Total Nitrogen Loading Rate Research Articles

Efficient partial denitrification-anammox process enabled by a novel denitrifier with truncated nitrite reduction pathway

Partial denitrification coupled with anaerobic ammonium oxidation (PD-anammox) is a promising technology for cost-effective nitrogen removal from wastewater. Nitrite availability is crucial to anammox performance but often limited by the slow partial denitrification process. Here we report an efficient PD-anammox system driven by the novel denitrifier Bacillus velezensis C1–3 with truncated nitrite reduction pathway. Whole-genome sequencing analysis revealed that the lack of nitrite reductase genes nirS/nirK and norBC in strain C1–3 enabled nitrite accumulation without the need for precise control of carbon dosage. By coupling it with anammox sludge, over 79 % total nitrogen (TN) removal was stably achieved, under a TN loading rate of 660 mg/L/d and a carbon/nitrogen ratio below 1.0. Mechanism explorations indicate that the niche differentiation of C1–3 and anammox bacteria facilitated their mutualism while avoiding nitrite competition. This study demonstrates a novel strategy for establishing efficient PD-anammox process by harnessing the unique metabolic deficiency of denitrifiers, shedding light on the development of stable and sustainable biological nitrogen removal technologies with minimal carbon footprint.

Lab-Scale Treatment of Anaerobic Co-Digestion Liquor from Kitchen Waste, Human Feces, and Municipal Sludge Using Partial Nitritation-Anammox Process

Effective nitrogen removal from anaerobic co-digestion is a major challenge to achieving dual-carbon goals. This study explored the acclimatization process of a lab-scale two-stage partial nitritation and anammox process of a stepwise increase in the percentage of raw anaerobic co-digestion liquor from kitchen waste, human feces, and municipal sludge in a venous industrial park in China, which has not been reported yet. Under limited dissolved oxygen (below 0.5 mg/L) and high ammonia levels (200–1500 mg/L), based on adjusting aeration rates, partial nitritation rapidly started up in 50 days. After acclimatization, partial nitritation still performed efficiently and stably, with the final total nitrogen loading rate (TNLR) of 1.24 ± 0.09 gN/L/d, nitrite accumulation rate of 99 ± 4%, and ratio of eff. nitrite/ammonia of 1.32 ± 0.13. In the anammox process, the final total nitrogen removal efficiency, total nitrogen removal rate, and TNLR reached 94 ± 5%, 1.27 ± 0.03 gN/L/d, and 1.36 ± 0.05 gN/L/d, respectively. Chemical oxygen demand (COD) was also reduced in both reactors, with COD removal rates of 0.7 gCOD/L/d in the partial nitritation and 0.4 gCOD/L/d in the anammox process. Overall, the PNA system demonstrated its feasibility in adapting to high ammonia, salinity, and iron levels, when treating anaerobic co-digestion liquor, particularly regarding resource recovery in venous industrial parks.

A pilot-scale SNAD-MBBR process for treating anaerobic digester liquor of swine wastewater: performance and microbial community.

In this pilot-scale study, simultaneous partial nitrification, anammox, and denitrification (SNAD) process was achieved successfully in a moving bed biofilm reactor (MBBR) for treating anaerobic digester liquor of swine wastewater. After 95days of operation, when the total nitrogen loading rate of SNAD-MBBR process was 1.09kg TN/m3/day, the total nitrogen removal rate could reach 0.87kg TN/m3/day, and the removal efficiencies of ammonium and total nitrogen were 92.0% and 79.7%, respectively. The optimum pH and temperature for SNAD-MBBR process were 8.5 and 35°C, respectively, and the optimum dissolved oxygen for SNAD1 and SNAD2 were 0.30 and 0.07mg/L, respectively. The 16S rRNA sequencing suggested that Candidatus Kuenenia, Candidatus Brocadia, Nitrosomonas, and Denitratisoma were the dominant nitrogen removal bacteria. Some of the co-existing bacteria (Truepera, Limnobacter, and Anaerolineaceae uncultured) promoted ammonium oxidation and guaranteed the growth of the anammox bacteria under adverse environmental conditions. Overall, this study demonstrated that the SNAD-MBBR process would be an energy-saving and cost-effective method for the removal of nitrogen from swine wastewater and provided important process parameters for stable operation of the full-scale SNAD process.

