Survie in vitro de Yersinia dans les eaux d'alimentation et recuperation par filtration sur membrane

This study was undertaken to determine the survival characters and optimal parameters for the recovery of Yersinia from drinking water samples. Experiments were done by artificial contamination of 4 different water samples with 4 Yersinia strains.The strains tested along this study are: Y. enterocolitica 4052, 0:3 and 4360, 0:9, Y. enterocolitica intermedia 3953, 0:17 and Y. pseudotuberculosis 0:1. The water samples are characterized by an increasing mineralization: Distillated water, Gerardmer water (

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), Nancy water (-4500 ω cm⁻¹—H = 10°) and Vittel water (-730 ω cm⁻¹, H = 71°).Total mineralization does not significantly affect the survival of Yersinia at 20°C, but causes a dramatic decrease of the Yersinia strains at 4°C for the most mineralized water. There is no pH effect from alkaline, neutral and acidic values until pH 4.4 but Yersinia is greatly affected by more acidic pH.The previous stay of Yersinia strains in artificially contaminated water causes a reduction of kinetic growth during cultivation on peptone-water but does not change the recovery rate by filtration method.The recovery rate of the filtration method using cellulose acetate membranes (mean porosity = 0.45 μm) is very poor, ranging from 0 to 8%. The efficiency is significantly higher with the aid of polyester membranes treated by laser (Nucleopore−0.40 μm) ranging from 12 to 53% according to the mineralization of the water. The best recovery rate is obtained with the moderately mineralized water.These results can explain the poor results obtained with the use of water bacteriology classical methods for the search of Yersinia.Thus the best results can be predicted from the concentration of fairly mineralized water by filtration on polyester membrane at neutral, alkaline or weakly acidic pH.     

Quantitative in situ monitoring of organohalogen compounds in domestic sewage resulting from the use of hypochlorite bleach

A field monitoring program was carried out on the sewage of five large apartment blocks in the city of Parma, Italy, to verify under realistic conditions existing laboratory data and model calculations on organohalogen formation by domestic hypochlorite (NaOCl) bleach usage. The average adsorbable organic halogens (AOX) level was determined for three distinct experimental phases: an “undisturbed period,” a “no bleach period,” and a “controlled bleach usage period.” The study involved participation of the site inhabitants in the second and third phases.In line with what could be predicted from the hypochlorite chemistry, an effect of the use of hypochlorite bleach on the AOX concentration in domestic sewage was detected. In a laboratory simulation conducted in parallel with the field study, the degree of NaOCl-to-AOX conversion ranged from 0.75 to 2.25% (w/w). The degree of conversion in the field study itself was of the order of 1.5% (or 0.075% when expressed for a typical bleach product containing 5% NaOCl). Under the specific conditions of the site, the difference in average AOX concentration in sewage between the “no bleach” and the “undisturbed” bleach use period was of the order of 37 μg·1⁻¹ (P < 0.05). The average bleach-related AOX emission at the study site was around 7 mg·(inhabitant·day)⁻¹. Overall, these figures correspond well with existing literature data. Linking the measured amounts of AOX with available ecotoxicity data for treated domestic effluents and their organohalogen constituents, it can be considered unlikely that the organohalogens formed by domestic bleaching will exert or trigger any adverse environmental effect.     

Variation de la plombemie en fonction de la contamination par le plomb de l'eau livree a la consommation: Variation of the blood lead level as a result of lead contamination of the subjects drinking water

