Influent Total Nitrogen Concentration Research Articles

Enhanced nitrogen removal by bioelectrochemical coupling anammox and characteristics of microbial communities

To investigate the bioelectrochemical enhanced anaerobic ammonia oxidation (anammox) nitrogen removal process, a bioelectrochemical system with coupled anammox cathode was constructed using a dual-chamber microbial electrolysis cell (MEC). Specifically, a dark incubation batch experiment was conducted at 30 ℃ with different influent total nitrogen concentrations under an applied voltage of 0.2 V, and the enhanced denitrification mechanism was investigated by combining various characterization methods such as cyclic voltammetry, electrochemical impedance spectroscopy and high-throughput sequencing methods. The results showed that the total nitrogen removal rates of 96.9%±0.3%, 97.3%±0.4% and 99.0%±0.3% were obtained when the initial total nitrogen concentration was 200, 300 and 400 mg/L, respectively. In addition, the cathode electrode biofilm showed good electrochemical activity. High-throughput sequencing results showed that the applied voltage enriched other denitrifying functional groups, including Denitratisoma, Limnobacter, and ammonia oxidizing bacteria SM1A02 and Anaerolineaceae, Nitrosomonas europaea and Nitrospira, besides the anammox bacteria. These electrochemically active microorganisms comprised of ammonium oxidizing exoelectrogens (AOE) and denitrifying electrotrophs (DNE). Together with anammox bacteria Candidatus Brocadia, they constituted the microbial community structure of denitrification system. Enhanced direct interspecies electron transfer between AOE and DNE was the fundamental reason for the further improvement of the total nitrogen removal rate of the system.

Insights into regulating influent nitrogen load to restore autotrophic nitrogen removal performance of a two-stage reactor

To better understand performance recovery and its mechanism, after the deterioration of an anaerobic ammonia oxidation (anammox) process, experiments were conducted in a UASB reactor. A two-stage anammox reaction was conducted in the reactor, and long-term continuous operation was conducted for 202 d. The mechanism of performance recovery was studied by adjusting the total nitrogen (TN) concentration and hydraulic retention time (HRT) of the influent. The results showed that after the long-term continuous operation, the TN removal efficiency decreased from 88.22 % before deterioration to 11.68 %, and then recovered to 80.63 %. The nitrogen loading rate decreased from 2.25 kg-N/m3/d before deterioration to 0.26 kg-N/m3/d and then recovered to 2.79 kg-N/m3/d. Nitrogen removal load (NRR) decreased from 1.98 kg-N/m3/d to 0.26 kg-N/m3/d before deterioration and recovered to 2.25 kg-N/m3/d. Microbial diversity was analyzed by high-throughput sequencing. During the operation, the dominant anammox strains changed from Candidatus Kuenenia (24.19 %) before deterioration to Candidatus Brocadia (11.90 %) after recovery. The influent TN concentration and HRT were the key factors that affected performance recovery. Reducing the influent TN concentration and shortening the HRT can effectively avoid the inhibition of anammox by the substrate and enable the rapid recovery of nitrogen removal performance. As the microorganisms in the reactor recovered their activity through enrichment, the influent TN gradually increased, and produced NRR higher than the pre-deterioration level, so the reactor performance was fully restored. This study provides a scientific support for recovering the two-stage anammox process performance after deterioration.

Enrichment of Ca. Jettenia in sequencing batch reactors operated with low nitrogen loading rate and high influent nitrogen concentration

To apply the anammox processes into the mainstream of domestic wastewater treatment plants, two laboratory-scale sequence batch reactors have been developed and used with two different activated sludges seeded in each sequence batch reactors with gradually increases influent total nitrogen concentrations under low nitrogen loading rates. During 320 days of operation, both sequence batch reactors showed high specific anammox activity (0.68 – 0.75 kgN kg−1VSS d−1) and a nitrogen removal efficiency of 97.50%. To monitor changes in microbial community dynamics during enrichment, high-throughput sequencing analysis was performed. Members taxonomically affiliated with Candidatus Jettenia were markedly enriched and predominant in both sequence batch reactors in response to the increasing influent total nitrogen concentrations. These results suggest that Candidatus Jettenia might be a prominent anammox genus under low nitrogen loading rate with high total nitrogen concentration conditions and could be suitably applied to the mainstream process of domestic wastewater treatment systems.

