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The goal of the study was to evaluate the possibility of applying disintegrated excess sludge as a source of organic carbon to enhance biological nitrogen and phosphorus removal. The experiment, performed in a sequencing batch reactor, consisted of two two-month series, without and with applying mechanically disintegrated excess sludge, respectively. The effects on carbon, nitrogen and phosphorus removal were observed. It was shown that the method allows enhancement of combined nitrogen and phosphorus removal. After using disintegrated sludge, denitrification effectiveness increased from 49.2 ± 6.8% to 76.2 ± 2.3%, which resulted in a decline in the NOx-N concentration in the effluent from the SBR by an average of 21.4 mg NOx-N/L. Effectiveness of biological phosphorus removal increased from 28.1 ± 11.3% to 96.2 ± 2.5%, thus resulting in a drop in the [Formula: see text] concentration in the effluent by, on average, 6.05 mg PO4(3-)-P/L. The application of disintegrated sludge did not deteriorate effluent quality in terms of COD and NH4(+)-N. The concentration of NH4(+)-N in both series averaged 0.16 ± 0.11 mg NH4(+)-N/L, and the concentration of COD was 15.36 ± 3.54 mg O2/L., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The integration of biological phosphorus removal (bio‐P) and shortcut nitrogen removal (SNR) processes is challenging because of the conflicting demands on influent carbon: SNR allows for upstream carbon diversion, but this reduction of influent carbon (especially volatile fatty acids [VFAs]) prevents or limits bio‐P. The objective of this study was to achieve SNR, either via partial nitritation/anammox (PNA) or partial denitrification/anammox (PdNA), simultaneously with biological phosphorus removal in a process with upstream carbon capture. This study took place in a pilot scale A/B process with a sidestream bio‐P reactor and tertiary anammox polishing. Despite low influent rbCOD concentrations from the A‐stage effluent, bio‐P occurred in the B‐stage thanks to the addition of A‐stage WAS fermentate to the sidestream reactor. Nitrite accumulation occurred in the B‐stage via partial denitrification and partial nitritation (NOB out‐selection), depending on operational conditions, and was removed along with ammonia by the tertiary anammox MBBR, with the ability to achieve effluent TIN less than 2 mg/L. Practitioner Points: A sidestream reactor with sufficient fermentate addition enables biological phosphorus removal in a B‐stage system with little‐to‐no influent VFA.Enhanced biological phosphorus removal is not inhibited by intermittent aeration and is stable at a wide range of process SRTs.Partial nitritation and partial denitrification are viable routes to produce nitrite within an A/B process with sidestream bio‐P, for downstream anammox in a polishing MBBR. [ABSTRACT FROM AUTHOR]

This study presents results from the City of St. Petersburg's (Florida) Southwest Water Reclamation Facility. This high‐rate BNR plant (SRT ~ 5 days; HRT < 8 hr) achieves combined bioP and shortcut simultaneous nitrification and denitrification (SND) via nitrite in a simple BNR configuration—an anaerobic–aerobic (A/O) process without mixed liquor recycle and a 25% unaerated fraction. N removal to low effluent and nitrate and nitrite (NO3- + NO2-) concentrations occurs mainly via SND by operating the aerated zone at low DO, but still achieving near‐complete ammonium (NH4+) removal. Despite the low DO operation, very good bioP performance is achieved. Full‐scale performance data and detailed bench‐scale testing were conducted to assess the nitrogen and phosphorus removal at low DO conditions. Full‐scale results showed that the plant achieves effluent total inorganic nitrogen (TIN) and total phosphorus (TP) concentrations of approximately 2.0 mgN/L and 0.5 mgP/L, respectively, at an average influent C:N ratio of 7:1 mgCOD:mgN. Practitioner points: Simple anaerobic–aerobic (A/O) process demonstrated combined N and P removalAmmonia oxidation was not hampered by low DO (<0.5 mg/L) operationLow DO (<0.5 mg/L) operation sustained SND via nitrite pathway in a high‐rate process (HRT < 6 hr)P uptake was demonstrated at low DO which counters to the widely held understanding that high DO (>1.5 mg/L) is necessaryHeterotrophic consumption of nitrite at low DO was the key to the out‐selection of nitrite‐oxidizing bacteria [ABSTRACT FROM AUTHOR]

