bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Diversity within Fragmented Cutthroat Trout Populations
Authors: Pritchard V. L. , Jones K. , Cowley D. E.
Published: April 2007

Interior cutthroat trout Oncorhynchus clarkii have undergone severe declines over the past 150 years. Many subspecies now persist in a highly fragmented state, primarily within headwater streams. We used 12 microsatellites to investigate the population genetic characteristics of 22 remnant populations of Rio Grande cutthroat trout O. c. virginalis isolated in montane streams in New Mexico. Populations varied markedly in the amount of genetic diversity they contained. There was no significant relationship between estimated adult population size or habitat size and heterozygosity; however, populations occurring above natural barriers were significantly less diverse. Seven population samples exhibited significant deviations from Hardy‐Weinberg equilibrium. Interlocus variance in the population inbreeding coefficient FIS was correlated with habitat size, and several population samples exhibited a significantly higher variance in interindividual relatedness, or a significantly higher median individual inbreeding coefficient, than would be expected by chance. These results suggest that cutthroat trout populations in headwater streams consist of multiple partially discrete subpopulations in which only a small number of adults successfully reproduce. The potential for such population substructure should be considered when planning management activities for stream‐dwelling cutthroat trout.
Effects of Habitat Volume and Fathead Minnow Introduction on Larval Survival of Two Endangered Sucker Species in Upper Klamath Lake, Oregon
Authors: Markle Douglas F. , Dunsmoor Larry K.
Published: April 2007

We used laboratory and field studies to evaluate the degree to which the abundance of introduced fathead minnow Pimephales promelas and volume of nursery habitat were limiting factors for survival of larval shortnose suckers Chasmistes brevirostris and Lost River suckers Deltistes luxatus in Upper Klamath Lake. In 20‐h experiments in which we manipulated water depth and vegetation, fathead minnow fed on sucker larvae, but deeper water and the presence of vegetation reduced predation, suggesting that predator and prey densities and cover influenced predation. Older larvae had higher survival than younger larvae in shallow water, and vegetation increased survival for all larvae in shallow water. We also used larval production estimates from 11 years of field surveys to calculate annual larval sucker survival. Average annual larval sucker survival from 10 to 15 mm total length was about 18% (range, 4.4‐48.0%). The shoreline abundance of adult fathead minnow had a negative relationship with—and appeared to set an upper limit on—annual larval sucker survival, which was consistent with the density relationship found in laboratory studies. In addition, the average shoreline abundance of fathead minnow was about three times that of any other species and had negative relationships with the abundance of all other species and lake elevation. Recent management of Upper Klamath Lake has kept June lake elevations near the 1981‐2004 mean, but it is unclear whether fluctuations in the lake's fishes are due to lake management, to larger‐scale processes such as climate, to biotic interactions resulting from environmental changes, or to a combination of those factors. This study illustrates the need to better understand the biological trade‐offs with management‐manipulated variables such as lake elevation. In addition, to manage the competing demands on Upper Klamath Lake, it will be important to recognize that high survival of larval suckers will be less frequent than in the period preceding fathead minnow presence.
Incidence of Hybridization between Naturally Sympatric Westslope Cutthroat Trout and Rainbow Trout in the Middle Fork Salmon River Drainage, Idaho
Authors: Kozfkay Christine C. , Campbell Matthew R. , Yundt Steven P. , Peterson Michael P. , Powell Madison S.
Published: April 2007

Introgressive hybridization has been widely reported for westslope cutthroat trout (WCT)Oncorhynchus clarkii lewisiand rainbow trout (RBT)O. mykissand is often a result of introductions of nonnative RBT into previously allopatric populations of westslope cutthroat trout. The WCT evolved in sympatry with RBT in a portion of its native range. Few studies have evaluated natural hybrid zone structure in sympatric populations or the effects of nonnative introductions within sympatric populations. We used one mitochondrial DNA marker and three co‐dominant nuclear DNA markers to examine 17 populations of WCT that were sympatric with native RBT‐steelhead (anadromous RBT). As 5 of the 11 sample locations were situated downstream of stocked headwater mountain lakes, we wanted to determine the effects of headwater lake introductions on naturally sympatric populations of WCT and RBT‐steelhead below the lakes. Hybrids were found in streams below stocked and unstocked headwater lakes. Our results indicated that the majority of the populations displayed a bimodal hybrid structure, linkage disequilibrium, and Hardy‐Weinberg disequilibrium. This suggests recent, ongoing hybridization but also strong assortative mating, which may be indicative of minimal impacts from stocking or independent events of natural hybridization. Natural hybrid zones should be addressed in current political deliberations about the inclusion of hybridized populations of WCT in Endangered Species Act considerations. A decision to discount protective actions for such stocks may lead to a loss of potentially adaptive genetic diversity and the fragmentation of populations.
Rat strain-dependent susceptibility to ischemia-induced retinopathy associated with retinal vascular endothelial growth factor regulation
Authors: Lu Kangmo , Zhou Yuehua , Kaufman Ken , Mott Robert , Ma Jian-xing
Published: April 2007

