Establishment and Validation of Pathogenic CS17+ and CS19+ Enterotoxigenic Escherichia coli Challenge Models in the New World Primate Aotus nancymaae.

Enterotoxigenic Escherichia coli (ETEC) is a common cause of diarrheal illness in the military, travelers, and children living in low- to middle-income countries. Increased antibiotic resistance, the absence of a licensed vaccine, and the lack of broadly practical therapeutics perpetuate the significant health and financial burden resulting from ETEC infection. A critical step in the evaluation of vaccines and therapeutics is preclinical screening in a relevant animal disease model that closely replicates human disease. We previously developed a diarrheal model of class 5a colonization factor (CF) CFA/I-expressing ETEC in the New World owl monkey species Aotus nancymaae using ETEC strain H10407. In order to broaden the use of the model, we report here on the development of A. nancymaae models of ETEC expressing the class 5b CFs CS17 and CS19 with strains LSN03-016011/A and WS0115A, respectively. For both models, we observed diarrheal attack rates of ≥80% after oral inoculation with 5 × 1011 CFU of bacteria. These models will aid in assessing the efficacy of future ETEC vaccine candidates and therapeutics.

Personalized Therapeutic Cocktail of Wild Environmental Phages Rescues Mice from Acinetobacter baumannii Wound Infections.

Multidrug-resistant bacterial pathogens are an increasing threat to public health, and lytic bacteriophages have reemerged as a potential therapeutic option. In this work, we isolated and assembled a five-member cocktail of wild phages against Acinetobacter baumannii and demonstrated therapeutic efficacy in a mouse full-thickness dorsal infected wound model. The cocktail lowers the bioburden in the wound, prevents the spread of infection and necrosis to surrounding tissue, and decreases infection-associated morbidity. Interestingly, this effective cocktail is composed of four phages that do not kill the parent strain of the infection and one phage that simply delays bacterial growth in vitro via a strong but incomplete selection event. The cocktail here appears to function in a combinatorial manner, as one constituent phage targets capsulated A. baumannii bacteria and selects for loss of receptor, shifting the population to an uncapsulated state that is then sensitized to the remaining four phages in the cocktail. Additionally, capsule is a known virulence factor for A. baumannii, and we demonstrated that the emergent uncapsulated bacteria are avirulent in a Galleria mellonella model. These results highlight the importance of anticipating population changes during phage therapy and designing intelligent cocktails to control emergent strains, as well as the benefits of using phages that target virulence factors. Because of the efficacy of this cocktail isolated from a limited environmental pool, we have established a pipeline for developing new phage therapeutics against additional clinically relevant multidrug-resistant pathogens by using environmental phages sourced from around the globe.

Evaluation of Gallium Citrate Formulations against a Multidrug-Resistant Strain of Klebsiella pneumoniae in a Murine Wound Model of Infection.

Skin and soft tissue infections (SSTIs) are a common occurrence in health care facilities with a heightened risk for immunocompromised patients. Klebsiella pneumoniae has been increasingly implicated as the bacterial agent responsible for SSTIs, and treatment can be challenging as more strains become multidrug resistant (MDR). Therefore, new treatments are needed to counter this bacterial pathogen. Gallium complexes exhibit antimicrobial activity and are currently being evaluated as potential treatment for bacterial infections. In this study, we tested a topical formulation containing gallium citrate (GaCi) for the treatment of wounds infected with K. pneumoniae. First, the MIC against K. pneumoniae ranged from 0.125 to 2.0 µg/ml GaCi. After this in vitro efficacy was established, two topical formulations with GaCi (0.1% [wt/vol] and 0.3% [wt/vol]) were tested in a murine wound model of MDR K. pneumoniae infection. Gross pathology and histopathology revealed K. pneumoniae-infected wounds appeared to close faster with GaCi treatment and were accompanied by reduced inflammation compared to those of untreated controls. Similarly, quantitative indications of infection remediation, such as reduced weight loss and wound area, suggested that treatment improved outcomes compared to those of untreated controls. Bacterial burdens were measured 1 and 3 days following inoculation, and a 0.5 to 1.5 log reduction of CFU was observed. Lastly, upon scanning electron microscopy analysis, GaCi treatment appeared to prevent biofilm formation on dressings compared to those of untreated controls. These results suggest that with more preclinical testing, a topical application of GaCi may be a promising alternative treatment strategy for K. pneumoniae SSTI.

Rare taxa have potential to make metabolic contributions in enhanced biological phosphorus removal ecosystems.