The efficiency of denitrification and enhanced biological phosphorus removal in biological nutrient removal activated sludge systems is strongly dependent on the availability of appropriate carbon sources. Due to high costs of commercial compounds (such as methanol, ethanol, acetic acid, etc.) and acclimation periods (usually) required, the effective use of internal substrates is preferred. The aim of this study was to determine the effects of slowly biodegradable compounds (particulate and colloidal), as internal carbon sources, on denitrification, phosphate release/uptake and oxygen utilization for a full-scale process mixed liquor from two large wastewater treatment plants located in northern Poland. Since it is difficult to distinguish the effect of slowly biodegradable substrate in a direct way, a novel procedure was developed and implemented. Four types of one- and two-phase laboratory batch experiments were carried out in two parallel reactors with the settled wastewater without pre-treatment (reactor 1) and pre-treated with coagulation-flocculation (reactor 2). The removal of colloidal and particulate fractions resulted in the reduced process rates (except for phosphate release). The average reductions ranged from 13 % for the oxygen utilization rate during the second phase of a two-phase experiment (anaerobic/aerobic), up to 35 % for the nitrate utilization rate (NUR) during the second phase of a conventional NUR measurement. [ABSTRACT FROM AUTHOR]

The present study describes the laboratory-scale evaluation of phosphorus removal uptake along with soluble chemical oxygen demand (COD) reduction in a sequencing batch reactor under anoxic–aerobic environment in sequence. The study includes the preparation of acclimatized seeds for phosphate removal and examining the effect of organic substrate like glucose and acetate on phosphate removal in different initial phosphate concentration under anoxic–aerobic conditions. Phosphorus removal efficiency was accelerated remarkably (24.83–88.19%) by the presence of readily biodegradable soluble COD in the form of acetate for an initial phosphate concentration of 10 mg/l as P during the anoxic–aerobic period. It was also observed that a change in sequence of the react phase from 5 h anoxic + 5 h aerobic to 4 h anoxic + 4 h aerobic + 2 h anoxic should be effective to produce marginal denitrified effluent at the end of the last 2.0 h of anoxic react phase. [ABSTRACT FROM PUBLISHER]

• Novel PDA-PFPN system was developed for real domestic wastewater and WAS treatment. • Nitrogen and phosphorus removal and sludge reduction were simultaneously achieved. • Effluent N and P reached 0 and 0.1 mg/L without addition of external carbon source. • Amino acids were important intracellular metabolites in biological P removal. • Tetrasphaera as simultaneous P removal and fermentation bacteria was dominant PAO. A novel process was developed for real domestic wastewater and waste activated sludge (WAS) treatment based on partial denitrification, anammox-biological phosphorus removal, fermentation and partial nitrification (PDA-PFPN). After 246 days of operation, the effluent concentrations of NH 4 +-N, NO 2 −-N and NO 3 −-N were below detection limits (0.1 mg/L), and the effluent concentration of PO 4 3−-P was 0.1 mg/L without the addition of external carbon source in PDA-PFPN system. Moreover, the sludge reduction efficiency reached 48.1% due to fermentation. The nitrite accumulation ratios by ammonia oxidation and nitrate reduction pathway were 60.6% and 87%, respectively. Intracellular metabolites measured by liquid chromatography mass spectrometer (LC-MS/MS) suggested that different intracellular amino acids were stored and consumed at different duration, and intracellular Valine, Glycine and Lysine were not utilized in oxic stage. Results of flow cytometry showed that the proportion of intact cells decreased from 94.7% to 82.9%, and necrotic cells increased from 5.3% to 17.1% with the increase of DNA content in sludge supernatant and cell decay rate, indicating the occurrence of cell death and lysis and leading to WAS reduction. Analysis of transcriptional community composition revealed that partial denitrification bacteria (Thauera), anammox bacteria (Candidatus Brocadia and Candidatus Kuenenia), simultaneous phosphorus removal and fermentation bacteria (Tetrasphaera) and partial nitrification bacteria (Nitrosomonas) coexisted and actually worked in PDA-PFPN system. The novel PDA-PFPN process simultaneously achieved highly efficient nitrogen and phosphorus removal and WAS reduction without the addition of external carbon source, which greatly reduced the operation cost of carbon source dosing and WAS treatment in wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, simultaneous denitrification and phosphorus (P) removal were investigated in batch tests using nitrified mixed liquor and secondary wastewater influent from a full-scale treatment plant and different levels of acetate and propionate as supplemental carbon sources. Without supplemental carbon source, denitrification occurred at low rate and P release and P uptake was negatively affected (i.e., P removal of only 59.7%). When acetate and propionate were supplied, denitrification and P release occurred simultaneously under anoxic conditions. For acetate and propionate at a C/N stoichiometric ratio of 7.6, P release was negatively affected by denitrification. For acetate, the percent P removal and denitrification were very similar for C/N ratios of 22 (5X stoichiometric) and 59 (10X stoichiometric). For propionate, both percent P removal and denitrification deteriorated for C/N ratios of 22 (5X stoichiometric) and 45 (10X stoichiometric). It was observed that carbon source added in excess to stoichiometric ratio was consumed in the aerobic zone, but P was not taken up. This implies that PAO bacteria may utilize the excess carbon source in the aerobic zone rather than their polyhydroxyalkanoate (PHA) reserves, thereby promoting deterioration of the system. [ABSTRACT FROM PUBLISHER]

