Maximum Total Nitrogen Removal Rate Research Articles

Resource-efficient nitrogen and salinity removal in a synergistic partial nitritation-anammox bioelectrochemical system

We investigated the performance of a two-stage partial-nitritation-anammox biocathode integrated microbial desalination cell (TNiAmoxMDC) for concurrent nitrogen removal, desalination, and bioelectricity generation at different aeration rates in the nitritation chamber. The TNiAmoxMDC system achieved a maximum total nitrogen removal rate of 50.4 ± 8.2 g-TN/m3/d with 300 mW/m2 of maximum power production utilizing 500 mg/L of glucose chemical oxygen demand (COD) in the anode. The organic removal in the anode chamber showed a good fit to first order reaction model with a rate constant of 0.036 h−1. The biocatalytic activity of anammox bacteria in the biocathode produced a current density of 0.7 A/m2 in the absence of oxygen. More than 98% of the salinity was removed at a rate of 1.48 mg/h. The energy consumption values for nitrogen removal at aeration rates of 0.7, 2.2, and 10 ml/min were 0.022, 0.55, and 0.20 kWh/kg-N, respectively. The maximum energy produced by the TNiAmoxMDC was 0.0157 kWh/m3. Excluding the energy consumption by the system, the net energy recovery was 0.0023 kWh/m3 at an airflow rate of 10 ml/min. Thus, the integration of the partial nitritation-anammox process with microbial desalination cell (MDC) provides energy-and resource-efficient synergy for bioelectrochemical wastewater treatment.

Performance of a continuous micro-oxygen up-flow sludge bed reactor for assimilation of partial nitrification/anammox sludge into a CANON granular-floc system

CANON process was established in a micro-oxygen up-flow sludge bed reactor through one-step inoculation of partial nitrification/anammox sludge. The process was divided into three stages according to the influent NH+4-N concentrations. The position of aeration played a vital role as low DO concentration and sludge loss showed evident negative effects. Placing the aeration device above the sludge bed significantly enhanced the stability of the system, and the DO concentrations were maintained between 0.4 and 0.8 mg/L. The total nitrogen (TN) removal efficiency reached ∼70% within 5 days in stage I, yet the reaction stoichiometric ratios deviated from theoretical values. As the activity of anaerobic anammox bacteria (AnAOB) exceeded ammonia oxidizing bacteria (AOB) in stage III, the maximum TN removal rate reached 350 mg N/ L·d and the TN removal efficiency was retained at a relatively high value of 83%. Flocculent sludge converged into a granular-floc hybrid system with the percentage of sludge mass for particle size between 0.4 and 1 mm increased from 0% to 43.48%, and the percentage of sludge mass for particle size between 0 and 0.2 mm remained at 22.76%. Following 135 days of continuous operation, an interaction balance between AOB and AnAOB was reached with high activities and dominant abundance while nitrite oxidizing bacteria (NOB) were suppressed.

Removal of pollutants and accumulation of high-value cell inclusions in a batch reactor containing Rhodopseudomonas for treating real heavy oil refinery wastewater

Treating wastewater using purple non-sulfur bacteria (PNSB) is an environmentally friendly technique that can simultaneously remove pollutants and lead to the accumulation of high-value cell inclusions. However, no PNSB system for treating heavy oil refinery wastewater (HORW) and recovering high-value cell inclusions has yet been developed. In this study, five batch PNSB systems dominated by Rhodopseudomonas were used to treat real HORW for 186 d. The effects of using different hydraulic retention times (HRT), sludge retention times (SRT), trace element solutions, phosphate loads, and influent loads were investigated, and the bacteriochlorophyll, carotenoid, and coenzyme Q10 concentrations were determined. The community structure and quantity of Rhodopseudomonas in the systems were determined using a high-sequencing technique and quantitative polymerase chain reaction technique. The long-term results indicated that phosphate was the limiting factor for treating HORW in the PNSB reactor. The soluble chemical oxygen demand (SCOD) removal rates were 67.03% and 85.26% without and with phosphate added, respectively, and the NH4+-N removal rates were 32.18% and 89.22%, respectively. The NO3−-N concentration in the effluent was stable at 0–3 mg/L with or without phosphate added. Adding phosphate increased the Rhodopseudomonas relative abundance and number by 13.21% and 41.61%, respectively, to 57.35% and 8.52 × 106 gene copies/μL, respectively. The SRT was the limiting factor for SCOD removal, and the bacteria concentration was the limiting factor for nitrogen removal. Once the inflow load had been increased, the total nitrogen (TN) removal rate increased as the HRT increased. Maximum TN removal rates of 64.46%, 68.06%, 73.89%, 82.15%, and 89.73% were found at HRT of 7, 10, 13, 16, and 19 d, respectively. The highest bacteriochlorophyll, carotenoid, and coenzyme Q10 concentrations were 2.92, 4.99, and 4.53 mg/L, respectively. This study provided a simple and efficient method for treating HORW and reutilizing resources, providing theoretical support and parameter guidance for the application of Rhodopseudomonas in treating HORW.

