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Advanced nitrogen removal without the addition of external carbon source is challenging in the conventional biological nitrogen removal processes. This study presented a novel anaerobic/aerobic/anoxic sequencing batch reactor (A/O/A SBR) based on endogenous nitrate (NO 3 -N) respiration to enhance nitrogen removal. The mean effluent total nitrogen (TN) in the A/O/A SBR could be reduced to as low as 3.5 mg/L, when the average influent TN and chemical oxygen demand (COD) were 52.7 and 235.4 mg/L, respectively. This advanced nitrogen removal was attributed to the post-denitrification, since 82.7% of TN removal was achieved in the post-anoxic stage. The post-denitrification rate with nitrite (NO - -N) respiration to enhance nitrogen removal. The mean effluent total nitrogen (TN) in the A/O/A SBR could be reduced to as low as 3.5 mg/L, when the average influent TN and chemical oxygen demand (COD) were 52.7 and 235.4 mg/L, respectively. This advanced nitrogen removal was attributed to the post-denitrification, since 82.7% of TN removal was achieved in the post-anoxic stage. The post-denitrification rate with nitrite (NO 2 - -N, 0.59 mg NO 2 -N/gMLVSS/h). Therefore, the post-anoxic time could be further optimized by achieving denitrification via NO - -N/gMLVSS/h) was higher than that with NO 3 - -N (0.35 mg NO 3 - -N/gMLVSS/h). Therefore, the post-anoxic time could be further optimized by achieving denitrification via NO 2 - -N. The A/O/A SBR has good potential in achieving advanced nitrogen removal, especially in nitrogen-sensitive rural areas.

The shortcut biological nitrogen removal (SBNR) process requires less aeration and external carbon due to the oxidization of ammonia into nitrite and its direct denitrification to nitrogen gas during the biological nitrogen removal process. However, this process produces a poor effluent containing NH 4 + ) concentration. To overcome this drawback, in this study, the solid retention time (SRT) and the dissolved oxygen (DO) concentration were controlled to achieve both a high ammonia removal rate and nitrite accumulation in the sequencing batch reactor (SBR) process, which can remove nitrogen from wastewater to the desired concentration and provide high free ammonia inhibition and continuous shock loading. When sufficient DO was supplied, nitrite did not accumulate with a 20-day SRT, but the wash-out of nitrite oxidizers in a shorter SRT resulted in a high nitrite accumulation. When DO acted as a limitation, nitrite accumulated at all SRTs. This indicates that nitrite accumulation is more highly influenced by SRT and DO concentration than by FA inhibition. Also, as nitrite accumulated over a 10-day SRT regardless of DO concentration, the accumulation was more highly influenced by SRT than by DO concentration.3 ) concentration. To overcome this drawback, in this study, the solid retention time (SRT) and the dissolved oxygen (DO) concentration were controlled to achieve both a high ammonia removal rate and nitrite accumulation in the sequencing batch reactor (SBR) process, which can remove nitrogen from wastewater to the desired concentration and provide high free ammonia inhibition and continuous shock loading. When sufficient DO was supplied, nitrite did not accumulate with a 20-day SRT, but the wash-out of nitrite oxidizers in a shorter SRT resulted in a high nitrite accumulation. When DO acted as a limitation, nitrite accumulated at all SRTs. This indicates that nitrite accumulation is more highly influenced by SRT and DO concentration than by FA inhibition. Also, as nitrite accumulated over a 10-day SRT regardless of DO concentration, the accumulation was more highly influenced by SRT than by DO concentration.

