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Phosphorus (P) discharge from anthropogenic sources, notably sewage effluent and agricultural runoff, significantly contributes to eutrophication in aquatic environments. Stringent regulations have heightened the need for effective P removal technologies in wastewater treatment processes. This paper provides a comprehensive review of current P removal methods, focusing on both biological and chemical approaches. Biological treatments discussed include enhanced biological P removal in activated sludge systems, biological trickling filters, biofilm reactors, and constructed wetlands. The efficiency of microbial absorption and novel biotechnological integrations, such as the use of microalgae and fungi, are also examined. Chemical treatments reviewed encompass the application of metal salts, advanced oxidation processes such as chlorination, ozonation, and the Fenton reaction, as well as emerging techniques including the Electro-Fenton process and photocatalysis. Analytical methods for P, including spectrophotometric techniques and fractionation analyses, are evaluated to understand the dynamics of P in wastewater. This review critically assesses the strengths and limitations of each method, aiming to identify the most effective and sustainable solutions for P management in wastewater treatment. The integration of innovative strategies and advanced technologies is emphasized as crucial for optimizing P removal and ensuring compliance with environmental regulations. [ABSTRACT FROM AUTHOR]

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office 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.)

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office 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.)

Recovering phosphorus (P) through combustion from waste streams, like wastewater sludge and animal manure, offers a promising solution. This research explores the P release patterns in different ashes derived from secondary raw materials, using a long-term soil incubation lasting 160 days. The study evaluated the P release dynamics in five types of ashes from enhanced biological phosphorus removal (EBPR) systems and pig slurry burned at different temperatures. According to the results, a primary effect was observed on P bioavailability during the initial incubation period. All tested ashes release more than 50% of the total P applied between days 5 and 10. Ashes from EBPR exhibited higher P release than those from pig manure, indicating ash origin as a key factor in P release. Additionally, combustion temperature was crucial, with higher temperatures resulting in increased P release rates. Furthermore, the Pearson correlation revealed a strong relationship between the characteristics of the ashes and the amount of P release. Overall, these findings suggest that ashes could be a valuable P-source for agriculture avoiding the process of wet chemical P extraction, thus reducing both economic and environmental costs. [ABSTRACT FROM AUTHOR]

Phosphorus (P) discharge from anthropogenic sources, notably sewage effluent and agricultural runoff, significantly contributes to eutrophication in aquatic environments. Stringent regulations have heightened the need for effective P removal technologies in wastewater treatment processes. This paper provides a comprehensive review of current P removal methods, focusing on both biological and chemical approaches. Biological treatments discussed include enhanced biological P removal in activated sludge systems, biological trickling filters, biofilm reactors, and constructed wetlands. The efficiency of microbial absorption and novel biotechnological integrations, such as the use of microalgae and fungi, are also examined. Chemical treatments reviewed encompass the application of metal salts, advanced oxidation processes such as chlorination, ozonation, and the Fenton reaction, as well as emerging techniques including the Electro-Fenton process and photocatalysis. Analytical methods for P, including spectrophotometric techniques and fractionation analyses, are evaluated to understand the dynamics of P in wastewater. This review critically assesses the strengths and limitations of each method, aiming to identify the most effective and sustainable solutions for P management in wastewater treatment. The integration of innovative strategies and advanced technologies is emphasized as crucial for optimizing P removal and ensuring compliance with environmental regulations.

While granulated activated sludge exhibits high productivity, the processes of granule formation are incompletely studied. The processes of granule formation and succession of communities were investigated in a laboratory sequencing batch reactor (SBR) under conditions for enhanced biological phosphorus removal (EBPR) using microbiological and molecular techniques. Active consumption of acetate, primarily by the phosphate-accumulating organisms (PAO), commenced at day 150 of cultivation. This was indicated by the high ratio of molar P-released/acetate uptake (0.73–0.77 P-mol/C-mol), characteristic of PAO. During this period, two types of granule-like aggregates formed spontaneously out of the activated sludge flocs. The aggregates differed in morphology and microbial taxonomic composition. While both aggregate types contained phosphorus-enriched bacterial cells, PAO prevailed in those of morphotype I, and glycogen-accumulating organisms (GAOs) were predominant in the aggregates of morphotype II. After 250 days, the elimination of the morphotype II aggregates from the reactor was observed. The subsequent selection of the community was associated with the development of the morphotype I aggregates, in which the relative abundance of PAO increased significantly, resulting in higher efficiency of phosphorus removal. Metagenomic analysis revealed a predominance of the organisms closely related to Candidatus Accumulibacter IС and IIС and of Ca. Accumulibacter IIB among the PAO. Based on the content of the genes of the key metabolic pathways, the genomes of potential PAO belonging to the genera Amaricoccus, Azonexus, Thauera, Zoogloea, Pinisolibacter, and Siculibacillus were selected. The patterns of physicochemical processes and the microbiome structure associated with granule formation and succession of the microbial communities were revealed.

Candidatus Accumulibacter belongs to phosphate-accumulating organisms (PAOs) which exhibit a cyclic metabolism and are capable of intracellular polyphosphate accumulation and their hydrolysis under feast-famine anaerobic-aerobic cycling. In consortia of activated sludge microorganisms, these bacteria are responsible for enhanced biological phosphorus removal (EBPR). The spectrum of the substrates used by Ca. Accumulibacter remains insufficiently studied. It was investigated by measuring the oxygen uptake rates (OUR) of Ca. Accumulibacter-enriched culture supplemented with 17 different organic substrates. The highest oxygen uptake rate values were observed in the presence of tryptone, volatile fatty acids (acetate, propionate, and butyrate), succinate, pyruvate, and amino acids (aspartate and glutamate). Phosphate dynamics in the medium under shifts from anaerobic to aerobic cultivation in batch experiments were studied for these compounds (except for tryptone). All tested substrates were shown to cause phosphate cycling (release in the anaerobic phase and uptake in the aerobic one), with OURs for the substrates correlating with the number of phosphates consumed during the aerobic phase. It was concluded that OUR may be used as an indicator of the monosubstrates used by Ca. Accumulibacter in the anaerobic/aerobic cycle. The possible pathways for substrate transport and metabolism by Ca. Accumulibacter are discussed using stoichiometric data and the results of metagenomic analysis. [ABSTRACT FROM AUTHOR]

Recovering phosphorus (P) through combustion from waste streams, like wastewater sludge and animal manure, offers a promising solution. This research explores the P release patterns in different ashes derived from secondary raw materials, using a long-term soil incubation lasting 160 days. The study evaluated the P release dynamics in five types of ashes from enhanced biological phosphorus removal (EBPR) systems and pig slurry burned at different temperatures. According to the results, a primary effect was observed on P bioavailability during the initial incubation period. All tested ashes release more than 50% of the total P applied between days 5 and 10. Ashes from EBPR exhibited higher P release than those from pig manure, indicating ash origin as a key factor in P release. Additionally, combustion temperature was crucial, with higher temperatures resulting in increased P release rates. Furthermore, the Pearson correlation revealed a strong relationship between the characteristics of the ashes and the amount of P release. Overall, these findings suggest that ashes could be a valuable P-source for agriculture avoiding the process of wet chemical P extraction, thus reducing both economic and environmental costs.

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology 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.)