The combination of the chemical aggressivity of water and lead piping, as is well known, can cause severe cases of lead poisoning in those who consume such water. After a great number of observations and epidemiological studies which have strongly incriminated this metal in a wide range of pathologic conditions, other materials have been gradually substituted for lead; however, the problem remains.In compliance with a European Directive to survey the risk of lead poisoning (Council Directive, 1977), a random sample of 321 residents was selected from the Vosgian Mountains of France. This region is noted for its high incidence of cases of lead poisoning: 150 reported during 8 months in 1983 (Barbier et al., 1983).During the course of a health evaluation, a blood sample was taken from each subject for lead analysis. At the same time, a sample of tap-water (after running for 5 s) was taken from each subject home. Both lead analyses (blood and water) were performed by electrothermal atomization-atomic absorption spectrophotometry. Because of the log-normality of the distributions of the blood lead levels and the concentrations of lead in the drinking water, a logarithmic transformation was performed so that the results are expressed as the geometric mean, which for the amount of lead in the drinking water of our sample was found to be 0.16 mg l^?1.Among the subjects of this study, 28% are served by water containing more than 0.10 mg l^?1 of lead (the standard for France) and 48% by water containing more than 0.05 mg l^?1 (the European and WHO standard). In concurrence with numerous authors, our study indicates that, among our subjects, the blood lead level is much higher in men than in women (geometric means 22.9 and 15.0 μg dl^?1 respectively); this difference is highly significant (t-test:P < 0.001). Table 1 summarizes the results, by sex, obtained in this region compared with those from a study (Huel, 1982) concerning an urban French population whose geometric mean blood lead levels were 15.9 μg dl^?1 for men and 11.4 μg dl^?1 for women. The irrespective of sex, is highly significant (P < 0.001). Table 2 shows the significance of the relation between these subjects, high blood lead levels and the concentration of lead in their drinking water, while Fig. 1 shows that for contamination levels up to 0.02 mg l^?1 of lead in water, the blood lead level remains relatively stable, while above this apparent “threshold” value, the blood lead level begins to increase finally reaching quite high values in response to high contamination levels, suggesting a direct translation of increases in the water above the 0.02 mg l^?1 level to increases in the blood.     

Influence of liquid holding recovery and photoreactivation on survival of ultraviolet-irradiated fish pathogenic bacteria

Survival of the fish pathogens Aeromonas salmonicida subsp. salmonicida, Vibrio anguillarum, and Yersinia ruckeri, when subjected to various post-u.v. irradiation treatments, was investigated in a laboratory model system. In A. salmonicida, 99.9% inactivation doses had to be increased from (a) 3.2 mWscm⁻² in the case of no post-irradiation recovery treatment to (b) 8.1 mWscm⁻² if liquid holding in nutrient-free buffer in the dark for 48 h was applied before plating, (c) 9.5 mWscm⁻² with visible light illumination at 1500 lx for 8 h and (d) 10.6 mWscm⁻² with illumination followed by liquid holding. The corresponding figures for V. anguillarum were 2.8, 8.1, 6.3 and 13.4 mWscm⁻² and for Y. ruckeri 1.2, 5.3, 4.9 and 8.5 mWscm⁻². On combined treatment, the latter two species showed distinct plateaus of no or very low sensitivities to increased irradiation doses, while this feature was not evident in A. salmonicida. Complete liquid holding recovery demanded from 48 to more than 72 h at 22°C, while photoreactivation was completed within 4–6 h in all three species at the same temperature. If illumination intensity was reduced from 1500 to 150 lx, recovery time was approximately doubled in A. salmonicida. During post-irradiation dark incubation photoreactivating capacity was lost within approximately 15 h. It is concluded that the potential of fish pathogenic bacteria for liquid holding recovery and photoreactivation should be taken into consideration when assessing the efficiency of u.v. disinfection of aquacultural water. Particular concern should be aimed at recovery processes after discharge to recipient water.     