Insights into nitrogen removal and microbial response of marine anammox bacteria-based consortia treating saline wastewater: From high to moderate and low salinities

Marine anammox bacteria (MAB) have promising nitrogen removal performance in high saline wastewater treatment. Nevertheless, the impact resulting from moderate and low salinities on MAB is still unclear. Herein, MAB were applied to treat saline wastewater from high to moderate and low salinities for the first time. Independent of salinities (35–3.5 g/L), MAB consistently exhibited good nitrogen removal performance, and maximum total nitrogen removal rate (0.97 kg/(m3·d)) occurred at 10.5 g/L salts. More extracellular polymeric substances (EPSs) were secreted by MAB-based consortia to resist hypotonic surroundings. However, a sharp EPS decrease was accompanied by the collapse of MAB-driven anammox process, and MAB granules disintegrated due to long-term exposure to salt-free environment. The relative abundance of MAB varied from 10.7% to 15.9% and 3.8% as salinity decreased from 35 to 10.5 and 0 g/L salts. These findings will provide practical implementation of MAB-driven anammox process treating wastewater with different salinities.

Using an innovative umbrella-shape membrane module to improve MBR for PN-ANAMMOX process.

Membrane fouling has been a key factor limiting the applications of membrane bioreactor (MBR). In this study, a novel umbrella-shape membrane module was applied to construct two MBRs for two-stage partial nitrification-anaerobic ammonia oxidation (PN-ANAMMOX) process. After 55days operation, the ANAMMOX process was started and the PN process was well controlled. Then, the ANAMMOX and PN process were successfully coupled to run the PN-ANAMMOX process. On 103days, the best nitrogen removing effect was achieved with the maximum nitrogen loading rate (NLR) of 0.4kgN·(m3·d)-1 and the corresponding maximum total nitrogen removal rate (TNRR) of 75.23%.The umbrella-shape membrane module in both reactors only needed to be cleaned once during the operation for 105days, indicating that the membrane module had better resistance to membrane fouling. The functional bacteria were cultivated in suspension state; moreover, the cell densities of ammonia oxidizing bacteria (AOB) and ANAMMOX bacteria (AnAOB) reached 58.32 × 1012 copies/g sludge and 28.39 × 1012 copies/g sludge. Their abundances reached 73.25% and 57.80% of the total bacteria, respectively. MBR improved by umbrella-shape membrane module could realize the rapid start-up of ANAMMOX process, effective control of PN process, and stable operation of PN-ANAMMOX process. This study provided a novel approach to control membrane fouling by optimizing the membrane module shape and widened applications of MBRs in PN-ANAMMOX process.

Performance, kinetics characteristics and enhancement mechanisms in anammox process under Fe(II) enhanced conditions.

In order to explore the performance, kinetics characteristics and enhancement mechanisms in anammox process under ferrous iron enhanced conditions, a laboratory-scale UASB anammox reactor has been built up and operated for 534days. Experimental results showed that the Anammox process was successfully started up in a short operation period and the TNRE reached 83.34 ± 2.96% with a maximum total nitrogen removal rate of 14.4kgm-3 d-1 after long-term operated under influent Fe(II) concentration of 5.3mgL-1. Simulation results using different kinetic models showed that the Stover-Kincannon model and the Grau second-order model were useful for describing the anammox performance under Fe(II) enhanced conditions. Extracellular polymeric substance (EPS) act a pivotal part in the granulation of Anammox sludge and the improvement of anammox activity. Iron improved the hydrophobicity of the sludge by reducing the PN/PS ratios, and also increased the Anammox granular diameter. The granular diameter of higher than 2.00 accounted for 58.3% of the total sludge. At the same time, the presence of iron decreased EPS levels, and also decreased the iron adsorption ability to sludge. More iron was transported into Anammox, which improved the nitrogen removal ability in the Anammox reactor.