Vascular endothelial growth factor (VEGF) is a potent inflammation, vascular permeability, and angiogenic factor. Variations of the VEGF gene are implicated in the pathogenesis of diabetic retinopathy. Previous studies have shown that Brown Norway (BN) rats have higher retinal VEGF levels and more severe retinal vascular leakage than Sprague–Dawley (SD) rats in response to ischemia and diabetes. To investigate the molecular mechanism of vascular leakage in this animal model, F2 progeny were generated by crossbreeding BN and SD rats. Neonatal rats were exposed to hyperoxia to induce oxygen-induced retinopathy (OIR) models. The F2 rats in response to ischemia have shown a linear distribution of retinal VEGF levels, which is significantly and positively correlated to retinal vascular leakage. We identified a single nucleotide polymorphism (SNP) at upstream stimulating factor-binding site in the VEGF promoter region between BN and SD rats. No differences were found in retinal vascular permeability or VEGF levels between F2 rats with BN, SD, and BN/SD alleles of VEGF SNP. The increased retinal VEGF levels are correlated to ischemia-induced retinal vascular leakage in the OIR rat model. The VEGF mRNA and promoter are not responsible for increased retinal VEGF level and vascular permeability. The up-regulation of VEGF expression activated by a yet to be identified upstream factor or mediator affecting VEGF stability may be associated with a high susceptibility to retinal vascular leakage in BN rats.
Larval zebrafish as a model for glucose metabolism: expression of phosphoenolpyruvate carboxykinase as a marker for exposure to anti-diabetic compounds
Authors: Elo B , Villano C M , Govorko D , White L A
Published: April 2007

The zebrafish model system is one of the most widely used animal models for developmental research and it is now becoming an attractive model for drug discovery and toxicological screening. The completion of sequencing the zebrafish genome and the availability of full-length cDNAs and DNA microarrays for expression analysis, in addition to techniques for generating transgenic lines and targeted mutations, have made the zebrafish model even more attractive to researchers. Recent data indicate that the regulation of glucose metabolism in zebrafish, through the production of insulin, is similar to mammalian models, and many of the genes involved in regulating blood glucose levels have been identified in zebrafish. The data presented here show that adult zebrafish respond to anti-diabetic drugs similarly to mammalian models, by reducing blood glucose levels. Furthermore, we show that the expression of phosphoenolpyruvate carboxykinase (PEPCK), which catalyzes a rate-limiting step in gluconeogenesis and is transcriptionally regulated by glucagon and insulin, is regulated in larval zebrafish similarly to that seen in mammalian systems, and changes in PEPCK expression can be obtained through real-time PCR analysis of whole larval RNA. Taken together, these data suggest that larval zebrafish may be an appropriate model for the examination of glucose metabolism, using PEPCK as an indicator of blood glucose levels.
Assessment of the anti-obesity effects of the TNP-470 analog, CKD-732
Authors: Kim Yoo Mee , An Juan Ji , Jin Yong-Jun , Rhee Yumie , Cha Bong Soo , Lee Hyun Chul , Lim Sung-Kil
Published: April 2007

The systemic treatment with angiogenesis inhibitor has been shown to result in weight reduction and adipose tissue loss in various models of obesity. To verify the mechanism of CKD-732 (TNP-470 analog) against obesity, we evaluated CKD-732’s peripheral and central anti-obesity effects. CKD-732 was injected subcutaneously (s.c.) for 7 days in various animal models and intracerebroventricularly (i.c.v.) in arcuate nucleus (ARC) lesion mice, ob/ob mice, and normal littermates. Modulation of the hypothalamic neuropeptide mRNAs after i.c.v. injection was evaluated in ARC lesion mice and normal littermates. A conditioned taste aversion (CTA) was performed using lithium chloride (LiCl) as a positive control agent in Long–Evans Tokushima Otsuka and Otsuka Long–Evans Tokushima fatty (OLETF) rats. As a result, 7 days of CKD-732 s.c. injection reduced the cumulative food intake and the body weight significantly in both treated obese (e.g. 114.8 ± 13.4 g vs 170.7 ± 20.6 g, 7.9 ± 0.5% decrease vs 0.3 ± 2.2% decrease; in treated OLETF rat versus control OLETF rat, P < 0.01 respectively) and non-obese models. Epididymal and mesenteric fat pads, and the size of adipocytes were significantly decreased in treated rats. A single i.c.v. injection decreased food intake and body weight in ARC lesion mice and ob/ob mice but not in normal littermates. Unexpectedly, the hypothalamic neuropeptide mRNAs were not altered by single i.c.v. injection. CKD-732 also induced a dose-dependent CTA comparable with LiCl injection, which is a commonly used agent to produce a CTA. In conclusion, CKD-732 causes significant body weight and appetite reduction, possibly by decreasing adiposity directly and inducing central anorexia, which is partly explained by a CTA. These results should be carefully verified to assess the utility of CKD-732 as an anti-obesity drug.
Signaling mechanisms leading to regulation of proliferation and differentiation of the mesenchymal chondrogenic cell line RCJ3.1C5.18 in response to IGF-I
Authors: Ciarmatori Sonia , Kiepe Daniela , Haarmann Anke , Huegel Ulrike , Tönshoff Burkhard
Published: April 2007