Influence of Asellus aquaticus on Escherichia coli, Klebsiella pneumoniae, Campylobacter jejuni and naturally occurring heterotrophic bacteria in drinking water

Water lice, Asellus aquaticus (isopoda), frequently occur in drinking water distribution systems where they are a nuisance to consumers and water utilities. Whether they are solely an aesthetic problem or also affect the microbial water quality is a matter of interest. We studied the influence of A. aquaticus on microbial water quality in non-chlorinated drinking water in controlled laboratory experiments. Pure cultures of the indicator organisms Escherichia coli and Klebsiella pneumoniae and the pathogen Campylobacter jejuni as well as naturally occurring heterotrophic drinking water bacteria (measured as heterotrophic plate counts, HPC) were investigated in microcosms at 7 °C, containing non-sterilised drinking water, drinking water sediment and A. aquaticus collected from a non-chlorinated ground water based drinking water supply system. Concentrations of E. coli, K. pneumoniae and C. jejuni decreased over time, following a first order decay with half lives of 5.3, 18.4 and 1.3 days, respectively. A. aquaticus did not affect survival of indicators and pathogens substantially whereas HPC were influenced by presence of dead A. aquaticus. Growth rates increased with an average of 48% for bacteria grown on R-2A agar and an average of 83% for bacteria grown on yeast extract agar when dead A. aquaticus were present compared to no and living A. aquaticus present. A. aquaticus associated E. coli, K. pneumoniae and C. jejuni were measured (up to 25 per living and 500 per dead A. aquaticus) and so were A. aquaticus associated heterotrophic bacteria (>1.8*10⁴ CFU per living and >6*10⁴ CFU per dead A. aquaticus). A. aquaticus did not serve as an optimised habitat that increased survival of indicators and pathogens, since A. aquaticus associated E. coli, K. pneumoniae and C. jejuni were only measured as long as the bacteria were also present in the water and sediment.     

Ability of three DNA-based assays to identify presumptive Escherichia coli colonies isolated from water by the culture-based mFC agar method

We tested the ability of three PCR assays, targeting uidA and tuf genes to correctly identify Escherichia coli colonies isolated from water and we compared them to two β-glucuronidase-based culture methods (Colilert^® and Readycult^®), in terms of specificity and sensitivity. E. coli isolates recovered on mFC agar were first tested for the presence of the uidA positive colonies were presumed to be E. coli. For further characterization, uidA-negative colonies were subsequently identified using the Vitek 2 automated system. Colilert^® and Readycult^® detected 436 and 442 of 468 colonies identified as E. coli on mFC corresponding to sensitivities of 93.2 and 94.4%, respectively. None of the 59 non-E. coli isolates was detected by both methods for a specificity of 100%. Two (2) uidA and 1 tuf PCR assays were also tested. The uidA PCR assays yielded positive signals for 447 (95.5%) and 434 (92.7%) of 468 E. coli isolates tested respectively, whereas the tuf PCR assay showed a sensitivity of 100%. None of the 59 non-E. coli isolates was detected by both uidA PCR assays (100% specificity), whereas tuf PCR false-positive signals were obtained with Escherichia fergusonii and Escherichia albertii. However, since these 2 species are principally found in the feces of mammals and birds, their detection indicates a fecal contamination. Consequently, using a 1-h tuf rtPCR assay to confirm the identity of E. coli colonies on mFC agar is as specific, more sensitive, and potentially more cost-efficient than culture methods based on β-glucuronidase detection.     

Variability of invertebrate abundance in drinking water distribution systems in the Netherlands in relation to biostability and sediment volumes

A survey of invertebrates in drinking water from treatment works, internal taps and hydrants on mains was carried out by almost all water companies in the Netherlands from September 1993 to August 1995. Aquatic sow bugs (Asellidae, 1-12 mm) and oligochaeta worms (Oligochaeta, 1-100 mm), both known to have caused rare though embarrassing consumer complaints, were found to form 98% of the mean biomass in water flushed from mains. Their numbers in the mains water ranged up to 1500 (mean 37) Asellidae m⁻³ and up to 9900 (mean 135) Oligochaeta m⁻³. Smaller crustaceans (0.5-2 mm) dominated the numbers in water from mains. e.g. water fleas (Cladocera and Copepoda up to 14,000 m⁻³). Common invertebrates in treated water and in tap water were Rotifera (<1 mm) and nematode worms (Nematoda, <2 mm). No Asellidae, large Oligochaeta (>5 mm) or other large invertebrates were found in 1560 samples of 200 l treated water or tap water.Large variations in invertebrate abundance were found within and between distribution systems. Of the variability of mean biomass in mains per system, 55%, 60% and 63% could statistically be explained by differences in the Biofilm Formation Rate, non-particulate organic matter and the permanganate index of the treated water of the treatment works respectively. A similar correlation was found between mean invertebrate biomass and mean sediment volumes in the distribution systems (R² = 52%).     