The aim of this study was to expand the International Water Association Activated Sludge Model No. 2d (ASM2d) to account for a newly defined readily biodegradable substrate that can be consumed by polyphosphate-accumulating organisms (PAOs) under anoxic and aerobic conditions, but not under anaerobic conditions. The model change was to add a new substrate component and process terms for its use by PAOs and other heterotrophic bacteria under anoxic and aerobic conditions. The Gdansk (Poland) wastewater treatment plant (WWTP), which has a modified University of Cape Town (MUCT) process for nutrient removal, provided field data and mixed liquor for batch tests for model evaluation. The original ASM2d was first calibrated under dynamic conditions with the results of batch tests with settled wastewater and mixed liquor, in which nitrate-uptake rates, phospho-rus-release rates, and anoxic phosphorus uptake rates were followed. Model validation was conducted with data from a 96-hour measurement campaign in the full-scale WWTP. The results of similar batch tests with ethanol and fusel oil as the external carbon sources were used to adjust kinetic and stoichiometric coefficients in the expanded ASM2d. Both models were compared based on their predictions of the effect of adding supplemental carbon to the anoxic zone of an MUCT process. In comparison with the ASM2d, the new model better predicted the anoxic behaviors of carbonaceous oxygen demand, nitrate-nitrogen (NO3-N), and phosphorous (PO4-P) in batch experiments with ethanol and fusel oil. However, when simulating ethanol addition to the anoxic zone of a full-scale biological nutrient removal facility, both models predicted similar effluent NO3-N concentrations (6.6 to 6.9 g N/m). For the particular application, effective enhanced biological phosphorus removal was predicted by both models with external carbon addition but, for the new model, the effluent PO4-P concentration was approximately one-half of that found from ASM2d. On a PO4-P removal percentage basis, the difference was small, that is, 94.1 vs 97.1%, respectively, for the ASM2d and expanded ASM2d. [ABSTRACT FROM AUTHOR]

In this paper, 16 denitrifying phosphate --accumulating organisms (DNPAOs) were isolated in the special medium from the anaerobic/aerobic/anoxic SBR reactor, and the most efficient DNPAOs called Q -- hrb05, was screened by a phosphate uptake experiment, where nitrates were denitrified to gas and through inspection of the poly -- P. Strain Q -- hrb05 was identified by 16S rDNA gene analysis, and the accession number of 16 S rDNA gene sequence of strain Q -- hrb05 in GenBank was GU214826. The result showed that the strain Q -- hrb05 belonged to Bacillus sp, of which the homology could reach to 99%, that also corresponded to the result of biochemical features. The average phosphorus uptake rate of strain Q -- hrb05 was at 85% within 12 hours, and it had the denitrification capacity in the aerobic condition. It could be found that the phosphorus uptake rate was related to the content change of PHB. Under anaerobic condition, the maximal P -- release rate was 66%, which could reach to 12% of the dry cell weight. The P -- uptake rate was 92% with the decreasing of PHB content. [ABSTRACT FROM AUTHOR]

The work reviewed here was published between 2008 and 2010 and describes research that involved aerobic and anoxic biofilm treatment of water pollutants. Biofilm denitrification systems are covered when appropriate. References catalogued here are divided on the basis of fundamental research area or reactor types. Fundamental research into biofilms is presented in two sections, Biofilm Measurement and Characterization and Growth and Modeling. The reactor types covered are: trickling filters, rotating biological contactors, fluidized bed bioreactors, submerged bed biofilm reactors, biological granular activated carbon, membrane bioreactors, and immobilized cell reactors. Innovative reactors, not easily classified, are then presented, followed by a section on biofilms on sand, soil and sediment. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of an experimental study for the modelling and calibration of denitrifying activity of polyphosphate accumulating organisms (PAOs) in full-scale WWTPs that incorporate simultaneous nitrogen and phosphorus removal. The convenience of using different yields under aerobic and anoxic conditions for modelling biological phosphorus removal processes with the ASM2d has been demonstrated. Thus, parameter η PAO in the model is given a physical meaning and represents the fraction of PAOs that are able to follow the DPAO metabolism. Using stoichiometric relationships, which are based on assumed biochemical pathways, the anoxic yields considered in the extended ASM2d can be obtained as a function of their respective aerobic yields. Thus, this modification does not mean an extra calibration effort to obtain the new parameters. In this work, an off-line calibration methodology has been applied to validate the model, where general relationships among stoichiometric parameters are proposed to avoid increasing the number of parameters to calibrate. The results have been validated through a UCT scheme pilot plant that is fed with municipal wastewater. The good concordance obtained between experimental and simulated values validates the use of anoxic yields as well as the calibration methodology. Deterministic modelling approaches, together with off-line calibration methodologies, are proposed to assist in decision-making about further process optimization in biological phosphate removal, since parameter values obtained by off-line calibration give valuable information about the activated sludge process such as the amount of DPAOs in the system. [ABSTRACT FROM AUTHOR]

