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Changes in the structure and properties of a microbial community of a sequencing batch reactor (SBR) enriched with phosphate-accumulating microorganisms (PAO) after a pH shift to more acidic values (pH 6.7‒7.1) were studied in. The relative abundance of Ca. Accumulibacter decreased from 43.6 to 13.9%, while abundance of potential PAO belonging to the genera Dechloromonas and Thauera increased. The overall share of PAO changed insignificantly (40‒43%). The share of glycogen-accumulating microorganisms (GAO), the main competitors of PAO, remained low throughout the experiment: abundance of the Competibacter 16S rRNA gene fragments before and after the pH shift was 2‒4%. While decrease in pH resulted in a drop in the amount of phosphates released during the anaerobic phase, the amount of phosphorus in the biomass (15‒17%) remained high, as well as phosphorus removal (92‒94%). [ABSTRACT FROM AUTHOR]

Tetracycline and copper ion are common pollutants in wastewater, and the effects of mixed pollutants on microorganisms in wastewater biological treatment have been less studied. In order to reveal the effects of mixed pollutants of tetracycline and copper ion on the microorganisms during the biological phosphorus removal, three ratios of tetracycline and copper ions were designed by the direct equipartition ray method. The relative abundance and diversity of microbial community were investigated, and the microbial interactions were revealed through microbiological methods. The results demonstrated that, for three different ratios, the inhibitory effect of specific phosphorus uptake rate became more significant with the increase of the tetracycline-copper ions concentration and the reaction time. The microbial community decreased with the increase of the proportion of tetracycline in different ratios. The relative abundance of Acinetobacter decreased with the increase of the proportion of tetracycline, while the relative abundance of Ca.Competibacter was higher under the conditions of low mixtures concentrations. Positive interactions and symbiotic relationships among microorganisms were predominant for three different ratios. However, as the proportion of tetracycline increased, the community structure of microorganisms shifted from phosphate-accumulating organisms to glycogen accumulating organisms and denitrifying bacteria. This study can provide a reference for the effect of mixed pollutants on microorganisms and the mechanism of wastewater treatment. [ABSTRACT FROM AUTHOR]

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Bioreactors are usually modelled as continuous stirred tank reactors (CSTRs) or CSTRs connected in series (Tanks-In-Series configuration). In large systems with non-ideal mixing, such approaches do not sufficiently capture the complex hydrodynamics, leading to model inaccuracies due to the lumping of spatial gradients. Highly detailed computational fluid dynamics (CFD) models provide insight into complex hydrodynamics but are computationally too expensive for flow-sheet models and digital twin applications. A compartmental model (CM) can be a middle-ground by providing a more realistic representation of the hydrodynamics and still being computationally affordable. However, the hydrodynamics of a plant can be very different under varying flow conditions. Dynamic CMs can capture these changes in an elegant way. So far, the application of CMs has been limited mostly to continuous flow systems. In this study, a dynamic CM of a sequencing batch reactor (SBR) is developed for a bio-P removal process. The SBR comes with challenges for CM development due to its distinct operational stages. The dynamic CM shows significant improvements over the CSTR model (using the same biokinetic parameters) for dissolved oxygen and phosphate predictions reducing the need for model recalibration that can lead to over-fitting and limited extrapolation capability of the model. HIGHLIGHTS CFD simulations showed incomplete mixing and stagnation zones in an SBR with an anaerobic/aerobic cycle.; A dynamic compartmental model was developed for an SBR with an anaerobic/aerobic cycle.; The impact of dynamic CM was investigated on biological phosphorus removal.; The dynamic CM showed significant improvement in the model prediction power.; CMs can reduce the calibration effort for the biokinetic models.;

Remove and recovery of phosphorus from wastewater is expected to be a promising strategy to solve the shortage of phosphorus resources and control the water environment pollution. In this study, induced crystallization coupled biological phosphorus removal (IC-BPR) process was established to achieve simultaneous removal and recovery of phosphorus in wastewater. The effects of side stream ratio (SSR) on the removal and recovery efficiency of phosphorus and the microbial community structure were explored. The results indicated that the SSR of 40% was optimal to phosphorus removal and recovery in the IC-BPR. The total phosphorus removal efficiency was 94.23% under the SSR of 40%, of which the phosphorus removal efficiency by IC accounted for 74.87%. And the total phosphorus recovery efficiency was 67.29%. The particle size and crystal structure analysis of the crystallized products indicated that the increase of SSR was conductive to heterogeneous crystallization. Furthermore, typical polyphosphate accumulation organisms (PAOs), including Rhodocyclaceae, Acinetobacter, and Dechloromonasin, were enriched under the side stream ratio of 40%. And functional genes related to amino acid transport and metabolism, energy production and conversion were activated. The above results indicated that the IC could significantly enhance the removal and recovery of phosphorus under a suitable SSR condition. It will provide important reference for wastewater treatment coupled phosphorus resource recovery technology. [ABSTRACT FROM AUTHOR]

As a typical representative of sulfonamides，sulfamethoxazole （SMZ） has a potential threat to biological phosphorus removal process. In order to explore its impact on biological phosphorus removal performance and its mechanism，a sequencing batch reactor was constructed to determine the impact of sulfamethoxazole on reactor performance，explore the impact of sulfamethoxazole on the content of microbial metabolic intermediates（poly-P，PHB and glycogen） and the activity of key enzymes（PPX，PPK）. Moreover， the micro mechanism of sulfamethoxazole on key enzymes were analyzed with molecular docking technology. The results showed that low concentrations of sulfamethoxazole（0.05 mg/L and 0.1 mg/L） had no significant effect on biological phosphorus removal performance，the content of metabolic intermediates and the activity of key enzymes. When the concentration of sulfamethoxazole increased to 1 mg/L，it began to inhibit biological phosphorus removal performance. With the increase of its concentration，the inhibition increased. Furthermore， the synthesis and degradation of poly-P and PHB in microbial cells decreased with the increase of the concentration of sulfamethoxazole， while the synthesis and degradation of glycogen will increase significantly. The inhibition rate of sulfamethoxazole on key enzyme activities increased with the rise of concentration. The molecular docking results showed that sulfamethoxazole combined with the amino acid residues in the enzyme activity center to form a complex，thus changing the structure of the enzyme.

