Prospective clinical-radiological study of the survival and behavior of short implants.

STATEMENT OF PROBLEM: Short implants are a therapeutic alternative for edentulous patients with severe bone resorption. Differences in peri-implant bone loss and complications of short implants depending on the type of connection are unclear. PURPOSE: The main purpose of this clinical study was to evaluate the survival rate after 2 years of the short implants in the Oxtein system (Proclinic). Secondary objectives were to compare implant survival, peri-implant bone loss, peri-implant mucosal status, and associated complications in internal hexagonal connection versus external hexagonal connection implants. MATERIAL AND METHODS: A randomized clinical trial was carried out in 14 patients with a mean age of 62.7 ±8.5 years, with a total of 61 Oxtein L35 and L6 Proclinic implants being placed at the Faculty of Dentistry. A descriptive analysis, simple binary logistic regression model using generalized estimating equations. and Kaplan-Meier survival analysis were carried out (α=.05). RESULTS: Implant survival was 85.2% (52/61). Failure of all implants occurred before prosthetic loading; bleeding after probing occurred in 28 implants, being greater among external connection implants (57.6%) P=.025. The presence of plaque appeared in 36 of the implants, without statistically significant differences between external connection (72.8%) and internal connection (60.0%) (P>.05). A total of 28 implants had at least 2 mm of keratinized mucosa, without statistically significant differences between external connection (63.6%) and internal connection (35.0%) P=.200. A total of 8 complications (13.1%) were recorded, including connection fractures, screw fracture, framework fracture, and buccal fenestrations. CONCLUSIONS: Short implants are a therapeutic solution to more complex surgical techniques. However, as lower survival has been reported, the characteristics of the implants and operator experience are important factors for their success.

Effects of a sidestream concentrated oxygen supply system on the membrane filtration performance of a high-loaded membrane bioreactor.

To investigate the influence of high-pressure and shear effects introduced by a concentrated oxygen supply system on the membrane filtration performance, a laboratory-scale membrane bioreactor (MBR) fed artificial municipal wastewater was operated continuously for 80 days in four phases equipped with different aerations systems: (P1) bubble diffusers (days 0-40), (P2) concentrated oxygen supply system, the supersaturated dissolved oxygen (SDOX) (days 41-56), (P3) bubble diffusers (days 57-74), and (P4) SDOX (days 75-80). Various sludge physical-chemical parameters, visual inspection of the membrane, and permeability evaluations were performed. Results showed that the high-pressure effects contributed to fouling of the membranes compared to the bubble diffuser aeration system. Biofouling by microorganisms appeared to be the main contributor to the cake layer when bubble diffusers were used, while fouling by organic matter seemed to be the main contributor to the cake layer when SDOX was used. Small particle size distribution (PSD) (ranging from 1 to 10 and 1-50 µm in size) fractions are a main parameter affecting the intense fouling of membranes (e.g., formation of a dense and thin cake layer). However, PSD alone cannot explain the worsened membrane fouling tendency. Therefore, it can be assumed that a combination of several factors (which certainly includes PSD) led to the severe membrane fouling caused by the high-pressure and shear.

Die-off of E. coli as fecal indicator organism on different surfaces after urban floods.

A better understanding of the effects of different urban and recreational surfaces on the die-off of water-borne pathogens that can cause infections after urban floods if released from surcharged combined sewers and other sources of fecal contamination is needed. The die-off of fecal indicator Escherichia coli was studied under controlled exposure to simulated sunlight on a range of different surfaces found in urban environments: gravel, sand, asphalt, pavement blocks, concrete, playground rubber tiles and grass, using glass as control. The surfaces were inoculated with artificial flooding water containing 105 colony forming units (CFU) of E. coli per mL and sampled periodically using the sterile cotton swab technique, after lowering the water level. The results show that dark inactivation was not statistically significant for any surface, suggesting that chemical composition and pH (varying between 6.5 ±â€¯0.8 and 9.2 ±â€¯0.4) did not affect the die-off rates. The highest light-induced die-off rates for E. coli after the floodwater recession, observed on rubber (>3.46 h-1) and asphalt (2.7 h-1), were attributed to temperature stress and loss of surface moisture.