Enhanced biological phosphorus removal (EBPR) relies on diverse but specialized microbial communities to mediate the cycling and ultimate removal of phosphorus from municipal wastewaters. However, little is known about microbial activity and dynamics in relation to process fluctuations in EBPR ecosystems. Here, we monitored temporal changes in microbial community structure and potential activity across each bioreactor zone in a pilot-scale EBPR treatment plant by examining the ratio of small subunit ribosomal RNA (SSU rRNA) to SSU rRNA gene (rDNA) over a 120 day study period. Although the majority of operational taxonomic units (OTUs) in the EBPR ecosystem were rare, many maintained high potential activities based on SSU rRNA : rDNA ratios, suggesting that rare OTUs contribute substantially to protein synthesis potential in EBPR ecosystems. Few significant differences in OTU abundance and activity were observed between bioreactor redox zones, although differences in temporal activity were observed among phylogenetically cohesive OTUs. Moreover, observed temporal activity patterns could not be explained by measured process parameters, suggesting that other ecological drivers, such as grazing or viral lysis, modulated community interactions. Taken together, these results point towards complex interactions selected for within the EBPR ecosystem and highlight a previously unrecognized functional potential among low abundance microorganisms in engineered ecosystems.

Validation of a novel murine wound model of Acinetobacter baumannii infection.

Patients recovering from traumatic injuries or surgery often require weeks to months of hospitalization, increasing the risk for wound and surgical site infections caused by ESKAPE pathogens, which include A. baumannii (the ESKAPE pathogens are Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). As new therapies are being developed to counter A. baumannii infections, animal models are also needed to evaluate potential treatments. Here, we present an excisional, murine wound model in which a diminutive inoculum of a clinically relevant, multidrug-resistant A. baumannii isolate can proliferate, form biofilms, and be effectively treated with antibiotics. The model requires a temporary, cyclophosphamide-induced neutropenia to establish an infection that can persist. A 6-mm-diameter, full-thickness wound was created in the skin overlying the thoracic spine, and after the wound bed was inoculated, it was covered with a dressing for 7 days. Uninoculated control wounds healed within 13 days, whereas infected, placebo-treated wounds remained unclosed beyond 21 days. Treated and untreated wounds were assessed with multiple quantitative and qualitative techniques that included gross pathology, weight loss and recovery, wound closure, bacterial burden, 16S rRNA community profiling, histopathology, peptide nucleic acid-fluorescence in situ hybridization, and scanning electron microscopy assessment of biofilms. The range of differences that we are able to identify with these measures in antibiotic- versus placebo-treated animals provides a clear window within which novel antimicrobial therapies can be assessed. The model can be used to evaluate antimicrobials for their ability to reduce specific pathogen loads in wounded tissues and clear biofilms. Ultimately, the mouse model approach allows for highly powered studies and serves as an initial multifaceted in vivo assessment prior to testing in larger animals.

Relationship between alcohol consumption prior to sex, unprotected sex and prevalence of STI/HIV among socially marginalized men in three coastal cities of Peru.

This article presents data about the relationship between alcohol consumption prior to sex and unprotected sex and the prevalence of at least one sexually transmitted infection (STI) including HIV among socially marginalized men in three coastal Peruvians cities. During an epidemiological survey with 2,146 men, we assessed their STI prevalence, frequency of alcohol consumption prior to sex, unprotected sex and other sexual risk behaviors. The overall prevalence of at least one STI/HIV was 8.5 % (95 % CI 7.3-9.7), the prevalence of unprotected sex was 79.1 % (95 % CI 77.8-80.3) and alcohol consumption prior to sex with any of the last five sex partners in the previous 6 months was 68.9 % (95 % CI 66.9-70.9). Bivariate and multivariate analysis showed that alcohol consumption of participants or their partners prior to sex were associated with the prevalence of at least one STI, adjusted Prevalence Ratio (aPR) = 1.3 (95 % CI 1.01-1.68). Unprotected sex was significantly associated with alcohol consumption prior to sex when both partners used alcohol, aPR = 1.15 (95 % CI 1.10-1.20) or when either one of them used alcohol aPR = 1.14 (95 % CI 1.09-1.18). These findings concur with previous literature suggesting a relationship between alcohol consumption prior to sex and STI and HIV. These data improve our understanding of this relationship in this context and could be used to enhance STI and HIV prevention strategies for socially marginalized men in Peru.