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sequencing batch moving bed biofilm reactors have been widely used in commercial wastewater treatment facilities for organic carbon and nitrogen removal. However, these reactors can remove low phosphorus (P) levels. Therefore, this study investigated the potential of SB-MBBRs for maximizing simultaneous nitrification-denitrification and P removal (SNDPR) potential from P-rich municipal wastewater impacted by industrial discharges. A series of experiments were carried out to investigate the effect of external volatile fatty acid (VFA) dosing, airflow rate, and temperature on SNDPR using pilot-scale SBMBBRs. Stable and robust SNDPR was achieved with an optimum acetic acid supply of 150 mg SCOD/L, at 20 oC and 2.5 L air/min. A low airflow rate (AFR) and high-temperature conditions affected P release and uptake kinetics. Efficient PHA storage, dissolved oxygen (DO) transfer (outer layer), DO diffusion limitation (inner layer) of biofilm, and conversion of NH4-N to NO2-N/NO3-N enhanced SNDPR in the two pilot SB-MBBRs.

Wastewater treatment companies are particularly confronted by the energy and supply crisis resulting from the war in the Ukraine. More specifically, production and supply problems with precipitant production have shown that today's wastewater treatment technology in Germany is not crisis-proofed and must become more resilient. The aim of this paper was to determine a required precipitant quantity for Germany with regard to chemical phosphorus elimination, as well as the expected shortfalls due to the shortage situation. Furthermore, possible solutions were identified for how the precipitant can be saved or substituted. Study surveys were conducted to gather data for a meaningful response regarding the operators (wastewater treatment plants, industry, and water suppliers), manufacturers, and the German federal states. A recommendation is given on what a path to more resilient wastewater management with a focus on phosphorus elimination could look like. Based on the data obtained, the report focused on wastewater engineering issues for wastewater treatment plants and industry. The results of the study are relevant for decision-makers, researchers, and operators in the wastewater sector in order to intervene in the market themselves if necessary, e.g., money for production or conversion to biological phosphorus elimination. [ABSTRACT FROM AUTHOR]

During long-term cultivation in a laboratory sequencing batch reactor in the phosphorus removal mode, granule-like aggregates of two morphotypes, differing in their physical structure and microbial composition, with predominance of different microbial physiological groups, were formed out of the activated sludge floccules. Phosphate-accumulating bacteria Candidatus "Accumulibacter" prevailed in one morphotype, and glycogen-accumulating bacteria Candidatus "Competibacter," in the other. These are aerobic microorganisms, known to compete for the substrate during the anaerobic period of the anaerobic/aerobic cultivation cycle. Aggregate formation paralleled development of phosphate-accumulating microorganisms, increase in their relative abundance, and higher phosphorus removal efficiency. [ABSTRACT FROM AUTHOR]

To reveal the effect of chlortetracycline and oxytetracycline on microorganisms in biological phosphorus removal system, three mixtures of chlortetracycline and oxytetracycline with different ratios (R1, R2 and R3) were designed by direct equipartition radiography. The effects of three mixtures on microorganisms were analyzed by high-throughput sequencing technology, the correlation between environmental factors and microorganisms was analyzed by RStudio, and the interrelationship between microorganisms was visualized with R-4.1.0 software and Gephi. The results show that when the ratio is R1, microorganisms are more sensitive and significant in response to environmental factors. When the ratio is R2, the correlation between microbial structure is more stable, and the correlation between microorganisms is closer. The abundance of biological phosphorus removal bacteria decreased under the three ratios. Among them, the abundance of Acinetobacter decreased most significantly at R3, with a decrease of 36.11%. Research showed that there were significant differences in the effects of different ratios of chlortetracycline and oxytetracycline on microorganisms during biological phosphorus removal systems. [ABSTRACT FROM AUTHOR]

In this study, the effect of anaerobic duration on phosphorus (P) removal in reversed AAO (anoxic-anaerobic-oxic) process was investigated using synthetic wastewater (with different volatile fatty acid (VFA) ratios) and real wastewater. The P, poly-hydroxyalkanoates (PHAs), dehydrogenase activity (DHA), polyphosphate kinases (PPK), electron transfer system (ETS), and adenosine 5′-triphosphate (ATP) were determined as indicators. The highest P removal efficiencies were achieved at an anaerobic duration of 3, 4, and 6 h for 15, 30, and 60% VFA ratio in synthetic wastewater. The amount of the released P and stored PHAs can be manipulated by different anaerobic durations, but the P removal efficiency cannot be guaranteed with higher stored PHAs. Additionally, the energy metabolism confirmed the significance of anaerobic duration extension on microbial activity. The highest values of four indicators were all achieved at anaerobic duration of 4 h with 30% VFAs ratio which achieved the highest P removal efficiency. Real wastewater experiments also proved the reproductivity of these results. We defined this phenomenon as the "hunger response" where microorganisms responded to suppression (anaerobic duration extension) with higher activity after the end of the anaerobic condition. These results can provide references for better design and operation of biological phosphorus removal in RAAO process. [ABSTRACT FROM AUTHOR]

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]

Previous research has demonstrated that biological phosphorus removal (bio‐P) occurs in the Great Lakes Water Authority (GLWA) water resource recovery facility (WRRF) high purity oxygen activated sludge (HPO‐AS) process, suggesting that sludge fermentation in the secondary clarifier sludge blanket is key to bio‐P occurrence. This study, combining batch reactor testing, the development of a process model for the HPO‐AS process using Sumo21 (Dynamita), and the analysis of eight and a half years of plant operating data, showed that bio‐P consistently occurs at the GLWA WRRF. This occurrence is attributed to the unique configuration of the HPO‐AS process, which has a relatively large secondary clarifier compared to the bioreactor, and the characteristics of the influent wastewater, primarily particulate matter with limited concentrations of dissolved biodegradable organic matter. The volatile fatty acids (VFAs) needed for polyphosphate accumulating organisms (PAOs) growth are produced in the secondary clarifier sludge blanket, which provides more than four times the anaerobic biomass inventory compared to the anaerobic zones in the bioreactor, thus facilitating bio‐P in the current system. Opportunities exist to further optimize the phosphorus removal performance of the HPO‐AS process and reduce the amount of ferric chloride used. These findings may be of interest to researchers investigating biological phosphorus removal in similar systems. Practitioner Points: Fermentation in the clarifier sludge blanket an essential component of bio‐P process at this facility.Results suggest simple adjustments to the system could lead to further improvements in bio‐P.It is possible to decrease the use of chemical phosphorus removal methods (i.e., ferric chloride) while simultaneously increasing bio‐P.Determining the phosphorus mass balance from sludge streams provides insight into evaluating the effectiveness of the phosphorus recovery system. [ABSTRACT FROM AUTHOR]