Recent advances in bio-P modelling - a new approach verified by full-scale observations.

This paper summarizes recent developments in biological phosphorus removal modelling, with special attention to side-stream enhanced biological phosphorus removal (S2EBPR) systems on which previous models proved to be ineffective without case-by-case parameter adjustments. Through the research and experience of experts and practitioners, a new bio-kinetic model was developed including an additional group of biomass (glycogen accumulating organisms - GAOs) and new processes (such as aerobic and anoxic maintenance for PAO and GAO; enhanced denitrification processes; fermentation by PAOs which - along with PAO selection - is driven by oxidation-reduction potential (ORP)). This model successfully described various conditions in laboratory measurements and full plant data. The calibration data set is provided by Clean Water Services from Rock Creek Facility (Hillsboro, OR) including two parallel trains: conventional A2O and Westbank configurations, allowing the model to be verified on conventional and side-stream EBPR systems as well.

A new photo-activated sludge system for nitrification by an algal-bacterial consortium in a photo-bioreactor with biomass recycle.

Wastewater treatment technologies requiring large areas may be less feasible in urbanizing regions of developing countries. Therefore, a new technology, named photo-activated sludge (PAS), was investigated to combine the advantages of regular activated sludge systems with those of algae ponds for the removal of ammonium. The PAS consisted of a mixed photo-bioreactor, continuously fed with BG-11 medium, adjusted to 66 mgN-NH4⁺/l. The reactor volume was 2 l, hydraulic retention time was 24 hours, with a depth of 8 cm, and continuous illumination at the water surface was 66 µmol PAR/m²/s (photosynthetically active radiation). Reactor effluent passed through a settler and settled biomass was returned to the reactor. A well settling biomass developed, that contained both algae and nitrifiers. Effluent contained 10 mgN-NH4⁺/L and 51 mgN-NOx⁻/L. Using a simplified model, the specific algae growth rate was estimated at about 0.62 day⁻¹, which was within the expected range. For nitrifiers (ammonia oxidizers), the specific growth rate was 0.11 day⁻¹, which was lower than reported for regular activated sludge. The in-situ photo-oxygenation process by algae contributed 82% of the oxygen input, whereas oxygen diffusion through the mixed surface provided the remaining 18%. The foreseen energy savings that a PAS system could achieve warrant further investigations with real wastewater.

Dental treatments under sedation-analgesia in patients who are unable to collaborate: a prospective observational study.

Background: Excessive fear of dental procedures leads to disruptive behavior during dental examinations and treatments. Dental examinations and treatments of these patients usually require additional techniques, such as sedation. The most commonly used techniques are inhalation of nitrous oxide, infusion of propofol with fentanyl, and premedication and infusion of midazolam. Methods: A prospective observational epidemiological study was conducted on patients who required sedoanalgesia techniques for dental exploration and procedures. The reasons for the inability of patients to cooperate (excessive fear or intellectual disability), age, sex, weight, systemic pathology, oral pathology, treatment performed, time of intervention, anesthetic technique performed, and occurrence of complications were recorded. Results: In total, 218 patients were studied. Sixty-five patients came for fear of dental treatment and 153 for presenting with a diagnosis of intellectual disability and not collaborating in the treatment with local anesthesia. The average age of all patients was 30.54 ± 17.30 years. The most frequent oral pathologies found in patients with excessive fear were tartar (6.8%) and wisdom teeth (6.4%), followed by missing teeth (5%). In patients with disabilities, a combination of tartar and cavities appeared most frequently (41.3%), followed by cavities (15.6%). The most frequently used sedoanalgesia technique was the infusion of propofol with fentanyl in both groups of patients, followed by nitrous oxide. Conclusion: The combination of propofol and fentanyl was the most frequently used alternative in patients who were unable to collaborate because of intellectual disability or carry out longer or more complex treatments. Inhaled nitrous oxide and midazolam were the sedative techniques of choice for simpler oral treatments, such as tartrectomies, shallow obturations, and shorter interventions, or in younger patients.