Adaptation and characterization of thermophilic anammox in bioreactors

Anammox, the oxidation of ammonium with nitrite, is a key microbial process in the nitrogen cycle. Under mesophilic conditions (below 40 °C), it is widely implemented to remove nitrogen from wastewaters lacking organic carbon. Despite evidence of the presence of anammox bacteria in high-temperature environments, reports on the cultivation of thermophilic anammox bacteria are limited to a short-term experiment of 2 weeks. This study showcases the adaptation of a mesophilic inoculum to thermophilic conditions, and its characterization. First, an attached growth technology was chosen to obtain the process. In an anoxic fixed-bed biofilm bioreactor (FBBR), a slow linear temperature increase from 38 to over 48 °C (0.05–0.07 °C d−1) was imposed to the community over 220 days, after which the reactor was operated at 48 °C for over 200 days. Maximum total nitrogen removal rates reached up to 0.62 g N L−1 d−1. Given this promising performance, a suspended growth system was tested. The obtained enrichment culture served as inoculum for membrane bioreactors (MBR) operated at 50 °C, reaching a maximum total nitrogen removal rate of 1.7 g N L−1 d−1 after 35 days. The biomass in the MBR had a maximum specific anammox activity of 1.1 ± 0.1 g NH4+-N g−1 VSS d−1, and the growth rate was estimated at 0.075–0.19 d−1. The thermophilic cultures displayed nitrogen stoichiometry ratios typical for mesophilic anammox: 0.93–1.42 g NO2--Nremoved g−1 NH4+-Nremoved and 0.16–0.35 g NO3--Nproduced g−1 NH4+-Nremoved. Amplicon and Sanger sequencing of the 16S rRNA genes revealed a disappearance of the original “Ca. Brocadia” and “Ca. Jettenia” taxa, yielding Planctomycetes members with only 94–95% similarity to “Ca. Brocadia anammoxidans” and “Ca. B. caroliniensis”, accounting for 45% of the bacterial FBBR community. The long-term operation of thermophilic anammox reactors and snapshot views on the nitrogen stoichiometry, kinetics and microbial community open up the development path of thermophilic partial nitritation/anammox. A first economic assessment highlighted that treatment of sludge reject water from thermophilic anaerobic digestion of sewage sludge may become attractive.

Ameliorating nitrite inhibition in a low-temperature nitritation–anammox MBBR using bacterial intermediate nitric oxide

The long-term sustainability of an anaerobic ammonium oxidation (anammox) process in a moving bed biofilm reactor (MBBR) treating highly concentrated (mean of 740 mg NH4 +-N L−1) wastewater was demonstrated by 1600 days of efficient operation. A high maximum total nitrogen removal rate (TNRR) of 1.5 g N m−2 d−1 was achieved at the low temperature of 20 °C. For nitrogen removal recovery in cases of nitrite inhibition, anammox intermediate nitric oxide (NO) was tested in batch experiments as an N-removal accelerating agent. The effect of the addition of various NO dosages (8–72 mg NO-N L−1) was studied under inhibitory nitrite concentrations (>100 mg NO2 −-N L−1) for anammox bacteria. Optimal maintained NO concentration was 58 mg NO-N L−1 and brought about the highest biofilm-specific anammox activity (SAA). Compared to a blank test, the minimum concentration of added NO of 40 mg NO-N L−1 showed a statistically significant (p < 0.05) accelerating effect on SAA. No inhibition of SAA by NO was observed, although at NO concentrations exceeding 72 mg NO-N L−1, the acceleratory effect upon SAA was decreased by 8%. Changes in the bacterial consortia involved in nitrogen conversion were determined concurrently for the different nitrogen removal rates and operational conditions. Quantities of Planctomycetales clone P4 strains, which are the closest (99% similarity) relative to Candidatus Brocadia fulgida, increased from 1 × 103 to 1 × 106 anammox gene copies per g total suspended solids during reactor operation days 568–1600, which was determined by quantitative polymerase chain reaction. During the operation of the MBBR, the abundance of ammonium-oxidizing bacteria (AOB) increased proportionally (up to 30%). The abundance of nitrite-oxidizing bacteria (NOB) did not increase (remaining below 10%) during days 232–860. AOB became predominant over NOBs owing to the inhibition of free ammonia spiking on NOBs.