Enterobacter sp. strain FL was newly isolated from activated sludge and exhibited significant capability of auto-aggregation as well as aerobic denitrification. The removal efficiencies of NO 3 - -N, total nitrogen (TN), and TOC by strain FL in batch culture reached 94.6, 63.9, and 72.5% in 24 h, respectively. The production of N 2 in the presence of oxygen demonstrated the occurrence of aerobic denitrification. The auto-aggregation index of strain FL reached 54.3%, suggesting a high tendency that the cells would agglomerate into aggregates. The production of extracellular polymeric substances (EPSs), which were mainly composed of proteins followed by polysaccharides, was considered to be related to the cell aggregation according to Fourier transform infrared (FT-IR) and confocal laser scanning microscopy (CLSM). The proteins in EPS were evenly and tightly combined to cells and altered the protein secondary structures of cell surface from random coils to β-sheets and three-turn helices. The alteration of protein secondary structures of cell surface caused by the proteins in EPS might play a dominant role in the auto-aggregation of strain FL. To further assess the feasibility of strain FL for synthetic wastewater treatment, a sequencing batch reactor (SBR), solely inoculated with strain FL, was conducted. During the 16 running cycles, the removal efficiency of NO 2 in the presence of oxygen demonstrated the occurrence of aerobic denitrification. The auto-aggregation index of strain FL reached 54.3%, suggesting a high tendency that the cells would agglomerate into aggregates. The production of extracellular polymeric substances (EPSs), which were mainly composed of proteins followed by polysaccharides, was considered to be related to the cell aggregation according to Fourier transform infrared (FT-IR) and confocal laser scanning microscopy (CLSM). The proteins in EPS were evenly and tightly combined to cells and altered the protein secondary structures of cell surface from random coils to β-sheets and three-turn helices. The alteration of protein secondary structures of cell surface caused by the proteins in EPS might play a dominant role in the auto-aggregation of strain FL. To further assess the feasibility of strain FL for synthetic wastewater treatment, a sequencing batch reactor (SBR), solely inoculated with strain FL, was conducted. During the 16 running cycles, the removal efficiency of NO 3 - -N was 90.2-99.7% and the auto-aggregation index was stabilized at 35.0-41.5%. The EPS promoted the biomass of strain FL to aggregate in the SBR.

In order to remove nitrogen effectively from the wastewater with a low C/N ratio, the feasibility of using spent mushroom compost (SMC) hydrolysates as carbon sources for denitrification was investigated in a sequencing batch reactor (SBR). With SMCs supplement, the SBR performance was improved obviously within the 180days of operation. The total nitrogen removal was promoted from 46.9% to 81-89.4%, and no negative impact induced by different SMCs on the SBR system was observed. The abundance of functional genes including amoA, nirS/K, norB and nosZ in the active sludge was quantified by qPCR, and most of them elevated after SMC was fed. 16S rRNA gene high-throughput sequencing showed that the significant change in microbial community not only promoted pollutants removal but also benefited the stability of the reactor. Therefore, SMC could be an extremely promising carbon source used for nitrogen removal due to its cost-effective and efficient characteristics., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The nonaerobic stage is critical for the processes of denitrification and phosphorus release in biological wastewater treatment. A lab-scale sequencing batch reactor (SBR) operating as nonaerobic/aerobic was used to treat synthetic wastewater, and the nutrients removal performance was investigated under different nonaerobic hydraulic retention times (HRTs). The results showed when the nonaerobic HRT changed from 0 to 4 h with constant aerobic HRT of 8 h [dissolved oxygen (DO) 0.50–1.50 mg·L−1 ], the removal efficiencies of PO43−─P and NH4+─N were all above 90.00%, respectively. The nonaerobic HRT could influence carbon utilization between denitrification and phosphorus release, which showed a close relationship with the ratio of consumed chemical oxygen demand (COD)phosphorus release to CODdenitrification (0.94). Specifically, the consumed CODphosphorus release increased with the increase of nonaerobic HRT (0.90), whereas the relationship between consumed CODdenitrification and nonaerobic HRT was limited (−0.60). Furthermore, internal carbon source produced through phosphorus release could promote simultaneous nitrification denitrification. This control strategy could be conveniently applied in intermittent-flow sewage treatment plant through adjusting nonaerobic HRT. [ABSTRACT FROM AUTHOR]