Extracellular polymeric substances and microbial community shift during the start-up of a single-stage partial nitritation/anammox process.

A sequencing batch reactor (SBR) was operated to investigate variations of extracellular polymeric substances (EPS) and microbial community during the start-up of the single-stage partial nitritation/anammox (SPN/A) process at intermittent aeration mode. The SPN/A system was successfully started on day 34, and the nitrogen removal efficiency and total nitrogen loading rate were 82.29% and 0.31 kg N/(m3 ·d), respectively. Furthermore, the relationship between the protein secondary structures and microbial aggregation was strongly related. The α-helix/ (β-sheet + random coil) ratios increased obviously from 0.20 ± 0.03 to 0.23 ± 0.01, with the sludge aggregation mean size increased from 56 to 107 μm during the start-up of SPN/A. During the start-up of SPN/A, Candidatus Kuenenia was the primary anammox bacteria, whereas Nitrospira was the main functional bacteria of nitrite-oxidizing bacteria. Correlation between the microbial community and EPS components was performed. The EPS and microbial community played important roles in keeping stable nitrogen removal and the formation of sludge granules.

Nitrogen removal characteristics of anammox biofilm and analyses of the dynamic network structure of functional microbes under gradient nitrogen stress

The universal porous gel/vertical fixed bed-anaerobic ammonia oxidation (UPG/VFB-A) is a complex efficient denitrification symbiotic system of microorganisms for leachate. However, the different gradient nitrogen loading lead to dynamic correlation and difference in biofilm formation remain unclear. Therefore, the UPG/VFB-A was operated for 300 days under gradient total nitrogen loading rate (TNLR) conditions, and its biofilm biomass characteristics, bacterial population succession and functional denitrification gene dynamic network were investigated to achieve strong impact resistance and recovery of the reactor for landfill leachate. The results showed that the total nitrogen removal efficiency (TNRE) was 92.4 ± 2.7% and the nitrogen removal (NR) up to 487.0 ± 20.5 mg/L. The system was highly resistant and resilient to high concentrations of FA (11.68 mg/L) and FNA (0.0467 mg/L) with total nitrogen removal rate (TNRR) up to 1.12 kg/m3/d. Candidatus Kuenenia (from 0.09% to 17.2%) with high tolerance to FA and FNA was superior to Candidatus Brocadia (from 9.7% to 4.7%) as the main AnAOB. Meanwhile, the gradient nitrogen had a significant effect on the abundance of genes related to nitrogen conversion, and the relative abundance of typical anammox genes hzs and hdh was highest at a feedwater load of 1.34 kg/m3/d, reaching 20.7% and 16.5%, respectively. This study can provide guidance for anammox treatment of landfill leachate in practical engineering.

Conductive carrier promotes synchronous biofilm formation and granulation of anammox bacteria

The extracellular electron transfer capability of some anaerobic ammonium oxidation (anammox) bacteria was confirmed in recent years. However, the effect of conductive carriers on the synchronous formation of anammox biofilm and granules is rarely reported. Anammox biofilm and granules with compact and stable structures accelerate the initiation and enhance the stability of the anammox process. In this study, we found that the conductive carbon fiber brush (CB) carrier promoted synchronous biofilm formation and granulation of anammox bacteria in the internal circulation immobilized blanket (ICIB) reactor. Compared with polyurethane sponge and zeolite carrier, the ICIB reactor packed with CB carrier can be operated under the highest total nitrogen loading rate of 6.53 kg-N/(m3·d) and maintain the effluents NH4+-N and NO2−-N at less than 1 mM. The volatile suspended solids concentration in the ICIB reactor packed with conductive carrier increased from 5.17 ± 0.40 g/L of inoculum sludge to 24.24 ± 1.20 g/L of biofilm, and the average particle size of granules increased from 222.09 µm to 879.80 µm in 150 days. Fluorescence in situ hybridization analysis showed that anammox bacteria prevailed in the biofilm and granules. The analysis of extracellular polymeric substances indicated that protein and humic acid-like substances played an important role in the formation of anammox biofilm and granules. Microbiome analysis showed that the relative abundance of Candidatus Jettenia was increased from 0.18% to 38.15% in the biofilm from CB carrier during start-up stage. This study provides a strategy for rapid anammox biofilm and granules enrichment and carrier selection of anammox process.