Research focused on interrogating post‐anoxic enhanced biological phosphorus removal (EBPR) at bench and pilot scales. Average bench‐scale effluent ranged from 0.33 to 1.4 mgP/L, 0.35 to 3.7 mgNH3‐N/L, and 1.1 to 3.9 mgNOx‐N/L. Comparatively, the pilot achieved effluent (50th percentile/average) of 0.13/0.2 mgP/L, 9.7/8.2 mgNH3‐N/L, and 0.38/3.3 mgNOx‐N/L under dynamic influent and environmental conditions. For EBPR process monitoring, P:C ratio data indicated that 0.2–0.4 molP/molC will result in stable EBPR; relatedly, a target design influent volatile fatty acid (VFA):P ratio would exceed 15 mgCOD/mgP. Post‐anoxic EBPR was enriched for Nitrobacter spp. at 1.70%–20.27%, with Parcubacteria also dominating; the former is putatively associated with nitritation and the latter is a putative fermenting heterotrophic organism. Post‐anoxic specific denitrification rates (SDNRs) (20°C) ranged from 0.70 to 3.10 mgN/gVSS/h; there was a strong correlation (R2 = 0.94) between the SDNR and %Parcubacteria for systems operated at a 20‐day solids residence time (SRT). These results suggest that carbon substrate potentially generated by this putative fermenter may enhance post‐anoxic EBPR. Practitioner Points: Post‐anoxic EBPR can achieve effluent of <0.2 mgP/L and <12 mgN/L.The P:C and VFA:P ratios can be predictive for EBPR process monitoring.Post‐anoxic EBPR was enriched for Nitrobacter spp. over Nitrospira spp. and also for Parcubacteria, which is a putative fermenting heterotrophic organism.Post‐anoxic specific denitrification rates (20°C) ranged from 0.70 to 3.10 mgN/gVSS/h.BLASTn analysis of 16S rDNA PAO primer set was shown to be improved to 93.8% for Ca. Accumulibacter phosphatis and 73.2%–94.0% for all potential PAOs. [ABSTRACT FROM AUTHOR]

In a wastewater treatment plant (WWTP), several sludge streams exist and the composition of their liquid phase varies with time and place. For evaluating the potential for formation of precipitates and equilibria for weak acids/bases, the ionic strength and chemical composition need to be known. This information is often not available in literature, and even neglected in chemical model-based research. Based on a literature review, we proposed three ranges of concentration (low, typical and high) for the major constituents of the liquid phase of the different streams in a WWTP. The study also discusses the reasons for the concentration evolution, and the exceptional cases, to allow readers to consider the right range depending on their situation. The ionic strength of the different streams and the contribution of its constituents were calculated based on the ionic composition. The major contributors to the ionic strength for the wastewater-based streams (influent, effluent and mixed sludge) were Na+, Cl−, Mg2+ and Ca2+, representing 50–70% of the ionic strength. For digestate, and accounted for 65–75% of the ionic strength. Even though the ionic strength is recognized to impact several important wastewater treatment processes, its utilization in literature is not always adequate, which is discussed in this study. HIGHLIGHTS The ionic strength for wastewater-based streams ranges from 0.003 to 0.1 M.; Na+, Cl−, Mg2+ and Ca2+ make 50–70% of the wastewater-based streams’ ionic strength.; The ionic strength for digestates ranges from 0.02 to 0.17 M.; NH4+ and account for 65–75% of the ionic strength of digestates.; Ionic strength is rarely determined and often misused in literature.;

• S2EBPRs have distinct microdiversity of known PAOs from conventional EBPRs. • Correlation analyses revealed performance implications of microdiversity of PAOs. • 16s rRNA gene oligotyping allowed taxonomic identification of sub-clades within known PAOs. • Different oligotype co-occurrence patterns were observed among PAOs sub-clades in EBPR and S2EBPR. • 16s rRNA gene oligotyping offers fast and cost-effective microbial microdiversity analysis. Polyphosphate Accumulating Organisms (PAOs) microdiversity is a key factor to elucidate the mechanisms involved in the side-stream enhanced biological phosphorus removal (S2EBPR) systems, which has been shown to improve the process stability over conventional EBPR. However, fast, effective and cost-efficient methods to resolve PAO microdiversity in real-world activate sludge samples is still in absence. In this study, we applied oligotyping analysis following the regular 16S rRNA gene amplicon sequencing standard operation pipeline (SOP) to resolve subgenus-level PAO oligotypes, which cannot be achieved using traditional 16S rRNA sequencing SOP. The identified oligotype profiles of PAO-containing genera Ca. Accumulibacter, Tetrasphaera and Comamonas showed distinguished community-level differences across 12 water resource recovery facilities (WRRFs), which would not be revealed at the genus level. The WRRF-level differences were observed larger than the temporal differences in the same WRRF, indicating intrinsic sub-genus level microdiversity fingerprint between EBPR/S2EBPR systems. The identified oligotypes can be associated with known PAO clades phylogenetically, suggesting that oligotyping can suffice as a fast and cost-efficient approach for PAO microdiversity profiling. In addition, network analysis can be used to identify coexistence patterns between oligotypes with respect to EBPR/S2EBPR configurations and performance, enabling more detailed analysis between EBPR system performance and PAOs microdiversity. Correlation analyses between oligotype profiles and key EBPR performance parameters revealed potential different biological functional traits among these PAO species with P-removal performance implications. [ABSTRACT FROM AUTHOR]

Candidatus Accumulibacter belongs to phosphate-accumulating organisms (PAOs) which exhibit a cyclic metabolism and are capable of intracellular polyphosphate accumulation and their hydrolysis under feast-famine anaerobic-aerobic cycling. In consortia of activated sludge microorganisms, these bacteria are responsible for enhanced biological phosphorus removal (EBPR). The spectrum of the substrates used by Ca. Accumulibacter remains insufficiently studied. It was investigated by measuring the oxygen uptake rates (OUR) of Ca. Accumulibacter-enriched culture supplemented with 17 different organic substrates. The highest oxygen uptake rate values were observed in the presence of tryptone, volatile fatty acids (acetate, propionate, and butyrate), succinate, pyruvate, and amino acids (aspartate and glutamate). Phosphate dynamics in the medium under shifts from anaerobic to aerobic cultivation in batch experiments were studied for these compounds (except for tryptone). All tested substrates were shown to cause phosphate cycling (release in the anaerobic phase and uptake in the aerobic one), with OURs for the substrates correlating with the number of phosphates consumed during the aerobic phase. It was concluded that OUR may be used as an indicator of the monosubstrates used by Ca. Accumulibacter in the anaerobic/aerobic cycle. The possible pathways for substrate transport and metabolism by Ca. Accumulibacter are discussed using stoichiometric data and the results of metagenomic analysis.

OBJECTIVE: The Coronavirus disease 2019 (COVID-19) infection is associated with autonomic dysfunction. Data on the long-term relationship between COVID-19 infection, heart rate recovery (HRR), and exaggerated blood pressure response to exercise (EBPR) are very limited. In our study, we aimed at investigating the longterm association between COVID-19, HRR, EBPR, metabolic, and echocardiographic parameters. PATIENTS AND METHODS: The study included 65 patients in the study group (33 female, median age 46) and 57 in the control group (30 female, 39 median age) between 1 April 2020 and 1 January 2021. Office blood pressure measurement, 24-hour ambulatory blood pressure monitoring, treadmill test, echocardiography, and metabolic parameters were evaluated. RESULTS: The frequency of blunted HRR (25 subjects, 38.5%, p < 0.001) and EBPR (7 subjects, 10.8%, p = 0.014) w ere significantly h igher i n study group. The study group had higher levels of white blood cell (p = 0.002), neutrophil, c-reactive protein, and uric acid (p < 0.001). Diameters of left atrium, aortic root, and ascending aorta were significantly higher in study group (p < 0.05). Age adjusted multiple logistic regression analysis showed that neutrophil levels (odds ratio (OR), 9.21; 95% confidence interval (CI), 1.52-55.75, p = 0.016), glomerular filtration rate (OR, 1.34; 95% CI, 1.13-1.59, p = 0.001), basal heart rate (OR, 1.58; 95% CI, 1.17-2.12, p = 0.003), and mean heart rate (OR, 1.22; 95% CI, 1.03-1.45, p = 0.0021) were independently associated with COVID-19 infection. CONCLUSIONS: The frequency of blunted HRR and EBPR, and uric acid levels were significantly higher in the study group compared to the control group, suggesting autonomic dysfunction as the possible sequelae of the COVID-19 infection and increased risk of cardiovascular events in the future. [ABSTRACT FROM AUTHOR]