Dental treatment under general anesthesia in patients with severe intellectual disability at the Gregorio Marañón General University Hospital: a 10-year retrospective study.

OBJECTIVES: There is a high demand for dental treatment in a hospital setting for patients with severe intellectual disability (ID), due to their inability to cooperate. The objective was to determine the types of dental treatment carried out on patients with severe ID, as well as the possibility of performing clinical and radiographic examinations prior to treatment and to identify their characteristics. METHOD AND MATERIALS: A retrospective observational study was performed, based on the medical histories of patients with severe ID or a disability included in the portfolio of dental services of Community of Madrid, who underwent dental treatment at the Stomatology Service of the Gregorio Marañón General University Hospital from the year 2009 to 2019. Data on age, sex, etiology of disability, and dental treatment were obtained. RESULTS: A total of 1,845 patients were included. The type of disability in the majority of cases was unknown, followed by encephalopathy, cerebral paralysis, and Down syndrome. In total, 8,439 dental extractions were performed on 1,548 patients (83.9%). Clinical and radiographic exploration were carried out on 874 patients (47.4%). CONCLUSIONS: Ultrasonic scaling was the most frequently performed treatment in patients. Dental extractions were the next most common treatment. An increase in age showed a higher demand for surgical procedures and extractions. Over half of the patients (52.6%) did not tolerate clinical or radiographic examinations.

Putative metabolism of Ca. Accumulibacter via the utilization of glucose.

Ca. Accumulibacter was the predominant microorganism (relative FISH bio-abundance of 67 ± 5%) in a lab-scale sequential batch reactor that accomplished enhanced biological phosphorus removal (EBPR) while using glucose and acetate as the carbon sources (1:1 COD-based ratio). Both organic compounds were completely anaerobically consumed. The reactor's performance in terms of P/C ratio, phosphorous release and uptake, and overall kinetic and stoichiometric parameters were on the high end of the reported spectrum for EBPR systems (100:9.3 net mg phosphate removal per mg COD consumed when using glucose and acetate in a 1:1 ratio). The batch tests showed that, to the best of our knowledge, this is the first time a reactor enriched with Ca. Accumulibacter can putatively utilize glucose as the sole carbon source to biologically remove phosphate (COD:P (mg/mg) removal ratio of 100:6.3 when using only glucose). Thus, this research proposes that Ca. Accumulibacter directly anaerobically stored the fed glucose primarily as glycogen by utilizing the ATP provided via the hydrolysis of poly-P and secondarily as PHA by balancing its ATP utilization (glycogen generation) and formation (PHA storage). Alternative hypotheses are also discussed. The reported findings could challenge the conventional theories of glucose assimilation by Ca. Accumulibacter, and can be of significance for the biological removal of phosphorus from wastewaters with high contents of fermentable compounds or low VFAs.

Brain complications from odontogenic infections: A systematic review.

PURPOSE: Odontogenic infections can spread through different routes to more remote anatomical areas, such as the brain. Brain abscesses have an incidence of 0.3-1.3 / 100,000 population and only 2-5% are of dental origin. The main objective is to research brain complications derived from odontogenic infections. Secondary objectives were to identify the most common symptoms in brain abscess, to describe the microbiology involved in these infectious processes, report which parts of the brain complex are most commonly affected and report the sequelae of this patients. METHODS: A systematic review following the PRISMA Guide and the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Case Reports was carried out in PubMed, Scopus and Web of Science. The search terms were: Brain infection, brain abscess, oral health oral origin, odont* infect*. RESULTS: The database search identified a total of 1000 articles. A total of 18 publications were identified after applying inclusion and exclusion criteria. A total of 38 patients were analyzed. Mean age was 49.64±18.80 years. CONCLUSION: The most common symptoms of patients with brain abscess are neurological affectations first and then fever and headache second, without necessarily presenting as a symptomatological triad. Microbiological diagnosis is key to determining the origin of the infection. Anaerobic pathogens such as Streptococcus (F. Milleri), Fusobacterium Nucleatum and Porfiromonas Gingivalis families are common bacterial agents. The frontal lobe is the most frequently affected, followed by the parietal and temporal lobe. The most frequent brain complications are neurological disorders. However, most patients with brain abscesses recover without sequelae.