Combined partial denitrification-anammox with urea hydrolysis (U-PD-Anammox) process: A novel economical low-carbon method for nitrate-containing wastewater treatment

For the sake of exploring a new economical and low-carbon alternative for real nitrate-containing wastewater treatment, a new combined partial denitrification-anammox with urea hydrolysis (U-PD-Anammox) process was developed. The nitrogen removal performance of this process was investigated through long-term operation in a sequencing batch reactor (SBR) and two submerged anaerobic biological filters (SABF). Results showed that the average NO3−-N to NO2–N transformation ratio improved to 82.6% with organic carbon source to NO3–N ratio of 1.8, and urea hydrolysis provided sufficient NH4+-N and inorganic carbon to anammox process for nitrogen removal. The influent NH4+-N/NO2−-N ratio for subsequent anammox reactor could be adjacent to the optimal ratio of 1.32 during the whole operation. The combined process showed efficient nitrogen removal performance with 85% NO3−-N removal, 93.8% total nitrogen removal and total nitrogen loading rate as 1.1 ± 0.5 kg N/(m3·d). High-throughput sequencing analysis results revealed that Genera Thauera, Hyphomicrobium and Candidatus Brocadia were the dominant species responsible for partial denitrification, urea hydrolysis and anammox, respectively. The proposed process was more economically and environmental-friendly than the traditional denitrification process with 51.7% operational cost reduction, 99.7% N2O and 60% CO2 emission decrement, facilitating the sustainable development of the nitrate-containing wastewater treatment industry in the future.

Effective nitrogen removal of wastewater from vitamin B2 production by a potential anammox process

The wastewater of vitamin B2 (VB2) production treated after anaerobic digesters contains high total nitrogen (TN) and low organic carbon. To efficiently remove nitrogen pollution in the wastewater, one lab-scale anaerobic ammonium oxidation (anammox) bioreactor was designed. Synthetic wastewater and proper conditions were used to startup the anammox process in the bioreactor. The stoichiometric parameters of the bioreactor showed that anammox process was successfully established during operation. Evaluation of the bioreactor with real VB2 wastewater suggested that the bioreactor can efficiently remove nitrogen pollution at low organic carbon situation. The optimal state of total nitrogen loading rate (TNLR) and the highest total nitrogen removal efficiency (TNRE) of the bioreactor were 0.35 kg/(m3·d) and 75%, respectively. The microbiota run at day 112 (named VBM112) was significantly different with the microbiotas of the two inoculation cultures. At the phylum level, the most abundant phylum was Proteobacteria in the inoculation culture, while Bacteroidetes was the most abundant phylum in VBM112. At the genus level, the composition of nitrogen removal related microbes significantly increased in VBM112. Especially, the anammox bacteria Candidatus Kuenenia increased from 0% of the inoculation culture to 2.2% of VBM112. The analyses of running parameters and microbiota profiles confirmed the well establishment of one lab-scale anammox bioreactor, which might be helpful for future full-scale VB2 wastewater treatment startup.

Two-step partial nitrification-anammox process for treating thermal-hydrolysis anaerobic digester effluent: Start-up and microbial characterisation

Abstract Although the thermal hydrolysis has been proven to be an effective pre-treatment method for anaerobic digestion (AD), the ammonium-rich anaerobic digester effluents are unavoidably produced by thermal hydrolysis pre-treatment AD (THP-AD). In this study, a two-step partial nitrification-anammox (PN-A) process was conducted for the anaerobic digester effluents. By combining control of the solid retention time (SRT), dissolved oxygen (DO) and hydraulic retention time (HRT) (SRT 20 d, DO concentration 0.5–0.8 mg/L, HRT 11 h), start-up of the PN reactor was achieved with a total nitrogen loading rate of 2.34 kg N/(m3·d), generating an NH4+-N/NO2−-N molar ratio of around 1.0–1.4 in the effluent. The anammox reactor was then successfully started by feeding the effluent of the PN reactor, with a total nitrogen removal rate of 1.25 kg N/(m3·d). The system became unstable after 100 days of operation, and surface analyses of the anammox sludge particles suggested that the main reason was the adsorption of microsized suspended organic flocs in the influent onto the anammox sludge particles. Further study showed that the microsized suspended organic flocs contained large quantities of bacteria, which can compete with anammox bacteria. In addition, analyses of the microbial community reveal that Nitrosomonas and Candidatus brocadia were the main ammonium-oxidising bacteria and anammox bacteria in this study, respectively. The trends of their relative abundance during the PN-A system process confirmed the successful start-up of the PN-A reactors and the effectiveness of the start-up operations. These findings are expected to provide references for the treatment of anaerobic digester effluents from THP-AD via the biological removal of nitrogen.