Since IGF-I is an important chondrocyte growth factor, we sought to examine the intracellular mechanisms by which it exerts two of its pivotal effects, stimulation of proliferation and differentiation. We used the mesenchymal chondrogenic cell line RCJ3.1C5.18, which progresses spontaneously to differentiated growth plate chondrocytes. This differentiation process could be enhanced by exogenous IGF-I. Pharmacological inhibition of the phosphatidylinositol-3 (PI-3) kinase by LY294002, mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK)1/2 by U0126, the protein kinase (PK) A pathway by H-89 or KT5720, and the PKC pathway by bisindolylmaleimide suppressed IGF-I-stimulated cell proliferation. In contrast, IGF-I-enhanced early cell differentiation, as assessed by collagen type II and aggrecan gene expression, was not affected by MAPK/ERK1/2 pathway inhibition, but significantly diminished by inhibition of the PI-3 kinase, the PKC and the PKA pathway. Moreover, terminal differentiation of chondrocytes in response to IGF-I, as assessed by gene expression of alkaline phosphatase, Indian hedgehog, and collagen type X, were only interrupted by PI-3 kinase pathway inhibition. In conclusion, IGF-I exerts its differential effect on chondrocyte proliferation vs differentiation through the use of at least four partially interacting intracellular signaling pathways, whose activity is temporarily regulated. When chondrocytes progress from proliferating cells to early and terminal differentiating cells, they progressively inactivate IGF-I-related intracellular signaling pathways. This mechanism might be essential for the complex and cell stage-specific anabolic action of IGF-I in the growth plate.
Briefing: Young engineers face up to delivering sustainability
Authors: Feretzakis Alexandros , Forbes Doug
Published: April 2007

Telford apprentices Alexandros Feretzakis and Doug Forbes, who were appointed by ICE president Quentin Leiper in November 2006, discuss the vital role younger civil engineers now need to play promoting and delivering sustainability.
Briefing: Solving the puzzle of Britain's underground assets
Authors: Brayshaw James
Published: April 2007

The UK's National Underground Asset Group was launched two years ago to coordinate and share data on the country's vast and inconsistently charted network of buried services. ICE's representative on the Group, James Brayshaw of Ordnance Survey, provides an update.
Briefing: Concrete takes the lead in sustainable construction
Authors: Georgopoulos Costas
Published: April 2007

If sustainability is measured simply in terms of embodied carbon dioxide emissions, concrete is ahead on points. But if you factor in cost, durability and other unique properties of concrete, Costas Georgopoulos of The Concrete Centre says it is the clear winner for sustainable construction.
Lin Au culvert, Hong Kong: taming the torrent
Authors: Corney Bruce , Meigh David , Hieatt Michael
Published: April 2007

A major new water treatment plant on a mountainside overlooking Tai Po in Hong Kong sits on top of a steep flood-prone watercourse, 500 m of which has had to be buried deep under the works in a substantial culvert. This paper describes the challenging design and construction of the 8 m wide concrete-arch culvert, which for the past seven years has successfully contained and dissipated high-speed, boulder-laden storm flows of up to 80 m3/s. The Lin Au culvert incorporates a series of four chutes and stilling basins as well as providing overflow facilities for the treatment works above it using a variety of drop structures. The structural integrity of the culvert is critical, both to support the massive overlying fill platform of the new treatment works as well as to protect it from being washed out by up to 60 MW of hydraulic energy.
CDM Regulations: 12 years of pain but little gain
Authors: Beal Alasdair N.
Published: April 2007

New Construction (Design and Management) Regulations were due out in the UK in April 2007, updating the original 1994 Regulations which came into force in 1995. This paper looks at the effects the original Regulations have actually had on the construction industry, particularly with regard to implementation costs and safety benefits. Analysis of site accident statistics shows that, despite having cost several billion pounds to implement, the Regulations have produced very little improvement in safety. It also appears that the EU research report which led to introduction of the regulations has been widely misrepresented, leading to unrealistic expectations about the effect designers can actually have on construction safety.
Substance Use During Sexual and Physical Assault in HIV-Infected Persons
Authors: Chuang Cynthia H. , Liebschutz Jane M. , Cheng Debbie M. , Raj Anita , Samet Jeffrey H.
Published: April 2007

Data from the HIV-Alcohol Longitudinal Cohort was used to determine the prevalence of substance use by victims and assailants during physical and sexual assault against HIV-infected persons and whether these findings differed by gender. Of the sexually assaulted participants, 31% of victims and 70% of assailant(s) had used drugs/alcohol during sexual assault. Compared with men, women had higher odds of substance use during sexual assault (adjusted odds ratio [OR] 3.8, 95% confidence interval [CI] 1.6 to 8.7) and of substance use by their assailant(s) during sexual assault (adjusted OR 5.9, 95% CI 1.7 to 20.6) in adjusted analysis. Of the physically assaulted participants, 66% of victims and 85% of assailants used drugs/alcohol during physical assault; these results did not differ by gender.
Personality and Psychopathological Profiles in Individuals Exposed to Mobbing
Authors: Girardi Paolo , Monaco Edoardo , Prestigiacomo Claudio , Talamo Alessandra , Ruberto Amedeo , Tatarelli Roberto
Published: April 2007