16S rRNA gene high-throughput sequencing reveals shift in nitrogen conversion related microorganisms in a CANON system in response to salt stress

Salinity is an important factor affecting the activity and community structure of nitrogen transformation-related microorganisms in natural and engineered ecosystems. However, salinity’s impact on microbial diversity in completely autotrophic nitrogen removal over nitrite (CANON) processes remains poorly described. In this study, the microbial community dynamic of a CANON system was comprehensively evaluated in response to increasing salt stress using 16S rRNA gene high-throughput sequencing technology. The CANON system can treat ammonia-rich (200mg/L) wastewater with salinity up to 15gNaCl/L after gradual acclimation to salt, and the maximum total nitrogen removal rate achieved was 0.23kg/m3/d at 10gNaCl/L. Salinity of 20gNaCl/L caused rapid deterioration of the nitrogen removal performance because of a sharp decline in the ammonia oxidation rate. Beta diversity with elevated salinity by redundancy analysis proved that salinity played an important role in the microbial community dynamics of the functional microbes in the CANON system. “Candidatus Kuenenia” anaerobic ammonia oxidation (anammox) bacteria and “Nitrosomonas europaea” ammonia oxidation bacteria were robust under salt stress and could survive at salinity up to 15gNaCl/L, while “Candidatus Jettenia” anammox bacteria were sensitive to salinity and even 5gNaCl/L caused a sharp decline in their abundance. The nitrite oxidation rate showed extreme sensitivity to 5gNaCl/L salinity; however, overgrowth of “Nitrospira” nitrite oxidation bacteria even at elevated salinity is a matter of concern for successful CANON operation. 16S rRNA gene high-throughput analyses offer new insights at high resolution and depth into the stability and dynamics of functional microbial communities in CANON systems under increasing salt stress, highlighting the importance of microbial diversity and balance in the CANON process.

Step-wise temperature decreasing cultivates a biofilm with high nitrogen removal rates at 9°C in short-term anammox biofilm tests

ABSTRACTThe anaerobic ammonium oxidation (anammox) and nitritation-anammox (deammonification) processes are widely used for N-rich wastewater treatment. When deammonification applications move towards low temperature applications (mainstream wastewater has low temperature), temperature effect has to be studied. In current research, in a deammonification moving bed biofilm reactor a maximum total nitrogen removal rate (TNRR) of 1.5 g N m−2 d−1 (0.6 kg N m−3 d−1) was achieved. Temperature was gradually lowered by 0.5°C per week, and a similar TNRR was sustained at 15°C during biofilm cultivation. Statistical analysis confirmed that a temperature decrease from 20°C down to 15° did not cause instabilities. Instead, TNRR rose and treatment efficiency remained stable at lower temperatures as well. Quantitative polymerase chain reaction analyses showed an increase in Candidatus Brocadia quantities from 5 × 103 to 1 × 107 anammox gene copies g−1 total suspended solids (TSS) despite temperature lowered to 15°C. Fluctuations in TNRR were rather related to changes in influent concentration. To study the short-term effect of temperature on the TNRR, a series of batch-scale experiments were performed which showed sufficient TNRRs even at 9–15°C (1.24–3.43 mg N g−1 TSS h−1, respectively) with anammox temperature constants (Q10) ranging 1.3–1.6. Experiments showed that a biofilm adapted to 15°C can perform N-removal most sufficiently at temperatures down to 9°C as compared with biofilm adapted to higher temperature. After biomass was adapted to 15°C, the decrease in TNRR in batch tests at 9°C was lower (15–20%) than that for biomass adapted to 17–18°C.

