and microbial community

Advances in research and technological development in the field of wastewater treatment encourage the implementation of engineered autotrophic nitrogen removal (ANR) systems based on the coupling of partial nitritation (PN) and anaerobic ammonium oxidation (anammox). Such processes can be conducted in two independent dedicated reactors (i.e., two-stage system) or, alternatively, in the same reactor under limited aeration (i.e., one-stage system). In this investigation, both configurations were successfully tested using the sequencing batch reactor (SBR) technology. Processed wastewater was supernatant from a sewage sludge anaerobic digester containing about 1 g NH4+-N/L and 0.3 g PO4-P/L. Pre-conditioning of the supernatant through dilution and magnesium phosphates (e.g., struvite) precipitation favored the anammox process performance under both configurations. The N loading rate (NLR) applied in the PN reactor was ≤1.3 g N/(L·d) with nitrite production efficiencies of about 48%, whereas the N removal rate (NRR) in the anammox reactor was 0.43–0.56 g N/(L·d). On the other hand, in the one-stage reactor, the NRR was approximately 0.27 g N/(L·d). Estimated emissions of nitrous oxide (N2O) in such bioreactors ranged from 0.4 to 4.6% of the N loaded. Comparatively, similar NRRs were achieved for both reactor configurations but the one-stage system used a smaller reaction volume, ran at a lower NLR, and emitted N2O at a lower rate than the two-stage system. The microbial community in both systems was dominated by aerobic ammonium-oxidizing bacteria of the genus Nitrosomonas and the anammox species Ca. Brocadia sinica.

Impact of Mn and ammonia on nitrogen conversion in biofilter coupling nitrification and ANAMMOX that simultaneously removes Fe, Mn and ammonia

One lab-scale biofilter coupling nitrification and anaerobic ammonium oxidation (ANAMMOX) that simultaneously removes Fe, Mn and ammonia from simulated groundwater was adopted to investigate the influence of Mn and ammonia on nitrogen conversion and Mn removal kinetics in this study. The results showed that autotrophic nitrogen removal proportion (ANRP) rose slightly with the raise of Mn concentration and declined along with the raise of ammonia; the average ratios were 49.6%, 51.5%, 51.8%, 52.3%, 52.6%, 48.9%, 47.4% and 38.8%, respectively. Relative constant or slight down trend of accumulated ANRP was detected in filter bed which indicated the superiority of nitrification in relevant areas. After reaching a certain value, Mn could promote ANAMMOX in the upper part of the filter bed and shorten the main ammonia conversion area. As ammonia content rising, the maximum accumulated ANRP reduced and the maximum value acquired height went up. Moreover, the ammonia inhibition threshold for ANAMMOX in the biofilter might be different from waste water treatment. Mn removal could be assessed by first order reaction in all the eight periods and the k values were more comparable than those in abiotic Mn oxidation.

Advanced nutrient removal from ammonia and domestic wastewaters by a novel process based on simultaneous partial nitrification-anammox and modified denitrifying phosphorus removal

A novel process combined simultaneous partial nitrification-anammox (SPNA) with modified denitrifying phosphorus removal (DPR) in two sequencing batch reactors (terms as SPNA-SBR and mDPR-SBR) was proposed for treating ammonia (NH4+-N) and domestic wastewaters. Firstly, NH4+-N contained wastewater was fed into SPNA-SBR for autotrophic nitrogen removal. Meanwhile, domestic wastewater was introduced to mDPR-SBR for anaerobic phosphorus release and intracellular carbon storage. Then, nitrate (NO3–-N) produced in SPNA-SBR was discharged to mDPR-SBR, where NO3–-N was reduced to dinitrogen gas (N2) via anoxic denitrifying phosphorus removal. Finally, the residual NH4+-N and PO43−-P in mDPR-SBR were removed via aerobic simultaneous nitrification, endogenous denitrification and phosphorus removal (SNEDPR). The long-term operation (235-day) suggested that a desirable nutrient removal performance was achieved in the SPNA-mDPR process, and the final effluent NH4+-N, total nitrogen and PO43−-P concentrations were 1.5, 5.0 and 0.2 mg·L−1, respectively. In the SPNA-SBR, SPNA contributed to ∼90% of NH4+-N removal at low aeration intensity (dissolved oxygen (DO): 0.1 mg·L−1); in the mDPR-SBR, ∼70% of PO43−-P and ∼100% of NO3–-N were simultaneously removed via anoxic DPR, and post-aerobic SNEDPR further reduced ∼30% of PO43−-P and ∼70% of NH4+-N. Stoichiometry-based microbial activity analysis demonstrated that, in the mDPR-SBR, high activity of denitrifying phosphorus accumulating organisms (DPAOs) over denitrifying glycogen accumulating organisms (DGAOs) in anoxic NO3–-N removal (71.1% > 28.9%) facilitated DPR, and high percentage of SNEDPR via nitrite (89.6%) over nitrate saved 52% intracellular carbon demand to realize the deep-level nutrient removal without external carbon addition.