Increasingly, mental health and medical professionals have been asked to assess claims of psychological harm arising from harassment at the workplace, or “mobbing.” This study assessed the personality and psychopathological profiles of 146 individuals exposed to mobbing using validity, clinical, and content scales of the Minnesota Multiphasic Personality Inventory 2. Profiles and factor analyses were obtained. Two major dimensions emerged among those exposed to mobbing: (a) depressed mood, difficulty in making decisions, change-related anguish, and passive-aggressive traits (b) somatic symptoms, and need for attention and affection. This cross-sectional pilot study provides evidence that personality profiles of mobbing victims and psychological damage resulting from mobbing may be evaluated using standardized assessments, though a longitudinal study is needed to delineate cause-and-effect relationships.
Do Hostile Sexual Beliefs Affect Men’s Perceptions of Sexual-Interest Messages?
Authors: Lopez Peter A. , George William H. , Davis Kelly Cue
Published: April 2007

This study tested the distorted cognitions component of Hall and Hirschman’s (1991) quadripartite model of sexual aggression. Men (N = 107) with and without hostile sexual beliefs viewed erotic slides with a female partner who provided one of four patterns of feedback: clear disinterest, token disinterest, compliant interest, and clear interest. Hostile men reported fewer differences between women, were unresponsive to their partner’s perceived embarrassment, and reported a consistent positive mood regardless of her feedback. Conversely, nonhostile men were more responsive to feedback, mirrored the partner’s embarrassment, and experienced a less positive mood when she communicated clear disinterest in the erotica. These findings support the distorted cognitions component of the quadripartite model of sexual aggression. The authors also discuss the strengths and limitations of this study’s methodology.
Children’s Direct Sensory Exposure to Substantiated Domestic Violence Crimes
Authors: Fantuzzo John , Fusco Rachel L
Published: April 2007

Police officers served as public health sentinels to collect data on children exposed to domestic violence events (DVEs) across an entire municipality for 1 year. These officers used a standard, validated protocol to collect data on all investigate DVEs. This study extended previous research by including data demographic data on children in the household at the time of the DVE and investigating children’s direct sensory exposure to DVEs. Findings revealed that almost half of all events had children present, and 81% of these children were directly exposed to DVEs. Children under the age of 6 years old were at greater risk of direct sensory exposure. Domestic violence households with children were more likely to be low-income, non-White, and headed by a single female compared to households at large. Logistic regressions revealed that six major DVE variables were related to children being directly exposed. These included father as perpetrator, victim injury, weapon use, non-White victim, mutual assault, and arrest of perpetrator.
Personal Predictors of Spectator Aggression at Little League Baseball Games
Authors: Hennessy Dwight A. , Schwartz Stephen
Published: April 2007

Parents from two baseball leagues completed questionnaires regarding their likelihood of engaging in various aggressive behaviors (yelling, swearing, shoving, fighting, humiliating) toward targets at youth baseball games (other spectators, umpires, coaches, other players, their child). Overall, the likelihood of all forms of aggression was very low, particularly physical aggression and swearing. Hierarchical entry stepwise regressions were calculated to determine predictors of yelling and humiliating using demographics, trait aggression, anger, hostility, and vengeance as predictors. Parents with greater hostility reported a greater likelihood of humiliating a child’s teammate, while those with elevated trait anger reported a greater likelihood of yelling at other spectators. Finally, parents with a more vengeful attitude reported a greater likelihood of humiliating umpires.
Development of a super high-rate Anammox reactor and in situ analysis of biofilm structure and function
Authors: Tsushima Ikuo , Ogasawara Yuji , Shimokawa Masaki , Kindaichi Tomonori , Okabe Satoshi
Published: April 2007

The anaerobic ammonium oxidation (Anammox) process is a new efficient and cost effective method of ammonium removal from wastewater. Under strictly anoxic condition, ammonium is directly oxidised with nitrite as electron acceptor to dinitrogen gas. However, it is extremely difficult to cultivate Anammox bacteria due to their low growth rate. This suggests that a rapid and efficient start-up of Anammox process is the key to practical applications. To screen appropriate seeding sludge with high Anammox potential, a real-time quantitative PCR assay with newly designed primers has been developed. Thereafter, the seeding sludge with high abundance of Anammox bacteria (1.7 × 108 copies/mg-dry weight) was selected and inoculated into an upflow anaerobic biofilters (UABs). The UABs were operated for more than 1 year and the highest nitrogen removal rate of 24.0 kg-N m−3 day−1 was attained. In addition, the ecophysiology of Anammox bacteria (spatial distribution and in situ activity) in biofilms was analysed by combining a full-cycle 16S rRNA approach and microelectrodes. The microelectrode measurement clearly revealed that a successive vertical zonation of the partial nitrification (NH4+ to NO2−), Anammox reaction and denitrification was developed in the biofilm in the UAB. This result agreed with the spatial distribution of corresponding bacterial populations in the biofilm. We linked the micro-scale information (i.e. single cell and/or biofilm levels) with the macro-scale information (i.e. the reactor level) to understand the details of Anammox reaction occurring in the UABs.
Full-scale granular sludge Anammox process
Authors: Abma W.R. , Schultz C.E. , Mulder J.W. , van der Star W.R.L. , Strous M. , Tokutomi T. , van Loosdrecht M.C.M.
Published: April 2007