This study re-evaluated the role of anoxic and anaerobic zones during the enhanced biological phosphorus (P) removal process by investigating the potential effect of introducing an anoxic zone into a high-rate microaerobic activated sludge (MAS) system (1.60–1.70 kg chemical oxygen demand (COD) m−3 d−1), i.e., a high-rate anoxic/microaerobic (A/M) system for sewage treatment. In the absence of a pre-anaerobic zone, introducing an anoxic zone considerably reduced effluent NO x −-N concentrations (7.2 vs. 1.5 mg L−1) and remarkably enhanced total nitrogen (75% vs. 89%) and total P (18% vs. 60%) removal and sludge P content (1.48% vs. 1.77% (dry weight)) due to further anoxic denitrifying P removal in the anoxic zone (besides simultaneous nitrification and denitrification in the microaerobic zone). High-throughput pyrosequencing demonstrated the niche differentiation of different polyphosphate accumulating organism (PAO) clades (including denitrifying PAO [DPAO] and non-DPAO) in both systems. Introducing an anoxic zone considerably reduced the total PAO abundance in sludge samples by 42% and modified the PAO community structure, including 17–19 detected genera. The change was solely confined to non-DPAOs, as no obvious change in total abundance or community structure of DPAOs including 7 detected genera was observed. Additionally, introducing an anoxic zone increased the abundance of ammonia-oxidizing bacteria by 39%. The high-rate A/M process provided less aeration, higher treatment capacity, a lower COD requirement, and a 75% decrease in the production of waste sludge than the conventional biological nutrient removal process. [Display omitted] • Distinguished denitrifying P removal takes place in the absence of pre-anaerobic phase. • Nitrate input during anaerobic phase adversely influenced non-DPAO rather than DPAO. • Enlarging the anoxic zone simultaneously promoted nitrogen and phosphorus removal. • High-rate A/M process had less waste sludge production, aeration and COD requirements. [ABSTRACT FROM AUTHOR]

• Successful granulation at 10 and 20 g/L NaCl and seawater condition. • Incomplete anaerobic substrate uptake at 30 g/L NaCl led to filamentous growth. • Ca. Accumulibacter was dominant at 10 and 20 g/L NaCl and seawater conditions. • Trehalose release from salt-adapted biomass during osmotic down shock. • Ionic composition of wastewater maybe more important than absolute concentration. Industrial wastewater often has high levels of salt, either due to seawater or e.g. sodium chloride (NaCl) usage in the processing. Previous work indicated that aerobic granular sludge (AGS) is differently affected by seawater or saline water at similar osmotic strength. Here we investigate in more detail the impact of NaCl concentrations and seawater on the granulation and conversion processes for AGS wastewater treatment. Glycerol was used as the carbon source since it is regularly present in industrial wastewaters, and to allow the evaluation of microbial interactions that better reflect real conditions. Long-term experiments were performed to evaluate and compare the effect of salinity on granulation, anaerobic conversions, phosphate removal, and the microbial community. Smooth and stable granules as well as enhanced biological phosphorus removal (EBPR) were achieved up to 20 g/L NaCl or when using seawater. However, at NaCl levels comparable to seawater strength (30 g/L) incomplete anaerobic glycerol uptake and aerobic phosphate uptake were observed, the effluent turbidity increased, and filamentous granules began to appear. The latter is likely due to the direct aerobic growth on the leftover substrate after the anaerobic feeding period. In all reactor conditions, except the reactor with 30 g/L NaCl, Ca. Accumulibacter was the dominant microorganism. In the reactor with 30 g/L NaCl, the relative abundance of Ca. Accumulibacter decreased to ≤1 % and an increase in the genus Zoogloea was observed. Throughout all reactor conditions, Tessaracoccus and Micropruina , both actinobacteria, were present which were likely responsible for the anaerobic conversion of glycerol into volatile fatty acids. None of the glycerol metabolizing proteins were detected in Ca. Accumulibacter which supports previous findings that glycerol can not be directly utilized by Ca. Accumulibacter. The proteome profile of the dominant taxa was analysed and the results are further discussed. The exposure of salt-adapted biomass to hypo-osmotic conditions led to significant trehalose and PO 4 3−-P release which can be related to the osmoregulation of the cells. Overall, this study provides insights into the effect of salt on the operation and stability of the EBPR and AGS processes. The findings suggest that maintaining a balanced cation ratio is likely to be more important for the operational stability of EBPR and AGS systems than absolute salt concentrations. [ABSTRACT FROM AUTHOR]

Biological nutrient removal grows into complicated scenario due to the microbial consortium shift and kinetic competition between phosphorus (P)-accumulating and nitrogen (N)-removing microorganisms. In this study, three sequential batch reactors with constant operational conditions except aeration patterns at 6 h cycle periods were tested. Intermittent aeration was applied to develop a robust nutrient removal system aimed to achieve high energy saving and removal efficiency. The results showed higher correspondence of P-uptake, polymeric substance synthesis and glycogen degradation in intermittent-aeration with longer interval periods compared to continuous-aeration. Increasing the intermittent-aeration duration from 25 to 50 min, resulted in higher process performance where the system exhibited approximately 30% higher nutrient removal. This study indicated that nutrient removal strongly depends on reaction phase configuration representing the importance of aeration pattern. The microbial community examined the variation in abundance of bacterial groups in suspended sludge, where the 50 min intermittent aeration, favored the growth of P-accumulating organisms and nitrogen removal microbial groups, indicating the complications related to nutrient removal systems. Successful intermittently aerated process with high capability of simple implementation to conventional systems by elemental retrofitting, is applicable for upgrading wastewater treatment plants. With aeration as a major operational cost, this process is a promising approach to potentially remove nutrients in high competence, in distinction to optimizing cost-efficacy of the system. [Display omitted] [ABSTRACT FROM AUTHOR]