Supersaturated-oxygen aeration effects on a high-loaded membrane bioreactor (HL-MBR): Biological performance and microbial population dynamics.

Conventional diffused aeration systems (such as fine-bubble diffusers) exhibit a poor oxygen transfer in wastewater treatment plants (WWTPs), particularly when operating at sludge concentrations higher than 15 g L-1. The supersaturated dissolved oxygen (SDOX) system has been proposed as an alternative for supplying dissolved oxygen (DO) at high mixed liquor suspended solids (MLSS) concentrations. The advantages introduced by such technology include the possibility of operating WWTPs at much higher than usual MLSS concentrations, increasing the treatment capacity of WWTPs. Recent studies have demonstrated that the SDOX system has higher oxygen transfer rates (OTRs) and oxygen transfer efficiencies (OTEs) relative to fine-bubble diffusers. However, it is unknown if the high-pressure conditions introduced by SDOX may possibly impact the biological performance of WWTPs. In this study, the effects of SDOX technology on the biological performance of a membrane bioreactor (MBR) were evaluated. The MBR was operated at an MLSS concentration of approximately 15 g L-1 in four phases as follows: (P1) with bubble diffusers, (P2) with an SDOX unit, (P3) with the bubble diffusers, and (P4) with the SDOX unit. The performance of the MBR was assessed by monitoring the sludge concentration, as well as changes in the particle size distribution (PSD), sludge activity, organic matter removal and nitrification performance, and changes in the microbial community within the MBR. The operational conditions exerted by the SDOX technology did not affect the concentration of active biomass during the study period. The biological performance of the MBR was not affected by the introduction of the SDOX technology. Finally, the microbial community was relatively stable although some variations at the family and genus level were evident during each of the study phases. Therefore, the SDOX system can be proposed as an alternative technology for DO supply in WWTPs increasing the overall treatment capacity.

Use of near-infrared spectroscopy on predicting wastewater constituents to facilitate the operation of a membrane bioreactor.

The use of near-infrared (NIR) spectroscopy in wastewater treatment has continuously expanded. As an alternative to conventional analytical methods for monitoring constituents in wastewater treatment processes, the use of NIR spectroscopy is considered to be cost-effective and less time-consuming. NIR spectroscopy does not distort the measured sample in any way as no prior treatment is required, making it a waste-free technique. On the negative side, one has to be very well versed with chemometric techniques to interpret the results. In this study, filtered and centrifuged wastewater and sludge samples from a lab-scale membrane bioreactor (MBR) were analysed. Two analytical methods (conventional and NIR spectroscopy) were used to determine and compare major wastewater constituents. Particular attention was paid to soluble microbial products (SMPs) and extracellular polymeric substances (EPSs) known to promote membrane fouling. The parameters measured by NIR spectroscopy were analysed and processed with partial least squares regression (PLSR) and artificial neural networks (ANN) models to assess whether the evaluated wastewater constituents can be monitored by NIR spectroscopy. Very good results were obtained with PLSR models, except for the determination of SMP, making the model qualitative rather than quantitative for their monitoring. ANN showed better performance in terms of correlation of NIR spectra with all measured parameters, resulting in correlation coefficients higher than 0.97 for training, testing, and validation in most cases. Based on the results of this research, the combination of NIR spectra and chemometric modelling offers advantages over conventional analytical methods.

Inactivation of indicator organisms on different surfaces after urban floods.