Reactor kinetics evaluation and performance investigation of a long-term operated UASB-anammox mixed culture process

To optimize the operation and know the relationships between operation and potential capability of UASB-anammox mixed culture process, reactor kinetic models were conducted and the potential nitrogen conversion rates were estimated. Total nitrogen (TN), NH4+-N and NO2−-N removal efficiency were simulated and predicted by modified Stovere-Kincannon model, Monod model, First-order model and Grau second-order substrate removal models. The nitrogen gas production rate was also evaluated by Van der meer and heertjes model. During the process, the nitrogen loading rate (NLR) was increased from 0.93 to 7.34 g L−1 d−1 following the substrate increased from 280 to 462 mg N L−1 and hydraulic residence times (HRT) decreased from 24 h to 1.5 h, the highest achieved removal efficiency of NH4+–N, NO2−–N and TN were 99, 95 and 90%, respectively. Simulation results proved that the Modified Stover-Kincannon model and the Grau second-order model were the most appropriate models with prospected maximum TN removal rate Umax and saturation value constant KB were 3.33 and 4.03 g N L−1 d−1, respectively. Validation of the linearity between the experimental data and predicted values of kinetics illustrated the two models appropriately described the kinetic behavior of UASB-anammox mixed culture. The reactor kinetic evaluation proved valuable information for guiding or optimizing the operation condition.

Nitrogen and carbon removal efficiency of a polyvinyl alcohol gel based moving bed biofilm reactor system.

In this study, the effectiveness of polyvinyl alcohol (PVA) gel beads in treating domestic wastewater was investigated: a moving bed biofilm reactor (MBBR) configuration (oxic-anoxic and oxic) with 10% filling fraction of biomass carriers was operated in a continuously fed regime at temperatures of 25, 20, 15 and 6 °C with hydraulic retention times (HRTs) of 32 h, 18 h, 12 h and 9 h, respectively. Influent loadings were in the range of 0.22-1.22 kg N m(-3) d(-1) (total nitrogen (TN)), 1.48-7.82 kg chemical oxygen demand (COD) m(-3) d(-1) (organic) and 0.12-0.89 kg NH4(+)-N m(-3)d(-1) (ammonia nitrogen). MBBR performance resulted in the maximum TN removal rate of 1.22 kg N m(-3) d(-1) when the temperature and HRT were 6 °C and 9 h, respectively. The carbon removal rate at this temperature and HRT was 6.82 kg COD m(-3) d(-1). Ammonium removal rates ranged from 0.13 to 0.75 kg NH4(+)-N m(-3) d(-1) during the study. Total phosphorus and suspended solid removal efficiency ranged from 84 to 98% and 85 to 94% at an influent concentration of 3.3-7.1 mg/L and 74-356 mg/L, respectively. The sludge wasted from the MBBR exhibited light weight features characterized by sludge volume index value of 185 mL/g. Experimental data obtained can be useful in further developing the concept of PVA gel based wastewater treatment systems.

Effects of redox mediators on nitrogen removal performance by denitrifying biomass and the activity of Nar and Nir

Abstract In this study, effects of four kinds of redox mediators on denitrification performance, nitrate and nitrite reductase activities were investigated, including anthraquinone (AQ), 2-methyl-1,4-naphthoquinone (ME), lawsone (LAW) and anthraquinone-2,6-disulphonate (AQDS). Experimental results demonstrated that the optimum dosing concentrations of AQ, ME and LAW were 75, 25 and 75 μM. The maximum total nitrogen removal rates increased to 26.02, 20.16 and 33.50 mg-N/g-VSS/h at each optimum dosing concentration, which were approximately 1.60, 1.25 and 2.08 times higher compared to that without redox mediator addition. Unlike AQ and ME, addition of LAW appeared to have suppressed the accumulation of nitrite with peak vales about 21.60 mg/L compared to that of 121.9 mg/L with AQ and 180 mg/L with ME addition. Among four kinds of redox mediators, ME increased the nitrate reductase activity about 1.97 folds, and AQDS enhanced the nitrite reductase activity about 2.08 folds compared to the controls. The unbalance of affected nitrate reductase and nitrite reductase activities by redox mediator was considered as the main reason for nitrite accumulation in this study.