Bottom-up approach in the assessment of environmental impacts and costs of an innovative anammox-based process for nitrogen removal

In recent decades, the wastewater treatment sector has undergone a shift to adapt to increasing discharge limits. In addressing the evaluation of innovative technologies, it is necessary to determine the scale at which reliable and representative values of environmental impacts and costs can be obtained, ensuring that the system under assessment follows the direction of eco-efficiency.This study has evaluated the environmental and economic indicators of an autotrophic nitrogen removal technology (ELAN®) from laboratory conception (1.5 L) to full scale (2 units of 115 m3) using the Life Cycle Assessment (LCA) methodology. Indirect emissions related to electricity consumption are the main contributor in all impact categories except eutrophication. Electricity consumption referred to the functional unit (1 m3 of treated wastewater) decreases as the scale increases. The rationale behind this can be explained, among other reasons, by the low energy efficiency of small-scale equipment (pumps and aerators). Accordingly, a value of approximately 25 kg CO2eq per m3 of treated water is determined for laboratory scale, compared to only 5 kg CO2eq per m3 at full-scale. When it comes to assessing the reliability of data, a pilot scale system of 0.2 m3 allowed to perform a trustworthy estimation of environmental indicators, which were validated at full-scale. In terms of operational costs, the scale of approximately 1 m3 provided a more accurate estimate of the costs associated with energy consumption.

The influence of dissolved oxygen on partial nitritation/anammox performance and microbial community of the 200,000 m3/d activated sludge process at the Changi water reclamation plant (2011 to 2016).

Mainstream partial nitritation/anammox (PN/A), coupled with excess biological phosphorus removal, in a 200,000 m3/d step-feed activated sludge process (Train 2) in the Changi Water Reclamation Plant (WRP), Singapore, has been studied and reported. This paper presents an overview of process performance and the microbial community during the period from 2011 to 2016. The site data showed that, along with the reduction of dissolved oxygen (DO) from 1.7 to 1.0 mg O2/L in the aeration zones, the concentrations of ammonium and nitrate of the final effluent increased, while nitrite decreased, resulting in an increase of 2.4 mg N/L of total inorganic nitrogen. Autotrophic nitrogen removal was higher than heterotrophic biological nitrogen removal under higher DO concentration conditions, but decreased under low DO operating condition. These macro-scale changes were caused by shifts of the nitrogen-converting microbial community. The ammonia oxidizing bacteria (AOB) population abundance was reduced by 30 times, while the nitrite oxidizing bacteria (NOB) population abundance and specific activity increased significantly with a shift of dominant genus from Nitrobacter to Nitrospira. The ratio of AOB and NOB specific activities were reduced from 12.8 to 1.6, and the ex situ nitrite accumulation ratio reduced from 76% to 29%. Changes in the microbial community and overall process performance illustrated that, compared to the excellent NOB suppression under high DO conditions, NOB were more active after the DO concentration reduction despite still being partly suppressed. This case study demonstrated, for the first time, the influence of DO reduction on the nitrogen conversion microbial community and PN/A process performance for a suspended growth system. Its relevance to biofilm and hybrid PN/A processes is also discussed.

Performance and microbial community of the completely autotrophic nitrogen removal over nitrite process with a submerged aerated biological filter.

Stable performance is a technical problem in the completely autotrophic nitrogen removal over nitrite (CANON) process with one single stage, which needs to be addressed. In the current work, a laboratory-scale submerged aerated biological filter (SABF) with a 3-L working volume was introduced into the CANON process to enhance its stable performance for 290 days under the following conditions: temperature of 30 ± 1 °C and dissolved oxygen (DO) level of 0.2-0.8 mg·L-1. The results showed that the average ammonium nitrogen removal efficiencies (ANRE) and total nitrogen removal efficiencies (TNRE) were 97.4% and 75.7%, respectively. A 16S rRNA gene high-throughput sequencing technology confirmed the phyla Proteobacteria and Planctomycetes as the ammonium oxidizing bacteria (AOB) and anaerobic ammonia-oxidizing bacteria (AnAOB) of this CANON process with SABF, respectively. The major contributor to nitrogen removal was the genus Candidatus Brocadia, in Brocadiae. The aim is to present an effective strategy as a reference for the design of full-scale plant for the CANON process.