Activated sludge from a local non-biological nutrient removal wastewater treatment plant was inoculated into a sequencing batch reactor (SBR) to investigate the techniques and required conditions for the selection and enrichment of denitrifying phosphorus accumulating organisms (DNPAOs). The SBR was operated under varying anaerobic, anoxic and aerobic conditions for 3 mon. In this study, it was demonstrated that Enhanced biological phosphorus removal (EBPR) was established rapidly by the application of the anaerobic/aerobic (A/O) process and the selection of DNPAOs was achieved by introducing an anoxic phase. With an extension of the anoxic period and increasing nitrate dosage, the community shift between aerobic phosphorus accumulating organisms (PAOs) and DNPAOs was observed. An approximate 60% DNPAO fraction was obtained from this experiment. [ABSTRACT FROM AUTHOR]

Batch experiments were performed to investigate simultaneous denitrification and phosphorus removal by denitrifying phosphorus accumulating organisms (DNPAO). The results showed that while using the same amount of carbon source, DNPAOs are able to uptake phosphorus by using nitrate as an electron acceptor. It was observed that higher nitrate concentration required a longer anoxic period for denitrifying phosphate uptake. In addition, the effect of the presence of nitrate in substrate was studied. Phosphorus release occurred as long as substrate was present in the anaerobic phase regardless of nitrate concentrations. It also was noticed that nitrate hindered the release of phosphorus in the anaerobic stage because of denitrifiers competing with phosphorus accumulating organisms for their carbon source. The DNPAOs, however, remained competitive in a system with nitrate in the anaerobic phase. [ABSTRACT FROM AUTHOR]

A sequencing batch reactor (SBR) was used for the treatment of abattoir wastewater to produce effluent with desirable nitrogen and phosphorus levels for irrigation. The SBR cycle consisted of an anaerobic phase with wastewater feeding, a relatively short aerobic period (allowing full ammonium oxidation), a second anoxic period with feeding, followed by settling and decanting. This design of operation allowed biological nitrification and denitrification via nitrite, and therefore with reduced demand for aeration and COD for nitrogen removal. The design also allowed ammonium, rather than oxidized nitrogen, being the primary nitrogen species in the effluent. Biological phosphorus removal was also achieved, with an effluent level desirable for irrigation. A high-level of nitrite accumulation (40 mg N/L) in the reactor caused inhibition to the biological P uptake. This problem was solved through process optimization. The cycle time of the SBR was reduced, with the wastewater load per cycle also reduced, while the daily hydraulic loading maintained. This modification proved to be an effective method to ensure reliable N and P removal. N2O accumulation was measured in two experiments simulating the anoxic phase of the SBR and using nitrite and nitrate respectively as electron donors. The estimated N2O emissions for both experiments were very low. [ABSTRACT FROM AUTHOR]

Abstract: It has been shown that by combining the patented process for biological phosphorus removal with post-denitrification without additional carbon dosing in membrane bioreactors (MBRs) good nutrient eliminations can be achieved. Especially, reported denitrification rates are higher than expected ones. The reason for this is not understood yet but a correlation between acetate dosing in batch trials and DNR has been reported. The present study investigated the influence of COD sludge loading and acetate inflow concentration on denitrification rates in continuous MBRs. A laboratory scale MBR operated with synthetic wastewater was switched from a multi to a mono substrate (acetate) wastewater and compared to three other MBR connected to separate sewer systems. Better eliminations for COD, TN and TP for the MBR operated with acetate were expected. However, elimination efficiencies were on a good level for all plants and configurations (eliminations: 94–97% COD, 86–94% TN, 92–99% TP) and no significant increase for mono substrate could be found. Average denitrification rate and TN elimination was even a bit lower with mono substrate. For increasing COD sludge loads increasing denitrification rates could be found. However, the variation within the rates has proved that many different influences have to be considered. [Copyright &y& Elsevier]

Removal of phosphate and nitrate from the effluent of a fish farm with a recirculation system was tested in à sequencing moving bed biofilm bioreactor (SMBBR) over a 160-day period. This bioprocess made use of a stock tank (ST) that allowed the same volume of anaerobic water to be reused from one batch to another. Water from the ST contained an excess of a carbon source (acetate), which made it possible to alternate between anaerobic (1.5 h) and aerobic/anoxic (4 h) conditions to achieve enhanced biological phosphorus removal (EBPR). The developed biomass (2,072 mg total solids nr2-d1' and 892 mg total volatile solids m-[2]'d-[1]) removed 7.5 mg of PO[sub 4]-P per litre and 8.5 mg of NO[sub 3]-N per litre from an influent containing 10 mg of PO[sub 4]-P per litre and 21 mg NO[sub 3]-N per litre. The dynamic variation of phosphate and chemical oxygen demand (COD) in the influent showed that the biomass was sensitive to the COD[sub available]/P[sub influent] ratio. A ratio of 10 to 15 mg of COD per milligram of P seemed to favour phosphorus accumulating organisms (PAOs). Differences between the nitrate, phosphate, and oxygen reduction kinetics suggested that the denitrification could be attributed to organisms other than PAOs. The SMBBR-ST showed potential for EBPR and for denitrification as well. However, the economic feasibility of implementing such a process in a full-scale operation remains to be demonstrated. [ABSTRACT FROM AUTHOR]