The start-up of the first full scale Anammox reactor is complete. The reactor shows stable operation, even at loading rates of 10 kg N/m3.d. This performance is the result of the formation of Anammox granules, which have a high density and settling velocities exceeding 100 m/h. With this performance, the Anammox granular sludge technology has been proven on full scale.
Nutrients removal in hybrid fluidised bed bioreactors operated with aeration cycles
Authors: Martín Martín M.A. , López Enríquez L. , Fernández-Polanco M. , Villaverde S. , García-Encina P.A.
Published: April 2007

Two hybrid fluidised bed reactors filled with sepiolite and granular activated carbon (GAC) were operated with short cycled aeration for removing organic matter, total nitrogen and phosphorous, respectively. Both reactors were continuously operated with synthetic and/or industrial wastewater containing 350–500 mg COD/L, 110–130 mg NKT/L, 90–100 mg NH3-N/L and 12–15 mg P/L for 8 months. The reactor filled with sepiolite, treating only synthetic wastewater, removed COD, ammonia, total nitrogen and phosphorous up to 88, 91, 55 and 80% with a hydraulic retention time (HRT) of 10 h, respectively. These efficiencies correspond to removal rates of 0.95 kgCODm−3d−1 and 0.16 kg total N m−3d−1.The reactor filled with GAC was operated for 4 months with synthetic wastewater and 4 months with industrial wastewater, removing 98% of COD, 96% of ammonia, and 66% of total nitrogen, with an HRT of 13.6 h. No significant phosphorous removing activity was observed in this reactor. Microbial communities growing with both reactors were followed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The microbial fingerprints, i.e. DGGE profiles, indicated that biological communities in both reactors were stable along the operational period even when the operating conditions were changed.
Comparing cost and process performance of activated sludge (AS) and biological aerated filters (BAF) over ten years of full sale operation
Authors: Hansen R. , Thøgersen T. , Rogalla F.
Published: April 2007

In the early 1990s, the Wastewater Treatment Plant (WWTP) of Frederikshavn, Denmark, was extended to meet new requirements for nutrient removal (8 mg/L TN, 1.5 mg TP/L) as well as to increase its average daily flow to 16,500 m3/d (4.5 MGD). As the most economical upgrade of the existing activated sludge (AS) plant, a parallel biological aerated filter (BAF) was selected, and started up in 1995. Running two full scale processes in parallel for over ten years on the same wastewater and treatment objectives enabled a direct comparison in relation to operating performance, costs and experience.

Common pretreatment consists of screening, an aerated grit and grease removal and three primary settlers with chemical addition. The effluent is then pumped to the two parallel biological treatment stages, AS with recirculation and an upflow BAF with floating media. The wastewater is a mixture of industrial and domestic wastewater, with a dominant discharge of fish processing effluent which can amount to 50% of the flow. The maximum hydraulic load on the pretreatment section as a whole is 1,530 m3/h.

Approximately 60% of the sewer system is combined with a total of 32 overflow structures. To avoid the direct discharge of combined sewer overflows into the receiving waters, the total hydraulic wet weather capacity of the plant is increased to 4,330 m3/h, or 6 times average flow. During rain, some of the raw sewage can be directed through a stormwater bypass to the BAF, which can be modified in its operation to accommodate various treatment needs:•either using simultaneous nitrification/denitrification in all filters with recirculation•introducing bottom aeration with full nitrification in some filters for storm treatment•and/or post-denitrification in one filter.

After treatment, the wastewater is discharged to the Baltic Sea through a 500 m outfall. The BAF backwash sludge, approximately 1,900 m3 per 24 h in dry weather, is redirected to the AS plant. Primary settler sludge and the combined biosolids from the AS plant are anaerobically digested, with methane gas being used for generation of heat and power.

On-line measurements for the parameters NO3, NO2, NH4, temperature as well as dissolved oxygen (DO) are used for control of aeration and external carbon source (methanol). Dosing of flocculants for P-removal is carried out based on laboratory analysis and jar tests. This paper discusses the experience gained from the plant operation during the last ten years, compiling comparative performance and cost data of the two processes, as well as their optimisation.
Influence of backwashing on the microbial community in a biofilm developed on biological activated carbon used in a drinking water treatment plant
Authors: Kasuga I. , Shimazaki D. , Kunikane S.
Published: April 2007

The influence of backwashing on the biofilm community developed on biological activated carbon (BAC) used in a drinking water treatment plant was investigated by means of bacterial cell enumeration and terminal-restriction fragment length polymorphism (T-RFLP) fingerprinting analysis of bacterial and eukaryotic ribosomal RNA genes (rDNA). After backwashing, the attached bacterial abundance in the top layer of the BAC bed decreased to 64% of that before backwashing. The community level changes caused by backwashing were examined through the T-RFLP profiles. In the bacterial 16S rDNA analysis, the relative abundances of some terminal-restriction fragments (T-RFs) including the Planctomycetes-derived fragment increased; however, the relative abundances of some T-RFs including the Betaproteobacteria-derived fragments decreased. In the eukaryotic 18S rDNA analysis, the relative abundances of some T-RFs including the protozoan Cercozoa-derived fragments increased; however, the relative abundances of some T-RFs including the metazoan Chaetonotus- and Paratripyla-derived fragments decreased. The T-RFLP analysis suggests that backwashing can cause changes in the relative compositions of microorganisms in a BAC biofilm in the top layer of the bed.
Investigation of microbial communities on reverse osmosis membranes used for process water production
Authors: Bereschenko L.A. , Stams A.J.M. , Heilig G.H.J. , Euverink G.J.W. , Nederlof M.M. , Van Loosdrecht M.C.M.
Published: April 2007