Start-up and long-term operation of the Anammox process in a fixed bed reactor (FBR) filled with novel non-woven ring carriers

A novel kind of non-woven ring carriers was used to improve a fixed bed reactor (FBR) as Anammox reactor. The improved FBR was operated for about 1year. The Anammox activity occurred on day 39. On day 367, the maximum total nitrogen removal rate reached 9.2kgNm−3d−1. FISH analysis showed that Anammox bacteria predominated in the mature sludge and accounted for 78% of the total bacteria. Phylogenetic analysis further showed that Candidatus Kuenenia stuttgartiensis occupied 70% of Anammox bacteria, which benefited keeping the stability of Anammox reactor. The FBR was proved to be a suitable reactor for start-up and long-term operation of Anammox process.

Modeling of Simultaneous Partial Nitrification, Anammox and Denitrification Process In a Single Reactor

One sequencing batch reactor (SBR) seeded with anaerobic granular sludge was started-up to enrich simultaneous partial nitrification and anaerobic ammonia oxidation (Anammox) bacteria. The SBR could be operated successfully through first enriching Anammox bacteria under strictly anaerobic condition during the first stage and then controlling the dissolved oxygen (DO) in the reactor between 0.3 and 0.6 mg/L during the second and third stage, and eventually the maximum total nitrogen removal rate could reach 63.7%. Besides, a dynamic mathematical model including nitrification, Anammox, COD oxidation and denitrification was developed for the simulation of the performance of biological processes. The dynamic mathematical model was extended with two parts: model correction factors of DO, and Haldane kinetics for Anammox. Subsequently, a set of experiments and simulations were carried out to analyze the effects of substrate nitrite and DO on SBR system, and to validate the model. Research results indicated that biological processes could be inhibited by a certain nitrite concentration 20~30mg/L, and high or low DO concentration was not in favor of operation of SBR system. In addition, the simulation results were consistent with the experimental results, which illuminated that the mathematical model was appropriate for the modeling of simultaneous partial nitrification, Anammox and denitrification process in a single reactor, thus it could estimate the impact of specific parameters and predict the efficiency of system.

Effect of concentration on anammox nitrogen removal rate in a moving bed biofilm reactor

Anammox biomass enriched in a moving bed biofilm reactor (MBBR) fed by actual sewage sludge reject water and synthetically added was used to study the total nitrogen (TN) removal rate of the anammox process depending on bicarbonate () concentration. MBBR performance resulted in the maximum TN removal rate of 1100 g N m−3 d−1 when the optimum concentration (910 mg L−1) was used. The average reaction ratio of removal, production and removal were 1.18/0.20/1. When the concentration was increased to 1760 mg L−1 the TN removal rate diminished to 270 g N m−3 d−1. The process recovered from bicarbonate inhibition within 1 week. The batch tests performed with biomass taken from the MBBR showed that for the concentration of 615 mg L−1 the TN removal rate was 3.3 mg N L−1 h−1, whereas for both lower (120 mg L−1) and higher (5750 mg L−1) concentrations the TN removal rates were 2.3 (±0.15) and 1.6 (±0.12) mg N L−1 d−1, respectively. PCR and DGGE analyses resulted in the detection of uncultured Planctomycetales bacterium clone P4 and, surprisingly, low-oxygen-tolerant aerobic ammonia oxidizers. The ability of anammox bacteria for mixotrophy was established by diminished amounts of nitrate produced when comparing the experiments with an organic carbon source and an inorganic carbon source.

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation (anammox) process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months. The average removal efficiencies of ammonia and nitrite were both over 80%, and the maximum total nitrogen removal rate of 1.85 kg N/(m3·day) was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids (MLSS)/L. Scanning electron microscope (SEM) observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity, and the cell size was quite uniform. Transmission electron microscope photos showed that cells were round or oval, the cellular diameter was 0.6-1.0 μm, and the percentage of the anammoxosome compartment was 51%–85% of the whole cell volume. Fluorescence in situ hybridization analysis (FISH) indicated that anammox bacteria became the dominant population in the community (accounting for more than 51% of total bacteria on day 250). Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp., a new anammox species. In addition, the average effluent suspended solid (MLSS) concentrations of outlets I (above the non-woven carrier) and II (below the non-woven carrier) were 0.0009 and 0.0035 g/L, respectively. This showed that the non-woven carrier could catch the biomass effectively, which increased biomass and improved the nitrogen removal rate in the reactor.