Enterobacter sp. strain FL was newly isolated from activated sludge and exhibited significant capability of auto-aggregation as well as aerobic denitrification. The removal efficiencies of NO3−-N, total nitrogen (TN), and TOC by strain FL in batch culture reached 94.6, 63.9, and 72.5% in 24 h, respectively. The production of N2O and N2 in the presence of oxygen demonstrated the occurrence of aerobic denitrification. The auto-aggregation index of strain FL reached 54.3%, suggesting a high tendency that the cells would agglomerate into aggregates. The production of extracellular polymeric substances (EPSs), which were mainly composed of proteins followed by polysaccharides, was considered to be related to the cell aggregation according to Fourier transform infrared (FT-IR) and confocal laser scanning microscopy (CLSM). The proteins in EPS were evenly and tightly combined to cells and altered the protein secondary structures of cell surface from random coils to β-sheets and three-turn helices. The alteration of protein secondary structures of cell surface caused by the proteins in EPS might play a dominant role in the auto-aggregation of strain FL. To further assess the feasibility of strain FL for synthetic wastewater treatment, a sequencing batch reactor (SBR), solely inoculated with strain FL, was conducted. During the 16 running cycles, the removal efficiency of NO3−-N was 90.2–99.7% and the auto-aggregation index was stabilized at 35.0–41.5%. The EPS promoted the biomass of strain FL to aggregate in the SBR. [ABSTRACT FROM AUTHOR]

Partial-denitrification (nitrate (NO 3 − -N) → nitrite (NO 2 − -N)) holds great potential in treating NO 3 − -N contained wastewater, by combining with anammox process. In this study, performance of NO 2 − -N production in partial-denitrification was investigated in two installations: sequencing batch reactor (SBR) and upflow sludge blanket (USB) reactor. Results indicated that partial-denitrification was established successfully in both of SBR and USB, with the NO 2 − -N production rate (NPR) of 0.13–2.11 kg N m −3 d −1 and 0.90–13.03 kg N m −3 d −1 , respectively. The NO 3 − -N to NO 2 − -N transformation ratio (NTR) was approximately 83.3% in SBR, while NTR of 51.0%–71.3% was obtained in USB. Sludge granulation was observed in both two reactors during the operation. In SBR, granular diameter of 1.5–2.0 mm was reached with sludge volume index (SVI) of 54.3 mL gSS −1 , and 2.0–3.0 mm in USB with SVI of 62.1 mL gSS −1 . Additionally, the ratio of COD to NO 2 − -N (COD/NO 2 − -N) and NO 3 − -N to NO X − -N percentage (NP) in partial-denitrification effluent demonstrated its suitability for subsequent anammox. While, partial-denitrification conducted in SBR was more suitable for low NO 3 − -N wastewater (30 mg L −1 ), and USB was appropriate for high-strength sewage. Results obtained in this study provide a solid foundation for future applying partial-denitrification combined with anammox process in treating NO 3 − -N contained wastewater. [ABSTRACT FROM AUTHOR]

The effect of titanium dioxide nanoparticles (TiO NPs) on biological wastewater treatment in a sequencing batch reactor was investigated. The overall removal of chemical oxygen demand (COD) and NH -N were relatively unaffected; efficiencies remained at >95 % and around 99 %, respectively, after 30 days of continuous exposure to the NPs. However, TiO NPs resulted in increased conversion of NO -N to NO -N and caused slight inhibition effect on denitrification, with the total nitrogen removal reduced from 95 to 90 %. Several shifts in the bacteria community composition were noted. However, the overall community structure and biodiversity remained relatively unchanged. The polysaccharide content in the extracellular polymeric substances (EPS) was generally unaffected, suggesting a low potential of substantial shock or damage that may result in cytoplasmic leakage. However, a decrease in protein content occurred and indicated the inhibitive effects of the NPs. TiO NPs were removed in the system mainly via deposition into the sludge. The removal efficiency decreased from 90 to 70 % after 4 weeks, due to sorption saturation as well as the change in the EPS content of the activated sludge. [ABSTRACT FROM AUTHOR]