Detection of human leptospirosis as a cause of acute fever by capture ELISA using a Leptospira interrogans serovar Copenhageni (M20) derived antigen.

BACKGROUND: Leptospirosis is a potentially lethal zoonosis mainly affecting low-resource tropical countries, including Peru and its neighbouring countries. Timely diagnosis of leptospirosis is critical but may be challenging in the regions where it is most prevalent. The serodiagnostic gold standard microagglutination test (MAT) may be technically prohibitive. Our objective in this study was to assess the sensitivity, specificity, and predictive value of an IgM antibody capture enzyme-linked immunoassay (MAC-ELISA) derived from the M20 strain of Leptospira interrogans serovar Copenhageni (M20) by comparison to MAT, which was used as the gold standard method of diagnosis. METHODS: Acute and convalescent sera from participants participating in a passive febrile surveillance study in multiple regions of Peru were tested by both IgM MAC-ELISA and MAT. The sensitivity, specificity, positive and negative predictive value (PPV, NPV) of the MAC-ELISA assay for acute, convalescent and paired sera by comparison to MAT were calculated. RESULTS: The sensitivity, specificity, PPV and NPV of the MAC-ELISA assay for acute sera were 92.3%, 56.0%, 35.3% and 96.6% respectively. For convalescent sera, the sensitivity, specificity, PPV and NPV of the MAC-ELISA assay were 93.3%, 51.5%, 63.6% and 89.5% respectively. For paired sera, the sensitivity, specificity, PPV and NPV of the MAC-ELISA assay were 93.6%, 37.5%, 59.2%, 85.7% respectively. CONCLUSIONS: The M20 MAC-ELISA assay performed with a high sensitivity and low specificity in the acute phase of illness. Sensitivity was similar as compared with MAT in the convalescent phase and specificity remained low. Paired sera were the most sensitive but least specific by comparison to MAT serodiagnosis. NPV for acute, convalescent and paired sera was high. The limited specificity and high sensitivity of the MAC-ELISA IgM suggests that it would be most valuable to exclude leptospirosis in low-resource regions that lack immediate access to definitive reference laboratory techniques such as MAT.

Biological removal of phyto-sterols in pulp mill effluents.

Phyto-sterols and extractives found in pulp mill effluents are suspected to cause endocrine abnormalities in receiving water fish. The control of sterols in pulp mill effluents through biological secondary wastewater treatment was studied using two lab-scale bioreactor systems. After achieving a stable performance, both bioreactor systems successfully removed (>90%) sterols and the estimated biodegradation was up to 80%. Reactor 1 system operating at 6.7 ± 0.2 pH effectively treated pulp mill effluent sterols spiked up to 4500 µg/L in 11 h HRT and 11 day SRT. However, Reactor 2 system operating at 7.6 ± 0.2 pH performed relatively poorly. Retention time reductions beyond critical values deteriorated the performance of treatment systems and quickly reduced the sterols biodegradation. The biodegradation loss was indicated by mixed liquor sterols content that started increasing. This biodegradation loss was compensated by the increased role of bio-adsorption and the overall sterols removal remained relatively high. Hence, a relatively small (20-30%) loss in the overall sterols removal efficiency did not fully reflect the associated major (60-70%) loss in the sterols biodegradation because the amount of sterols accumulated in the sludge due to adsorption increased so the estimate of sterols removal through adsorption increased from 30-40% to 70-80% keeping the overall sterols removal still high.

Antibody induction in mice by liposome-displayed recombinant enterotoxigenic Escherichia coli (ETEC) colonization antigens.

BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) strains cause infectious diarrhea and colonize host intestine epithelia via surface-expressed colonization factors. Colonization factor antigen I (CFA/I), a prevalent ETEC colonization factor, is a vaccine target since antibodies directed to this fimbria can block ETEC adherence and prevent diarrhea. METHODS: Two recombinant antigens derived from CFA/I were investigated with a vaccine adjuvant system that displays soluble antigens on the surface of immunogenic liposomes. The first antigen, CfaEB, is a chimeric fusion protein comprising the minor (CfaE) and major (CfaB) subunits of CFA/I. The second, CfaEad, is the adhesin domain of CfaE. RESULTS: Owing to their His-tag, recombinant CfaEB and CfaEad, spontaneously bound upon admixture with nanoliposomes containing cobalt-porphyrin phospholipid (CoPoP), as well as a synthetic monophosphoryl lipid A (PHAD) adjuvant. Intramuscular immunization of mice with sub-microgram doses CfaEB or CfaEad admixed with CoPoP/PHAD liposomes elicited serum IgG and intestinal IgA antibodies. The smaller CfaEad antigen benefitted more from liposome display. Serum and intestine antibodies from mice immunized with liposome-displayed CfaEB or CfaEad recognized native CFA/I fimbria as evidenced by immunofluorescence and hemagglutination inhibition assays using the CFA/I-expressing H10407 ETEC strain. CONCLUSION: These data show that colonization factor-derived recombinant ETEC antigens exhibit immunogenicity when delivered in immunogenic particle-based formulations.