ABSTRACT Natural microbial communities consist of closely related taxa that may exhibit phenotypic differences and inhabit distinct niches. However, connecting genetic diversity to ecological properties remains a challenge in microbial ecology due to the lack of pure cultures across the microbial tree of life. “Candidatus Accumulibacter phosphatis” (Accumulibacter) is a polyphosphate-accumulating organism that contributes to the enhanced biological phosphorus removal (EBPR) biotechnological process for removing excess phosphorus from wastewater and preventing eutrophication from downstream receiving waters. Distinct Accumulibacter clades often coexist in full-scale wastewater treatment plants and laboratory-scale enrichment bioreactors and have been hypothesized to inhabit distinct ecological niches. However, since individual strains of the Accumulibacter lineage have not been isolated in pure culture to date, these predictions have been made solely on genome-based comparisons and enrichments with varying strain compositions. Here, we used genome-resolved metagenomics and metatranscriptomics to explore the activity of coexisting Accumulibacter strains in an engineered bioreactor environment. We obtained four high-quality genomes of Accumulibacter strains that were present in the bioreactor ecosystem, one of which is a completely contiguous draft genome scaffolded with long Nanopore reads. We identified core and accessory genes to investigate how gene expression patterns differed among the dominating strains. Using this approach, we were able to identify putative pathways and functions that may confer distinct functions to Accumulibacter strains and provide key functional insights into this biotechnologically significant microbial lineage. IMPORTANCE “Candidatus Accumulibacter phosphatis” is a model polyphosphate-accumulating organism that has been studied using genome-resolved metagenomics, metatranscriptomics, and metaproteomics to understand the EBPR process. Within the Accumulibacter lineage, several similar but diverging clades are defined by the shared sequence identity of the polyphosphate kinase (ppk1) locus. These clades are predicted to have key functional differences in acetate uptake rates, phage defense mechanisms, and nitrogen-cycling capabilities. However, such hypotheses have largely been made based on gene content comparisons of sequenced Accumulibacter genomes, some of which were obtained from different systems. Here, we performed time series genome-resolved metatranscriptomics to explore gene expression patterns of coexisting Accumulibacter clades in the same bioreactor ecosystem. Our work provides an approach for elucidating ecologically relevant functions based on gene expression patterns between closely related microbial populations.

The inhibiting effects of ciprofloxacin (CIP) on enhanced biological phosphorus removal (EBPR) were investigated with no change in reactor operation and with increased aeration rate and sludge retention time (SRT) to explore inhibition-alleviating solutions. Additionally, performance recoverability was evaluated. The results showed that the phosphorus removal efficiency in the presence of 0.002–0.092 mg/L CIP for 7 days was only 12.5%. Increasing the aeration rate relieved inhibition (33.5% phosphorus removal efficiency on Day 7), and increasing SRT slowed EBPR performance deterioration. The EBPR performance recovered from CIP inhibition and increases in the aeration rate and SRT resulted in different recovery phenomena. The maximum PO 4 3--P release rate continued to decrease in the first 2 days of the recovery stage and then gradually increased. However, the maximum PO 4 3--P uptake rate immediately increased at different rates among reactors, which might be attributed to variations in the microbial community structure, decreased poly-P content, and enhanced abundances of ABC transporters and quorum sensing. It was found that some microorganisms associated with phosphorus removal were more tolerant to CIP than glycogen accumulating organisms. Moreover, the increased relative abundance of the qepA gene indicated that the microorganisms in the EBPR system had strong antibiotic resistance capacity. The bacterial community structure was significantly affected by CIP and could not recover to the initial structure. The results help to provide technical support for the operation of the EBPR process in the presence of CIP and to increase the understanding of system recoverability. [Display omitted] • Increasing aeration rate and sludge retention time alleviated the inhibition. • Ciprofloxacin inhibition on phosphorus removal performance was recoverable. • The bacterial community was affected and could not recover to the initial structure. • The maximum PO 4 3--P uptake rate increased immediately in the recovery stage. • The maximum PO 4 3--P release rate decreased and then increased in the recovery stage. [ABSTRACT FROM AUTHOR]

Candidatus Accumulibacter phosphatis is an important microorganism for enhanced biological phosphorus removal (EBPR). In a previous study, we found a remarkable flexibility regarding salinity, since this same microorganism could thrive in both freshwater- and seawater-based environments, but the mechanism for the tolerance to saline conditions remained unknown. Here, we identified and described the role of trehalose as an osmolyte in Ca. Accumulibacter phosphatis. A freshwater-adapted culture was exposed to a single batch cycle of hyperosmotic and hypo-osmotic shock, which led to the release of trehalose up to 5.34 mg trehalose/g volatile suspended solids (VSS). Long-term adaptation to 30% seawater-based medium in a sequencing batch reactor (SBR) gave a stable operation with complete anaerobic uptake of acetate and propionate along with phosphate release of 0.73 Pmol/Cmol, and complete aerobic uptake of phosphate. Microbial analysis showed Ca. Accumulibacter phosphatis clade I as the dominant organism in both the freshwater- and seawater-adapted cultures (> 90% presence). Exposure of the seawater-adapted culture to a single batch cycle of hyperosmotic incubation and hypo-osmotic shock led to an increase in trehalose release upon hypo-osmotic shock when higher salinity is used for the hyperosmotic incubation. Maximum trehalose release upon hypo-osmotic shock was achieved after hyperosmotic incubation with 3× salinity increase relative to the salinity in the SBR adaptation reactor, resulting in the release of 11.9 mg trehalose/g VSS. Genome analysis shows the possibility of Ca. Accumulibacter phosphatis to convert glycogen into trehalose by the presence of treX, treY, and treZ genes. Addition of trehalose to the reactor led to its consumption, both during anaerobic and aerobic phases. These results indicate the flexibility of the metabolism of Ca. Accumulibacter phosphatis towards variations in salinity. Key points: • Trehalose is identified as an osmolyte in Candidatus Accumulibacter phosphatis. • Ca. Accumulibacter phosphatis can convert glycogen into trehalose. • Ca. Accumulibacter phosphatis clade I is present and active in both seawater and freshwater. [ABSTRACT FROM AUTHOR]

A systematic comparison framework for selecting the best retrofitting alternative for a water resource recovery facility (WRRF) is proposed in this work. The procedure is applied comparing different possible plant configurations to retrofit an existent anoxic/oxic (A/O) WRRF (Manresa, Spain) aiming to include enhanced biological phosphorus removal (EBPR). The framework for comparison was built on system analysis using a calibrated IWA ASM2d model. A multicriteria set of performance variables, as the operational and capital expenditures (OPEX and CAPEX, respectively) and robustness tests for measuring how fast the plant configuration refuses external disturbances (like ammonium and phosphate peak loads), were used for comparison. Starting from the existent WRRF, four plant configurations were tested: single A2/O (only one anoxic reactor converted to anaerobic), double A2/O (two anoxic reactors converted to anaerobic), BARDENPHO, and UCT. The double A2/O plant configuration was the most economical and reliable alternative for improving the existent Manresa WRRF capacity and implementing EBPR, since the effluent quality increased 3.8% compared to the current plant configuration. In addition, the double A2/O CAPEX was close to €165,000 which was at the same order of the single A2/O and lower than the BARDENPHO and UCT alternatives. Practitioner points: Four configurations including EBPR were evaluated for retrofitting an A/O WRRF.A new multicriteria comparison framework was used to select the best configuration.Up to 13 criteria related to effluent quality, robustness and costs were included.A single function based on the combination of all the criteria was also evaluated. [ABSTRACT FROM AUTHOR]

Tetrasphaera are an attractive putative group of polyphosphate accumulating organisms (PAOs) that may play an important role in the enhanced biological phosphorus removal (EBPR) process. Unlike conventional PAOs that mostly rely on volatile fatty acids (VFAs), Tetrasphaera can assimilate a wide range of carbon substrates including glucose and various amino acids (e.g., glycine, glutamate, and aspartate). In addition, they have the ability to produce VFAs. This functional versatility confers significant performance and economic benefits for its application in EBPR processes. However, before the wastewater industry can harness these benefits, fundamental knowledge of their taxonomy, classification and identification in EBPR and activated sludge systems must be understood. This review provides a summary of the polyphasic approach: use of phenotypic, genotypic, and chemotaxonomic methods for bacterial classification and its application in the classification of Tetrasphaera. A review of molecular tools currently used to identify Tetrasphaera in activated sludge systems is also provided. In addition, this review discusses how challenges with molecular tools limit our understanding and application of Tetrasphaera in EBPR processes. [ABSTRACT FROM AUTHOR]