Anammox (anaerobic ammonium oxidation) is an attractive option for the treatment of wastewaters with a low carbon/nitrogen ratio. This is due to its low operating costs when compared to the classical nitrification-denitrification processes. However, one of the main disadvantages of the Anammox process is slow biomass growth, meaning a relatively slow reactor start-up. This becomes even more complicated when Anammox microorganisms are not present in the inoculum. Four inocula were studied for the start-up of Anammox sequencing batch reactors (SBRs) 2 L in volume agitated at 100 rpm, one of them using zeolite as a microbial support. Two inocula were taken from UASB reactors and two from aerobic reactors (activated sludge and SBR). The Anammox SBRs studied were operated at 36 ± 0.5°C. The results showed that the only inoculum that enabled the enrichment of the Anammox biomass came from an activated sludge plant treating wastewaters from a poultry slaughterhouse. This plant was designed for organic matter degradation and nitrogen removal (nitrification). This could explain the presence of Anammox microorganisms. This SBR operated without zeolite and achieved nitrite and ammonium removals of 96.3% and 68.4% respectively, at a nitrogen loading rate (NLR) of 0.1 kg N/m3/d in both cases. The lower ammonium removal was due to the fact that a sub-stoichiometric amount of nitrite (1 molar ratio) was fed. The specific Anammox activity (SAA) achieved was 0.18 g N/g VSS/d. [ABSTRACT FROM PUBLISHER]

Aerobic granules were cultivated in a sequencing batch reactor (SBR) fed with sucrose as a sole carbon source at superficial upflow air velocity of 1.9 cm/s and under an organic loading rate (OLR) of 2 g COD/L.d. This study shows that cultivated granules during 1 year were stable and had capability in simultaneous removal of carbon, nitrogen and phosphorus from wastewater. At a 6 h SBR cycle removal efficiency of chemical oxygen demand (COD), N-NH4+, P-PO43- were 93%, 66% and 83%, respectively. The value of sludge volume index (SVI) was between 90-110 mL/g and biomass concentration reached up to 8.0 g/L. With the granulation, the specific gravity and surface hydrophobicity of sludge increased and aerobic granules mean diameter was 4.9 mm. [ABSTRACT FROM AUTHOR]

Abstract: In this study the evaluation of nitrogen removal in wastewater from a meat products processing company was performed, using a Sequencing Batch Reactor (SBR) at pilot scale. The phases of the SBR operation were: filling, reaction (aeration and intermittent anoxia), sedimentation and discharge. In each of these phases analyses of ammonium (), nitrite (), nitrate (), pH and dissolved oxygen (DO) were carried out to monitor the process of nitrification–denitrification. The results showed that stage IV had the best performance (2.49g CODF/Ld and ) with a removal of 71%. The transformation of much of the to gaseous nitrogen was confirmed, with the concentration of and increasing during the reaction phase but decreasing in the effluent due to its transformation to gaseous nitrogen. [ABSTRACT FROM AUTHOR]

Monoethanolamine (MEA) is widely used in many industries and its proper treatment is important for protecting the water environment. As MEA contains an amine group, nitrogen removal by nitrification/denitrification as well as biodegradation of MEA is necessary for wastewater treatment. In this study the effects of adaptation and inhibition of MEA on biological degradation, and the removal of amine were investigated in a laboratory scale sequencing batch reactor (SBR). In addition, the denitrification characteristics of nitrate, and nitrite with MEA as the electron donor, were compared to the other electron donor (acetate). In the aerobic SBR, the removal efficiency of 9,000 mg/L MEA reached 92% at the hydraulic retention time (HRT) of 10.5 days. Ammonium hydrolyzed from the MEA was nitrified after 8 weeks from the start-up showing that adaptation time is needed for nitrification. Non-linear curve fitting of the specific MEA biodegradation gave the maximum specific activity (V), the half saturation constant (K), and the inhibition constant (K) of 2.81 g/(g VSS·d), 102.1 mg/L, and 1149.6 mg/L, respectively. Batch denitrification showed that MEA is a competitive electron donor to acetate. [ABSTRACT FROM AUTHOR]