Supernatant organics from anaerobic digestion after thermal hydrolysis cause direct and/or diffusional activity loss for nitritation and anammox

Treatment of sewage sludge with a thermal hydrolysis process (THP) followed by anaerobic digestion (AD) enables to boost biogas production and minimize residual sludge volumes. However, the reject water can cause inhibition to aerobic and anoxic ammonium-oxidizing bacteria (AerAOB & AnAOB), the two key microbial groups involved in the deammonification process. Firstly, a detailed investigation elucidated the impact of different organic fractions present in THP-AD return liquor on AerAOB and AnAOB activity. For AnAOB, soluble compounds linked to THP conditions and AD performance caused the main inhibition. Direct inhibition by dissolved organics was also observed for AerAOB, but could be overcome by treating the filtrate with extended aerobic or anaerobic incubation or with activated carbon. AerAOB additionally suffered from particulate and colloidal organics limiting the diffusion of substrates. This was resolved by improving the dewatering process through an optimized flocculant polymer dose and/or addition of coagulant polymer to better capture the large colloidal fraction, especially in case of unstable AD performance. Secondly, a new inhibition model for AerAOB included diffusion-limiting compounds based on the porter-equation, and achieved the best fit with the experimental data, highlighting that AerAOB were highly sensitive to large colloids. Overall, this paper for the first time provides separate identification of organic fractions within THP-AD filtrate causing differential types of inhibition. Moreover, it highlights the combined effect of the performance of THP, AD and dewatering on the downstream autotrophic nitrogen removal kinetics.

The effect and biological mechanism of granular sludge size on performance of autotrophic nitrogen removal system.

The autotrophic process for nitrogen removal has attracted worldwide attention in the field of wastewater treatment, and the performance of this process is greatly influenced by the size of granular sludge particles present in the system. In this work, the granular sludge was divided into three groups, i.e. large size (> 1.2mm), medium size (0.6-1.2mm) and small size (< 0.6mm). The medium granular sludge was observed to dominate at high volumetric nitrogen loading rates, while offering strong support for good performance. Its indispensable contribution was found to originate from improved settling velocity (0.84 ± 0.10cm/s), high SOUR-A (specific oxygen uptake rate for ammonia oxidizing bacteria, 25.93mg O2/g MLVSS/h), low SOUR-N (specific oxygen uptake rate for nitrite oxidizing bacteria, 3.39mg O2/g MLVSS/h), and a reasonable microbial spatial distribution.

Effects of extremely low bulk liquid DO on autotrophic nitrogen removal performance and NOB suppression in side‐ and mainstream one‐stage PNA

AbstractBACKGROUNDResults in the literature are divergent regarding dissolved oxygen (DO) level to ensure nitrite‐oxidizing bacteria (NOB) suppression in mainstream conditions. In this study, a one‐stage granular partial‐nitritation (PNA) was operated controlling the oxygen transfer over ammonium loading rate (OTR/ALR). The effects of extremely low DO availability on autotrophic nitrogen removal (ANR) performance and NOB suppression were assessed.RESULTSThe strategy applied in the sequencing batch reactor (SBR) in sidestream and mainstream conditions (temperature at 25 °C) allowed micromolar bulk liquid DO concentrations to be obtained. Nitrite production rate (NPR) by aerobic ammonium‐oxidizing bacteria (AOB) was sufficient to provide nitrite to anammox bacteria (AnAOB) and sustain nitrogen removal rates (NRR) of 0.34 ± 0.05 and 0.37 ± 0.07 kg N m−3 d−1 during sidestream and mainstream operation, respectively. Extremely low DO assisted by free ammonia (FA; ≤6.2 mg N L−1) in sidestream conditions resulted in complete nitratation suppression. In mainstream conditions, Nitrospira spp. growth led to limited nitratation rates. Decreasing the OTR/ALR resulted in lower oxygen consumption by AOB than by NOB, as well as reduced nitrite consumption by AnAOB, which is likely to be due to granule structure.CONCLUSIONSLow DO availability did not compromise ANR. Micromolar DO allowed complete NOB suppression only with FA assistance (sidestream) but was sufficient to keep nitratation limited in mainstream conditions. © 2018 Society of Chemical Industry

Predictions of the Influent and Operational Conditions for Partial Nitritation with a Model Incorporating pH Dynamics.