The high frequency and intensity of urban floods caused by climate change, urbanisation and infrastructure failures increase public health risks when the flood water contaminated from combined sewer overflows (CSOs) or other sources of faecal contamination remains on urban surfaces. This study contributes to a better understanding of the effects of urban and recreational surfaces on the occurrence of waterborne pathogens. The inactivation of selected indicator organisms was studied under controlled exposure to artificial sunlight for 6 h followed by 18 h in dark conditions. Concrete, asphalt, pavement blocks and glass as control were inoculated with artificial floodwater containing, as indicator organisms, Escherichia coli bacteria, which are common faecal indicator bacteria (FIB) for water quality assessment, Bacillus subtilis spores chosen as surrogates for Cryptosporidium parvum oocysts and Giardia cysts, and bacteriophages MS2 as indicators for viral contamination. On practically all the surfaces in this study, E. coli had the highest inactivation under light conditions followed by MS2 and B. subtilis, except asphalt where MS2 was inactivated faster. The highest inactivation under light conditions was seen with E. coli on a concrete surface (pH 9.6) with an inactivation rate of 1.85 h-1. However, the pH of the surfaces (varying between 7.0 and 9.6) did not have any influence on inactivation rates under dark conditions. MS2 bacteriophage had the highest inactivation under light conditions on asphalt with a rate of 1.29 h-1. No die-off of B. subtilis spores was observed on any of the surfaces during the experiment, neither in light nor in dark conditions. This study underpins the need to use different indicator organisms to test their inactivation after flooding. It also suggests that given the sunlight conditions, concentration of indicator organisms and type of surface, the fate of waterborne pathogens after a flood could be estimated.

Plant Organellar DNA Polymerases Evolved Multifunctionality through the Acquisition of Novel Amino Acid Insertions.

The majority of DNA polymerases (DNAPs) are specialized enzymes with specific roles in DNA replication, translesion DNA synthesis (TLS), or DNA repair. The enzymatic characteristics to perform accurate DNA replication are in apparent contradiction with TLS or DNA repair abilities. For instance, replicative DNAPs incorporate nucleotides with high fidelity and processivity, whereas TLS DNAPs are low-fidelity polymerases with distributive nucleotide incorporation. Plant organelles (mitochondria and chloroplast) are replicated by family-A DNA polymerases that are both replicative and TLS DNAPs. Furthermore, plant organellar DNA polymerases from the plant model Arabidopsis thaliana (AtPOLIs) execute repair of double-stranded breaks by microhomology-mediated end-joining and perform Base Excision Repair (BER) using lyase and strand-displacement activities. AtPOLIs harbor three unique insertions in their polymerization domain that are associated with TLS, microhomology-mediated end-joining (MMEJ), strand-displacement, and lyase activities. We postulate that AtPOLIs are able to execute those different functions through the acquisition of these novel amino acid insertions, making them multifunctional enzymes able to participate in DNA replication and DNA repair.

Temperature effects on glycogen accumulating organisms.

Glycogen accumulating organisms (GAO) compete for substrate with polyphosphate-accumulating organisms (PAO), which are the microorganisms responsible for the enhanced biological phosphorus removal (EBPR) in activated sludge wastewater treatment systems. This can lead to the deterioration of the EBPR process. In this paper, the long-term temperature effects on the anaerobic and aerobic stoichiometry and conversion rates on adapted enriched cultures of Competibacter (a known GAO) were evaluated from 10 to 40 degrees C. The anaerobic stoichiometry of Competibacter was constant from 15 to 35 degrees C, whereas the aerobic stoichiometry was insensitive to temperature changes from 10 to 30 degrees C. At 10 degrees C, likely due to the inhibition of the anaerobic conversions of Competibacter, a switch in the dominant bacterial population to an enriched Accumulibacter culture (a known PAO) was observed. At higher temperatures (35 and 40 degrees C), the aerobic processes limited the growth of Competibacter. Due to the inhibition or different steady-state (equilibrium) conditions reached at long-term by the metabolic conversions, the short- and long-term temperature dependencies of the anaerobic acetate uptake rate of Competibacter differed considerably between each other. Temperature coefficients for the various metabolic processes are derived, which can be used in activated sludge modeling. Like for PAO cultures: (i) the GAO metabolism appears oriented at restoring storage pools rather than fast microbial growth, and (ii) the aerobic growth rate of GAO seems to be a result of the difference between PHA consumption and PHA utilization for glycogen synthesis and maintenance. It appears that the proliferation of Competibacter in EBPR systems could be suppressed by adjusting the aerobic solids retention time while, aiming at obtaining highly enriched PAO cultures, EBPR lab-scale reactors could be operated at low temperature (e.g. 10 degrees C).