Enhanced biological phosphorus removal (EBPR) is an obscure but economical and helpful technology for removing phosphorus biologically from wastewater. A 3-MLD capacity pre-anoxic selector-attached sequencing batch reactor (SBR) treated municipal wastewater from the residents of IIT Roorkee. The treatment in the plant satisfied the effluent discharge standards in all respects except phosphorus, observed during an intensive two-year study. An elaborated 80-day study was performed to enhance and improve the plant's performance in terms of phosphorus removal specifically, with run 1: solid retention times (SRT) reduced from 56 to 20 days (t = 35 d), run 2: lowering the diffuser's running time from 15 min to 10 min in anoxic cum anaerobic selector chambers (dissolved oxygen (DO) concentration reduced to <0.15 mg/L) along with reducing SRT to 15 days (t = 25 d), and run 3:intensive reduction in SRT to ≤10 days (t = 20 d). During run 3, the increment in the enhanced biological phosphorus removal (EBPR) efficiency was three times that of the initial run (ηmax~65%) with a readily biodegradable chemical oxygen demand to total phosphorus ratio (rbCOD/TP) of 7.8. The 16SrRNA sequencing revealed the microbial community structure before and after the changes in SRT and EBPR efficiencies, to correlate the biochemical processes and functional organisms. [ABSTRACT FROM AUTHOR]

In addition to many other well-documented factors, local conditions are rudimentary conditions of sharp change observed in wastewater characteristics from place to place. The monitoring of 3 million liters per day-capacity full-scale Sequencing Batch Reactor (SBR) at Roorkee (India) drew attention to the processes involving simultaneous nitrification and denitrification (SND) and biological phosphorous removal (BPR) undergoing with the variations in influent wastewater, particularly the readily biodegradable chemical oxygen demand (rbCOD). Regular monitoring of all the units revealed that the nutrient removal efficiencies were 94.9 ± 3.6% Chemical Oxygen Demand (COD) (17.9 ± 7.7 mg/L in effluent), 95.4 ± 2.7% Biochemical Oxygen Demand (BOD5) (6.0 ± 2.2 mg/L in effluent), 95.4 ± 1.6% Total Suspended Solids (TSS) (9.4 ± 2.1 mg/L in effluent), 96.7 ± 2.6% Ammonia-N (0.7 ± 0.5 mg/L in effluent), 69.1 ± 11.5% Total Nitrogen (TN) (9.7 ± 3.0 mg/L in effluent), 31.3 ± 24.9% orthophosphate (1.8 ± 0.7 mg/L in effluent) and 42.0 ± 15.3% Total Phosphorus (TP) (3.6 ± 1.8 mg/L in effluent) and achieved < 50 MPN/100 mL fecal coliform in the final effluent after disinfection. Anoxic tri-sectional selector and an aeration tank constituted one SBR followed by the other, availed 76.4 ± 9.2% SND at rbCOD/COD of 0.12 ± 0.04 and showed linear relationship at R2 > 0.8, and COD/TN of 12.3 ± 4.7. The study clarifies the degree of variations in key factors included in design guidelines for laying out an optimized treatment system for COD, Nitrogen, and Phosphorus removal in the Indian scenario. [ABSTRACT FROM AUTHOR]

Wastewater treatment companies are particularly confronted by the energy and supply crisis resulting from the war in the Ukraine. More specifically, production and supply problems with precipitant production have shown that today’s wastewater treatment technology in Germany is not crisis-proofed and must become more resilient. The aim of this paper was to determine a required precipitant quantity for Germany with regard to chemical phosphorus elimination, as well as the expected shortfalls due to the shortage situation. Furthermore, possible solutions were identified for how the precipitant can be saved or substituted. Study surveys were conducted to gather data for a meaningful response regarding the operators (wastewater treatment plants, industry, and water suppliers), manufacturers, and the German federal states. A recommendation is given on what a path to more resilient wastewater management with a focus on phosphorus elimination could look like. Based on the data obtained, the report focused on wastewater engineering issues for wastewater treatment plants and industry. The results of the study are relevant for decision-makers, researchers, and operators in the wastewater sector in order to intervene in the market themselves if necessary, e.g., money for production or conversion to biological phosphorus elimination.

The research progress of the impacts of chemical phosphorus removal reagents on biological phosphorus removal in wastewater treatment was reviewed. The impacts and its mechanisms of two widely used phosphorus removal reagents, aluminum salts and iron salts, were emphatically introduced. This paper summarized the existing problems in the researches on the mechanisms of chemical phosphorus removal reagents affecting biological phosphorus removal. Besides, suggestions and prospects for the future research direction of chemical phosphorus removal reagents on biological phosphorus removal were also discussed, which provided reference for maximizing the biological-chemical synergistic phosphorus removal effect in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