Measurement and interpretation of microbial adenosine tri-phosphate (ATP) in aquatic environments

There is a widespread need for cultivation-free methods to quantify viability of natural microbial communities in aquatic environments. Adenosine tri-phosphate (ATP) is the energy currency of all living cells, and therefore a useful indicator of viability. A luminescence-based ATP kit/protocol was optimised in order to detect ATP concentrations as low as 0.0001 nM with a standard deviation of <5%. Using this method, more than 100 water samples from a variety of aquatic environments (drinking water, groundwater, bottled water, river water, lake water and wastewater effluent) were analysed for extracellular ATP and microbial ATP in comparison with flow-cytometric (FCM) parameters. Microbial ATP concentrations ranged between 3% and 97% of total ATP concentrations, and correlated well (R² = 0.8) with the concentrations of intact microbial cells (after staining with propidium iodide). From this correlation, we calculated an average ATP-per-cell value of 1.75 × 10⁻¹⁰ nmol/cell. An even better correlation (R² = 0.88) was observed between intact biovolume (derived from FCM scatter data) and microbial ATP concentrations, and an average ATP-per-biovolume value of 2.95 × 10⁻⁹ nmol/μm³ was calculated. These results support the use of ATP analysis for both routine monitoring and research purposes, and contribute towards a better interpretation of ATP data.     

Biodegradation of geosmin by a novel Gram-negative bacterium; isolation, phylogenetic characterisation and degradation rate determination

Biologically active sand filters within water treatment plants (WTPs) are now recognised as an effective barrier for the removal of geosmin. However, little is known regarding the actual microbiological processes occurring or the bacteria capable of degrading geosmin. This study reports the enrichment and isolation of a Gram-negative bacterium, Geo48, from the biofilm of a WTP sand filter where the isolate was shown to effectively degrade geosmin individually. Experiments revealed that Geo48 degraded geosmin in a planktonic state by a pseudo-first-order mechanism. Initial geosmin concentrations ranging from 100 to 1000 ng/l were shown to directly influence geosmin degradation in reservoir water by Geo48, with rate constants increasing from 0.010 h⁻¹ (R² = 0.93) to 0.029 h⁻¹ (R² = 0.97) respectively. Water temperature also influenced degradation of geosmin by Geo48 where temperatures of 11, 22 and 30 °C resulted in rate constants of 0.017 h⁻¹ (R² = 0.98), 0.023 h⁻¹ (R² = 0.91) and 0.019 h⁻¹ (R² = 0.85) respectively. Phylogenetic analysis using the 16S rRNA gene of Geo48 revealed it was a member of the Alphaproteobacteria and clustered with 99% bootstrap support with an isolate designated Geo24, a Sphingopyxis sp. previously described as degrading geosmin but only as a member of a bacterial consortium. Of the previously described bacteria, Geo48 was most similar to Sphingopyxis alaskensis (97.2% sequence similarity to a 1454 bp fragment of the 16S rRNA gene). To date, this is the only study to report the isolation and characterisation of a Gram-negative bacterium from a biologically active sand filter capable of the sole degradation of geosmin.     