Antimicrobial susceptibility of Brucella melitensis isolates in Peru.

Brucellosis is an important public health problem in Peru. We evaluated 48 human Brucella melitensis biotype 1 strains from Peru between 2000 and 2006. MICs of isolates to doxycycline, azithromycin, gentamicin, rifampin, ciprofloxacin, and trimethoprim-sulfamethoxazole were determined by the Etest method. All isolates were sensitive to tested drugs during the periods of testing. Relapses did not appear to be related to drug resistance.

Production and characterization of foam in the anoxic zone of a membrane-enhanced biological phosphorus removal process.

A pilot-scale membrane-enhanced biological phosphorus removal process accumulated substantial quantities of stable foam on the surface of the anoxic zone. The foam contained 4 to 6% dry matter, with specific nitrogen and phosphorus contents that were similar to those of the underlying anoxic zone mixed liquor. Kinetic studies demonstrated that the specific rate of phosphorus release from the foam was only 25 to 30% of that observed with mixed liquor from the aerobic zone. Molecular techniques demonstrated that the calculated similarity of the microbial communities in the foam and the underlying mixed liquor was approximately 80%, with two phylotypes (Gordonia amarae and Microthrix parvicella) being uniquely enriched in the foam and one phylotype (Epistylis sp.) more abundant in the underlying mixed liquor. The production of foam was demonstrated to be a consistent phenomenon that depended on the concentration of the suspended solids in the bioreactor.

Capsule polysaccharide conjugate vaccine against diarrheal disease caused by Campylobacter jejuni.

The capsule polysaccharide (CPS) of Campylobacter jejuni is one of the few identified virulence determinants of this important human pathogen. Since CPS conjugate vaccines have been so effective against other mucosal pathogens, we evaluated this approach using CPSs from two strains of C. jejuni, 81-176 (HS23 and HS36 serotype complex) and CG8486 (HS4 serotype complex). The CPSs of 81-176 and CG8486 were independently linked to the carrier protein CRM(197) by reductive amination between an aldehyde(s), strategically created at the nonreducing end of each CPS, and accessible amines of CRM(197). In both cases, the CPS:CRM(197) ratio used was 2:1 by weight. Mass spectrometry and gel electrophoresis showed that on average, each glycoconjugate preparation contained, at least in part, two to five CPSs attached to one CRM(197). When administered subcutaneously to mice, these vaccines elicited robust immune responses and significantly reduced the disease following intranasal challenge with the homologous strains of C. jejuni. The CPS(81-176)-CRM(197) vaccine also provided 100% protection against diarrhea in the New World monkey Aotus nancymaae following orogastric challenge with C. jejuni 81-176.

Age-related susceptibility to infection with diarrheagenic Escherichia coli among infants from Periurban areas in Lima, Peru.

BACKGROUND: Diarrheagenic Escherichia coli strains are being recognized as important pediatric enteropathogens worldwide. However, it is unclear whether there are differences in age-related susceptibility to specific strains, especially among infants. METHODS: We conducted a passive surveillance cohort study of diarrhea that involved 1034 children aged 2-12 months in Lima, Peru. Control stool samples were collected from randomly selected children without diarrhea. All samples were analyzed for common enteric pathogens and for diarrheagenic E. coli with use of multiplex real-time polymerase chain reaction. RESULTS: The most frequently isolated pathogens in 1065 diarrheal episodes were diarrheagenic E. coli strains (31%), including enteroaggregative (15.1%) and enteropathogenic E. coli (7.6%). Diarrheagenic E. coli, Campylobacter species, and rotavirus were more frequently isolated from infants aged >or=6 months. Among older infants, diffusely adherent E. coli and enterotoxigenic E. coli were more frequently isolated from diarrheal samples than from control samples (P <.05). Children aged >or=6 months who were infected with enterotoxigenic E. coli had a 4.56-fold increased risk of diarrhea (95% confidence interval, 1.20-17.28), compared with younger children. Persistent diarrhea was more common in infants aged <6 months (13.5% vs 3.6%; P <.001). Among children with diarrheagenic E. coli-positive samples, coinfections with other pathogens were more common in children with diarrhea than in control children (40.1% vs 15.6%; P <.001). CONCLUSIONS: Diarrheagenic E. coli strains were more frequently isolated in samples from older infants. In this setting with high frequency of pathogen exposure and high frequency of breastfeeding, we hypothesize that the major age-related differences result from decreased exposure to milk-related protective factors and from increased exposure to contaminated food and water.