A microbial community enriched with phosphate-accumulating organisms (PAO) was obtained in a laboratory sequencing batch reactor after 150 days of cultivation. Analysis of phosphate dynamics in the medium and the results of Raman scattering spectroscopy indicated the cycle of phosphate consumption and release during cultivation under oxic and anoxic conditions, respectively, which was typical of PAO. The highest content of intracellular phosphorus was 16.5 ± 0.15% of the dry ash-free biomass. Molecular genetic analysis and FISH revealed the taxonomic diversity of the microbial community, in which members of the "Ca. Аccumulibacter" group were the major PAO. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel single stage oxic process for rapid nutrient recovery via bioflocs technology. • Achieved up to 5.5 mgP/gTSS/d phosphate removal efficiency in high nitrate conditions. • Amplified genes linked to phosphate transport and aerobic assimilation. • More frequent carbon usage shortens phosphorus removal times and enhances rates. • Converting waste into feed supports the circular economy in aquaculture. Intensive aquaculture systems often contain high concentrations of nitrate and phosphate, leading to environmental and economic burdens. Bioflocs technology, a novel approach in aquaculture, addresses these issues by removing these nutrients and producing protein rich microbial biomass. This study explored a novel single stage oxic process for simultaneous rapid recovery of phosphate and nitrate using different carbon addition strategies in bioflocs growth reactors. Our findings revealed that bioflocs rapidly and effectively assimilated nutrients from high concentration environments. The phosphate removal mechanism involved biomass formation, achieving simultaneous removal efficiencies of 5.5 ± 0.2 mgP/gTSS/d for phosphate and 41.8 ± 2.0 mgN/gTSS/d for nitrate, harvesting biofloc concentrations of 3599 ± 33 mg/L. The crude protein content of the bioflocs exceeded 50 %, with essential amino acid indices over 0.9, indicating potential for high quality aquafeed. Actinobacteriota and Bacteroidota were dominant during the phosphorus removal process, with significant proliferation of Nakamurella. Additionally, gene amplification related to assimilation, aerobic denitrification and inorganic phosphate transport was observed, suggesting biofloc technology is a promising method for efficient phosphate and nitrate removal. This research promotes the circular economy by recovering nutrients, reducing reliance on traditional feed sources, and minimizing environmental contamination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Membrane aerated biofilm has optimal thickness for simultaneous C, N, P removal. • Air scouring aided by CFD was used to detach outer biofilm for thickness control. • Biofilm yield stress was matched with air scouring induced shear stress on biofilm. • Periodic air scouring enhanced nitrogen removal and reduced biofilm thickness. • Intermittent aeration and air scouring in one cycle simultaneously removed C, N, P. Membrane aerated biofilm reactor (MABR) is challenged by biofilm thickness control and phosphorus removal. Air scouring aided by computational fluid dynamics (CFD) was employed to detach outer biofilm in sequencing batch MABR treating low C/N wastewater. Biofilm with 177–285 µm thickness in cycle 5–15 achieved over 85 % chemical oxygen demand (COD) and total inorganic nitrogen (TIN) removals at loading rate of 13.2 gCOD/m2/d and 2.64 gNH 4 +-N/m2/d. Biofilm rheology measurements in cycle 10–25 showed yield stress against detachment of 2.8–7.4 Pa, which were equal to CFD calculated shear stresses under air scouring flowrate of 3–9 L/min. Air scouring reduced effluent NH 4 +-N by 10 % and biofilm thickness by 78 µm. Intermittent aeration (4h off, 19.5h on) and air scouring (3 L/min, 30 s before settling) in one cycle achieved COD removal over 90 %, TIN and PO 4 3−-P removals over 80 %, showing great potential for simultaneous carbon, nitrogen and phosphorus removals. [ABSTRACT FROM AUTHOR]

The representative processes in the field of wastewater phosphorus removal in recent years are reviewed, and the mechanism, characteristics and research status of phosphorus removal methods such as chemical precip让ation, biological, adsorption, and crystallization are discussed. The development of more economical and effective new materials, combining different methods, exploring the best parameters and scope of application in practical applications, and maximizing the removal rate and recovery rate of phosphorus are the focus of subsequent research in this field. [ABSTRACT FROM AUTHOR]

Sialic acids are a family of nine-carbon negatively charged carbohydrates. In animals, they are abundant on mucosa surfaces as terminal carbohydrates of mucin glycoproteins. Some commensal and pathogenic bacteria are able to release, take up and catabolize sialic acids. Recently, sialic acids have been discovered to be widespread among most microorganisms. Although the catabolism of sialic acids has been intensively investigated in the field of host–microbe interactions, very limited information is available on microbial degradation of sialic acids produced by environmental microorganisms. In this study, the catabolic pathways of sialic acids within a microbial community dominated by ' Candidatus Accumulibacter' were evaluated. Protein alignment tools were used to detect the presence of the different proteins involved in the utilization of sialic acids in the flanking populations detected by 16S rRNA gene amplicon sequencing. The results showed the ability of Clostridium to release sialic acids from the glycan chains by the action of a sialidase. Clostridium and Chryseobacterium can take up free sialic acids and utilize them as nutrient. Interestingly, these results display similarities with the catabolism of sialic acids by the gut microbiota. This study points at the importance of sialic acids in environmental communities in the absence of eukaryotic hosts. [ABSTRACT FROM AUTHOR]

Mathematical modelling was used to investigate the possibility to use membrane aerated biofilm reactors (MABRs) in a largely anoxic suspended growth bioreactor to produce the nitrate-nitrogen required for heterotrophic denitrification and the growth of denitrifying phosphorus accumulating organisms (DPAOs). The results indicate that such a process can be used to achieve a variety of process objectives. The capture of influent biodegradable organic matter while also achieving significant total inorganic nitrogen (TIN) removal can be achieved with or without use of primary treatment by operation at a relatively short suspended growth solids residence time (SRT). Low effluent TIN concentrations can also be achieved, irrespective of the influent wastewater chemical oxygen demand (COD)/total nitrogen (TN) ratio, with somewhat larger suspended growth SRT. Biological phosphorus and nitrogen removal can also be effectively achieved. Further experimental work is needed to confirm these modelling results. HIGHLIGHTS Hybrid MABRs can achieve lower effluent TIN concentrations, and more carbon capture, at lower SRTs than conventional systems.; Influent carbon composition affects denitrification, but modelling shows better performance in hybrid MABR systems.; Primary treatment benefits carbon capture, but can be eliminated depending on treatment goals.; Combined biological nitrogen and phosphorus removal is possible and improved in hybrid MABRs.;

Understanding the effects of antibiotics on enhanced biological phosphorus removal (EBPR), which has been widely accepted as the most economical and sustainable process for removing phosphorus from wastewater to control eutrophication problems, is very important. The potential role of ciprofloxacin (CIP) in inhibiting wastewater phosphorus removal during short-term exposure and the associated mechanisms were investigated in this study. The results showed that the inhibitory effect of CIP on phosphorus removal efficiency was dose- and time-dependent. Total extracellular polymeric substances and polysaccharide (PS) production were immediately enhanced as the CIP concentration increased, implying that PS was secreted to resist toxicity. However, these parameters decreased with increasing reaction cycles. Reactive oxygen species (ROS) increased remarkably during the aerobic phase, resulting in a decreased oxygen uptake rate. Moreover, variations in stoichiometric parameters and kinetic rates showed that anaerobic and aerobic metabolism was affected by CIP, with the aerobic metabolism of phosphate-accumulating organisms being more sensitive to CIP than anaerobic metabolism, probably due to the increase in ROS. Furthermore, glycogen production was strongly inhibited by CIP, and the tricarboxylic acid cycle might be involved in anaerobic metabolism. The results of this study offer insights into the short-term effects of CIP on biological phosphorus removal from the view of anaerobic and aerobic metabolism, which enables further study on control strategies for reducing CIP inhibition and maximizing the reliability and efficiency of EBPR. [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]