A method of reducing drag and fluctuating side force on bluff bodies

Measurements have been made of the forces imposed on typical two-dimensional bluff bodies with a small circular cylinder (here called a “rod”) placed upstream on the stagnation line. In most cases, the interaction was beneficial in that the drag of the overall system was lower with the rod than without it. Fluctuating side forces due to vortex shedding from the main body were also reduced for most rod positions and diameters.Three two-dimensional bluff bodies were investigated: a flat plate, a square and a circular cylinder. Reynolds numbers were in the range of 1 × 10⁴ to 7 × 10⁴.The measured overall drag coefficient at various rod spacing showed a discontinuous “jump” at some critical “jump” spacing. This change corresponded to the elimination of the usual single stagnation point on the bluff body centre line and the appearance of two stagnation points symmetrically placed, close to the lateral edges of the body.Significant drag reductions were obtained for all bluff body shapes when a front rod was located near the “jump” spacing. The fluctuating side force on the circular cylinder was reduced by the rod at high Re. On the square cylinder, the reduction in fluctuating side force was large (up to 90%) for any Re and rod size investigated.     

Solar radiation disinfection of drinking water at temperate latitudes: Inactivation rates for an optimised reactor configuration

Solar radiation-driven inactivation of bacteria, virus and protozoan pathogen models was quantified in simulated drinking water at a temperate latitude (34°S). The water was seeded with Enterococcus faecalis, Clostridium sporogenes spores, and P22 bacteriophage, each at ca 1 × 10⁵ m L⁻¹, and exposed to natural sunlight in 30-L reaction vessels. Water temperature ranged from 17 to 39 °C during the experiments lasting up to 6 h. Dark controls showed little inactivation and so it was concluded that the inactivation observed was primarily driven by non-thermal processes. The optimised reactor design achieved S₉₀ values (cumulative exposure required for 90% reduction) for the test microorganisms in the range 0.63-1.82 MJ m⁻² of Global Solar Exposure (GSX) without the need for TiO₂ as a catalyst. High turbidity (840-920 NTU) only reduced the S₉₀ value by <40%. Further, when all S₉₀ means were compared this decrease was not statistically significant (prob. > 0.05). However, inactivation was significantly reduced for E. faecalis and P22 when the transmittance of UV wavelengths was attenuated by water with high colour (140 PtCo units) or a suboptimally transparent reactor lid (prob. < 0.05). S₉₀ values were consistent with those measured by other researchers (ca 1-10 MJ m⁻²) for a range of waters and microorganisms. Although temperatures required for SODIS type pasteurization were not produced, non-thermal inactivation alone appeared to offer a viable means for reliably disinfecting low colour source waters by greater than 4 orders of magnitude on sunny days at 34°S latitude.     

Determination of sorption of seventy-five pharmaceuticals in sewage sludge

Sorption of 75 active pharmaceutical ingredients (APIs) to three different types of sludge (primary sludge, secondary sludge with short and long sludge age respectively) were investigated. To obtain the sorption isotherms batch studies with the APIs mixture were performed in four nominal concentrations to water containing 1 g of sludge. The range of APIs concentrations was between ng L⁻¹ to μg L⁻¹ which are found in the wastewater effluents. Isotherms were obtained for approximately 45 of the APIs, providing distribution coefficients for linear (K_d), Freundlich (K_f) and Langmuir (K_L) isotherms. K_d, K_f and K_L ranging between 7.1 × 10⁴ and 3.8 × 10⁷, 1.1 × 10⁻² and 6.1 × 10⁴ and 9.2 × 10⁻³ and 1.1 L kg⁻¹, respectively. The obtained coefficients were applied to estimate the fraction of APIs in the water phase (see Abstract Graphic). For 37 of the 75 APIs, the predicted presence in the liquid phase was estimated to >80%. 24 APIs were estimated to be present in the liquid phase between 20 and 80%, and 14 APIs were found to have <20% presence in the liquid phase, i.e. high affinity towards sludge. Furthermore, the effect of pH at values 6, 7 and 8 was evaluated using one way ANOVA-test. A significant difference in K_ds due to pH changes were found for 6 of the APIs (variation 10-20%).     