Impacts of hydraulic retention time and inflow water quality on algal growth in a shallow lake supplied with reclaimed water

Landscape lakes supplied with reclaimed water often face the threats of algal blooms. To guarantee the water quality in an artificial shallow lake (Lake M), algal growth and water quality changes were predicted by Delft3D. When the concentrations of influent total nitrogen (TN) and total phosphorous (TP) were fixed at 10 ​mg ​N/L and 0.2 ​mg ​P/L, respectively, increases in the hydraulic retention time (HRT) which was induced by water depth increased algal growth. The average algal density in Lake M was 6.42 ​× ​104 ​cells/mL when the HRT was 4 ​d, which increased to 2.14 ​× ​105 ​cells/mL when the HRT was 8 ​d. These results showed that the shallowness of the lake contributed positively to algae control. The shallower water depth came with the shorter HRT while nutrient load and light intensity were increased subsequently, which usually favor algal growth but not the dominant factors of algal density in Lake M. When the influent TN concentration was between 2 and 15 ​mg ​N/L of which nitrate changed, the HRT was fixed at 8 ​d, and the influent TP concentration was 0.2 ​mg/L, the algal density was approximately 2 ​× ​105 ​cells/mL. Algae were not sensitive to changes in the influent TN concentration, and TN should be considered as a secondary factor in algal growth. Increases in the TP concentration promoted algal growth because phosphorous is the dominant nutrient for algae to acquire from reclaimed water if there is sufficient nitrogen. When the HRT of the lake was 8 ​d and the influent TN concentration was 10 ​mg/L, the average algal density in the lake was on the order of 104 ​cells/mL as the TP concentration was 0.1 ​mg/L. Because the water depth determines the HRT, it should be carefully considered during design and construction of artificial lakes. Influent phosphorus should be monitored to control algal blooms during maintenance of artificial lakes.

Simultaneous nitrogen removal and phosphorus recovery using an anammox expanded reactor operated at 25 °C

While anammox is a cost-effective nitrogen treatment process for wastewater with high nutrient strength, phosphorus remains untouched during this process and needs further treatment. In this study, the nitrogen removal and phosphorus recovery were achieved simultaneously at 25 °C using an anammox expanded bed. A stable high nitrogen removal efficiency of 83.7 ± 4.8% at a 1500 mgN/L influent total nitrogen concentration and a phosphorus removal efficiency of 94.2 ± 1.2% at 100 mg P/L influent total phosphorus were obtained during continuous operation. The effects of the nitrogen loading rate, hydraulic retention time (HRT), pH, Ca2+ and PO43- concentration on the phosphorus removal was verified in the long-term operation of the reactor. The sludge produced contained a high content of phosphorus mainly in the form of hydroxyapatite (HAP), and the sludge composition strongly reflected the nitrogen and phosphorus loading. The structure of the anammox-HAP composite granules was illustrated by the use of fluorescence in situ hybridization (FISH) and Raman spectroscopic mapping analysis. The results in this study indicate that by controlling the operation parameters, it is possible to integrate a high efficiency phosphorus recovery with the anammox process, and significantly reduce the nutrient loading for further wastewater treatment.

Pollutant removal performance of an integrated system that combines a baffled vertical-flow wetland and a scenic water body.