Setup and Microbial Community Analysis of ANAMMOX System for Landfill Leachate Treatment Coupling Partial Nitrification-Denitrification Process

In order to upgrade the current shortcut nitrification and denitrification process for landfill leachate treatment and to stimulate nitrification-denitrification coupled with anaerobic ammonia oxidation (ANAMMOX) at a landfill, an ANAMMOX process was started using an up-flow anaerobic sludge bed (UASB) reactor seeded with nitrification and denitrification sludge. The performances of the reactor were investigated, including the nitrogen loading and nitrogen removal rates. Moreover, Illumina Miseq sequencing was conducted to analyze the microbial community dynamics under long-term operation on a molecular level. The results showed that the ANAMMOX reactor was successfully started in 149 days. The total nitrogen loading rate reached 4000.00 mg·(L·d)-1, and the total nitrogen removal rate reached 3885.76 mg·(L·d)-1 after stable operation. The average ammonium and nitrite removal efficiencies were more than 95%. In 250 days, the Planctomycetes in the reactor experienced rapid growth, and its abundance reached 54.94%. The abundance of Candidatus Kuenenia reached 49.66%. The upgrading process of landfill leachate treatment by coupling ANAMMOX based on short-cut nitrification and denitrification was confirmed to be feasible.

Biological Nitrogen Removal Process in a Microbubble-aerated Biofilm Reactor Treating Low C/N Wastewater

The microbubble-aerated biofilm reactor as a new treatment process combines microbubble aeration technology with aerobic biological treatment. A microbubble aerated biofilm reactor was used in this study to treat low C/N ratio wastewater at a low air/water ratio. The process and performance of biological nitrogen removal were investigated, and the functional bacterial populations for nitrogen removal in the biofilm were analyzed. The results showed that the biological nitrogen removal process was converted from simultaneous nitrification-denitrification to simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) processes when DO concentration was controlled by an air/water ratio of lower than 1:2 and the influent C/N ratio was reduced. As a result, the efficient biological nitrogen removal performance was achieved when treating low C/N ratio wastewater. When the DO concentration was lower than 1.0 mg·L-1 and the influent C/N ratio was 1:2.8, the SNAD process became dominant for biological nitrogen removal. In this case, the average total nitrogen (TN) removal efficiency was 76.3%, and the average TN loading rate removed was 1.42 kg·(m3·d)-1. In addition, it was estimated that 86.0% of TN removal was attributed to the ANAMMOX process. The relative abundances of ammonia-oxidizing bacteria populations and ANAMMOX bacteria populations in the biofilm increased gradually, while the relative abundances of nitrite-oxidizing bacteria populations and denitrifying bacteria populations decreased gradually, with a decrease in influent C/N ratio. The variation of functional bacterial populations for nitrogen removal was consistent with the conversion of nitrogen removal process to SNAD process.

Deciphering the evolution characteristics of extracellular microbial products from autotrophic and mixotrophic anammox consortia in response to nitrogen loading variations

Extracellular microbial products (EMP) in biological wastewater treatment systems vary with operational conditions and in turn indicate the metabolic status of functional bacteria. In this study, the response of EMP from autotrophic and mixotrophic anammox consortia (AAC and MAC) to the variation of total nitrogen loading rates (TNLR) were investigated as well as their correlations with the community evolution. The variation of TNLR showed a significantly negative correlation with the production of bound microbial products (BMP) but a significantly positive correlation with the production of soluble microbial products (SMP). The presence of organic matters with COD/TN ratio of 0.15 limited the abundance of anammox bacteria in MAC at the full-load phase and suppressed their proliferation at the restart phase. Due to the improved abundance of carbohydrate metabolism genes, MAC with lower abundance of anammox bacteria produced lower soluble polysaccharides than AMC at the full-load phase. Furthermore, four components (C1–4) were identified on the excitation–emission matrix fluorescence spectra of SMP using parallel factor analysis. C1 exhibited a relative higher proportion at the full-load phase, whereas C4 was generated only at the light-load phase or empty-load phase. At the restart phase, C2 and C3 appeared simultaneously and accounted for a high proportion. The information of four components also suggested the metabolic status of AC as revealed by the specific anammox activity, which therefore provided a novel complementary but direct approach for monitoring the operation status of anammox bioreactors.