Wastewater treatment models in teaching and training: the mismatch between education and requirements for jobs.

As mathematical modeling of wastewater treatment plants has become more common in research and consultancy, a mismatch between education and requirements for model-related jobs has developed. There seems to be a shortage of skilled people, both in terms of quantity and in quality. In order to address this problem, this paper provides a framework to outline different types of model-related jobs, assess the required skills for these jobs and characterize different types of education that modelers obtain "in school" as well as "on the job". It is important to consider that education of modelers does not mainly happen in university courses and that the variety of model related jobs goes far beyond use for process design by consulting companies. To resolve the mismatch, the current connection between requirements for different jobs and the various types of education has to be assessed for different geographical regions and professional environments. This allows the evaluation and improvement of important educational paths, considering quality assurance and future developments. Moreover, conclusions from a workshop involving practitioners and academics from North America and Europe are presented. The participants stressed the importance of non-technical skills and recommended strengthening the role of realistic modeling experience in university training. However, this paper suggests that all providers of modeling education and support, not only universities, but also software suppliers, professional associations and companies performing modeling tasks are called to assess and strengthen their role in training and support of professional modelers.

Comparison of nitrification rates in conventional and membrane-assisted biological nutrient removal processes.

A membrane-assisted and a conventional activated sludge system, both operated in an enhanced biological phosphorus removal (EBPR) mode and under identical operating conditions, were studied to investigate the effect of the membrane solids-liquid separation on nitrification activity. Both the membrane EBPR (MEBPR) and conventional EBPR (CEBPR) processes achieved stable and complete removal of ammonium-nitrogen from the influent wastewater. However, when the intrinsic nitrification activity was assessed in offline batch tests, the CEBPR mixed liquor exhibited 15 to 75% greater nitrification potential than the MEBPR counterpart. These results were further validated by monitoring nitrification rates of conventional mixed liquor as it evolved toward a membrane mixed liquor. It was also demonstrated that the larger aerobic mass fraction of the MEBPR system could not be the only factor influencing the reduced intrinsic nitrification rate. The present study strongly suggests that the presence of a membrane solids-liquid separation per se may be sufficient to alter the nitrification kinetics of an EBPR mixed liquor and that this possibility should be considered in arriving at an appropriate process design.

Retention of microplastics in a major secondary wastewater treatment plant in Vancouver, Canada.

Municipal wastewater treatment plants (WWTPs) are conduits through which microplastics (MPs) are released into aquatic environments. However, the technical challenges in working with wastewater sample matrices have precluded reliable particle count budget calculations. We applied newly-adapted methods for MP collection and analysis to a study of a major WWTP serving a population of 1.3 million people near Vancouver, Canada. Suspected MP particles, including fibres, were counted and categorized using light microscopy in influent, primary effluent, secondary effluent, primary sludge and secondary sludge. Fourier Transform Infrared Spectroscopy (FT-IR) confirmed that just 32.4% of the suspected MPs were plastic polymers. Using FT-IR corrected data, we estimate that 1.76 ±â€¯0.31 trillion MPs enter the WWTP annually, with 1.28 ±â€¯0.54 trillion MPs settling into primary sludge, 0.36 ±â€¯0.22 into secondary sludge, and 0.03 ±â€¯0.01 trillion MPs released into the receiving environment. This corresponds to a retention of microplastics of up to 99% in the WWTP.

Transcriptomics investigation of thyroid hormone disruption in the olfactory system of the Rana [Lithobates] catesbeiana tadpole.