Distribution of Asellus aquaticus and microinvertebrates in a non-chlorinated drinking water supply system--effects of pipe material and sedimentation

Danish drinking water supplies based on ground water without chlorination were investigated for the presence of the water louse, Asellus aquaticus, microinvertebrates (<2 mm) and annelida. In total, 52 water samples were collected from fire hydrants at 31 locations, and two elevated tanks (6000 and 36,000 m³) as well as one clean water tank at a waterworks (700 m³) were inspected. Several types of invertebrates from the phyla: arthropoda, annelida (worms), plathyhelminthes (flatworms) and mollusca (snails) were found. Invertebrates were found at 94% of the sampling sites in the piped system with A. aquaticus present at 55% of the sampling sites. Populations of A. aquaticus were present in the two investigated elevated tanks but not in the clean water tank at a waterworks. Both adult and juvenile A. aquaticus (length of 2-10 mm) were found in tanks as well as in pipes. A. aquaticus was found only in samples collected from two of seven investigated distribution zones (zone 1 and 2), each supplied directly by one of the two investigated elevated tanks containing A. aquaticus. Microinvertebrates were distributed throughout all zones. The distribution pattern of A. aquaticus had not changed considerably over 20 years when compared to data from samples collected in 1988-89. Centrifugal pumps have separated the distribution zones during the whole period and may have functioned as physical barriers in the distribution systems, preventing large invertebrates such as A. aquaticus to pass alive. Another factor characterising zone 1 and 2 was the presence of cast iron pipes. The frequency of A. aquaticus was significantly higher in cast iron pipes than in plastic pipes. A. aquaticus caught from plastic pipes were mainly single living specimens or dead specimens, which may have been transported passively trough by the water flow, while cast iron pipes provided an environment suitable for relatively large populations of A. aquaticus. Sediment volume for each sample was measured and our study described for the first time a clear connection between sediment volume and living A. aquaticus since living A. aquaticus were nearly only found in samples with sediment contents higher than 100 ml/m³ sample. Presence of A. aquaticus was not correlated to turbidity of the water. Measurements by ATP, heterotrophic plate counting and Colilert^® showed that the microbial quality of the water was high at all locations with or without animals. Four other large Danish drinking water supplies were additionally sampled (nine pipe samples and one elevated tank), and invertebrates were found in all systems, three of four containing A. aquaticus, indicating a nationwide occurrence.     

Health risk assessment of inorganic arsenic intake of Cambodia residents through groundwater drinking pathway

In order to compare the magnitudes and health impacts of arsenic and other toxic trace elements in well water, groundwater and hair samples were collected from three areas with different arsenic exposure scenarios in the Mekong River basin of Cambodia. Ampil commune in Kampong Cham province was selected as an uncontaminated area, Khsarch Andaet commune in Kratie province was selected as a moderately contaminated area, and Kampong Kong commune in Kandal Province was selected as an extremely contaminated area. Results of ICP-MS analyses of the groundwater samples revealed that As, Mn, Fe and Ba concentrations were significantly different among the three study areas (Kruskal-Wallis test, p < 0.0001). Out of 46 observed wells in the Kandal province study area, 100% detected As > 50 μg L⁻¹ and Fe > 300 μg L⁻¹; 52.17% had Mn > 400 μg L⁻¹ and 73.91% found Ba > 700 μg L⁻¹. In the Kratie province study area (n = 12), 25% of wells showed elevated arsenic levels above 10 μg L⁻¹ and 25% had Mn > 400 μg L⁻¹, whereas samples from Kampong Cham province study area (n = 18) were relatively clean, with As < 10 μg L⁻¹. A health risk assessment model derived from the USEPA was applied to calculate individual risks resulting from drinking groundwater. Computational results indicated that residents from Kandal Province study area (n = 297) confronted significantly higher non-carcinogenic and carcinogenic risks than those in Kratie (n = 89) and Kampong Cham (n = 184) province study areas (Kruskal-Wallis test, p < 0.0001). 98.65% of respondents from the Kandal province study area were at risk for the potential non-cancer effect and an average cancer risk index was found to be 5 in 1000 exposure. The calculations also indicated that, in the Kratie province study area, 13.48% of respondents were affected by non-cancer health risks and 33.71% were threatened by cancer, whereas none of respondents in the Kampong Cham province study area appeared to have non-carcinogenic effect. Positively significant correlations of the arsenic content in scalp hair (As_h) with both arsenic levels in groundwater (As_w) (r_s (304) = 0.757, p < 0.0001) and individual average daily doses (ADD) of arsenic (r_s (304) = 0.763, p < 0.0001) undoubtedly indicated that arsenic accumulation in the bodies of Cambodia residents in the Mekong River basin was mainly through a groundwater drinking pathway. To the best of our knowledge, this is the first comprehensive report comparing individual health risk assessments of arsenic exposure through a groundwater drinking pathway to enriched arsenic levels from groundwater in the Mekong River basin, Cambodia. This study indicates that elevated arsenic concentrations in groundwater may lead to thousands of cases of arsenicosis in the near future if mitigating actions are not taken.     