Achieving completely anaerobic ammonium removal over nitrite (CAARON) in one single UASB reactor: Synchronous and asynchronous feeding regimes of organic carbon make a difference

At least 11% of total nitrogen (TN) remains in the anammox effluent, making it difficult to meet increasingly stringent discharge standards. To overcome this bottleneck, an innovative process to achieve completely anaerobic ammonium removal over nitrite (CAARON) in one single up-flow anaerobic sludge blanket reactor was proposed in this study. The synchronous feeding of acetate at a C/N (nitrite) ratio of 0.6 significantly reduced the nitrogen removal capacity of anammox reactor by limiting the abundance and metabolism of anammox bacteria. In contrast, the asynchronous feeding of acetate optimized the partition of the reactor column into two specific compartments: the lower half favoring anammox and the upper half dominated by DEAMOX (DEnitrifying AMmonium Oxidation). A high TN removal efficiency of 96.2±0.4% and a low effluent TN concentration of 9.3±0.9mgL−1 were obtained under a high TN loading rate of 9.0kgNm−3d−1. The dominant functional microbes in the CAARON process were identified as Candidatus Kuenenia and Thauera, which were responsible for the anammox and denitratation reactions, respectively. Overall, the results in this study provide valuable insight into the coupling of anammox with denitratation, which is a cost-efficient approach for treating ammonium-rich wastewaters.

Influence of saturated zone depth and vegetation on the performance of vertical flow-constructed wetland with continuous feeding.

The object of this study was to investigate the effect of saturated zone depth (SZD) and plant on the removal of organics and nitrogen in four continuous-feed vertical flow-constructed wetlands (VFCWs). Three VFCWs were planted with Iris pseudacorus and operated at different SZDs (19, 51, and 84cm), and the other one was non-planted and operated at 51cm SZD. The VFCWs were operated with an organic loading rate (OLR) of 79g chemical oxygen demand (COD)m-2day-1, a total nitrogen loading rate (NLR) of 11g Nm-2day-1, and a hydraulic loading rate (HLR) of 0.35m3m-2day-1. Simultaneous transformation of ammonium and nitrate occurred in all of the four systems. In the planted bed with 51cm SZD, suitable conditions for nitrification and denitrification could be created and the best performance for total nitrogen (TN) removal was realized via simultaneous nitrification and denitrification (SND), achieving TN removal efficiency of 67.4-80.3%. Higher ammonium nitrogen (NH4+-N) and COD removal efficiency was obtained in the system operated with 19cm SZD, whereas higher NO3--N removal could be achieved in the bed with 84cm SZD. With the same SZD of 51cm, the planted VFCW performed preferable removal of COD, NH4+-N, and TN in comparison with the non-planted one. All the VFCWs showed high removal efficiencies for total phosphorus (> 60.15%). Adsorption of phosphorus was primarily observed in the top and upper-middle layers filled with carbon burn slag. It has been proved that the partially saturated VFCW operated with continuous feed could achieve good performance in removal of organic matter and nitrogen by SZD adjustment to develop appropriate aerobic and anoxic regions.