In the present study, the diversity and the phylogenetic affiliation of bacteria in a biofouling layer on reverse osmosis (RO) membranes were determined. Fresh surface water was used as a feed in a membrane-based water purification process. Total DNA was extracted from attached cells from feed spacer, RO membrane and product spacer. Universal primers were used to amplify the bacterial 16S rRNA genes. The biofilm community was analysed by 16S rRNA-gene-targeted denaturing gradient gel electrophoresis (DGGE) and the phylogenetic affiliation was determined by sequence analyses of individual 16S rDNA clones. Using this approach, we found that five distinct bacterial genotypes (Sphingomonas, Beta proteobacterium, Flavobacterium, Nitrosomonas and Sphingobacterium) were dominant genera on surfaces of fouled RO membranes. Moreover, the finding that all five “key players” could be recovered from the cartridge filters of this RO system, which cartridge filters are positioned before the RO membrane, together with literature information where these bacteria are normally encountered, suggests that these microorganisms originate from the feed water rather than from the RO system itself, and represent the fresh water bacteria present in the feed water, despite the fact that the feed water passes an ultrafiltration (UF) membrane (pore size approximately 40 nm), which is able to remove microorganisms to a large extent.
Simultaneous visualisation of biofouling, organic and inorganic particle fouling on separation membranes
Authors: Spettmann D. , Eppmann S. , Flemming H.-C. , Wingender J.
Published: April 2007

Fouling is a major problem in membrane processes of water treatment. It can be caused by the deposition of inorganic and organic particulate material, and of microbial cells which may subsequently form biofilms. In practice, usually more than one foulant participates in the formation of membrane deposits. Knowledge of the composition of fouling layers is important for the development of appropriate countermeasures. For this purpose, an experimental system was established for the generation and microscopic visualisation of mixed deposits, using fluorescently labelled model foulants: (i) drinking-water bacteria stained with nucleic acid-specific dyes (biofouling), (ii) synthetic clay mineral laponite stained with rhodamine 6G (inorganic particle fouling), and (iii) fluorescently labelled polystyrene microspheres (organic particle fouling). Polycarbonate and polyethersulfone membranes were challenged with these foulants by dead-end filtration. On the basis of different fluorescent labels, the single foulants in these mixed deposits could be visualised separately by confocal laser scanning microscopy which, in combination with image analysis, allowed the generation of three-dimensional views of the complete deposits. This method offers the possibility for the estimation of quantitative surface coverage by foulants and for the determination of the efficacy of cleaning measures with respect to the removal of different foulants.
Assessing chemical cleaning of nanofiltration membranes in a drinking water production plant: a combination of chemical composition analysis and fluorescence microscopy
Authors: Di Martino P. , Doumeche B. , Galas L. , Vaudry H. , Heim V. , Habarou H.
Published: April 2007

The efficiency of cleaning procedures to remove the fouling deposit from the surface of NF membranes operating in the drinking water plant of Méry sur Oise (Val d'Oise, France) was assessed by a combination of chemical analysis and fluorescence microscopy. The ATR-FTIR spectra of the fouled membranes revealed the presence of biological matter at the membrane surface, mainly composed of polysaccharides, nucleic acids and proteins. IR bands corresponding to the membrane material were detected for stage 1 but not for stage 3. Confocal laser scanning microscopy (CLSM) observations confirmed the microbial origin of the fouling deposit.

After chemical cleaning, the analysis of the inorganic foulants revealed a significant decrease of the inorganic content. Moreover, ATR-FTIR spectra of the fouled membranes were modified, mainly in a broad complex region corresponding to polysaccharides and nucleic acids. The amide bands were also altered for stage 1, and some peaks corresponding to the clean membrane appeared for stage 3 after cleaning. CLSM observations revealed a general decrease of the lectin staining for the two stages with some variations between lectins. A decrease of the DAPI staining indicative of the removal of some microbial cells was also observed for stage 1.

In conclusion, cleaning of the NF fouled membranes decreased significantly the inorganic foulants but only partially removed the organic fouling deposit characteristic of a microbial biofilm.
Stochastic modeling for characterisation of biofilm development with discrete detachment events (sloughing)
Authors: Bohn A. , Zippel B. , Almeida J.S. , Xavier J.B.
Published: April 2007

The monitoring of biofilm development at a small-scale is often observed to be a stochastic process. This raises important issues concerning the reproducibility of biofilm growth monitoring experiments. By realising that there are limits to the latter, a model of biofilm accumulation curves that takes into account the dynamics of seemingly random fluctuations resulting from sloughing events is proposed. The model is derived from a stochastic differential equation (SDE) based on the logistic equation, adding a stochastic term for the sloughing events and measurement noise. Experimental light absorbance data that correlate with biofilm biomass obtained from the development of phototrophic biofilms are analysed to illustrate the use of SDE modeling.
Toward an operational dynamic model for tertiary nitrification by submerged biofiltration
Authors: Vigne E. , Choubert J.M. , Canler J.P. , Héduit A. , Lessard P.
Published: April 2007