In this study, a novel laboratory-scale synchronous enhanced biological phosphorus removal and semi-nitritation (termed as EBPR-SN) combined with anammox process was put forward for achieving nutrient elimination from municipal wastewater at 27 ℃. This process consisted of two 10 L sequencing batch reactors (SBRs), i.e. EBPR-SN SBR followed by Anammox SBR. The EBPR-SN SBR was operated for 400 days with five periods and the Anammox SBR was operated starting on period IV. Eventually, for treating municipal wastewater containing low chemical oxygen demand/nitrogen (COD/N) of 3.2 (mg/mg), the EBPR-SN plus Anammox system performed advanced total inorganic nitrogen (TIN) and P removal, with TIN and P removal efficiencies of 81.4% and 94.3%, respectively. Further analysis suggested that the contributions of simultaneous partial nitrification denitrification, denitrification, and anammox to TIN removal were 15.0%, 45.0%, and 40.0%, respectively. The enriched phosphorus-accumulating organisms (PAOs) in the EBPR-SN SBR facilitated P removal. Besides, the EBPR-SN SBR achieved P removal and provided stable anammox substrates, suggesting a short sludge retention time (SRT 12 d) could achieve synergy between ammonia-oxidizing bacteria and PAOs. These results provided an alternative process for treating municipal wastewater with limited organics. [ABSTRACT FROM AUTHOR]

Phosphorus as a fundamental element for growth and metabolism of living organisms, yet problematic to water quality, is an irreplaceable component. Application of enhanced biological phosphorus removal (EBPR) technology in wastewater treatment plants offers phosphorus removal and recovery in addition to potential eutrophication prevention. This process is dependable on enrichment of phosphorus accumulating organisms in activated sludge to accumulate great amount of poly-phosphate inside their cell interior for enhancement of phosphorus removal. Yet, inadequate removal performance in pilot and full-scale systems, rises the need for optimization in operation and design of applicable configuration. In addition to applying advancement strategies to minimize the growth of undesirable microorganisms through cost effective phosphorus removal along with potential P-recovery and sustainability. Preceding research has certainly advanced the insight on this area of investigation. Notwithstanding, there are still numerous unresolved issues to be undertaken. This comprehensive review paper aims to revisit the current knowledge and fundamental understanding on microbiology and biochemical transformations in EBPR process. In view of application and structure, EBPR design and operation considerations along with process configurations is critically reviewed. This comprehensive review hopes to touch on the critical points of operation to help in understanding the overall EBPR process and to farther provide insights on future work onto EBPR process developments. [ABSTRACT FROM AUTHOR]

Under normal temperature and sufficient carbon source conditions, with simulated sewage as the treatment object, the characteristics, and advantages of phosphorus removal in the two-stage sequencing batch reactor (SBR) dephosphorization and denitrification process were investigated through comparative analysis. The phosphorus removal characteristics of the single-stage enhanced biological phosphorus removal-sequencing batch reactor (EBPR-SBR) were also discussed. Results showed that the phosphorus removal grade SBR1 of the two-stage SBR phosphorus removal and denitrification system has similar anaerobic phosphorus release and aerobic phosphorus uptake processes to the single-stage SBR. However, the phosphorus removal efficiency of the SBR1 system with low sludge age and high organic load is higher than that of the single-stage SBR system. The rate of specific phosphorus release of the fast phosphorus-releasing segment (0-0.5 h) and the rate of specific phosphorus absorption of the fast phosphorus-absorbing segment (0-1 h) of the SBR1 system are 1.43 and 1.79 times higher than those of the single-stage SBR system, respectively. The effluent total phosphorus (TP) of the single-stage EBPR-SBR system can be no higher than 1.0 mg/L but not 0.5 mg/L. Phosphorus release occurs in polyphosphate-accumulating organisms at the beginning of EBPR-SBR system sedimentation, and the rate of phosphorus release increases over time. The rate of phosphorus release is constant after 40 min of sedimentation. The average rate of phosphorus release is 0.0138 mg P/L min. The final effluent TP of the two-stage SBR phosphorus removal and denitrification system may not be affected by the fluctuation of the effluent phosphorus concentration of the phosphorus removal grade SBR1. Thus, the TP can be easily and stably kept equal to or lower than 0.5 mg/L. [ABSTRACT FROM AUTHOR]

Sidestream EBPR (S2EBPR) is an emerging alternative process to address common challenges in EBPR related to weak wastewater influent and may improve EBPR process stability. A systematic evaluation and comparison of the process performance and microbial community structure was conducted between conventional and S2EBPR facilities in North America. The statistical analysis suggested higher performance stability in S2EBPR than conventional EBPR, although possible bias associated with other plant‐specific factors might have affected the comparison. Variations in stoichiometric values related to EBPR activity and discrepancies between the observed values and current model predictions suggested a varying degree of metabolic versatility of PAOs in S2EBPR systems that warrant further investigation. Microbial community analysis using various techniques suggested comparable known candidate PAO relative abundances in S2EBPR and conventional EBPR systems, whereas the relative abundance of known candidate GAOs seemed to be consistently lower in S2EBPR facilities than conventional EBPR facilities. 16S rRNA gene sequencing analysis revealed differences in the community phylogenetic fingerprints between S2EBPR and conventional facilities and indicated statistically higher microbial diversity index values in S2EBPR facilities than those in conventional EBPRs. Practitioner Points: Sidestream EBPR (S2EBPR) can be implemented with varying and flexible configurations, and they offer advantages over conventional configurations for addressing the common challenges in EBPR related to weak wastewater influent and may improve EBPR process stability.Survey of S2EBPR plants in North America suggested statistically more stable phosphorus removal performance in S2EBPR plants than conventional EBPRs, although possible bias might affect the comparison due to other plant‐specific factors.The EBPR kinetics and stoichiometry of the S2EBPR facilities seemed to vary and are associated with metabolic versatility of PAOs in S2EBPR systems that warrant further investigation.The abundance of known candidate PAOs in S2EBPR plants was similar to those in conventional EBPRs, and the abundance of known candidate GAOs was generally lower in S2EBPR than conventional EBPR facilities. Further finer‐resolution analysis of PAOs and GAOs, as well as identification of other unknown PAOs and GAOs, is needed.Microbial diversity is higher in S2EBPR facilities compared with conventional ones, implying that S2EBPR microbial communities could show better resilience to perturbations due to potential functional redundancy. [ABSTRACT FROM AUTHOR]

Investigations of the impact of solid residence time (SRT) on microbial ecology and performance of enhanced biological phosphorus removal (EBPR) process in full‐scale systems have been scarce due to the challenges in isolating and examining the SRT from other complex plant‐specific factors. This study performed a comprehensive evaluation of the influence of SRT on polyphosphate‐accumulating organisms (PAOs) and glycogen‐accumulating organisms (GAOs) dynamics and on P removal performance at Clark County Water Reclamation District Facility in Las Vegas, USA. Five parallel treatment trains with separated clarifiers were operated with five different SRTs ranging from 6 to 40 days. Microbial community analysis using multiple molecular and Raman techniques suggested that the relative abundances and diversity of PAOs and GAOs in EBPR systems are highly affected by the SRT. The resultant EBPR system stability and performance can be potentially controlled and optimized by manipulating the system SRT, and shorter SRT (<10 days) seems to be preferred. Practitioner points: Phosphorus removal performance and kinetics are highly affected by the operational solid residence time (SRT), with lower and more stable effluent P level achieved at SRT < 10 days.Excessive long SRTs above that needed for nitrification may harm EBPR performance; additionally, excessive long SRT may favor GAOs to dominate over PAOs and thus further reducing efficient use of rbCOD for EBPR.Microbial population abundance and diversity, especially those functionally relevant PAOs and GAOs, can impact the P removal performances, and they are highly dependent on the operational solid residence time.EBPR performance can be potentially controlled and optimized by manipulating the system SRT, and shorter SRT (≤10 days) seems to be preferred at the influent rbCOD/P ratio and environmental conditions as in the plant studied. [ABSTRACT FROM AUTHOR]