Stormwater treatment requires effective control measures and development of low-cost and high-efficiency technologies. An integrated system is developed by combining a baffled vertical-flow constructed wetland (BVFCW) and a scenic water body for stormwater quality control purpose. The objectives of the study are to compare the pollutant removal performance of the full-scale integrated system with four groups of wetland-to-scenic water body area ratios (WSARs) including 1/11, 2/11, 3/11, 4/11 and investigate its treatment efficiency. Results show that the system performs better in the removal of chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH4+-N), nitrate-nitrogen (NO3-N), and total phosphorus (TP) at the WSAR of 4/11 than that at 3/11 in sixteen-day operation, while it reaches the highest total nitrogen (TN) removal efficiency of 74.0% at the WSAR of 2/11 due to relatively rich carbon source and high influent TN concentration. The integrated system may prove the most effective COD removal at the WSAR of 4/11 for four-time aerobic/anaerobic alternating conditions, a longer flow path and more time to contact with substrates, although the influent COD is lower than that at 2/11 and 1/11. After sixteen-day operation, BVFCW achieved COD removal rate of 90.3%, NH4+-N removal rate of 85.7%, NO3-N removal rate of 68.6%, and TP removal rate of 52.5% at the WSAR of 4/11. At the WSAR of 1/11, effluent met the Class IV requirements in Chinese standards after one-week operation, while effluent met the Class III requirements under the rest conditions. Since effluent in all WSARs met the standards, WSARs of 1/11 and 2/11 were recommended.

Nitrogen removal efficiencies and pathways from unsaturated and saturated zones in a laboratory-scale vertical flow constructed wetland

A laboratory-scale vertical flow constructed wetland system was designed and monitored to compare nitrogen removal rates and pathways from both saturated and unsaturated zones under a hydraulic loading rate and influent total nitrogen concentration of 1.5 m3/m2.d and 508 mg/L respectively. Weekly measurements of the concentrations of nitrogen compounds, chemical oxygen demand, temperature, dissolved oxygen, oxidation-reduction potential, and hydrogen ion concentration were taken throughout the study. At the end of the experiments, PCR analysis of 16S rRNA gene sequencing was performed to identify microbial communities in the unsaturated and saturated parts of the system. The nitrogen compounds were removed from the system after 182 days, with similar total nitrogen removal efficiencies (94% and 93%) for the unsaturated and saturated zones respectively. Heterotrophic nitrification/aerobic denitrification was the major pathway responsible for the removal of nitrogen compounds. Adsorption into the gravel bed also contributed to ammonium removal. Proteobacteria were the dominant bacterial strains involved in nitrogen transformation and accounted for 80% of the total bacteria in the unsaturated zone and 60% in the saturated zone. With little difference in the concentration removal efficiencies of the unsaturated and saturated zones, a more effective design would be an entirely saturated wetland as the total mass removal of nitrogen depends on the water volume stored, which at full saturation in this design was seven times greater per unit wetland volume than the unsaturated zone.

Feed distribution based on sensing ammonium concentration after sub-feeding to achieve target effluent nitrogen concentration in sequencing batch reactors

Conventional sequencing batch reactors (SBRs) have been developed based on nitrogen removal efficiency rather than the effluent nitrogen concentration as a design factor. The purpose of this study was to achieve the target effluent total nitrogen (TN) concentration regardless of the influent nitrogen concentration at 10 m3 pilot SBR. The desired nitrogen removal efficiency was achieved by distributing the influent one to four times in one cycle, but effluent TN concentration fluctuated as the influent nitrogen concentration varied. To achieve the target effluent TN concentration, the residual ammonia concentration after sub-feeding was adjusted to the target nitrogen concentration based on real-time ammonia sensing. When the residual ammonia concentration after sub-feeding was set at 10 or 5 mg NH4+-N L−1, the effluent TN concentration was 9.3 ± 0.6 or 4.6 ± 0.3 mg L−1, respectively, regardless of the influent TN concentration. Furthermore, complete nitrification was achieved under low temperature, from 7.2 to 13.1 °C, by controlling the aeration phase end point based on the real-time ammonia sensing. However, when the residual nitrate concentration was adjusted to a low level, the total phosphorus (TP) removal efficiency was high owing to an increase of phosphate release activity by polyphosphate accumulating organisms.