Treatment of domestic sewage by sequential batch processes has been shown to be quite attractive, mainly because it allows the maintenance of anaerobic, anoxic and aerobic conditions, which are necessary for the removal of nitrogen and phosphorus, in a single reactor. The aim of this study was to evaluate the behavior of a new reactor known as “cyclic sequential batch reactor” on the removal of organic matter, nitrogen and phosphorus from domestic sewage in a tropical climate. The removal of organic matter, nitrogen and phosphorus reached values of 90.6%, 90.5%, and 89.1%, respectively. Effluent quality of less than 8.3 mg N/L total nitrogen, 4.6 mg N/L ammonia nitrogen, and 0.8 mg P/L of total phosphorus were routinely obtained in reactor conditions as following: temperature about 26°C, a solids retention time of 12 d, a hydraulic retention time of 4 h, organic loading rate of 2.1 g COD/L d, nitrogen loading rate of 0.24 g TKN/L d, phosphorus loading rate of 0.03 g P/L d and food-to-mass ratios of 0.76 g COD/g MLVSS d. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of ferrous salt with different concentrations on metabolism transformation of phosphate accumulating organisms. The high-throughput sequencing technology was employed to analyze the changes of micro-bial community structure. Redundancy analysis was used to analyze the factors leading to changes in mi-crobial community structure. Analysis of alpha diversity shows that low concentration ferrous salt can promote the growth of phosphate accumulating organisms, while high concentration ferrous salt can inhibit the growth of phosphate accumulating organisms. Distribution charts of microbial species show that metabolism of phosphate accumulating organisms will gradually be replaced by the metabolism of glycogen accumulating organisms when ferrous salt is excessive. Redundancy analysis showed that ferrous salt was the most important factor, and that there was a negative correlation between ferrous salt and phosphate accumulating organisms, and a positive correlation between ferrous salt and glycogen accumulating organism. The experiment is significant for further research of ferrous salt cooperative biological phosphorus removal process. [ABSTRACT FROM AUTHOR]

• Hybrid MABR process makes understanding the metabolism of purely anoxic suspended growth more important. • Only 60 % of particulate and colloidal organic matter metabolized under anoxic versus aerobic conditions. • Fully anoxic suspended growth treatment benefits MABR technology by providing sCOD removal and pCOD/cCOD capture. • Bio-P removal under strict anaerobic/anoxic conditions significantly reduced compared to anaerobic/aerobic conditions. • Reduced anoxic bio-P due to less hydrolysis and fermentation and reduced carbon processing efficiency of denitrifying PAOs. Fully anoxic suspended growth treatment of domestic wastewater is rarely performed in practice at large scale. However, recent advances in membrane aerated biofilm reactor (MABR) technology can enable the "hybrid" concept that couples nitrification in the MABR with anoxic suspended growth for biological nitrogen removal. Small scale sequencing batch reactors were constructed to compare high-rate anoxic metabolization of influent carbon and biological phosphorus removal side-by-side with a conventional aerated system in a low-strength domestic wastewater (COD/TN ratio of approximately 6). Little differences existed in the oxidation of soluble readily biodegradable organic material between the two systems, but hydrolysis of particulate and colloidal organic matter in the anoxic reactor over a range of solid retention times was 60 % of the aerobic reactor. Reduced hydrolysis limited the amount of carbon available to ferment to volatile fatty acid (VFA), adversely impacting anoxic biological phosphorus removal (bio-P) process rates, and ortho-P removal performance was diminished by more than half at equivalent SRTs. At optimal growth conditions, i.e., an SRT of approximately 8 days and with supplementary VFA, ortho-P removal from the influent averaged roughly 75 %. Experimentation with supplemented acetic acid showed reduced anoxic metabolic efficiency, quantified via a P/O ratio of 0.90 versus 1.7 for the aerobic system, although overall anoxic bio-P removal demonstrably increased with external carbon. [Display omitted] [ABSTRACT FROM AUTHOR]

Increased pressure is being applied to industrial wastewater treatment facilities to adhere to more stringent regulations for the discharge of treated wastewater and to improve energy efficiency of the process. Nitrogen and phosphorous removal can be challenging to achieve efficiently, and in the case of phosphorous removal, can often necessitate the use of chemicals. There is a major drive globally to improve wastewater treatment infrastructure, whilst simultaneously reducing the carbon footprint of the process. The intermittently aerated sequencing batch reactor offers a modification of the well-known sequencing batch reactor process that can enable lower energy requirements than conventional sequencing batch reactor processes and can facilitate enhanced nutrient removal capacities. However, to date much of the previous literature has focused on relatively short laboratory-scale trials (often with synthetic wastewater) which may not be representative of larger scale system performance. This study explored the intermittently aerated sequencing batch reactor technology via a case-study deployment at a dairy production facility, in terms of treatment efficiency and energy efficiency with a focus on optimisation between phases. High treatment capacity and operational flexibility was achieved with NH4-N removals averaging >89%, PO4-P removal averaging >90% and total suspended solids removal averaging >97%. This research demonstrates the characteristics of intermittently aerated sequencing batch reactor technology at scale to effectively achieve biological nutrient removal. In addition, this study demonstrated that when effectively managed, energy savings and reductions in carbon emissions in the region of 36–68% are achievable through optimisation of reactor operation.

The review examines the microbiological aspects of the biological phosphorus removal from wastewater. The history of the development of biotechnology and the discovery of the physiological group of phosphate-accumulating organisms (PAOs), which biologically remove phosphorus via the phosphate uptake and storage in the form of intracellular polyphosphates, is briefly described. PAOs are characterized by a cyclic type of metabolism that occurs when the anaerobic/aerobic conditions cyclically change. Under anaerobic conditions, PAOs uptake and store organic compounds through the energy of degradation of intracellular polyphosphates. When anaerobic conditions change to aerobic or an alternative electron acceptor appears, PAOs uptake phosphates and synthesize intracellular polyphosphates using the intracellular polymeric sources of carbon and energy accumulated under anaerobic conditions. The main representatives of the PAOs, their metabolic models, and physiological characteristics are described. The basic principles of the implementation of biotechnology used in the practice of wastewater treatment for phosphorus and other nutrients are considered. [ABSTRACT FROM AUTHOR]