This work deals with the methodology put in place to fit and validate the parameters of a biofiltration model (BAF) in tertiary nitrification treatment and dynamic conditions. For an average loading rate of 0.65 kg NH4-N/m3 media/d, different time loading rates are applied inside a filtration-backwash run using a semi-industrial pilot. Comparisons between predicted and observed values on the NH4-N, NO3-N and TSS in treated water and the total head loss ΔP are carried out firstly using default values of BAF parameters. Model predictions overestimate values measured but trends are well reproduced. A sensitivity analysis is carried out and the hierarchy of BAF parameters has been set up classifying them into strong and low influence on the effluent concentrations. Among parameters revealing the strongest influence are those of the filtration module and the mean density of biofilm for the TSS effluent and the total ΔP, the specific autotrophic growth rate, the maximum biofilm thickness and the reduction coefficient of diffusivity in the biofilm for the NH4-N, NO3-N effluent. Finally, this classification leads to setting a calibration procedure, thanks to specific experimental tests directly measuring some BAF parameters.
Microbial motility involvement in biofilm structure formation – a 3D modelling study
Authors: Picioreanu C. , Kreft J.-U. , Klausen M. , Haagensen J.A.J. , Tolker-Nielsen T. , Molin S.
Published: April 2007

A computational model explaining formation of mushroom-like biofilm colonies is proposed in this study. The biofilm model combines for the first time cell growth with twitching motility in a three-dimensional individual-based approach. Model simulations describe the tendency of motile cells to form flat biofilms spreading out on the substratum, in contrast with the immotile variants that form only round colonies. These computational results are in good qualitative agreement with the experimental data obtained from Pseudomonas aeruginosa biofilms grown in flowcells. Simulations reveal that motile cells can possess a serious ecological advantage by becoming less affected by mass transfer limitations. Twitching motility alone appears to be insufficient to generate mushroom-like biofilm structures with caps on stalks. Rather, a substrate limitation-induced detachment of motile cells followed by reattachment could explain this intriguing effect leading to higher-level biofilm structure.
Study of rotating biological contactor performance in wastewater treatment using multi-culture biofilm model
Authors: Dutta S. , Hoffmann E. , Hahn H.H.
Published: April 2007

The rotating biological contactor (RBC) process offers the specific advantages of a biofilm system in treatment of wastewater for removal of soluble organic substances and stabilisation of nitrogen compounds. Being a unique adaptation of the moving-medium biofilm system, it facilitates easy and effective oxygen transfer. However, process optimisation and adaptability under different conditions remain challenging tasks for the efficient use of this technology. Although modelling helps to study system performance under various external conditions, satisfactory mathematical representation is lacking due to the dynamic nature of the RBC system. In this work, it has been attempted to frame a mathematical model for a three-stage RBC process in simple and realistic ways. The model is based on the well-known principles of one-dimensional mass transfer and transport of substances. The biochemical conversion process is adopted from the Activated Sludge Model No. 3 which represents a mixed-culture biomass environment. Owing to the dynamic nature of oxygen transfer, which is the typical limiting substrate in municipal wastewaters, the boundary layer is assumed to be completely mixed and concentrations averaged over the entire volume. A part of the boundary layer is assumed to be exposed to air and the rest submerged in bulk liquid at all times. The model results are compared with laboratory-scale experimental data available at 25 °C. Sensitivity analysis is performed with the model to study the significance of variation of different system parameters or the surrounding environment. In essence, the model helps to explore the flexibilities within a RBC system and optimise the process design accordingly.
Performance and microbial ecology of the hybrid membrane biofilm process for concurrent nitrification and denitrification of wastewater
Authors: Downing L.S. , Nerenberg R.
Published: April 2007

We report on a novel process for total nitrogen (TN) removal, the hybrid membrane biofilm process (HMBP). The HMBP uses air-supplying hollow-fibre membranes inside an activated sludge tank, with suppressed aeration, to allow concurrent nitrification and denitrification. We hypothesised that a nitrifying biofilm would form on the membranes, and that the low bulk-liquid BOD concentrations would encourage heterotrophic denitrifying bacteria to grow in suspension. A nitrifying biofilm was initially established by supplying an influent ammonia concentration of 20 mgN/L. Subsequently, 120 mg/L acetate was added to the influent as BOD. With a bulk-liquid SRT of only 5 days, nitrification rates were 0.85 gN/m2 per day and the TN removal reached 75%. The biofilm thickness was approximately 500 μm. We used DGGE to obtain a microbial community fingerprint of suspended and attached growth, and prepared a clone library. The DGGE results, along with the clone library and operating data, suggest that nitrifying bacteria were primarily attached to the membranes, while heterotrophic bacteria were predominant in the bulk liquid. Our results demonstrate that the HMBP is effective for TN removal, achieving high levels of nitrification with a low bulk-liquid SRT and concurrently denitrifying with BOD as the sole electron donor.
Changes in ammonia oxidiser population during transition to low pH in a biofilm reactor starting with Nitrosomonas europaea
Authors: Tarre S. , Shlafman E. , Beliavski M. , Green M.
Published: April 2007