Ammonium partial oxidation to nitrite (i.e., partial nitritation) is required in a two-stage autotrophic nitrogen removal system, to provide effluent suitable for the anammox reaction. This study aims to establish influent (ammonium and bicarbonate concentrations) and operational (dissolved oxygen (DO) concentration and solids retention time (SRT)) conditions that favor partial nitritation. This is achieved through extending the nitritation and nitratation models to predict pH variation as well as the effects of pH, free ammonia (NH3), and free nitrous acid (HNO2) on the two reactions. Experiments were performed on a lab-scale sequencing batch reactor (SBR) operated for over 500 days to provide dynamic data for the calibration of model parameters, particularly those related to the NH3 and HNO2 inhibition on nitrite-oxidizing bacteria (NOB). The influent ammonium (19-84 mM) and bicarbonate (23-72 mM) were varied, which led to dynamic ammonium, nitrite, and nitrate data suitable for model calibration and validation. The model was able to well-describe pH dynamics as well as the inhibitory effects of NH3 and HNO2 on NOB. Model-based scenario analysis was then undertaken to establish the joint regions of influent ammonium and bicarbonate concentrations and the operational DO, temperature, and SRT conditions that favor partial nitritation. The results provide support to the design and optimization of partial nitritation reactors.

Optimization of the Nitrogen Removal Performance on the CANON Process in a Biofilm Reactor: From FBBR to MBBR

To optimize the performance of completely autotrophic nitrogen removal over nitrite (CANON), a CANON process with modified polyethylene as carriers was operated in a moving-bed biofilm reactor (MBBR), using synthetic inorganic ammonia-rich wastewater (NH4+-N about 400 mg ·L-1) as influent at 30℃±1℃. With an HRT of 6 h, pH at 7.8, and filling rate of 35%, the average removal rate of NH4+-N and TN reached 74.28% and 87.93%, respectively, and the highest removals reached 84.68% and 98.82%, respectively, while the value of ΔNO3-/ΔTN was 0.12, which was close to the theoretical value of 0.127. This suggested that CANON sludge gradually adapted to the environment in the MBBR and began to enter the stable stage. Compared with a fixed-bed biofilm reactor (FBBR) under the same influent and operating conditions, the mean square error of MBBR and FBBR in terms of NH4+-N removal rate, TN removal rate, and TN removal load were 8.31% and 14.06%, 7.09% and 1.79%, 0.17 kg ·(m3 ·d)-1 and 0.27 kg ·(m3 ·d)-1, respectively, the former are lower than the latter. Moreover, while DO concentrations of MBBR and FBBR were 1.96 mg·L-1 and 3.09 mg ·L-1, respectively, their TN removals of per liter carriers were 0.53 kg ·(m3 ·d)-1 and 0.37 kg ·(m3 ·d)-1. Therefore, it was concluded that:① MBBR had a more stable nitrogen removal performance than did of FBBR, and ② MBBR had a higher TN removals of per liter carriers than did FBBR in addition to the higher utilization rate of oxygen.

Research advances and challenges in anammox immobilization for autotrophic nitrogen removal

AbstractApplication of the anaerobic ammonium oxidation (anammox) process using suspended or attached growth technology has limitations of slow growth rate such as biomass washout, and large footprint. This has led to the development of smaller, compact immobilized systems. In recent years, wastewater treatment using anammox immobilized cells has received much attention due to its advantages of high biomass content, retention of biomass by prevention of washout, good solid–liquid separation and lower toxicity to microorganisms. This article critically reviews the existing literature on autotrophic nitrogen removal using anammox bacteria in its immobilized form. Different methods of using immobilized anammox bacteria were identified. Characteristics of various polymeric gels such as solubility, biodegradability, stability, diffusivity and growth of biomass in the polymeric gel were studied. However, there is insufficient study of disposal methods and costs involved in anammox immobilization to guide future implementation of immobilized anammox technologies for autotrophic nitrogen removal. © 2018 Society of Chemical Industry