Biological phosphorus removal (BPR) is an economical and sustainable processes for the removal of phosphorus (P) from wastewater, achieved by recirculating activated sludge through anaerobic and aerobic (An/Ae) processes. However, few studies have systematically analyzed the optimal hydraulic retention times (HRTs) in anaerobic and aerobic reactions, or whether these are the most appropriate control strategies. In this study, a novel optimization methodology using an improved Q-learning (QL) algorithm was developed, to optimize An/Ae HRTs in a BPR system. A framework for QL-based BPR control strategies was established and the improved Q function, Q t + 1 ( s t , s t + 1 ) = Q t ( s t , s t + 1 ) + k · [ R ( s t , s t + 1 ) + γ · max a t Q t ( s t , s t + 1 ) − Q t ( s t , s t + 1 ) ] was derived. Based on the improved Q function and the state transition matrices obtained under different HRT step-lengths, the optimum combinations of HRTs in An/Ae processes in any BPR system could be obtained, in terms of the ordered pair combinations of the . Model verification was performed by applying six different influent chemical oxygen demand (COD) concentrations, varying from 150 to 600 mg L−1 and influent P concentrations, varying from 12 to 30 mg L−1. Superior and stable effluent qualities were observed with the optimal control strategies. This indicates that the proposed novel QL-based BPR model performed properly and the derived Q functions successfully realized real-time modelling, with stable optimal control strategies under fluctuant influent loads during wastewater treatment processes. Image 1 • A fluctuant influent responsive QL-based BPR optimizing control method was developed. • Q t + 1 ( s t , s t + 1 ) = Q t ( s t , s t + 1 ) + k · [ R ( s t , s t + 1 ) + γ · max a t Q t ( s t , s t + 1 ) − Q t ( s t , s t + 1 ) ] was derived. • State transition matrices obtained under different HRT step-lengths were developed. • Ordered pair of corresponds optimal control strategy. • Superior effluents achieved by optimal control strategies confirm the model validity. [ABSTRACT FROM AUTHOR]

Online monitoring of water quality parameters can provide better control over various operations in wastewater treatment plants. However, a lack of physical online sensors, the high price of the available online water-quality analyzers, and the need for regular maintenance and calibration prevent frequent use of online monitoring. Soft-sensors are viable alternatives, with advantages in terms of price and flexibility in operation. As an example, this work presents the development, tuning, implementation, and validation of an Extended Kalman Filter (EKF) on a grey-box model to estimate the concentration of volatile fatty acids (VFA), soluble phosphates (PO4-P), ammonia nitrogen (NH4-N) and nitrate nitrogen (NO3-N) using simple and inexpensive sensors such as pH and dissolved oxygen (DO). The EKF is implemented in a sequential batch moving bed biofilm reactor (MBBR) pilot scale unit used for biological phosphorus removal from municipal wastewater. The grey-box model, used for soft sensing, was constructed by fitting the kinetic data from the pilot plant to a reduced order version of ASM2d model. The EKF is successfully validated against the standard laboratory measurements, which confirms its ability to estimate various states during the continuous operation of the pilot plant. [ABSTRACT FROM AUTHOR]

In this study, the influence of the anaerobic mixed feeding rate on granule stability and reactor performance in a conventional sequencing batch reactor (C-SBR) was investigated while treating various industrial wastewaters. A laboratory-scale SBR fed with malting wastewater rich in phosphorus was operated for approximately 250 days, which was divided into two periods: (I) mixed pulse feed and (II) prolonged mixed feed. Initially, no bio-P activity was observed. However, by lowering the feeding rate biological P-removal was rapidly established and no effect on the aerobic granular sludge (AGS) characteristics was observed. Additionally, to investigate the effect of the mixed feeding rate when treating an industrial effluent with low phosphorus content, i.e. brewery wastewater, a laboratory-scale reactor was operated for approximately 400 days applying different mixed feeding rates. Morphological and molecular analysis indicated that a low substrate concentration promoted the enrichment of anaerobic carbon storing filaments when fed with brewery wastewater. Findings suggest that a prolonged mixed feeding regime can be used as a tool to easily establish bio-P removal in a C-SBR system for the treatment of phosphorus-rich wastewaters. It should however be considered that under P-limiting conditions, enrichment of poly-P storing filaments may occur, possibly due to their higher substrate affinity under anaerobic conditions. [ABSTRACT FROM AUTHOR]

Two metagenome-assembled genomes (MAGs), obtained from laboratory-scale enhanced biological phosphorus removal bioreactors, were analyzed. The values of 16S rRNA gene sequence identity, average nucleotide identity, and average amino acid identity indicated that these genomes, designated as RT and SSD2, represented two novel species within the genus Thiothrix, ‘Candidatus Thiothrix moscowensis’ and ‘Candidatus Thiothrix singaporensis’. A complete set of genes for the tricarboxylic acid cycle and electron transport chain indicates a respiratory type of metabolism. A notable feature of RT and SSD2, as well as other Thiothrix species, is the presence of a flavin adenine dinucleotide (FAD)-dependent malate:quinone oxidoreductase instead of nicotinamide adenine dinucleotide (NAD)-dependent malate dehydrogenase. Both MAGs contained genes for CO2 assimilation through the Calvin–Benson–Bassam cycle; sulfide oxidation (sqr, fccAB), sulfur oxidation (rDsr complex), direct (soeABC) and indirect (aprBA, sat) sulfite oxidation, and the branched Sox pathway (SoxAXBYZ) of thiosulfate oxidation to sulfur and sulfate. All these features indicate a chemoorganoheterotrophic, chemolithoautotrophic, and chemolithoheterotrophic lifestyle. Both MAGs comprise genes for nitrate reductase and NO-reductase, while SSD2 also contains genes for nitrite reductase. The presence of polyphosphate kinase and exopolyphosphatase suggests that RT and SSD2 could accumulate and degrade polyhosphates during the oxic-anoxic growth cycle in the bioreactors, such as typical phosphate-accumulating microorganisms.

An enhanced biological phosphorus removal (EBPR) process operated at a relatively high temperature, 28 °C, removed 85% carbon and 99% phosphorus from wastewater over a period of two years. This study investigated its microbial community through fluorescent in situ hybridization (FISH) and clone library generation. Through FISH, considerably more Candidatus “Accumulibacter phosphatis” (Accumulibacter)-polyphosphate accumulating organisms (PAOs) than Candidatus ‘Competibacter phosphatis’ (Competibacter)-glycogen accumulating organisms were detected in the reactor, at 36 and 7% of total bacterial population, respectively. A low ratio of Glycogen/Volatile Fatty Acid of 0.69 further indicated the dominance of PAOs in the reactor. From clone library generated, 26 operational taxonomy units were retrieved from the sludge and a diverse population was shown, comprising Proteobacteria (69.6%), Actinobacteria (13.7%), Bacteroidetes (9.8%), Firmicutes (2.94%), Planctomycetes (1.96%), and Acidobacteria (1.47%). Accumulibacter are the only recognized PAOs revealed by the clone library. Both the clone library and FISH results strongly suggest that Accumulibacter are the major PAOs responsible for the phosphorus removal in this long-term EBPR at relatively high temperature.