The Impact of Carbon Source as Electron Donor on Composition and Concentration of Dissolved Organic Nitrogen in Biosorption-Activated Media for Stormwater and Groundwater Co-Treatment.

Eutrophication has been a long-term issue in aquatic environments, where dissolved organic nitrogen (DON) recalcitrance is important. Bioavailable nitrogen qualification and quantification for effluents from stormwater and wastewater are always a challenge. The information in this study deepens the understanding of the interactions between carbon addition and DON decomposition through linear-ditch best management practices for stormwater and groundwater cotreatment. By running a laboratory-scale column study for nitrogen removal using green sorption media, the variation in composition and concentration of DON can be further linked to the population dynamics of microbial species that dominate the nitrification and denitrification processes. With the varying levels of influent total nitrogen concentration, the efficacy of nitrogen removal via biosorption activated media may be realized at the molecular level with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry.

Effects of salinity on the nitrogen removal efficiency and bacterial community structure in fixed-bed biofilm CANON bioreactors

The discovery of anaerobic ammonium oxidation processes led to the development of innovative nitrogen removal technologies, which are more cost-effective and environmentally friendly than conventional activated sludge systems. In this study, the bacterial community structure was determined as well as the nitrogen removal efficiencies in four fixed-bed biofilm bioreactors, working under different salt concentrations (0, 3, 25, and 45 g L−1 of sodium chloride (NaCl)) and at hydraulic retention times (HRT) of 6 and 12 h. The influent total nitrogen concentration was 250 mg L−1. The results showed a clear inhibition in the nitrogen removal capacity of the process that was directly related to the salt concentration in the influent, most likely due to changes in the bacterial community structure; increases in the NaCl concentration provoked the inhibition of Candidatus Brocardia and Nitrosomonas, whereas heterotrophic phylotypes such as Marinobacter proliferated. An evident adaptation of the anammox microorganisms at 3 g NaCl L−1 was observed, whereas ammonia and nitrite oxidizing bacteria drastically decreased at 25 and 45 g NaCl L−1. Total nitrogen efficiencies for 6 h of HRT were 87.68, 64.25, 38.79, and 19.74%, for 0, 3, 25, and 45 g NaCl L−1, respectively. No significant effects were detected on the performance of the bioreactors and bacterial diversity under different HRT. Our study may be useful for the implementation of CANON systems at real-scale, by increasing the knowledge on the bacterial community at different NaCl concentrations and the performance of this novel technology for saline wastewater treatment.

Substrate inhibition and concentration control in an UASB-Anammox process

An UASB-Anammox reactor was operated for more than one year to study the process performance variations respond to the nitrogen loading rate (NLR) and substrate concentration. The IC10 (451.1mg/L), IC50 (725.3mg/L) and the prospected threshold of influent total nitrogen (TN) concentration were simulated. A stable TN removal efficiency was obtained when the TN influent was controlled. The disequilibrium distribution of the substrate following the plug flow with the height of the reactor resulted in significant variations in specific Anammox activity from the bottom to the top of the reactor (348→3mgN/gVSS/d). With long term acclimation, the nitrogen removal capacity of Anammox sludge varied significantly, with the most activated sludge obtained in the bottom part a 100 times capacity greater than that of the top. A stable performance with high removal efficiency in the constructed UASB-Anammox reactor was obtained when the influent TN concentration was below 451.1mg/L.