Modeling the PAO-GAO competition: effects of carbon source, pH and temperature.

The influence of different carbon sources (acetate to propionate ratios), temperature and pH levels on the competition between polyphosphate- and glycogen-accumulating organisms (PAO and GAO, respectively) was evaluated using a metabolic model that incorporated the carbon source, temperature and pH dependences of these microorganisms. The model satisfactorily described the bacterial activity of PAO (Accumulibacter) and GAO (Competibacter and Alphaproteobacteria-GAO) laboratory-enriched cultures cultivated on propionate (HPr) and acetate (HAc) at standard conditions (20 degrees C and pH 7.0). Using the calibrated model, the effects of different influent HAc to HPr ratios (100-0, 75-25, 50-50 and 0-100%), temperatures (10, 20 and 30 degrees C) and pH levels (6.0, 7.0 and 7.5) on the competition among Accumulibacter, Competibacter and Alphaproteobacteria-GAO were evaluated. The main aim was to assess which conditions were favorable for the existence of PAO and, therefore, beneficial for the biological phosphorus removal process in sewage treatment plants. At low temperature (10 degrees C), PAO were the dominant microorganisms regardless of the used influent carbon source or pH. At moderate temperature (20 degrees C), PAO dominated the competition when HAc and HPr were simultaneously supplied (75-25 and 50-50% HAc to HPr ratios). However, the use of either HAc or HPr as sole carbon source at 20 degrees C was not favorable for PAO unless a high pH was used (7.5). Meanwhile, at higher temperature (30 degrees C), GAO tended to be the dominant microorganisms. Nevertheless, the combined presence of acetate and propionate in the influent (75-25 and 50-50% HAc to HPr ratios) as well as a high pH (7.5) appear to be potential factors to favor the metabolism of PAO over GAO at higher sewage temperature (30 degrees C).

Manejo quirúrgico del paciente con patología pseudoquística sinusal: a propósito de un caso / Surgical management of the patient with sinusal pseudocyst pathology: a case report

Introducción: la patología sinusal puede comprometer el éxito del tratamiento de implantes. Existe una elevada incidencia de patología sinusal. El tratamiento de esta patología puede implicar a otros profesionales, lo que supone un mayor coste sanitarios y demora en la realización de los tratamientos de implantes. El objetivo del presente artículo es presentar un caso clínico representativo de la patología pseudoquística del seno maxilar y una alternativa de su manejo quirúrgico simultáneo a la regeneración ósea requerida para su posterior rehabilitación mediante implantes, así como actualizar la evidencia científica disponible. Caso clínico: se presenta una paciente de 46 años con una lesión pseudoquística sinusal que es remitida para rehabilitar mediante implantes en 1.4 y 1.7, por movilidad y dolor en relación a prótesis fija dentosoportada en maxilar derecho. Se realiza el tratamiento quirúrgico de exodoncias, elevación de seno maxilar y eliminación de la lesión pseudoquística de manera simultánea. Discusión: existe controversia sobre el momento idóneo para realizar el tratamiento sinusal. Algunos estudios muestran éxito de la cirugía endoscópica simultáneamente a la eliminación de la fuente odontogénica. Otros han demostrado que realizar primero la cirugía sinusal tiene el mismo porcentaje de curación que realizar primero el tratamiento odontológico. Conclusión: el diagnóstico de la patología y la planificación quirúrgica deben tener en cuenta el tipo de patología, la extensión y las necesidades de tratamiento del paciente. El manejo quirúrgico de la patología sinusal de manera simultánea a la regeneración ósea es una alternativa segura y beneficiosa para el paciente. (AU)