Abstract: Analyses of the nitrite reductase gene diversities (nirK and nirS) in an activated sludge community fed with both nitrite and glucose were conducted. Results suggest that the topology of nirK and nirS gene fragment-based phylogenetic trees is influenced more by the available electron acceptor than by the carbon source. A denitrification reactor was operated for 53 days and a clone library constructed when the denitrifying communities in the SBR were supplied with both nitrite and glucose. Half of the nirK and nearly all the nirS gene fragments formed a cluster that was separate from a cluster containing nirK and nirS sequences derived from other communities in nitrate-fed reactors. On the other hand, nirK and nirS fragments obtained with glucose as the carbon source were similar to those detected in communities fed with other carbon sources. [Copyright &y& Elsevier]

When treating effluents from anaerobic processing of organic wastes, the challenge lies in the large quantity of recalcitrant COD and in the high nitrogen content. The data presented in this study illustrate an advanced SBR concept that is able to significantly reduce the organic load. It was found that undigested mashed bio-waste bypassing the anaerobic digestion is highly suitable as an external carbon source to compensate deficiencies of readily biodegradable BOD required for denitrification. In order to utilize the carbon source as efficiently as possible, the SBR was operated in a mode by which nitrification/denitrification is achieved by a shortcut process using nitrite. This procedure reduced the requirement of an external carbon source to only 5% (v/v). Moreover, through an optimized SBR sequence for an influent concentration of 14,000mgCOD/l and 3,800 mg TN/l, nearly complete removal of nitrogen (.95%) was achieved. The average removal rates for COD and BOD were 83% and 86%, respectively. The applied hydraulic retention time (HRT) of the SBR was 6.8 days. The elevated temperature of 30-41°C in the reactor as a result of the high biological activity was advantageous in terms of enhanced reaction kinetics and also provided better process stability. [ABSTRACT FROM AUTHOR]

The removal efficiency of sequencing batch reactor (SBR) system with synthetic industrial estate wastewater (SIEWW) containing Ni2+ or Pb2+ was increased with the increase of mixed liquor suspended solids (MLSS). But, the sludge volume index (SVI) of the system was increased up to higher than 100mL/g under MLSS of up to 4000mg/L. Also, the effluent NO3 − was decreased with the increase of MLSS. The heavy metals (Ni2+ or Pb2+), BOD5, COD and TKN removal efficiencies of SBR system with SIEWW containing 5mg/L heavy metal (Ni2+ or Pb2+) under MLSS of 3000mg/L were 83–85%, 96–97%, 95–96% and 83–94%, respectively. The increase of heavy metal (Ni2+ or Pb2+) concentrations of SIEWW from 5 to 50mg/L were not significantly effected to both COD and BOD5 removal efficiencies (they were reduced by only 4–5%), but they were strongly effected to both TKN and heavy metals removal efficiencies (they were reduced by 15 and 20–30%, respectively). Both Ni2+ and Pb2+ could repress the growth of both nitrification and denitrification bacteria. And Ni2+ was more effective than Pb2+ to reduce the heavy metals removal efficiency. The SBR system could be applied to treat the industrial estate wastewater (IEWW) containing both Pb2+ and Ni2+ even the heavy metals concentrations was up to 5mg/L, but the removal efficiency was quite low and excess bio-sludge did not produce. However, the system efficiency could be increased with the increase of BOD5 concentration of the wastewater. The Pb2+, Ni2+, COD, BOD5 and TKN removal efficiencies of the system with IEWW containing 500mg/L BOD5, 5mg/L Ni2+ and 5mg/L Pb2+ under HRT of 3 days were 85.68±0.31%, 87.03±0.21%, 86.0±0.5%, 94.04±0.4% and 90.5±0.9%, respectively. And the effluent SRT, SS and SVI of the system were 44.7±0.6 days, 150±6mg/L and 100mL/g, respectively. [Copyright &y& Elsevier]

Two types of operation means “SBR reactor alone (control reactor)” and “adding zeolite powder into SBR reactor (test reactor)” were used to treat municipal wastewater. The test results revealed that zeolite powder addition could improve the activity of the activated sludge. It was investigated the specific oxygen utilization rate (SOUR) of the tested zeolite sludge were about double times that of the control activated sludge, and the nitrification rate and settling property of zeolite-activated sludge were both improved. Due to the combination of zeolite adsorption for NH4 +-N and enhanced simultaneous nitrification and de-nitrification (SND), a higher nitrogen removal was observed in test reactor compared to the control reactor, and the addition of zeolite powder is helpful to inhabit sludge bulking. In addition, through long-term parallel shock load test, it was found that the zeolite powder addition could enhance the ability of activated sludge in resisting the shock load of organics and ammonium. Compared to the control activated sludge, zeolite powder added activated sludge could remove COD, NH4 +-N, TN and TP significantly in a shorter cycle time. At the same operational time period, the test SBR could treat wastewater quantity 1. 22 times that treated in control SBR. [Copyright &y& Elsevier]