Abstract Denitrifying sulfur conversion-associated enhanced biological phosphorous removal (DS-EBPR) system is not only a novel wastewater treatment process, but also an ideal model for microbial ecology in a community context. However, it exists the knowledge gap on the roles and interactions of functional microorganisms in the DS-EBPR system for carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) bioconversions. We use genome-resolved metagenomics to build up an ecological model of microbial communities in a lab-scale DS-EBPR system with stable operation for more than 400 days. Our results yield 11 near-complete draft genomes that represent a substantial portion of the microbial community (39.4%). Sulfate-reducing bacteria (SRB) and sulfide-oxidizing bacteria (SOB) promote complex metabolic processes and interactions for C, N, P and S conversions. Bins 1–4 and 10 are considered as new potential polyphosphate-accumulating organisms (PAOs), in which Bins 1–4 can be considered as S-related PAOs (S-PAOs) with no previously cultivated or reported members. Our findings give an insight into a new ecological system with C, N, P and S simultaneous bioconversions and improve the understanding of interactions among SRB, SOB, denitrifiers and PAOs within a community context. Graphical abstract Image 1 Highlights • The DS-EBPR system is an ideal model for microbial ecology with C, N, P & S bioconversions. • Metagenomics was used to establish an ecological model in a DS-EBPR system. • SRB and SOB promote complex interactions for C, N, P and S conversions. • Four genomes are identified as new S-related PAOs. [ABSTRACT FROM AUTHOR]

Meeting stringent phosphorus (P) discharge standards remains one of the major challenges for wastewater utilities due to increased economic burdens associated with advanced (i.e., secondary, tertiary) treatment processes. In a trade-off between higher treatment cost and enhanced P removal, it is critical for the treatment plants to be able to select the most appropriate technology. To this end, established/emerging high performing P removal/recovery technologies (e.g., Modified University of Cape Towne process, Bardenpho process, membrane bioreactors, IFAS-EBPR, struvite recovery, tertiary reactive media filtration) were identified and full-scale treatment plant designs were developed. Using advanced mathematical modeling techniques, six different treatment configurations were evaluated in terms of performance and cost effectiveness ($/lb of P removed). Results show that the unit cost for P removal in different treatment alternatives range from $42.22 to $60.88 per lb of P removed. The MUCT BNR + tertiary reactive media filtration proved to be one of the most cost effective configurations ($44.04/lb P removed) delivering an effluent with total P (TP) concentration of only 0.05 mg/L. Although struvite recovery resulted in significant reduction in biosolids P, the decrease in effluent TP was not sufficient to meet very stringent discharge standards. [ABSTRACT FROM AUTHOR]

A new excess phosphate uptaking in an anoxic-aerobic sequencing batch reactor (SBR) using starch as sole carbon source that was different from the traditional biological phosphorus removal in anaerobic-aerobic alternation condition was confirmed and reported previously. To reveal its mechanism and biochemical pathway of metabolism, this study was conducted. Nuclear magnetic resonance (NMR) technique was applied to trace the carbon metabolism in the SBR applied by supplying 13 C label starch. Results show that the phosphorus removal reached 80% without any P release during the whole process. The sludge had a very lower accumulation of polyhydroxyalkanoates (PHAs) but a higher accumulation of glycogen. The metabolic pathway of glycogn synthesis and phosphorus removal was proposed that during the anoxic phase, the starch was hydrolyzed and then converted to lactic acid by lactic acid producing organism (LPO). Adenosine triphosphate (ATP) was generated from the lactic acid formation, and used for polyphosphate (poly-P) synthesis. In the meantime, lactic acid was used to synthesize glycogen by phosphate accumulating organisms (PAOs). In the aerobic stage, PAOs oxidized glycogen to release energy for cell growth and its maintenance, as well as phosphate uptake and poly-P synthesis. The LPO performed the majority of the P removal in the SBR during the anoxic stage. This study improves our understanding to how phosphorus removed in the anoxic-aerobic system. [ABSTRACT FROM AUTHOR]

In simultaneous precipitation, interaction between chemical and biological P removal could not be ignored. Thiswork investigated effects of ferrous sulfate and Fe precipitates onmetabolic behavior of bio- P and its counter cation of potassium. After dosing,mixed liquid suspended solids (MLSS) increased 9%, pH decreased from 7.35 to 7.00, sludge volume index (SVI) decreased, electrical conductivity increased. Chemical oxygen demand (COD) and NH3 removalwas not affected. Fe dosing initially showed synergistic effect, and then inhibition appeared at accumulative dose above 10mgFe/gMLSS. Both precipitate FePO4 and Fe(OH)3 deteriorated effluent P. FePO4 dissolved 35% in anaerobic phase which failed to be totally reprecipitated in oxic phase, resulting in increased effluent P. FePO4 inhibited K uptake rather than bio-P uptake. Fe(OH)3 caused reduction of bio-P release, meanwhile, its inhibition on K and bio-P uptake was greater than FePO4. Phosphorus metabolism was inhibited when sludge contained 0.15 mM FePO4 or 0.10 mMFe(OH)3. Increased K/Pmolar ratio and coefficient b could be indicators for Fe residual in sludge. Intermittent dosing was suggested for wastewater treatment plant (WWTP) operation. [ABSTRACT FROM AUTHOR]

In order to find a biological phosphorus removal enrichment method with high performance and low energy consumption, two enrichment methods were used in this study, namely gradient carbon source addition (S1) and fixed carbon source addition (S2). The two enrichment methods were applied to the enrichment of phosphorus removing bacteria in an independent biological phosphorus removal system based on nitrogen removal by immobilized fillers. The phosphorus removal performance, stoichiometry and microbial structure were compared for the two enrichment methods. It was found that PO 4 3--P remained 0.15–0.2 mg/L at the end of enrichment in S1, while PO 4 3--P increased from 0.27 to 0.38 mg/L at the end of enrichment in S2. Stoichiometric analysis showed that S1 used more PHAs (1.47 molC/L) for phosphorus absorption, while S2 used nearly half of the PHAs (0.87 molC/L) for glycogen synthesis. Moreover, the absorbed phosphorus content in S2 was significantly less than S1 (5.67 < 8.65 mg/L). As a result, denitrifying phosphorus-removing bacteria predominated S1, while phosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) both played a role in S2. Dechloromonas , the dominant denitrifying PAO in both S1 and S2 increased from 0.26 % to 3.34 % and 1.04 %, respectively, while Defluviicoccus , a typical GAO, changed from 0.24 % to 0.2 % and 2.01 %, respectively. As a result, gradient carbon source enrichment demonstrated a better phosphorus removal effect and dominant bacteria, whereas the fixed carbon source enrichment increased the abundance of GAOs while negatively impacting the phosphorus removal effect. • The enrichment mode of an independent biological phosphorus removal (IPR) system was established. • The enrichment mode of gradient carbon source is more conducive to phosphorus removal. • Calculation of PAOs and GAOs ratios of different enrichment methods by stoichiometric analysis. • The abundance of Dechloromonas in the gradient carbon source was higher (3.34 %). [ABSTRACT FROM AUTHOR]