Introduction: Sinus pathology can compromise the success of implant treatment. There is a high incidence of sinus pathology. The treatment of this pathology may involve other professionals, which means higher healthcare costs and delays in carrying out implant treatments. Besides updating available scientific evidence, the objective of this article is to present a representative clinical case of pseudocystic pathology of the maxillary sinus and an alternative to its simultaneous surgical management in the bone regeneration required for subsequent rehabilitation using implants. Clinical case: A 46-year-old patient with a pseudocystic sinus lesion, referred for rehabilitation using implants in 1.4 and 1.7, due to mobility and pain in relation to a tooth-supported fixed prosthesis in the right maxilla. The surgical treatment, consisting of extractions, maxillary sinus elevation and removal of the pseudocystic lesion, was performed simultaneously. Discussion: There is controversy about the ideal time to perform sinus treatment. Some studies show success of endoscopic surgery simultaneously with removal of the odontogenic source. Others have shown that performing sinus surgery first has the same cure rate as performing dental treatment first. Conclusion: Pathology diagnosis and surgical planning must take into account the type and extent of the pathology and the treatment needs of the patient. Surgical management of sinus pathology simultaneously with bone regeneration is a safe and beneficial alternative for the patient. (AU)

Effect of Lactate on the Microbial Community and Process Performance of an EBPR System.

Candidatus Accumulibacter phosphatis is in general presented as the dominant organism responsible for the biological removal of phosphorus in activated sludge wastewater treatment plants. Lab-scale enhanced biological phosphorus removal (EBPR) studies, usually use acetate as carbon source. However, the complexity of the carbon sources present in wastewater could allow other potential poly-phosphate accumulating organism (PAOs), such as putative fermentative PAOs (e.g., Tetrasphaera), to proliferate in coexistence or competition with Ca. Accumulibacter. This research assessed the effects of lactate on microbial selection and process performance of an EBPR lab-scale study. The addition of lactate resulted in the coexistence of Ca. Accumulibacter and Tetrasphaera in a single EBPR reactor. An increase in anaerobic glycogen consumption from 1.17 to 2.96 C-mol/L and anaerobic PHV formation from 0.44 to 0.87 PHV/PHA C-mol/C-mol corresponded to the increase in the influent lactate concentration. The dominant metabolism shifted from a polyphosphate-accumulating metabolism (PAM) to a glycogen accumulating metabolism (GAM) without EBPR activity. However, despite the GAM, traditional glycogen accumulating organisms (GAOs; Candidatus Competibacter phosphatis and Defluvicoccus) were not detected. Instead, the 16s RNA amplicon analysis showed that the genera Tetrasphaera was the dominant organism, while a quantification based on FISH-biovolume indicated that Ca. Accumulibacter remained the dominant organism, indicating certain discrepancies between these microbial analytical methods. Despite the discrepancies between these microbial analytical methods, neither Ca. Accumulibacter nor Tetrasphaera performed biological phosphorus removal by utilizing lactate as carbon source.

Limitations imposed by conventional fine bubble diffusers on the design of a high-loaded membrane bioreactor (HL-MBR).