Recent experiments in our laboratory using both biofilm and suspended biomass reactors have demonstrated high rate nitrification at low pH with known autotrophic nitrifying bacteria originating from wastewater treatment plants refuting previous assumptions that nitrification is significantly inhibited at low pH. Since much of the earlier microbiological work regarding ammonia oxidising bacteria (AOB) physiology was carried out using Nitrosomonas europaea, this model bacterium's capability for high rate nitrification at low pH in a continuous biofilm reactor was tested. A biofilm reactor filled with sintered glass particles was inoculated with a pure culture of N. europaea. The reactor was first operated to high nitrification rates under conditions favourable to N. europaea (pH > 7; high ammonium concentrations). To eliminate inhibitory concentrations of nitrite at low pH, an enriched culture of Nitrospira (a nitrite oxidising bacterium) was then added. The transition from neutral to acidic conditions was attempted by sharply lowering the nitrification rate and by using a feeding solution containing insufficient buffer for complete nitrification. As opposed to other successful transitions, the pH in the N. europaea/Nitrospira reactor initially dropped only slightly and maintained pH > 6 for over two weeks. The reactor reached pH 4.5 only after four weeks. FISH results showed that while the percent of AOB and Nitrospira to eubacteria remained relatively constant at 51.1±8.2% and 40.8±6.4%, respectively, the AOB community changed completely in 60 days from 100% N. europaea to 100% Nitrosomonas oligotropha. Even though N. oligotropha was not intentionally introduced into the reactor, it is apparently much better adapted to conditions of low pH.
Occurrence and persistence of bacterial and viral faecal indicators in wastewater biofilms
Authors: Skraber S. , Helmi K. , Willame R. , Ferréol M. , Gantzer C. , Hoffmann L. , Cauchie H.-M.
Published: April 2007

Biofilms within wastewater treatment plants can capture enteric microorganisms initially present in the water phase immobilising them either definitively or temporarily. Consequently, fates of microorganisms may totally change depending on whether they interact or not with biofilms. In this study, we assessed the stability of wastewater biofilms comparing the evolution of the concentrations of bacteria (heterotrophic plate count [HPC], thermotolerant coliforms [TC]) and viral (somatic coliphages [SC] and F-specific phages [F+]) indicators in the biofilms and in the corresponding wastewaters at 4 and 20 °C. Additionally, we assessed the monthly occurrence of these bacterial and viral indicators as well as of pathogenic protozoa (Cryptosporidium oocysts and Giardia cysts) in three native wastewater biofilms for four months. Our results show that viral indicators (SC and F+) persist longer in biofilms than in the corresponding wastewaters at 4 °C as well as at 20 °C. In contrast, persistence of bacterial indicators (TC and HPC) depends on both the temperature and the matrix. Differences between viral and bacterial persistence are discussed. Monthly analysis of native wastewater biofilms shows that bacterial and viral indicators, as well as Cryptosporidium oocysts and Giardia cysts, attach to wastewater biofilms to a concentration that remains stable in time, probably as a result of a dynamic equilibrium between attachment and detachment processes.
Comparison of some characteristics of aerobic granules and sludge flocs from sequencing batch reactors
Authors: Li J. , Garny K. , Neu T. , He M. , Lindenblatt C. , Horn H.
Published: April 2007

Physical, chemical and biological characteristics were investigated for aerobic granules and sludge flocs from three laboratory-scale sequencing batch reactors (SBRs). One reactor was operated as normal SBR (N-SBR) and two reactors were operated as granular SBRs (G-SBR1 and G-SBR2). G-SBR1 was inoculated with activated sludge and G-SBR2 with granules from the municipal wastewater plant in Garching (Germany). The following major parameters and functions were measured and compared between the three reactors: morphology, settling velocity, specific gravity (SG), sludge volume index (SVI), specific oxygen uptake rate (SOUR), distribution of the volume fraction of extracellular polymeric substances (EPS) and bacteria, organic carbon and nitrogen removal. Compared with sludge flocs, granular sludge had excellent settling properties, good solid–liquid separation, high biomass concentration, simultaneous nitrification and denitrification. Aerobic granular sludge does not have a higher microbial activity and there are some problems including higher effluent suspended solids, lower ratio of VSS/SS and no nitrification at the beginning of cultivation. Measurement with CLSM and additional image analysis showed that EPS glycoconjugates build one main fraction inside the granules. The aerobic granules from G-SBR1 prove to be heavier, smaller and have a higher microbial activity compared with G-SBR2. Furthermore, the granules were more compact, with lower SVI and less filamentous bacteria.
Cohesion and detachment in biofilm systems for different electron acceptor and donors
Authors: Coufort C. , Derlon N. , Ochoa-Chaves J. , Liné A. , Paul E.
Published: April 2007

This work deals with the cohesion and detachment in biofilm systems for two electron acceptors and for two electron donors. Biofilms were developed on plates, under very low shear stress for one month and then subjected to an erosion test for two hours in a Couette-Taylor reactor. Biofilm was characterised in terms of average thickness and residual TOC mass. It was found that the biofilm structure is very heterogeneous and stratified. The top layer, which represents 60% of the biofilm mass, is very fragile and can be easily detached; the basal layer, which represents 20% of the biofilm mass, is very cohesive and can resist shear stresses up to 13 Pa. Between these two layers, a middle layer of intermediary cohesion represents 20% of the initial biofilm mass.