A new process was developed to achieve denitrifying biological phosphorus removal in wastewaters containing high levels of nitrate and phosphate with a low level of organic matter. This could particularly be useful in recirculating systems such as aquariums or fish farms to prevent accumulation of nitrate and phosphates and to avoid regular cost extensive and polluting water replacement. Phosphorus (P) was removed from the influent in a sequencing moving bed biofilm reactor, stored in the attached biomass and then cyclically removed from the biomass by filling the reactor with anaerobic water from a stock tank. Phosphate was accumulated in the stock tank which allowed for use as fertilizer. The feasibility of the experimental design was demonstrated by using the activated sludge model No. 3 (ASM3) complemented by the EAWAG Bio-P module implemented in the WEST simulation software. A pilot scale experiment was conducted in two identical reactors in two runs: one to treat water from a marine mesocosm, the other to treat a synthetic freshwater influent. No biological phosphorus removal was achieved during the seawater run. During the freshwater run, average P removal efficiency was 20%, of which 80% was attributed to biological removal and 20% to chemical precipitation. The absence of efficiency in seawater was attributed to the high concentration of calcium. [ABSTRACT FROM AUTHOR]

Since metabolic pathway and enzymatic clarification of poly-phosphate accumulating organisms (PAOs) are still unclear, biological phosphorus removal (BPR) sometimes become unstable. We have focused on nitrite as one of unknown factors deteriorating BPR performance. And we obtained some findings from previous studies, namely 1) nitrite inhibits phosphate uptake and growth of PAOs, 2) nitrite inhibition persists even after nitrite disappearance, 3) PAOs with the higher relative anoxic activity are less sensitive to nitrite exposure. This study provides the modified Activated Sludge Model No.2d (ASM2d) to express nitrite inhibition properly by incorporating the assumed intracellular reaction product (reaction complex) of nitrite. The model also considers the tolerance mechanism of nitrite inhibition by the denitrifying activity of PAOs. From the results of previous experiments and relevant references, the modified model called "Nitrite-Complex model" incorporates new components, namely nitrite (SNO2 ) and reaction complex (Xcomplex), to ASM2d. The model incorporation only nitrite inhibition was able to fit with measured phosphate concentration while nitrite exists. Whereas, this model couldn't describe the persistence of nitrite inhibition after nitrite disappeared. However, result of nitrite-complex model incorporating nitrite and reaction complex inhibition, it fits well with measured phosphate concentration not only before nitrite disappeared but also after nitrite disappeared. [ABSTRACT FROM AUTHOR]

The influence of the wastewater composition on the denitrification and biological P-elimination in the Sorption Denitrification P-eliminations Process (S-DN-P-process) was examined. Batch type experiments were performed to examine the influence of various substrates. Among the three different substrates prepared, only 11% CODfilt was taken up from starch containing wastewater (starch preparation). Acetate is an easily degradable substrate for the biological P-elimination, and showed ca. 30% more acetate was taken up compared to the raw wastewater (wastewater preparation). Starch is a barely degradable substance, because it must be hydrolysed before digestion. Starch initially sorbs slowly (approximately 30 min), and may be hydrolysed during this time. During the investigations, the biological P-elimination and the denitrification were found to be dependent on the wastewater composition. The P-elimination rate was determined to be 38% with the acetate preparation, while a P-elimination of 6% was obtained with the starch preparation. The wastewater preparation showed a P-elimination of 56%, the value of which was almost 18% more than the acetate preparation. The biological P-elimination and denitrification depend not only on the dissolved parts in the wastewater, but also on the undissolved content. [ABSTRACT FROM AUTHOR]

For membrane bioreactors (MBR) with enhanced nutrients removal, rather complex recirculation schemes based on the biological requirements are commonly recommended. The aim of this work was to evaluate other recirculation options. For a laboratory scale MBR, four different recirculation schemes were tested. The MBR was operated with COD degradation, nitrification, post-denitrification without carbon dosing and biological phosphorus removal. For all configurations, efficient COD, nitrogen and phosphorus removal could be achieved. There were no big differences in elimination efficiency between the configurations (COD elimination: 96.6-97.9%, nitrogen removal: 89.7-92.1% and phosphorus removal: 97.4-99.4%). Changes in the degradation, release and uptake rates were levelled out by the changes in contact time and biomass distribution. With relatively constant outflow concentrations, different configurations are still interesting with regard to oxygen consumption, simplicity of plant operation or support of certain degradation pathways such as biological phosphorus removal or denitrification. [ABSTRACT FROM AUTHOR]