A laboratory-scale sequencing batch reactor (SBR) is used to treat landfill leachate containing high concentration of ammonium nitrogen with municipal fecal supernatant. The SBR system is operated in the following sequential phases: fill period, anoxic period, aeration period, settling period, decant and idle period. The results indicated that the average removal efficiencies of COD, BOD5, TN, NH-N were 93.76%, 98.28%, 84.74% and 99.21%, respectively. The average sludge removal loading rates of COD, BOD5, TN and NH-N were 0.24 kg/(kg SS·d), 0.08 kg/(kg SS·d), 0.04 kg/(kg SS·d) and 0.036 kg/(kg SS·d), respectively. Highly effective simultaneous nitrification and denitrification was achieved in the SBR system. The ratio of nitrification and denitrification was 99% and 84%, respectively. There was partial NO denitrification in the system. [ABSTRACT FROM AUTHOR]

Laboratory batch experiments were conducted to investigate pH profiles during partial and complete denitrification with sufficient organic carbon source. Five stirred tank-type glass vessels, with a 7 L working volume for each, were used as SBR reactors that were all operated in denitrification mode. Five levels of initial proportion of nitrogen substances, i.e. nitrate and nitrite, were used in five reactors, respectively. Results showed that, at given temperature and mixed liquor suspended solids (MLSS), partial denitrification could attain a higher pH value than complete denitrification at the end of denitrification with the same initial NOx- concentration. The larger proportion the nitrite took in initial NOx- concentration, the higher pH peak would be obtained on pH profiles during denitrification despite the same total alkalinity produced. It was found that different types of alkalinity were produced during biological denitrification with different nitrogen substances. Partial denitrification could more carbonate alkalinity produce than complete denitrification. Furthermore, some characteristic points were identified on pH profiles which could indicate the disappearance of not only nitrate, but also nitrite in system. When computers are used to detect these features, they can provide rapid, real-time information, regarding the biological state of the system. [ABSTRACT FROM AUTHOR]

The effect of sludge retention time on biological nutrient removal in a sequencing batch reactor was investigated in this study. The effect of three different sludge ages (10, 15 and 25 d) on phosphorus release and uptake as well as on nitrification and denitrification was tested in a lab scale sequencing batch reactor having a simultaneous fill and draw system operating according to anaerobic-anoxic-aerobic principles. It was found that the system possessed better P removal (98 %) with shorter SRT (10 d). The phosphorus concentration in the effluent changed between 0 and 1.0 mg/l at this sludge age. When SRT was increased to 25 d, in contrast to decrease in effluent ammonium concentration (3 mg/l), P concentration increased in the effluent (5 mg/l). The system showed a very stable chemical oxygen demand removal efficiency during the entire operational period. [ABSTRACT FROM AUTHOR]

Abstract: An anaerobic–anoxic sequencing batch reactor (A2 SBR) coupled with a fixed-bed nitrification reactor for simultaneous carbon, nitrogen and phosphorus removal was evaluated using slaughterhouse wastewater. Whereas the treatment could not be successfully carried out on the raw wastewater, the process showed very good nutrient removal performances after prefermentation. The removals of COD, N-NH4 and P-PO4 achieved were 99%, 85% and 99%, respectively. The increase in volatile fatty acid (VFA) and phosphate concentrations in the effluent after prefermentation may explain the high levels of biological carbon, nitrogen and phosphorus removal observed. A simple prefermentation is, therefore, necessary but sufficient to ensure good performances of the denitrifying enhanced biological phosphorus removal (EBPR) process. [Copyright &y& Elsevier]