An innovative U-shaped sludge bed anammox process for nitrogen removal

In this study, we proposed an innovative U-shaped sludge bed reactor which could be a cost effective and simplified approach for the operation of an anammox reactor. The performance for nitrogen removal and the composition of bacterial communities were investigated for about 500 days of operation. The nitrogen removal rate could be approximately 85% when the total nitrogen loading rate was about 0.54 kg N/m3/d. The 16S rRNA gene pyrosequencing analysis of the bacterial community determined that Betaproteobacteria (class level) of the ammonia-oxidizing bacteria (AOB) community, Nitrospira (genus level) of the nitrite-oxidizing bacteria (NOB) community, and Brocadia (genus level) of the anammox bacteria community simultaneously coexisted in the reactor sludge. These results demonstrated that simultaneous growth and coexistence of AOB, NOB, and anammox were capable within the reactor. Furthermore, a mathematical modeling system was developed to simulate the nitrification and anammox processes. The model simulation showed that the oxygen was rapidly depleted and that led to a drop in the activity of AOB and NOB, then the growth of anammox bacteria started under anaerobic conditions.

Core-shell structured poly(vinyl alcohol)/sodium alginate bead for single-stage autotrophic nitrogen removal

A core-shell structured poly(vinyl alcohol)/sodium alginate gel bead was fabricated and the thickness of the outer layer was controlled. Immobilized ammonia-oxidizing bacteria (AOB) and ANAMMOX bacteria in outer and inner parts of the beads, respectively, cooperate to perform single-stage autotrophic nitrogen removal (SANR). As a critical designing factor, oxygen penetration depth according to the oxygen concentration in bulk phase and nitrifying biomass concentration in the outer layer were examined to protect strictly anaerobic ANAMMOX bacteria from oxygen inhibition. Oxygen penetrated up to a depth of 2350±360μm with the lowest nitrifying biomass of 703mg-VSS/L at a dissolved oxygen concentration of 8mg/L. However, a thick shell layer of more than 3mm effectively protected the ANAMMOX bacteria from oxygen inhibition. The applicability of the core-shell structured gel bead for single-stage autotrophic nitrogen removal was validated in batch and continuous modes. A continuous bioreactor with a synthetic ammonia wastewater showed a maximum nitrogen removal efficiency of 80.4±1.20% with a total nitrogen loading rate of 590±12.1g-N/m3-d. Findings of this study suggest that start-up strategy of SANR using the core-shell structured gel bead can minimize the adaptation period without scarifying the ANAMMOX activity.

Performance of Anammox process and low-oxygen adaptability of Anammox biofilms in a FBR with small ring non-woven carriers

Performance of Anammox process and low-oxygen adaptation of the cultivated Anammox biofilms were investigated in a lab-scale fixed-bed reactor filled with small ring non-woven carriers. (NH4)2SO4 and NaNO2 provided NH4+-N and NO2−-N in the synthetic wastewater. Anammox reaction occurred on day 17. After 67 days operation, start-up of Anammox was achieved with a total nitrogen loading rate (NLR) of 5.78×10−2kgNm−3d−1 and nitrogen removing rate (NRR) of 4.64×10−2kgNm−3d−1 on day 131. Under the strict anaerobic condition, the max total NLR and NRR reached 4.35×10−1kgNm−3d−1 and 3.83×10−1kgNm−3d−1. Subsequently, a stepwise oxygen adaptation strategy was applied by increasing influent dissolved oxygen (DO) to 8mgL−1 with each increment of 2mgL−1. The Anammox biofilms manifested a satisfactory oxygen adaptability. The reactor performance was only slightly affected as the average total NLR and NRR decreased by 7.08% and 4.39% respectively. Fluorescent in situ hybridization analysis further confirmed that, after low-oxygen adaptation, Anammox bacteria occupied 70.2% of the total bacteria and aerobic ammonium oxidizers moderately increased to 8.5%, which could alleviate the impact of influent DO on the reactor performance. Utilization of the low-oxygen adaptability of Anammox biofilms can markedly reduce energy and material consumption of Anammox operation.

Performance and microbial response during the fast reactivation of Anammox system by hydrodynamic stress control