Treatment of high-strength rare-earth ammonia wastewater with two-stage anammox process

<p>In this study, a two-stage anaerobic ammonium oxidation (anammox) system—including a partial nitritation system with a biological selector (PNBS) and a granular activated carbon-based granule anammox process (GAP) —was used for the treatment of real high-strength rare-earth ammonia wastewater (HRAW). A nitrogen removal rate of 89% on average was achieved at the end of the study with the influent total nitrogen concentration of 2200 mg l<sup>-1</sup>. The nitrogen-loading rate (NLR) of 17 kg N/(m<sup>3</sup>×d) was achieved in the PNBS, and a reduced NLR of 6 kg N/(m<sup>3</sup>×d) was maintained in the GAP. To our knowledge, this is the highest NLR applied to a two-stage anammox system. A genetic analysis of the sludge samples revealed that a <em>Nitrosomonas</em><em> sp.</em> was enriched in the PNBS reactor, while, <em>Kuenenia stuttgartiensis</em><sub>,</sub><em> Uncultured bacterium clone KIST-JJY001</em>, and <em>Uncultured anoxic sludge bacterium KU2</em> were enriched in the GAP reactor.</p>

NaH2PO4 as pH buffer in an anaerobic ammonium oxidation (anammox) reactor treating high-strength livestock manure digester liquor

AbstractIn order to use livestock manure digester liquor (LMDL) as liquid fertilizer, NaH2PO4 was evaluated for its effectiveness as pH buffer in an anaerobic ammonium oxidation (anammox) reactor treating high-strength LMDL. The results show that influent total nitrogen (TN) concentration was increased from 500 to 2,200 mg/L with the addition of NaH2PO4 as a pH buffer. To the best of our knowledge, this is the highest influent TN concentration for anammox reactor in treating LMDL. An average TN removal efficiency of 85% was observed in LMDL treatment without dilution. The treated effluent may be applied directly as a terrestrial liquid fertilizer, as the effluent has a suitable balance of nitrogen and phosphorus (approximately 1:1). 16S rRNA gene analysis showed that Kuenenia stuttgartiensis and Uncultured bacterium clone KIST-JJY001, known as anammox bacteria, shared approximately 26% in genus level in the reactor. Uncultured bacterium clone Dok53, Uncultured bacterium clone KIST-JJY024, Uncultured bacte...

Use of duckweed-based constructed wetlands for nutrient recovery and pollutant reduction from dairy wastewater

Over the last few decades, constructed wetlands have increasingly been designed and implemented to treat agricultural wastewaters. However, while treatment of manure-containing wastewaters protects water quality, it also eliminates a valuable source of nutrient-laden soil amendments. The goal of this research is to investigate the ability of wetlands to simultaneously treat high-strength manure-containing wastewaters while recovering nutrients from the manures in plant biomass. Diluted raw dairy waste was fed to a combination of duckweed-based surface flow and subsurface flow wetlands. Nutrient recovery through duckweed harvesting and waste treatment, characterized by chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and E. coli removal, were assessed under steady-state conditions for three strengths of waste. Duckweed-based wetlands used for primary treatment had higher removal rates of COD and TN than those used for secondary treatment; however, no significant difference was observed for TP removal rates. COD removal ranged from 3 to 81% in primary duckweed wetlands and from −35% to 38% in secondary duckweed wetlands. Areal removal rates for nutrients in primary duckweed wetlands were 194.9±18.9gTN/m2/yr and 13.0±3.0gTP/m2/yr, while removal rates in secondary duckweed wetlands were 104.1±13.1gTN/m2/yr and 9.3±2.1gTP/m2/yr. Removal of COD, TN, and TP more closely followed first-order removal to a background concentration than first-order removal or a previously published model for duckweed ponds. Mean log E. coli reduction of 0.30 obtained in this experiment was within the range reported in literature. Duckweed production in the wetlands was satisfactorily described as a second-order polynomial function of influent TN concentration. More N and P was recovered from primary wetlands as compared to secondary wetlands. Average N and P recovered by harvesting duckweed across all the wetlands were 22.4gN/m2/yr and 7.4P/m2/yr, respectively.

Overall functional gene diversity of microbial communities in three full-scale activated sludge bioreactors.