Nitrate can affect phosphate release and lead to reduced efficiency of biological phosphorus removal process. The inhibition effect of remaining nitrate at the anaerobic/anoxic phases was investigated in a lab scale sequencing batch reactor. In this study the influence of denitrification process on reactor performance and phosphorus removal was examined. The experiments were carried out through simultaneous filling and decanting, mixing, mixing-aeration and settling modes. Glucose and acetate were used as carbon sources. The proposed treatment system was capable of removing approximately 80% of the influent PO4-P, 98% NH4-N and 97% COD at a SRT of 25 days. In the fill/decant phase, anoxic and anaerobic conditions prevailed and a large quantity of nitrate was removed in this stage. In the anoxic phase the remaining nitrate concentration was quickly reduced and a considerable amount of phosphate was released. This was attributed to the availability of acetate in this stage. For effective nitrogen and phosphate removal, a short anoxic phase was beneficial before an aerobic phase. [Copyright &y& Elsevier]

The aim of this study was to investigate efficiency of ammonium nitrogen removal from municipal landfill leachate in activated sludge in two-stage SBR reactors. Treated leachate contains low concentrations of organic substances measured as chemical oxygen demand (COD)-757 mg O2/dm³ and high concentrations of ammonium -362 mgNNH4/dm³. Nitrification was studied in two parallel, aerated SBR reactors with two different hydraulic retention times (HRT), 3 and 2 days, respectively. We have found that 2 days HRT was sufficient to achieve complete nitrification. In the effluent ammonium, nitrite and nitrate nitrogen concentrations were 0.08 mgNNH4/dm³, 0.04 mgNNO2/dm³ and 320 mgNNO3/dm³, respectively. The ammonium nitrogen removal rate was 20.2 The ammonium nitrogen removal rate was 20.2 mgNNH4/dm³h. The effluent from aerobic reactors (HRT 2 days) was fed to the anoxic SBR reactors. An external carbon source (methanol) was added to promote denitrification. In the anoxic reactor, at a methanol dosage 3.6 mg COD/mg NNO3 and HRT of 1 day complete denitrification was achieve with nitrate nitrogen residual concentrations of 0.9 mgNNO3/dm³. The maxmum denitrification rate aws 48.4 mgNNOx/dm³. The highest values of the yield methanol coefficient Ymn/N-NOx were determined for dosages 3.6 mg COD/mg NNO3 and 5.4 mg COD/mg NNO3, the lowest for 1.8 mg COD/mg NNO3. [ABSTRACT FROM AUTHOR]

Aims: The aim of this study was the optimization of the SBR system for enhanced biological phosphorus and nitrogen removal. Materials And Methods: A lab-scale SBR consisting filling, pre-anoxic, anerobic, anoxic, aerobic, settling, decanting, and idle phases was proposed for simultaneous enhanced biological phosphorus and nitrogen removal (SEBPNR) from wastewater. Synthetic wastewater was used in this research. Glucose was used as a carbon source. The SBR was seeded with sludge from a local municipal wastewater treatment plant. Results: The results indicates that the lab-scale SBR was capable to remove soluble phosphorus (SP), SCOD, TCOD, and ammonia, with efficiencies of around 92%, 95%, 80%, and 85%, respectively. Optimized lab-scale SBR operational condition for SEBPNR consists of a fill (15 min), pre-anoxic (30 min), anerobic (90 min), 1st aerobic (210 min), 2nd anoxic (55 min), 2nd aerobic (10 min), settling (90 min), decant (10 min), and idle (10 min) phases. Conclusion: This study concludes that effective biological removal of phosphorus and nitrogen from wastewater using SBR occurs in sufficient HRT in the anaerobic and aerobic stages, adequate COD/TP ratios (up to 35). This system is suitable for high removal of P and N in both municipal and industrial wastewater.