The aim of the present paper was to investigate the effect of solids (SRT) and hydraulic (HRT) retention time on Integrated Fixed Film Activated Sludge (IFAS) University of Cape Town (UCT) membrane Bioreactor (MBR). In particular, three different pairs of SRT and HRT values were analysed, namely, Phase I 56 d/30 h, Phase II 31 d/15 h and Phase III 7 d/13 h. The short-term effect of these three SRT/HRT conditions was assessed by analysing several system performance indicators: organic carbon and biological nutrient (nitrogen and phosphorus) removal, biomass respiratory activity, activated sludge filtration properties and membrane fouling. The results showed that the decrease of SRT/HRT had a positive influence on system performance. Specifically, the IFAS-UCT-MBR showed excellent removal of organic matter - highest value (99%) at the shortest SRT/HRT (7 d/13 h). Also, the increase in organic loading rate resulting from the decrease of SRT and HRT led to improved nitrogen removal due to higher N removal by sludge wasting requiring less N removal (as N 2 ) by denitrification. Complete nitrification of influent ammonia was achieved at all three SRT/HRT phases, guaranteed by the presence of biofilm carriers in the aerobic reactor, which ensured a higher media SRT than suspended biomass SRT. The increase of the organic loading rate and decrease in SRT led also to a higher heterotrophic activity as demonstrated by the respirometric batch tests, which is due to the increasing active biomass fraction of the volatile suspended solids as SRT decreases. The SRT/HRT decrease over the three phases resulted in an overall increase of the Extracellular Polymeric Substance concentration, which caused an increase in membrane fouling. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extended ASM2 model for the modeling and calibration of the role of extracellular polymeric substances (EPS) in phosphorus (P) removal in an anaerobic-aerobic process. In this extended ASM2 model, two new components, the bound EPS ( X EPS ) and the soluble EPS ( S EPS ), are introduced. Compared with the ASM2, 7.71, 8.53, and 9.28% decreases in polyphosphate (polyP) were observed in the extended ASM2 in three sequencing batch reactors feeding with different COD/P ratios, indicating that 7.71–9.28% of P in the liquid was adsorbed by EPS. Sensitive analysis indicated that, five parameters were the significant influential parameters and had been chosen for further model calibration by using the least square method to simulate by MATLAB. This extended ASM2 has been successfully established to simulate the output variables and provides a useful reference for the mathematic simulations of the role of EPS in biological phosphorus removal process. [ABSTRACT FROM AUTHOR]

"n "nBackgrounds and Objectives: Now a days modified activated sludge ways are used for standard removing nutrient substances from waste water that is named Enhanced biological phosphorus removal One of the most suitable ways is Anoxic-Oxic(A/O) process. The goal of this research is investigation and solving existing problems of Khoy power plant(P.P) waste water treatment plant(WWTP)and optimizing of phosphorus removal in it."nMaterials and Methods: This research is done full scale in this treatment plant. The treatment plant was operating with extended aeration process, and some problems had, so in the first stage with in investigation of total efficiency, problems and their reasons determined. In the second stage after operational modifications existing problems was solved and real efficiency of treatment plant particularly for phosphorus(P) removal determined. In the third stage changes, system converted to A/O process and new system was tested with Changing parameters like food/microorganism(F/M), return sludge ratio(RAS)and sludge retention time(SRT)"nRisults: In the first stage the most important problems were over concentration of BOD,TSS, and P in effluent of treatment plant and overgrows of alga observed in parts of treatment plant and effluent receiving conduit. The main reason of high concentration of P was considered releasing of sludge. In the second stage operating condition modification efficiency of P removal increased from 50to 62 percent. In the end of third stage value of P removal reached to %82 and the most suitable of anoxic contact time was determined 3to4 hours, SRT terry day and F/M ratio o.12,that the most effective change has been the decrease of SRT to three days. "nConclusion: Adjusting of operating factors like SRT,RAS, sludge processing way in WWTP can increase P removal in them with in total efficiency remaining, such as in this case it was %12. In waste water treatment particularly for P removal the A/O process is suitable so in this project its effect on P removal efficiency has been %20.

In traditional biological phosphorus removal (BPR), phosphorus release in anaerobic stage is the prerequisite of phosphorus excessive uptake in aerobic conditions. Moreover, when low molecular weight of the organic substance such as volatile fatty acids (VFAs) is scarce in bulk liquid or anaerobic condition does not exist, phosphate accumulating organisms (PAOs) have difficulty removing phosphorus. However, in this work, phosphorus removal in two anoxic-aerobic sequencing batch reactors (SBRs) was observed when starch was supplied as a sole carbon source. The relations of the BPR with idle period were investigated in the two identical SBRs; the idle times were set to 0.5 hr (R1) and 4 hr (R2), respectively. Results of the study showed that, in the two SBRs, phosphorus concentrations of 0.26-3.11 mg/L in effluent were obtained after aeration when phosphorus concentration in influent was about 8 mg/L. Moreover, lower accumulations/transformations of polyhydroxyalkanoates (PHAs) and higher transformation of glycogen occurred in the SBRs, indicating that glycogen was the main energy source that was different from the traditional mechanism of BPR. Under the different idle time, the phosphorus removal was a little different. In R2, which had a longer idle period, phosphorus release was very obvious just as occurs in a anaerobic-aerobic regime, but there was a special phenomenon of chemical oxygen demand increase, while VFAs had no notable change. It is speculated that PAOs can assimilate organic compounds in the mixed liquor, which were generated from glycolysis by fermentative organisms, coupled with phosphorus release. In R1, which had a very short idle period, anaerobic condition did not exist; phosphorus removal rate reached 63%. It is implied that a new metabolic pathway can occur even without anaerobic phosphorus release when starch is supplied as the sole carbon source. [ABSTRACT FROM AUTHOR]