Two membrane bioreactors were operated with biological phosphorus removal, carbon degradation and denitrification to check how comparable and representative they were compared to full-scale plants. One was fed with synthetic municipal wastewater and was switched from pre-to post-denitrification without carbon dosing. The influent of the second plant was drawn from a separate sewer. This plant worked the whole time with post-denitrification without carbon dosing. The synthetic wastewater was designed to achieve a realistic COD:TN:TP ratio and tested for long time biodegradability. The eliminations were >94% (COD) and >97% (TP) for both plants. This was within the range of commercial plants, as well as the TN elimination for the pre-denitrification of plant I (>75%). The eliminations of TN for post-denitrification were above 80% for both plants despite the high influent concentrations and the missing carbon source for post-DN. A calculation of the nitrification rates gave values similar to those found in literature (1–6mgN/(gMLVSSh)). A comparison of the denitrification showed expected rates for pre-denitrification (7.5mgN/(gMLVSSh)) for plant I. The values (on average 1.8mgN/(gMLVSSh)) for post-denitrification in plant II were higher than endogenous denitrification rates which are commonly reported as 0.2–0.8mgN/(gMLVSSh). The rates for post-denitrification in plant I were only slightly higher than endogenous ones (0.9mgN/(gMLVSSh)). [Copyright &y& Elsevier]

Abstract: The paper described a laboratory scale experiment using an airlift loop sequencing batch biofilm reactor (SBBR) to enhance biological nitrogen and phosphorus removal by integrating nitrification and denitrifying dephosphatation. In the reactor, fibrous carriers were packed in aeration zone and reverse flow zone for the attached growth of nitrifiers and denitrifying polyphosphate accumulating organisms (DNPAOs), respectively. After periodically operating the reactor for 234 days with synthetic wastewater, optimal operation conditions were established to obtain stable and highest removal rates of COD, NH4 +–N, and PO4 3−–P. Adequate cycle and phase duration, packing density were established and organic load were obtained for optimal operation. Under optimal conditions, the mean concentrations of influent were about 309.8±8.7mg COD/l, 116.0±11.3mg N/l and 10.5±0.4mg P/l and the removal efficiencies of them were about 95.3±3.3%, 94.6±4.1% and 73.1±8.3%, respectively. [Copyright &y& Elsevier]

Abstract: The formation and performance of granular sludge was studied in an 8l sequencing batch reactor (SBR) treating an abattoir (slaughterhouse) wastewater. Influent concentrations averaged 1520mgl−1 volatile suspended solids (VSS), 7685mgl−1 Chemical oxygen demand (COD), 1057mgl−1 total kjeldahl nitrogen (TKN), 217mgl−1 total P. The COD loading was 2.6kgm−3 d−1. The SBR was seeded with flocculating sludge from a SBR with an 1h settle time, but granules developed within 4 days by reducing the settle time to 2min. The SBR cycle also had 120min mixed (anaerobic) fill, 220min aerated react, and 18min draw/idle. The granules had a mean diameter of 1.7mm, a specific gravity of 1.035, a density of 62gVSSl−1, a zone settling velocity (ZSV) of 51mh−1, and a sludge volume index (SVI) of 22mlg−1. Without optimizing process conditions, removal of COD and P were over 98%, and removal of N and VSS were over 97%. Nitrification and denitrification occurred simultaneously during react. The results indicate that conventional SBRs treating wastewaters with flocculating sludge can be converted to granular SBRs by reducing the settle time. [Copyright &y& Elsevier]

Biological carbon, nitrogen, and phosphorus removal from wastewater has become an established process in wastewater treatment practice. Despite the broad knowledge and practical experience that has been accumulated in previous years, there are still certain aspects of nitrification–denitrification–biological enhanced phosphorus removal (NDBPR) which require further research. In this study, biological carbon, nitrogen, and phosphorous removal in a municipal wastewater treatment plant (MWWTP) was investigated using batch tests. These tests include: anaerobic phosphorus release, released phosphorus uptake in aerobic, and anoxic conditions, nitrification, denitrification, and endogenous phosphorus release. Two different substrates: acetate and glucose were used in anaerobic P release tests. Average phosphorus release rate was 0.019 mg P/g VSS min for glucose addition and maximal anaerobic P release rate was 1.63 mg P/g VSS min as an average for acetate addition. Following the anaerobic P release test, P uptake tests were conducted for aerobic and anoxic conditions. The average P uptake rates were 0.0031 and 0.0046 mg P/g VSS min, respectively. In nitrification tests, average NO3–N production rate was determined as 0.034 mg N/g VSS min. In denitrification tests with the addition of acetate, average NO3–N consuming rate was 0.026 mg N/g VSS min and with the addition of glucose NO3–N consuming rate was 0.020 mg N/g VSS min. In endogenous P release tests, average P release rate was determined as 0.0025 mg P/g VSS min. Simple batch methods were proposed to determine Y, kd, μmax, and Ks, which are important for NDBPR process design. In biological kinetic parameter estimation, according to the Monod model, Y and kd coefficients were found 0.70 mg VSS/mg COD and 0.0022 h-1, respectively. The specific nitrification rate (qN) and the specific denitrification rate (qD) were determined 6.87×10-4 mg NO3–N/mgVSS/h and 3.36×10-4 mg NO3–N/mgVSS/h. The kinetic parameters determined in this study can be used to improve the design and operation of wastewater treatment plants. [Copyright &y& Elsevier]