• SBR integrated with CEPS and acidogenic fermentation for enhanced nutrient removal. • Organics in wastewater were reserved and utilized for biological denitrification. • Acidogenic fermentation greatly improved the biodegradability of CEPS sludge. • Self-sufficient carbon supply in side-stream was achieved for nitrogen removal. To treat municipal wastewater with a low carbon to nitrogen ratio, the addition of an external carbon source is often needed to achieve enhanced nutrient (nitrogen and phosphorus) removal. To meet this need, this research developed an innovative strategy for reserving and utilizing organic pollutants to achieve a self-sufficient organic carbon supply for wastewater treatment. In the new system, before biological treatment by a sequencing batch reactor (SBR), Fe-based chemically enhanced primary sedimentation (CEPS) was used to reserve part of the organics from the wastewater in the CEPS sludge. By acidogenic fermentation in the side-stream, the settled organics in the CEPS sludge were converted into volatile fatty acids and other soluble organics to provide a suitable carbon source for denitrification in the anoxic phase of the SBR. The experimental results showed that the new SBR system integrated with CEPS and acidogenic sludge fermentation removed up to 89% of the total phosphorus (TP) and 83% of the total nitrogen (TN) from the wastewater. Compared with the conventional SBR system, TP and TN removal was increased by more than 65% and 50%, respectively. As well as increasing nutrient removal efficiency without the need for external carbon addition, the Fe-based CEPS greatly reduced the organic load on the SBR biological treatment process, reducing the aeration cost. Overall, a cost-effective wastewater treatment process is developed that can be used to upgrade existing wastewater treatment plants to improve the nutrient removal performance and meet more stringent discharge standards. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Biological phosphorus and nitrogen removal in biofilm processes havea potential advantage compared to activated sludge processes, because of less vulnerability with respect to sludge loss and because biofilm processes, in general, are more compact with a smaller footprint. Experiments have been carried out in a moving bed biofilm reactor operated as a sequencing batch reactor (SBR), with simultaneous nitrification, phosphorus uptake and denitrification in the aerobic phase. Inorder to achieve good phosphorus and nitrogen removal, the length ofthe anaerobic period should be tuned to achieve near complete removal of easily biodegradable COD in the anaerobic period, and the lengthof the aerobic period should be long enough for complete nitrification. The total COD-loading rate must be at the same time be kept high enough to achieve a net growth of biomass in the reactor. [ABSTRACT FROM AUTHOR]

A separate sludge system incorporating sequencing batch reactor (SBR) for sequestered denitrification and an immobilized fixed-film reactor for nitrification was investigated in this study. Emphases were placed on the preservation of organic matter as an electron donor for denitrification and the improvement of nitrification efficiency by using an immobilization technique with alginate coating. To preserve organic materials in the sludge required for denitrification, a study was made with a contact process. The contactor, when operated with a short detention time, gave incomplete metabolism of organic matter. With 64% of the influent soluble chemical oxygen demand (SCOD) was adsorbed to activated sludge within 30 min. The specific mass of organic matter uptaken was 55 mg SCOD/g mixed liquor suspended solids (MLSS), which enhanced the denitrification efficiency up to 63% in the following denitrification step. Thus, the required COD in the proposed system can be saved up to 63% as an available electron donor for the conventional aerobic process. The immobilized nitrification unit showed over 90% of nitrate production rate up to 50 mg/l of influent ammonia load. [ABSTRACT FROM AUTHOR]

A sequencing batch reactor (SBR) was operated to selectively grow a nitrite oxidising microbial community and was called the nitrite oxidising SBR (NOSBR). The nitrite oxidising characteristics of the reactor biomass were studied as well as the microbial composition. Molecular biological methods of clone libraries were used to evaluate the microorganisms in both the seed sludge and in the NOSBR sludge. We havefound that the nitrite oxidation in the NOSBR was due the presence of bacteria from the Nitrospira phylum and not because of the presenceof Nitrobacter which were in very low numbers in the NOSBR and not detected in the seed sludge. We hypothesize that the unknown nitrite oxidising bacteria in wastewater treatment plants are a range of species related to Nitrospira moscoviensis. A suite of primers were developed from the clone sequence data and used in a diagnostic polymerase chain reaction to prove the presence of these novel nitrite oxidisersin a range of full scale and laboratory scale activated sludge plants. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved. [ABSTRACT FROM AUTHOR]