Effects of Environmental Factors on the Synergy of Functional Bacteria in Completely Autotrophic Granular Sludge

To obtain experimental evidences for optimizing a completely autotrophic nitrogen removal process based on granules, the effects of dissolved oxygen (DO) concentration, temperature (t), initial ammonium (NH4+-N) concentration, and solution pH conditions on the synergy between the aerobic and anaerobic ammonium-oxidizing bacteria (AOB and AMX) were investigated using a single factor batch experiment, while the analysis of the microbial community structure within them was conducted using MiSeq high-throughput pyrosequencing. Results revealed that AOB (genus Nitrosomonas) and AMX (genus Candidatus Kuenenia) dominated in the granules, representing relative abundances of 32.9% and 9.8%, respectively. For the granules, the highest specific nitrogen removal rate of q(TN)=(17.7±1.0) mg·(g·h)-1 was obtained at a DO concentration of 2 mg·L-1, while the initial NH4+-N concentration was set at 100 mg·L-1. And a lower DO level resulted in partial nitritation became the rate-limiting step of process, otherwise, it would be the ANAMMOX reaction instead. According to the free energy of the reactions, the activity of AMX was more sensitive to low temperature than that of AOB. When the reaction temperature was lower than 30℃, nitrite accumulation could be observed in bulk liquid, with the significant decrease of q(TN) for the granules. Under the same oxygen supply conditions, an initial NH4+-N concentration lower than 100 mg·L-1 could inhibit the activity of AMX partly. However, with an initial NH4+-N concentration over 150 mg·L-1, either oxygen-limiting or high free ammonia concentration could lead to the dramatic decrease of q(TN). In addition, the effective synergy of the two types of ammonium oxidizers in granules was always achieved at solution pH in the range of 7.0-8.5.

Granulation of anammox microorganisms for autotrophic nitrogen removal from wastewater

Excessive discharge of nutrients in waters induces pollution such as such as eutrophication. Conventional methods to treat waters are expensive. Alternatively, anaerobic ammonium oxidation, termed “anammox”, has been recently developped with benefits such as low sludge production, 50% less aeration demand, no external carbon supply, 60% less power consumption, and 90% reduction of greenhouse gas emissions. However, anammox is limited by long start-up periods due to the low growth rate of anammox bacteria. This issue can be solved by complete retention of biomass by reactor modification or by formation of anammox granules. This article reviews the mechanisms of anammox granulation and biogranulation models. We present factors involved in the granulation processes such as hydrodynamic shear force, extracellular polymeric substances, hydraulic retention time, seed sludge and bioreactors. We also discuss the interaction of proteins and polysaccharides in anammox granules.

Enhanced retention of deammonification microorganisms for the treatment of psycrophilic anaerobic digestate

This study focused on the treatment of psychrophilic anaerobic digestate from pig slurry digestion through a single-stage Sequencing Batch Reactor (SBR) accomplishing the autotrophic nitrogen removal (ANR). In period 1, the combination of the high sludge retention time (>50 days) and the presence of significant concentrations of biodegradable organic carbon favoured the uncontrolled growth of the denitrifying bacteria (HDB) and the nitrite oxidizing bacteria (NOB), affecting negatively the deammonification (DAM) activity from 14 to 15 mgN/gMLVSS·h to only 2.2 mgN/gMLVSS·h. In Period 2, the sieving of the suspended biomass at 125 µm was evaluated to enhance the retention time of DAM microrganisms in granular sludge into the SBR. This strategy allowed the recovery of 60% of the initial specific deammonification activity (sDAA) and to promote the wash-out of the NOB, obtaining a nitrogen removal efficiency of 81%. This method was never applied to increase the robustness and reliability of ANR during the treatment of livestock streams, so it could be considered after optimization as a potential option to increase the sustainability of smaller and local farms.