Assessment of Inocula and N-Removal Performance of Anaerobic Ammonium Oxidation (ANAMMOX) for the Treatment of Aged Landfill Leachates

Three kinds of seeding sludge, i.e. conventional activated sludge, anaerobic granular sludge and the nitrifying activated sludge from the nitritation reactor treating aged leachates were evaluated in batch mode to screen the optimized inoculum for the rapid start-up of ANAMMOX reactor. The feasibility of the ANAMMOX process for the treatment of aged leachates was also investigated in a modified upflow anaerobic sludge blanket (UASB, 0.05m3). The batch experiments revealed that the nitrifying activated sludge from the nitritation reactor could respectively achieve the NRR (nitrogen removal rate) of 0.0365 kg N/(m3.d) and the ARR (ammonium removal rate) of 0.013 kg N/(m3.d) on day 12, which were greatly higher than those of the other two tested sludge samples. The mixture of the aforementioned nitrifying activated sludge and anaerobic granular sludge was established as an effective inoculum for the prompt start-up of ANAMMOX reactor. The maximum total nitrogen removal rate of 0.826 kg N/(m3.d) could be obtained for the treatment of “old” leachates under NLR (nitrogen loading rate) of 1.028 kg N/(m3.d). It is concluded that the N-removal performance of ANAMMOX process is still to be improved for actual engineering application to aged landfill leachates.

Anammox enrichment from reject water on blank biofilm carriers and carriers containing nitrifying biomass: operation of two moving bed biofilm reactors (MBBR)

The anammox bacteria were enriched from reject water of anaerobic digestion of municipal wastewater sludge onto moving bed biofilm reactor (MBBR) system carriers-the ones initially containing no biomass (MBBR1) as well as the ones containing nitrifying biomass (MBBR2). Duration of start-up periods of the both reactors was similar (about 100days), but stable total nitrogen (TN) removal efficiency occurred earlier in the system containing nitrifying biomass. Anammox TN removal efficiency of 70% was achieved by 180days in both 20l volume reactors at moderate temperature of 26.0°C. During the steady state phase of operation of MBBRs the average TN removal efficiencies and maximum TN removal rates in MBBR1 were 80% (1,000g-N/m(3)/day, achieved by 308days) and in MBBR2 85% (1,100g-N/m(3)/day, achieved by 266days). In both reactors mixed bacterial cultures were detected. Uncultured Planctomycetales bacterium clone P4, Candidatus Nitrospira defluvii and uncultured Nitrospira sp. clone 53 were identified by PCR-DGGE from the system initially containing blank biofilm carriers as well as from the nitrifying biofilm system; from the latter in addition to these also uncultured ammonium oxidizing bacterium clone W1 and Nitrospira sp. clone S1-62 were detected. FISH analysis revealed that anammox microorganisms were located in clusters in the biofilm. Using previously grown nitrifying biofilm matrix for anammox enrichment has some benefits over starting up the process from zero, such as less time for enrichment and protection against severe inhibitions in case of high substrate loading rates.

Assessment of inocula and n-removal performance of anaerobic ammonium oxidation (annamox) for the treatment of "old" landfill leachates

Three kinds of seeding sludge, i,e, conventional activated sludge, anaerobic granularsludge and the nitrifying activated sludge from the nitritation reactor treating agedleachates were evaluated in batch mode to screen the optimized inoculum for the rapidstart-up of ANAMMOX reactor. The feasibility of the ANAMMOX process for thetreatment of aged leachates was also investigated in a modified upflow anaerobic sludgeblanket (UASB, 0,05 m\ The batch experiments revealed that the nitrifying activatedsludge from the nitritation reactor could respectively achieve the NRR (nitrogenremoval rate) of 0,0365 kg N/(m3,d) and the ARR (ammonium removal rate) of 0,013kg N/(m3.d) on day 12, which were greatly higher than those of the other two testedsludge samples, The mixture of the aforementioned nitrifying activated sludge andanaerobic granular sludge was established as an effective inoculum for the prompt startup of ANAMMOX reactor. The maximum total nitrogen removal rate of 0,826 kgN/(m3,d) could be obtained for the treatment of "old" leachates under NLR (nitrogenloading rate) of 1.028 kg N/(m3.d), It is concluded that the N-removal performance ofANAMMOX process is still to be improved for actual engineering application to agedlandfill leachates,