Feasibility of a combined system consisting of an anaerobic up-flow anaerobic sludge blanket (UASB) followed by anoxic unit then aerobic activated sludge (AS) was investigated. The system was fed with normal domestic wastewater, then medium loading wastewater using activated sludge from El Berka WWTP, then high strength sewage having a chemical oxygen demand (COD) of 2635 mg COD/L. The organic loading rate (OLR) was increased gradually from 0.5 to 4.43 kg COD/m3/day. The HRT was changed for each loading from 10.5 to 15 h. The internal recirculation (IR) was tested at 100%, 200% and 300% for each loading run. The return activated sludge was adjusted to maintain a mixed liquor suspended solids of greater than 2500 ppm. At steady state conditions, the UASB reactor achieved removal efficiency up to 79.13% of the total COD. The combined system performed an excellent organic removal pushing the overall removal efficiency of the total COD, TN and TP to 95.87%, 84.95% and 87.59%, respectively. When the OLR increased to 4.43 kg COD/m3/day, the effluent quality of the UASB deteriorated reaching a percent of 48.20 for COD removal efficiency dropped to 62.90%, 29.90% and 46.90% respectively. The optimum operational conditions for the system on different organic loadings were HRT = 15 h and the IR = 200%.

The aim of this study was to identify, quantify and prioritize for the first time the sources of uncertainty in a mechanistic model describing the anaerobic-aerobic metabolism of phosphorus accumulating organisms (PAO) in enhanced biological phosphorus removal (EBPR) systems. These wastewater treatment systems play an important role in preventing eutrophication and metabolic models provide an advanced tool for improving their stability via system design, monitoring and prediction. To this end, a global sensitivity analysis was conducted using standard regression coefficients and Sobol sensitivity indices, taking into account the effect of 39 input parameters on 10 output variables. Input uncertainty was characterized with data in the literature and propagated to the output using the Monte Carlo method. The low degree of linearity between input parameters and model outputs showed that model simplification by linearization can be pursued only in very well defined circumstances. Differences between first and total-order sensitivity indices showed that variance in model predictions was due to interactions between combinations of inputs, as opposed to the direct effect of individual inputs. The major sources of uncertainty affecting the prediction of liquid phase concentrations, as well as intra-cellular glycogen and poly-phosphate was due to 64% of the input parameters. In contrast, the contribution to variance in intra-cellular PHA constituents was uniformly distributed among all inputs. In addition to the intra-cellular biomass constituents, notably PHB, PH2MV and glycogen, uncertainty with respect to input parameters directly related to anaerobic propionate uptake, aerobic poly-phosphate formation, glycogen formation and temperature contributed most to the variance of all model outputs. Based on the distribution of total-order sensitivities, characterization of the influent stream and intra-cellular fractions of PHA can be expected to significantly improve model reliability. The variance of EBPR metabolic model predictions was quantified. The means to account for this variance, with respect to each quantity of interest, given knowledge of the corresponding input uncertainties, was prescribed. On this basis, possible avenues and pre-requisite requirements to simplify EBPR metabolic models for PAO, both structurally via linearization, as well as by reduction of the number of non-influential variables were outlined.

While granulated activated sludge exhibits high productivity, the processes of granule formation are incompletely studied. The processes of granule formation and succession of communities were investigated in a laboratory sequencing batch reactor (SBR) under conditions for enhanced biological phosphorus removal (EBPR) using microbiological and molecular techniques. Active consumption of acetate, primarily by the phosphate-accumulating organisms (PAO), commenced at day 150 of cultivation. This was indicated by the high ratio of molar P-released/acetate uptake (0.73-0.77 P-mol/C-mol), characteristic of PAO. During this period, two types of granule-like aggregates formed spontaneously out of the activated sludge flocs. The aggregates differed in morphology and microbial taxonomic composition. While both aggregate types contained phosphorus-enriched bacterial cells, PAO prevailed in those of morphotype I, and glycogen-accumulating organisms (GAOs) were predominant in the aggregates of morphotype II. After 250 days, the elimination of the morphotype II aggregates from the reactor was observed. The subsequent selection of the community was associated with the development of the morphotype I aggregates, in which the relative abundance of PAO increased significantly, resulting in higher efficiency of phosphorus removal. Metagenomic analysis revealed a predominance of the organisms closely related to Candidatus Accumulibacter IС and IIС and of Ca. Accumulibacter IIB among the PAO. Based on the content of the genes of the key metabolic pathways, the genomes of potential PAO belonging to the genera Amaricoccus, Azonexus, Thauera, Zoogloea, Pinisolibacter , and Siculibacillus were selected. The patterns of physicochemical processes and the microbiome structure associated with granule formation and succession of the microbial communities were revealed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2023 Pelevina, Gruzdev, Berestovskaya, Dorofeev, Nikolaev, Kallistova, Beletsky, Ravin, Pimenov and Mardanov.)

Polyphosphate (poly-P) is a major constituent in activated sludge from wastewater treatment plants with enhanced biological phosphorus removal due to poly-P synthesis by poly-P accumulating organisms where it plays an important role for recovery of phosphorus from waste water. Our aim was to develop a reliable protocol for poly-P quantification by 31P NMR spectroscopy. This has so far been complicated by the risks of inefficient extraction and poly-P hydrolysis in the extracts. A protocol for complete extraction, identification and quantification of poly-P in activated sludge from a waste water treatment plant was identified based on test and evaluation of existing extraction protocols in combination with poly-P determination and quantification by solution and solid state 31P NMR spectroscopy. The total poly-P middle group content was quantified by solid state NMR for comparison with the poly-P middle groups quantified by solution NMR, which is novel. Three different extraction protocols previously used in literature were compared: 1) a single 0.25 M NaOH-0.05 M EDTA extraction, 2) a 0.05 M EDTA pre-extraction followed by a 0.25 M NaOH main extraction and 3) a 0.05 M EDTA pre-extraction followed by a 0.25 M NaOH-0.05 M EDTA main extraction. The results showed that the extraction protocol 2 was optimal for fresh activated sludge, extracting 10.8 ± 0.4 to 11.4 ± 1.2 mgP/gDW poly-P. Extraction protocols 1 and 3 extracted less than 9.4 ± 0.5 mgP/gDW poly-P. A comparison of the quantification of poly-P by 31P solution NMR and by 31P solid state NMR spectroscopy of lyophilised activated sludge showed 86 ± 9% extraction efficiency of poly-P, which confirms that the extraction protocol recovered most of the poly-P from the samples without pronounced poly-P degradation. Image 1 • 31P solution NMR spectroscopy for quantification of poly-P extracted from activated sludge. • Three extraction protocols for poly-P from activated sludge were compared. • Two-step EDTA and NaOH extraction extracts all poly-P from activated sludge. • Rotary evaporation of extracts gives less poly-P degradation than lyophilisation. • Poly-P extraction efficiency was evaluated by comparison with solid state NMR results. [ABSTRACT FROM AUTHOR]