The operation of membrane bioreactors (MBRs) at higher than usual mixed liquor suspended solids (MLSS) concentrations may enhance the loading rate treatment capacity while minimizing even further the system's footprint. This requires operating the MBR at the highest possible MLSS concentration and biomass activity (e.g., at high loading rates and low solid retention times (SRTs)). Both a negative effect of the MLSS concentrations and a positive effect of the SRT on the oxygen transfer have been reported when using conventional fine bubble diffusers. However, most of the evaluations have been carried out either at extremely high SRTs or at low MLSS concentrations eventually underestimating the effects of the MLSS concentration on the oxygen transfer. This research evaluated the current limitations imposed by fine bubble diffusers in the context of the high-loaded MBR (HL-MBR) (i.e., high MLSS and short SRT-the latter emulated by concentrating municipal sludge from a wastewater treatment plant (WWTP) operated at a short SRT of approximately 5 days). The high MLSS concentrations and the short SRT of the original municipal sludge induced a large fraction of mixed liquor volatile suspended solids (MLVSS) in the sludge, promoting a large amount of sludge flocs that eventually accumulated on the surface of the bubbles and reduced the free water content of the suspension. Moreover, the short SRTs at which the original municipal sludge was obtained eventually appear to have promoted the accumulation of surfactants in the sludge mixture. This combination exhibited a detrimental effect on the oxygen transfer. Fine bubble diffusers limit the maximum MLSS concentration for a HL-MBR at 30 g L-1; beyond that point is either not technically or not economically feasible to operate; an optimum MLSS concentration of 20 g L-1 is suggested to maximize the treatment capacity while minimizing the system's footprint.

Temperature effects on the aerobic metabolism of glycogen-accumulating organisms.

Short-term temperature effects on the aerobic metabolism of glycogen-accumulating organisms (GAO) were investigated within a temperature range from 10 to 40 degrees C. Candidatus Competibacter Phosphatis, known GAO, were the dominant microorganisms in the enriched culture comprising 93 +/- 1% of total bacterial population as indicated by fluorescence in situ hybridization (FISH) analysis. Between 10 and 30 degrees C, the aerobic stoichiometry of GAO was insensitive to temperature changes. Around 30 degrees C, the optimal temperature for most of the aerobic kinetic rates was found. At temperatures higher than 30 degrees C, a decrease on the aerobic stoichiometric yields combined with an increase on the aerobic maintenance requirements were observed. An optimal overall temperature for both anaerobic and aerobic metabolisms of GAO appears to be found around 30 degrees C. Furthermore, within a temperature range (10-30 degrees C) that covers the operating temperature range of most of domestic wastewater treatment systems, GAOs aerobic kinetic rates exhibited a medium degree of dependency on temperature (theta = 1.046-1.090) comparable to that of phosphorus accumulating organisms (PAO). We conclude that GAO do not have metabolic advantages over PAO concerning the effects of temperature on their aerobic metabolism, and competitive advantages are due to anaerobic processes.

Factors affecting the microbial populations at full-scale enhanced biological phosphorus removal (EBPR) wastewater treatment plants in The Netherlands.

The influence of operating and environmental conditions on the microbial populations of the enhanced biological phosphorus removal (EBPR) process at seven full-scale municipal activated sludge wastewater treatment plants (WWTPs) in The Netherlands was studied. Data from the selected WWTPs concerning process configuration, operating and environmental conditions were compiled. The EBPR activity from each plant was determined by execution of anaerobic-anoxic-aerobic batch tests using fresh activated sludge. Fractions of Accumulibacter as potential phosphorus accumulating organisms (PAO), and Competibacter, Defluviicoccus-related microorganisms and Sphingomonas as potential glycogen accumulating organisms (GAO) were quantified using fluorescence in situ hybridization (FISH). The relationships among plant process configurations, operating parameters, environmental conditions, EBPR activity and microbial populations fractions were evaluated using a statistical approach. A well-defined and operated denitrification stage and a higher mixed liquor pH value in the anaerobic stage were positively correlated with the occurrence of Accumulibacter. A well-defined denitrification stage also stimulated the development of denitrifying PAO (DPAO). A positive correlation was observed between Competibacter fractions and organic matter concentrations in the influent. Nevertheless, Competibacter did not cause a major effect on the EBPR performance. The observed Competibacter fractions were not in the range that would have led to EBPR deterioration. Likely, the low average sewerage temperature (12+/-2 degrees C) limited their proliferation. Defluviicoccus-related microorganisms were seen only in negligible fractions in a few plants (<0.1% as EUB), whereas Sphingomonas were not observed.