Thyroid hormones (THs) regulate vertebrate growth, development, and metabolism. Despite their importance, there is a need for effective detection of TH-disruption by endocrine disrupting chemicals (EDCs). The frog olfactory system substantially remodels during TH-dependent metamorphosis and the objective of the present study is to examine olfactory system gene expression for TH biomarkers that can evaluate the biological effects of complex mixtures such as municipal wastewater. We first examine classic TH-response gene transcripts using reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) in the olfactory epithelium (OE) and olfactory bulb (OB) of premetamorphic Rana (Lithobates) catesbeiana tadpoles after 48 h exposure to biologically-relevant concentrations of the THs, 3,5,3'-triiodothyronine (T3) and L-thyroxine (T4), or 17-beta estradiol (E2); a hormone that can crosstalk with THs. As the OE was particularly sensitive to THs, further RNA-seq analysis found >30,000 TH-responsive contigs. In contrast, E2 affected 267 contigs of which only 57 overlapped with THs suggesting that E2 has limited effect on the OE at this developmental phase. Gene ontology enrichment analyses identified sensory perception and nucleoside diphosphate phosphorylation as the top affected terms for THs and E2, respectively. Using classic and additional RNA-seq-derived TH-response gene transcripts, we queried TH-disrupting activity in municipal wastewater effluent from two different treatment systems: anaerobic membrane bioreactor (AnMBR) and membrane enhanced biological phosphorous removal (MEBPR). While we observed physical EDC removal in both systems, some TH disruption activity was retained in the effluents. This work lays an important foundation for linking TH-dependent gene expression with olfactory system function in amphibians.

O3:K6 serotype of Vibrio parahaemolyticus identical to the global pandemic clone associated with diarrhea in Peru.

OBJECTIVES: To determine if the Vibrio parahaemolyticus O3:K6 global pandemic clone has spread into Peru. METHODS: A collection of 100 V. parahaemolyticus strains isolated from diarrhea cases in Peru were serotyped for O:K antigens and genotyped for the presence of the species-specific toxR gene and for the tdh and trh genes. In addition, the group-specific PCR (GS-PCR) and PCR for the presence of the open reading frame ORF8 of the filamentous phage f237 was performed to determine the pandemic status of the strains. RESULTS: Fifty strains of V. parahaemolyticus in this collection were identified as pandemic strains. Forty-six ORF8 and GS-PCR positive strains were identical to the global pandemic clone O3:K6, while four strains that also possessed the pandemic genotype and were ORF8 and GS-PCR positive belonged to serotypes O3:K68, O3:K58 and OUT (untypable):K6. One of the O3:K6 strains was isolated in 1996, indicating that the pandemic strain was present in Peru at about the same time that it caused the first outbreak in Calcutta in February 1996. CONCLUSIONS: Based on this first report in Peru of such strains, we recommend including V. parahaemolyticus in the differential diagnosis of the etiologic agents for diarrhea in this part of the world.

A comparative study of fouling-related properties of sludge from conventional and membrane enhanced biological phosphorus removal processes.

The physical and biochemical properties of activated sludge mixed liquor, including floc size distribution, zeta potential, relative hydrophobicity, and bound and unbound (soluble) extracellular polymeric substances (EPS), were examined in this study to evaluate their relationship to membrane fouling. Mixed liquors from a membrane enhanced biological phosphorus removal (MEBPR) process and a conventional enhanced biological phosphorus removal (CEBPR) process were compared. It was found that the floc size distribution and the amount of soluble EPS in the mixed liquor were the most important properties that significantly influenced the fouling propensity of sludge. Contrary to the literature, the content of EPS bound in activated sludge flocs was not found to be directly associated with membrane fouling, and sludge surface properties such as zeta potential and relative hydrophobicity were not closely related to the observed differences in the fouling tendencies of the two types of sludge.

Toward a high-rate enhanced biological phosphorus removal process in a membrane-assisted bioreactor.

A membrane enhanced biological phosphorus removal (MEBPR) process was studied to determine the impact of hydraulic retention time (HRT) and solids retention time (SRT) on the removal of chemical oxygen demand (COD), nitrogen, and phosphorus from municipal wastewater. The MEBPR process was capable of delivering complete nitrification independent of the prevailing operating conditions, whereas a significant improvement in COD removal efficiency was observed at longer SRTs. In the absence of carbon-limiting conditions, the MEBPR process was able to achieve low phosphorus concentrations in the effluent at increasingly higher hydraulic loads, with the lowest HRT being 5 hours. The MEBPR process was also able to maintain optimal phosphorus removal when the SRT was increased from 12 to 20 days. However, at higher suspended solids concentrations, a substantial increase was observed in carbon utilization per unit mass of phosphorus removed from the influent. These results offer critical insights to the application of membrane technology for biological nutrient removal systems.