Effect of inocula on performance of bio-cathode denitrification and its microbial mechanism

Bio-cathode denitrification is a new and unique technology for autotrophic nitrogen removal, which uses electricity instead of chemical matter as electron donor. Functional microorganisms are the driver of bio-cathode denitrification and inocula are the origin of functional microorganisms, so three typical inocula, denitrifying, denitratating and anammox (anaerobic ammonia oxidizing) sludge, were chosen to investigate their effect on the performance of bio-cathode denitrification in this work. The results showed that the nitrogen removal rate of denitrifying, denitratating and anammox bio-cathodes was around 101.79 mg/L·d, 47.31 mg/L·d and 100.04 mg/L·d respectively. The output power was 24.01 mW/m2, 14.11 mW/m2 and 45.93 mW/m2. The denitrifying, denitratating and anammox biofilms were observed to grow on cathodes, indicating that the functional microorganisms could use electricity as the sole electron donor and so they were named as electrotrophic microorganisms. The growth rate and the cell yield of denitrifying, denitratating and anammox biofilms were 24 g/m2·d and 1.71 × 10−3g/g NO3−-N, 7.67 g/m2·d and 1.94 × 10−3g/g NO3−-N, 41 g/m2·d and 2.32 × 10−3g/g NO2−-N, respectively. Pseudomonas, Glycocaulis and SM1A02 were found to be enriched in the three biofilms, and Pseudomonas stutzeri was deduced to be the key functional microorganism. Denitrifying sludge was the optimal inoculum when wastewater treatment was the main purpose; however, Anammox sludge turned to be the optimal inoculum when wastewater treatment and energy recovery were combined. The functional microorganisms and their metabolic characteristics were revealed to be the critical factor that determined the enrichment of electrotrophic microorganisms from inocula and the performance of bio-cathode denitrification. These findings are significant to get an insight into the new electrotrophic microorganism and to develop the novel bio-cathode denitrification technology.

Linking the Effect of Antibiotics on Partial-Nitritation Biofilters: Performance, Microbial Communities and Microbial Activities.

The emergence and spread of antibiotics resistance in wastewater treatment systems have been pointed as a major environmental health problem. Nevertheless, research about adaptation and antibiotics resistance gain in wastewater treatment systems subjected to antibiotics has not been successfully developed considering bioreactor performance, microbial community dynamics and microbial activity dynamics at the same time. To observe this in autotrophic nitrogen removal systems, a partial-nitritation biofilter was subjected to a continuous loading of antibiotics mix of azithromycin, norfloxacin, trimethoprim, and sulfamethoxazole. The effect of the antibiotics mix over the performance, bacterial communities and bacterial activity in the system was evaluated. The addition of antibiotics caused a drop of ammonium oxidation efficiency (from 50 to 5%) and of biomass concentration in the bioreactor, which was coupled to the loss of ammonium oxidizing bacteria Nitrosomonas in the bacterial community from 40 to 3%. Biomass in the partial nitritation biofilter experienced a sharp decrease of about 80% due to antibiotics loading, but the biomass adapted and experienced a growth by stabilization under antibiotics feeding. During the experiment several bacterial genera appeared, such as Alcaligenes, Paracoccus, and Acidovorax, clearly dominating the bacterial community with >20% relative abundance. The system reached around 30% ammonium oxidation efficiency after adaptation to antibiotics, but no effluent nitrite was found, suggesting that dominant antibiotics-resistant phylotypes could be involved in nitrification–denitrification metabolisms. The activity of ammonium oxidation measured as amoA and hao gene expression dropped a 98.25% and 99.21%, respectively, comparing the system before and after the addition of antibiotics. On the other hand, denitrifying activity increased as observed by higher expression of nir and nos genes (83.14% and 252.54%, respectively). In addition, heterotrophic nitrification cyt c-551 was active only after the antibiotics addition. Resistance to the antibiotics was presumably given by ermF, carA and msrA for azithromycin, mutations of the gyrA and grlB for norfloxacin, and by sul123 genes for sulfamethoxazole. Joined physicochemical and microbiological characterization of the system were used to investigate the effect of the antibiotics over the bioprocess. Despite the antibiotics resistance, activity of Bacteria decreased while the activity of Archaea and Fungi increased.

New concepts in anammox processes for wastewater nitrogen removal: recent advances and future prospects.

The discovering of anaerobic ammonium oxidation (anammox) process led to the development of autotrophic nitrogen removal systems for the treatment of effluents with low C:N rate. The anammox processes provide an efficient way to remove high concentrations of ammonium compounds from industrial and urban wastewater and covert them to dinitrogen. Nevertheless, recently obtained results suggest new ways for research on autotrophic nitrogen removal system including possibility for low temperature operation, adaptation to high organic matter loads and antibiotics inhibition effect. For these reasons, the prevalence and spatial distribution of anammox communities in autotrophic nitrogen removal wastewater treatment technologies, as well as their role in formation of fixed biofilms, are reviewed here in order to illustrate the present and future significance of these microorganisms in environmental biotechnology.