Experiments in a lab-scale SBR were conducted to demonstrate the feasibility of using an internal carbon source (non-digested pig manure) for biological nitrogen and phosphorus removal in digested piggery wastewater. The internal C-source used for denitrification had similar effects to acetate. 99.8% of nitrogen and 97.8% of phosphate were removed in the SBR, from an initial content in the feed of 900 mg/l ammonia and 90 mg/l phosphate. [Copyright &y& Elsevier]

The effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by denitrifying phosphorus removal bacteria sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in the anoxic phase increased with the high initial anaerobic carbon source addition. However, once the initial COD concentration reached a certain level, which was in excess of the PHB saturation of Poly-p bacteria, residual COD carried over to the anoxic phase inhibited the subsequent denitrifying phosphorus uptake. This was equal to supplementing the external carbon source to the anoxic phase, furthermore the higher the external carbon source concentration the more powerful the inhibition caused. High nitrate concentration in the anoxic phase increased the initial denitrifying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to phosphate release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found that ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the dinitrification and anoxic phosphorus uptake operations. [ABSTRACT FROM AUTHOR]

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]

Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in anoxic phase increased with the high initial anaerobic carbon source addition. However once the initial COD concentration reached a certain level, which was in excess to the PHB saturation of poly-P bacteria, residual COD carried over to anoxic phase inhibited the subsequent denitrifying phosphorus uptake. Simultaneously, phosphate uptake continued until all nitrate was removed, following a slow endogenous release of phosphate. High nitrate concentration in anoxic phase increased the initial denitrifying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the denitrificaion and anoxic phosphorus uptake operations. [ABSTRACT FROM AUTHOR]

Sewage sludge pre-fermentation process produces readily biodegradable carbon, which is essential for reliable biological phosphorus removal and efficient denitrification. This bench scale study was to develop site-specific design parameters for a sludge fermentation process, and to look into the effects of various influential factors. The key factors investigated included solids retention time (4~8 days), temperature (9~19 °C) and sludge concentrations (0.5%~4%DS). The optimum Volatile Fatty Acids yield was found at a sludge concentration of 1%~1.5%DS. A solid retention time of 4 days at 15~20 °C was found to be most cost effective. The fermentation reaction was temperature sensitive, which was found to be inefficient at temperature below 12~15 °C. Under the optimum conditions, 80~100 mgVFA g-1 VSS can be generated from fermentation process, which will result in an increase of 20~24 mg l-1 in the settled sewage based on average flow. A significant pathogen reduction level was also demonstrated over the fermentation period. Liquid sludge from the small rural wastewater treatment plants is often imported to a regional sludge treatment centre for more advanced treatment to comply with the Regulations. The suitability of this imported sludge for pre-fermentation process was also investigated in this study. [ABSTRACT FROM AUTHOR]

This study investigated the characteristics of denitrifying phosphorus removal bacteria by using three different types of electron acceptors as well as the positive role of nitrite in phosphorus removal process. Denitrifying phosphorous removal bacteria was enriched under anaerobic–anoxic (A/A) condition. To understand A/A sludge better, sludge from two other sources were also studied. These include sludges obtained from a lab-scale anaerobic–anoxic–aerobic (A/A/O) system and a local sewage treatment plant. Three types of possible electron acceptors (oxygen, nitrate and nitrite) were examined for their roles in phosphorus uptake. The results obtained indicated that oxygen, nitrate and nitrite were able to act as electron acceptors successfully. This observation suggested that in addition to the two well-accepted groups of phosphorus removal bacteria (one can only utilize oxygen to take up phosphorus, PO, while the other can use both oxygen and nitrate, PON), a new group of phosphorus removal bacteria, PONn, which could use oxygen, nitrate or nitrite to take up phosphorus was identified. The relative population of these three types of bacteria could be calculated from results obtainable from phosphorus uptake batch experiments with either oxygen or nitrate or nitrite as electron acceptor. The results obtained in this study showed that A/A sludge had similar phosphorus removal performance as the A/A/O sludge. However, it has better denitrifying phosphorus removal capability, which was demonstrated by the relative population of the three groups of bacteria. The results also suggested that nitrite was not an inhibitor to phosphorus removal process. Instead, it is an alternative electron acceptor to oxygen or nitrate. [Copyright &y& Elsevier]