Anaerobic ammonium oxidation (Anammox) has become a promising method for biological nitrogen removal. However, this biotechnology application is always limited due to the low growth rate and biomass yield of Anammox bacteria. This study investigated the process of fast reactivation of an Anammox consortium idled for 2years via hydrodynamic stress control. The results showed that the Anammox system was efficiently and quickly reactivated by shortening of the hydraulic retention time (HRT) of the reactor from 12 to 6hr within 68days of operation. Moreover, at a 4-hr HRT with an influent total nitrogen loading rate of 1.2kg N/(m3·day), the reactor maintained high biological performance with an ammonium removal loading rate of 0.52kg N/(m3·day) and a nitrite removal rate of 0.59kg N/(m3·day). In the reactivated Anammox reaction, the stoichiometric coefficients of NH4+–N to NO2−–N and NH4+–N to NO3−–N were 1:1.04±0.08 and 1:0.31±0.03, respectively. The specific Anammox activity and hydrazine oxidoreductase activity, both of which represent the degree of Anammox bacteria present, increased as the hydrodynamic stress increased and were maximally (125.38±3.01mg N/(g VSS·day) and 339.42±6.83μmol/(min·g VSS), respectively) at 4-hr HRT. Microbial response analysis showed that the dominant microbial community was obviously shifted and the dominance of Anammox bacteria was enhanced during the hydrodynamic selection.

Nitritating-anammox biomass tolerant to high dissolved oxygen concentration and C/N ratio in treatment of yeast factory wastewater

Maintaining stability of low concentration (<1 g L−1) floccular biomass in the nitritation-anaerobic ammonium oxidation (anammox) process in the sequencing batch reactor (SBR) system for the treatment of high COD (>15,000 mg O2 L−1) to N (1680 mg N L−1) ratio real wastewater streams coming from the food industry is challenging. The anammox process was suitable for the treatment of yeast factory wastewater containing relatively high and abruptly increased organic C/N ratio and dissolved oxygen (DO) concentrations. Maximum specific total inorganic nitrogen (TIN) loading and removal rates applied were 600 and 280 mg N g−1 VSS d−1, respectively. Average TIN removal efficiency over the operation period of 270 days was 70%. Prior to simultaneous reduction of high organics (total organic carbon>600 mg L−1) and N concentrations>400 mg L−1, hydraulic retention time of 15 h and DO concentrations of 3.18 (±1.73) mg O2 L−1 were applied. Surprisingly, higher DO concentrations did not inhibit the anammox process efficiency demonstrating a wider application of cultivated anammox biomass. The SBR was fed rapidly over 5% of the cycle time at 50% volumetric exchange ratio. It maintained high free ammonia concentration, suppressing growth of nitrite-oxidizing bacteria. Partial least squares and response surface modelling revealed two periods of SBR operation and the SBR performances change at different periods with different total nitrogen (TN) loadings. Anammox activity tests showed yeast factory-specific organic N compound-betaine and inorganic N simultaneous biodegradation. Among other microorganisms determined by pyrosequencing, anammox microorganism (uncultured Planctomycetales bacterium clone P4) was determined by polymerase chain reaction also after applying high TN loading rates.

Treatment of synthetic wastewater and hog waste with reduced sludge generation by the multi-environment BioCAST technology

Simultaneous removal of carbon, nitrogen and phosphorus was examined along with reduced generation of biological sludge during the treatment of synthetic wastewater and hog waste by the BioCAST technology. This new multi-environment wastewater treatment technology contains both suspended and immobilized microorganisms, and benefits from the presence of aerobic, microaerophilic, anoxic and anaerobic conditions for the biological treatment of wastewater. The influent concentrations during the treatment of synthetic wastewater were 1,300-4,000 mg chemical oxygen demand (COD)/L, 42-115 mg total nitrogen (TN)/L, and 19-40 mg total phosphorus (TP)/L. The removal efficiencies reached 98.9, 98.3 and 94.1%, respectively, for carbon, TN and TP during 225 days of operation. The removal efficiencies of carbon and nitrogen showed a minimal dependence on the nitrogen-to-phosphorus (N/P) ratio, while the phosphorus removal efficiency showed a remarkable dependence on this parameter, increasing from 45 to 94.1% upon the increase of N/P ratio from 3 to 4.5. The increase of TN loading rate had a minimal impact on COD removal rate which remained around 1.7 kg/m(3) d, while it contributed to increased TP removal efficiency. The treatment of hog waste with influent COD, TN and TP concentrations of 960-2,400, 143-235 and 25-57 mg/L, respectively, produced removal efficiencies up to 89.2, 69.2 and 47.6% for the three contaminants, despite the inhibitory effects of this waste towards biological activity. The treatment system produced low biomass yields with average values of 3.7 and 8.2% during the treatment of synthetic wastewater and hog waste, respectively.