Abstract Further biological polishing of micropollutants in WWTP effluents is limited by the lack of available carbon for cometabolic degradation. Metabolism of polyhydroxyalkanoates (PHAs) stored intracellularly during enhanced biological phosphorus removal (EBPR) could serve as carbon source for post-denitrification and micropollutant cometabolism. The removal of nine micropollutants (i.e., pharmaceuticals and corrosion inhibitors) was investigated by using Moving Bed Biofilm Reactors (MBBRs), selecting phosphorus (PAO) or glycogen (GAO) accumulating organisms under different redox conditions. Three laboratory-scale MBBRs were operated in sequencing-batch mode under cyclical anaerobic and aerobic/anoxic conditions for phosphorus removal. Batch experiments were performed to evaluate the biodegradation potential of micropollutants along with the utilization of internally stored PHA. Experiments showed that aerobic PAO were able to efficiently remove most of the targeted micropollutants. The removal of benzotriazole, 5‑methyl‑1H‑benzotriazole, carbamazepine, ketoprofen and diclofenac occurred simultaneously to phosphorus uptake and terminated when phosphorus was no longer available. Denitrifying PAO and aerobic GAO exhibited lower removal of micropollutants than aerobic PAO. Degradation profiles of stored PHA suggested a diverse utilization of the different fractions of PHA for phosphorus and micropollutant removal, with PHV (poly 3‑hydroxyvalerate) most likely used for the cometabolism of targeted micropollutants. Graphical abstract Unlabelled Image Highlights • MBBR operated for biological phosphorus removal under different redox conditions • Aerobic PAO efficiently removed nine targeted micropollutants. • Removal occurred simultaneously to phosphorus uptake for several micropollutants. • Denitrifying PAO and GAO exhibited lower removal than aerobic PAO. • PHV and PHB contributed differently to removal of phosphorus and micropollutants. [ABSTRACT FROM AUTHOR]

A comprehensive assessment of full-scale enhanced biological phosphorus removal (EBPR) plants (five plants, 19 independent tests) was undertaken to determine their effectiveness in terms of aerobic and anoxic P removal. By comparing parallel P uptake tests under only aerobic or under anoxic-aerobic conditions, results revealed that introducing an anoxic stage led to an overall P removal of on average 90% of the P removed under only aerobic conditions. This was achieved with negligible higher PHA and glycogen requirements, 30% lower overall oxygen consumption and with the simultaneous removal of nitrate, reducing up to an estimate of 70% of carbon requirements for simultaneous N and P removal. Varying fractions of denitrifying polyphosphate accumulating organisms (DPAOs), from an average of 25% to 84%, were found in different plants. No correlation was found between the DPAO fractions and EBPR configuration, season, or the concentration of any of the microbial groups measured via quantitative fluorescence in situ hybridisation. These included Type I and Type II Ca. Accumulibacter and glycogen accumulating organisms, suggesting that chemical batch tests are the best methodology for quantifying the potential of anoxic P removal in full-scale wastewater treatment plants. [ABSTRACT FROM AUTHOR]

In this study, a lab-scale continuous flow side-stream enhanced biological phosphorus (P) removal (S2EBPR) reactor was operated for 247 days treating synthetic wastewater with influent carbon to phosphorus (C/P) ratio of 25.0 g COD/g P and influent PO 4 3–-P of 7.4 ± 0.3 mg P/L. The effect of the return activated sludge (RAS) diversion ratio on S2EBPR reactor was investigated by comparing P removal performance, microbial activity, and community structure. The results showed that the RAS diversion ratio of 8.0%, by yielding a side-stream sludge retention time (SRT SS) of ∼60 h, resulted in the lowest effluent PO 4 3–-P concentration of 0.5 ± 0.3 mg P/L. The results of in situ process profiles and ex situ P release and uptake batch tests under different RAS diversion conditions showed that the more anaerobic P release was obtained in the side-stream reactor, the higher the P removal efficiency and EBPR activity were achieved. The stoichiometric ratios observed in EBPR activity tests indicated a polyphosphate accumulating organisms (PAOs) metabolism mainly dependent on the glycolysis pathway. The results of microbial ecology analysis revealed that the optimized SRT SS would give a competitive advantage to PAOs in the S2EBPR process. By obtaining statistically reliable results, this study would provide guidance for wastewater treatment plants to achieve optimal P removal performance in S2EBPR configuration. • A 3 L/h continuous flow S2EBPR reactor was started up and operated for 247 days. • The optimum sludge residence time was about 60 h in the side-stream reactor. • A good P removal efficiency can be achieved by adjusting side-stream ratio only. • The PAO/GAO value was well used to evaluate EBPR activity. [ABSTRACT FROM AUTHOR]

The removal of phosphorus (P) from domestic wastewater is primarily to reduce the potential for eutrophication in receiving waters, and is mandated and common in many countries. However, most P-removal technologies have been developed for use at larger wastewater treatment plants that have economies-of-scale, rigorous monitoring, and in-house operating expertise. Smaller treatment plants often do not have these luxuries, which is problematic because there is concern that P releases from small treatment systems may have greater environmental impact than previously believed. Here P-removal technologies are reviewed with the goal of determining which treatment options are amenable to small-scale applications. Significant progress has been made in developing some technologies for small-scale application, namely sorptive media. However, as this review shows, there is a shortage of treatment technologies for P-removal at smaller scales, particularly sustainable and reliable options that demand minimal operating and maintenance expertise or are suited to northern latitudes. In view of emerging regulatory pressure, investment should be made in developing new or adapting existing P-removal technologies, specifically for implementation at small-scale treatment works.

Enhanced biological phosphorus removal (EBPR) is an economical and sustainable process for phosphorus removal from wastewater. Despite the widespread application of EBPR for low-strength domestic wastewater treatment, limited investigations have been conducted to apply EBPR to the high-strength wastewaters, particularly, the integration of EBPR and the short-cut nitrogen removal process in the one-stage system remains challenging. Herein, we reported a novel proof-of-concept demonstration of integrating EBPR and nitritation (oxidation of ammonium to nitrite) in a one-stage sequencing batch reactor to achieve simultaneous high-strength phosphorus and short-cut nitrogen removal. Excellent EBPR performance of effluent 0.8 ± 1.0 mg P/L and >99% removal efficiency was achieved fed with synthetic high-strength phosphorus wastewater. Long-term sludge acclimation proved that the dominant polyphosphate accumulating organisms (PAOs), Candidatus Accumulibacter, could evolve to a specific subtype that can tolerate the nitrite inhibition as revealed by operational taxonomic unit (OTU)-based oligotyping analysis. The EBPR kinetic and stoichiometric evaluations combined with the amplicon sequencing proved that the Candidatus Competibacter, as the dominant glycogen accumulating organisms (GAOs), could well coexist with PAOs (15.3-24.9% and 14.2-33.1%, respectively) and did not deteriorate the EBPR performance. The nitrification activity assessment, amplicon sequencing, and functional-based gene marker quantification verified that the unexpected nitrite accumulation (10.7-21.0 mg N/L) in the high-strength EBPR system was likely caused by the nitritation process, in which the nitrite-oxidizing bacteria (NOB) were successfully out-selected (<0.1% relative abundance). We hypothesized that the introduction of the anaerobic phase with high VFA concentrations could be the potential selection force for achieving nitritation based on the literature review and our preliminary batch tests. This study sheds light on developing a new feasible technical route for integrating EBPR with short-cut nitrogen removal for efficient high-strength wastewater treatment.