Understanding microbial community composition is thought to be crucial for improving process functioning and stabilities of full-scale activated sludge reactors in wastewater treatment plants (WWTPs). However, functional gene compositions of microbial communities within them have not been clearly elucidated. To gain a complete picture of microbial community, in this study, GeoChip 4.2 was used to profile the overall functional genes of three full-scale activated sludge bioreactors, the 16S rRNA gene diversities of which had been unveiled by 454-pyrosequencing in our previous investigation. Triplicate activated sludge samples from each system were analyzed, with the detection of 38,507 to 40,654 functional genes. A high similarity of 77.3-81.2% shared functional genes was noted among the nine samples, verified by the high 16S rRNA gene similarity with shared operational taxonomic units (OTUs) constituting 66.4-70.0% of the detected sequences in each system. Correlation analyses showed that the abundances of a wide array of functional genes were associated with system performances. For example, the abundances of carbon degradation genes were strongly correlated to chemical oxygen demand (COD) removal efficiencies (r = 0.8697, P < 0.01). Lastly, we found that sludge retention time (SRT), influent total nitrogen concentrations (TN inf), and dissolved oxygen (DO) concentrations were key environmental factors shaping the overall functional genes. Together, the results revealed vast functional gene diversity and some links between the functional gene compositions and microbe-mediated processes.

Nitrogen removal from wastewater plant secondary effluent in a compound natural treatment system

A method for removal of low concentrations of nitrogen in the secondary effluent from a wastewater plant was evaluated. The method can be summarized as follows: Primary Subsurface Vertical Flow Wetland (PSVFW)→Submerged Macrophyte Oxidation Ponds (SMOPs)→Secondary Subsurface Vertical Flow Wetland (SSVFW). Pilot experiments were conducted to assess the efficiency of total nitrogen (TN) removal from secondary effluent from the Chengjiang Wastewater Treatment Plant, China. At a total hydraulic retention time (HRT) of 21.38 days and a hydraulic loading (HL) of 0.024m3m−2d−1, the average TN concentration in the influent decreased from 6.60mgL−1 in the influent to 0.87mgL−1 in the effluent, thus meeting the Class-III surface water standards. PSVFW mediated the ammonification of organic nitrogen (ORG-N) and the nitrification of NH3-N (ammonia), resulting in a TN reduction of 7.58%. In the SMOPs, the concentration of NH3-N was further reduced, and most NO3−-N (nitrate nitrogen) was denitrified under aerobic conditions, resulting in a 63.18% TN reduction. In the SSVFW, the concentrations of the remaining NO3−-N and ORG-N declined even further so that the whole process accounted for an 86.82% TN removal efficiency relative to the influent TN concentrations.

Nitrogen Removal from Wastewater Using a Hybrid Membrane‐Biofilm Process: Pilot‐Scale Studies

The hybrid membrane biofilm process (HMBP) is a new approach to achieving total nitrogen removal from wastewater. Air-filled, hollow-fiber membranes are placed into an activated sludge basin and bulk aeration is suppressed. A nitrifying biofilm develops on the membranes, exporting nitrate and nitrite to the bulk liquid. The nitrate and nitrite are reduced by suspended biomass using influent BOD as the electron donor. Previous research demonstrated the HMBP concept at the bench scale and explored process fundamentals. This research explored the HMBP at the pilot scale, with a 120-L reaction tank, real wastewater, and a potentially scalable configuration. Nitrification rates averaged 0.5 g N m(-2)/d(-1), which were lower than found at the bench scale, and lower than predicted by a mathematical model, but still allowed effluent total nitrogen concentrations below 6 mg N/L with an average influent total nitrogen concentration of 25 mg N/L and a hydraulic retention time of 12 hours. More than 75% of the produced nitrate and nitrite was reduced with an average influent sCOD of only 68 mg/L and an average C:N ratio of 3.1. Mass balances on carbon and nitrogen suggest that nitrogen removal via nitrite occurred. This research confirms that the HMBP process is effective for BOD and nitrogen removal from wastewater, and suggests that the grid configuration is viable for scale-up.