Nutrients in piggery wastewater with high organic matter, nitrogen (N) and phosphorus (P) content were biologically removed in a sequencing batch reactor (SBR) with anaerobic, aerobic and anoxic stages.The SBR was operated with 3 cycles/day, temperature 30 °C, sludge retention time (SRT) 1 day and hydraulic retention time (HRT) 11 days. With a wastewater containing 1500 mg/l ammonium and 144 mg/l phosphate, a removal efficiency of 99.7% for nitrogen and 97.3% for phosphate was obtained.Experiments set up to evaluate the effect of temperature on the process showed that it should be run at temperatures higher than 16 °C to obtain good removals (>95%).Batch tests (ammonia utilization rate, nitrogen utilization rate and oxygen utilization rate) proved to be good tools to evaluate heterotrophic and autotrophic biomass activity.The SBR proved to be a very flexible tool, and was particularly suitable for the treatment of piggery wastewater, characterized by high nutrient content and by frequent changes in composition and therefore affecting process conditions. [Copyright &y& Elsevier]

Although anoxic phosphorus uptake has been demonstrated, the conditions that stimulate or inhibit the anoxic uptake are not fully understood. In this study, the possibility of achieving biological excess phosphorus removal in sequencing batch reactors using nitrate as an electron acceptor without including an aerobic phase has been confirmed. The use of an anaerobic/anoxic/aerobic sequencing batch reactor allows anoxic phosphorus uptake to be achieved, in spite of the low fraction of denitrifying phosphorus accumulating organisms present in the inoculum. Biomass characterisation was carried out to determine the denitrifying fraction of the phosphorus accumulating organisms in sequencing batch reactors operating at different operational conditions. With an anaerobic/anoxic/aerobic cycle, it was demonstrated that the disadvantage of denitrifying phosphorus accumulating organisms due to the lower substrate utilisation efficiency in anoxic conditions relative to aerobic conditions, is not so effective to cause the “strictly aerobic” phosphorus accumulating organisms to dominate in the system. [ABSTRACT FROM PUBLISHER]

The continuous introduction of a biological phosphorus removal (BPR) promoting organic substrate to the denitrifying reactor of a BPR process is examined through a series of batch experiments using acetate as model organic substrate. Several observations are made regarding the influence of substrate availability on PHA storage/utilization and phosphate uptake/release. Under anoxic conditions PHB is utilized and phosphate is taken up, indicating that at least a fraction of the PAO can denitrify. The rates of anoxic Puptake, PHB utilization and denitrification are found to increase with increasing initial PHB level. At low acetate addition rates the P-uptake and PHB utilization rates are reduced compared to when no acetate is available. At higher acetate addition rates a net P-release occurs and PHB is accumulated. For certain intermediate acetate addition rates the PHB level can increase while a net P-release occurs. Whether the introduction of BPR promoting organic substrates to the denitrifying reactor is detrimental to overall Premoval appears to be dependent on the interaction between aerobic P-uptake, which is a function of PHB level, and the aerobic residence time. [ABSTRACT FROM AUTHOR]

Thames Water have built a three-stage Bardenpho activated sludge plant to treat 50% of the wastewater flow at Slough in the United Kingdom. Following commissioning, the plant performed well in terms of nitrification and denitrification but did not produce an effluent with a low phosphorus concentration. One possible explanation for the poor performance was the mixing of the anaerobic zone. The flow characteristic of the anaerobic zone was identified by tracer tests and alternative mixing regimes were tested. The results showed that reducing the mixing energy in the anaerobic zone had no detrimental effect on the effluent quality. The plant has operated with the reduced mixing input for nine months and the effluent phosphorus concentration has been reduced from 2.1 mgl-1 to 0.8 mgl-1. [ABSTRACT FROM AUTHOR]

The effect of nitrate on phosphorus release by biological phosphorus removing organisms has been studied. Denitrifying (DPB) or aerobic phosphorus removing bacteria were enriched in an anaerobic-anoxic or anaerobic-aerobic sequencing batch reactor (SBR). The enrichment sludges were used in batch tests, in which the effect of simultaneous presence of substrate (HAc) and nitrate was studied on the phosphorus release. It could be concluded that a reduction of the phosphorus release by nitrate in biological phosphorus removal systems is partly due to the presence of DPB, which utilize HAc for denitrification, not for phosphorus release. PHB (poly-β-hydroxybutyrate) was always produced and phosphorus was released by DPB sludge when nitrate and HAc were simultaneously present. The reducing power (NADH2) and the energy (ATP) for this process seemed to be obtained from HAc oxidation by nitrate as well as from polyphosphate degradation. After removal of the HAc, PHB degradation and phosphorus uptake occurred. [ABSTRACT FROM AUTHOR]