In this study, the IWA Activated Sludge Model No. 2d (ASM2d) was expanded to identify the most important mechanisms leading to the anoxic nitrous oxide (N 2 O) production in the combined nitrogen (N) and phosphorus (P) removal activated sludge systems. The new model adopted a three-stage denitrification concept and was evaluated against the measured data from one/two-phase batch experiments carried out with activated sludge withdrawn from a local, large-scale biological nutrient removal wastewater treatment plant. The experiments were focused on investigating the effects of different external carbon sources (acetate, ethanol) and electron acceptors (nitrite, nitrate) on the mechanisms of N 2 O production in enhanced biological P removal by polyphosphate accumulating organisms (PAOs) and external carbon-based denitrification by ordinary heterotrophic organisms (OHOs). The experimental results explicitly showed that N 2 O production was predominantly governed by the presence of nitrite in the reactor regardless of the examined carbon source and the ratio COD/N in the reactor. The model was capable of accurately predicting (with R 2  > 0.9) the behavior of not only N 2 O-N, but also NO 3 -N, NO 2 -N, soluble COD, and PO 4 -P. The simulation results revealed that only OHOs were responsible for N 2 O production, whereas the present denitrifying PAOs reduced only nitrate to nitrite. [ABSTRACT FROM AUTHOR]

The structure of Accumulibacter lineage was examined over a three-year period in six full-scale wastewater treatment plants and compared to the population in a laboratory-scale reactor. The Accumulibacter lineage reached 69% of all bacteria in the laboratory-scale reactor and contained clades IA and IIA,C,D only. In full-scale plants, Accumulibacter constituted up to 12%, correlated with sludge loading with BOD, COD, N and P. Clade IA was more abundant after periods with low temperatures, whereas clades IIA,C,D presented opposite variations. The fraction, unrevealed by clade-specific probes, constituted 31-62% of the Accumulibacter lineage in all but one full-scale plant - the population in the plant with significant industrial contribution in the influent resembled the low diversity in the laboratory-scale reactor. Selection of specific clades in the laboratory-scale reactor was associated with its different performance, despite stable operational conditions being maintained through the study. It implies that high relative abundance of Accumulibacter in bacterial community is not enough for efficient P removal and the effectiveness may also be associated with the presence of specific clades. A considerable fraction of Accumulibacter in full-scale plants, which is not targeted by clade-specific probes, should be further investigated to better characterize clades that may affect effectiveness of phosphorus removal. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N 2 O), a significant contributor to the greenhouse effect, is generated during the biological nutrient removal in wastewater treatment plants (WWTPs). Developing mathematical models estimating the N 2 O dynamics under changing operational conditions (e.g. dissolved oxygen, DO) is essential to design mitigation strategies. Based on the activated sludge models (ASM) structure, this work presents an ASM2d-N 2 O model including all the biological N 2 O production pathways for a municipal anaerobic/anoxic/oxic (A 2 /O) WWTP with biological removal of organic matter, nitrogen and phosphorus, and its application in different dynamic scenarios. Three microbial N 2 O production pathways were considered: nitrifier denitrification, hydroxylamine oxidation, and heterotrophic denitrification, with the first two being activated by ammonia oxidizing bacteria (AOB). A stripping effectivity (SE) coefficient was added to reflect the non-ideality of the stripping model. Partial nitrification and high N 2 O production via nitrifier denitrification were observed when the range of DO in the aerobic compartment was 1.8 to 2.5 mg·L −1 . It could imply that low aeration strategies lead to low overall carbon footprint provided complete nitrification is not hindered. The model predicted high N 2 O emissions when low DO (∼1.1 mg L −1 ) and high ammonium concentration concurred. With the AOB prevailing over the nitrite oxidizing bacteria (NOB), nitrite was accumulated, triggering the activation of the nitrifier denitrification pathway. After suddenly increasing the influent ammonium load, the AOB had a greater growth compared to the NOB and the same pathway was considered as N 2 O hotspot. Especially under conditions promoting partial nitrification (i.e. low DO) and raising the stripping effect importance (i.e. high SEs), the highest N 2 O emission factors were predicted. [ABSTRACT FROM AUTHOR]

Despite their stability and the widespread use of enhanced biological phosphorus removal (EBPR), little is known about their microbial composition and activity. In our study we investigated highthroughput pyrosequencing of bacterial communities from two full-scale EBPR reactors of South Africa. Findings indicated that both EBPRs harboured high bacterial similarity, ranging from 83 to 100% with a diverse community dominated by Proteobacteria (57.04 to 79.48% for failed EBPR and 61.7 to 85.39% for successful EBPR) throughout the five selected treatment zones with the exception of the fermenter (Bacteroidetes: 55.84%) from the successful EBPR. However, a lower dissimilarity was observed with the presence of 70 unique bacterial genera from successful EBPRs belonging to Gammaproteobacteria, Betaproteobacteria, and Actinobacteria, while 69 unique genera from failed EBPR belonged to Alphaproteobacteria, Betaproteobacteria, and Clostridia. The failed EBPR (54.58%) revealed less fermenting bacteria in the fermenter as compared to the successful EBPR (73.58%). More detrimental organisms and less nitrifying/denitrifying bacteria were also found in failed EBPR than in the successful EBPR, as well as phosphate-accumulating bacteria. Canonical correspondence analysis (CCA) displayed a very low relationship between microbial patterns, pH and DO - suggesting that these environmental factors played a major role in community dissimilarity. Aerobic zones appeared to have the highest dissimilarity between both EBPRs, with the failed EBPR predominated by Acidovorax (26.2%) and the successful EBPR with unclassified Rhodocyclaceae (37.24%). Furthermore, 21.47% of readings (failed EBPR) and 17.18% of readings (successful EBPR) could not be assigned to taxonomic classifications, highlighting the high diversity level of novel microbial species in such an environment. [ABSTRACT FROM AUTHOR]

Understanding the microbiology of phosphorus (P) removal is considered essential to knowledge-based optimization of enhanced biological P removal (EBPR) systems. Biological P removal is achieved in these systems by promoting the growth of organisms collectively known as the polyphosphate accumulating organisms (PAOs). Also considered important to EBPR are the glycogen accumulating organisms (GAOs), which are theorized to compete with the PAOs for resources at the expense of P removal efficiency. Numerous studies have sought to identify the PAOs and their GAOs competitors, with several candidates proposed for each over the last few decades. The current study collectively assessed the abundance and diversity of all proposed PAOs and GAOs in 18 Danish full-scale wastewater treatment plants with well-working biological nutrient removal over a period of 9 years using 16S rRNA gene amplicon sequencing. The microbial community structure in all plants was relatively stable over time. Evidence for the role of the proposed PAOs and GAOs in EBPR varies and is critically assessed, in light of their calculated amplicon abundances, to indicate which of these are important in full-scale systems. Bacteria from the genus Tetrasphaera were the most abundant of the PAOs. The “Candidatus Accumulibacter” PAOs were in much lower abundance and appear to be biased by the amplicon-based method applied. The genera Dechloromonas, Microlunatus, and Tessaracoccus were identified as abundant putative PAO that require further research attention. Interestingly, the actinobacterial Micropruina and sbr-gs28 phylotypes were among the most abundant of the putative GAOs. Members of the genera Defluviicoccus, Propionivibrio, the family Competibacteraceae, and the spb280 group were also relatively abundant in some plants. Despite observed high abundances of GAOs (periodically exceeding 20% of the amplicon reads), P removal performance was maintained, indicating that these organisms were not outcompeting the PAOs in these EBPR systems. Phylogenetic diversity within each of the PAOs and GAOs genera was observed, which is consistent with reported metabolic diversity for these. Whether or not key traits can be assigned to sub-genus level clades requires further investigation.