Measurements of Unsaturated Hydraulic Conductivity Functions of Two Fine-Grained Materials

Water unsaturated hydraulic conductivity (k_w) functions of two remolded fine-grained materials were measured over a wide range of degrees of saturation (S_r) with two methods. The instantaneous profile method (IPM) was used for S_r>50%. An original vapor equilibration method (also known as the vapor equilibrium technique, VET) was used for S_r<50%. Both materials compacted at the standard Proctor optimum water content and maximum density, have saturated hydraulic conductivities (k_sat)<10^-7 m/s. The VET couples the total soil suction (s) control from desiccators with saturated salt solutions with water mass measurements from a digital laboratory balance. The k_w measurements of the two techniques are consistent and complementary. The effect of hysteresis on the k_w functions at higher s values was also investigated. The experimental results suggest that the hysteretic effect on the k_w-S_r and k_w-s relationships cannot be neglected, and that the measured k_w are significantly dependent on the initial S_r. The VET tests on the specimens that were initially dried give the lowest values of k_w and the tests on the specimens that were initially saturated give the highest values of k_w. The relative hydraulic conductivity values are very small (k_rw<2×10^-5) in this saturation range (S_r<50%) for the tested materials.     

Whole lake selective withdrawal experiment to control harmful cyanobacteria in an urban impoundment

Different environmental conditions support optimal growth by Aphanizomenon and Microcystis in Ford Lake, Michigan, USA, based on weekly species biovolume and water chemistry measurements from June through October 2005-2007. Experimental withdrawal of hypolimnetic water through the outlet dam was conducted in 2006, with 2005 and 2007 acting as control years, to test theory regarding management of nuisance and toxic cyanobacteria. The dynamics of Aphanizomenon and Microcystis blooms in Ford Lake appear to be driven largely by NO₃⁻ concentrations, with higher levels shifting the advantage to Microcystis (P < 0.0001). Aphanizomenon was most successful with a mean TN:TP ratio (mol:mol) of 48.3:1, whereas Microcystis thrived with a mean ratio of 70.1:1. Withdrawal of hypolimnetic water successfully destabilized the water column and led to higher levels of NO₃⁻ and the near elimination of the Aphanizomenon bloom in 2006 (P < 0.0001). Selective withdrawal did not reduce Microcystis biovolume or microcystin toxicity. Microcystis biovolume and NO₃⁻ levels were positively correlated with microcystin toxin (P = 0.01) and jointly accounted for 30.5% of the variability in the data. Selective withdrawal may be a viable management option for improving water quality under certain circumstances. To fully address the problem of nuisance and toxic algal blooms in Ford Lake, however, an integrated approach is required that targets cyanobacteria biovolume dynamics as well as conditions suited for toxin production.     

Microbiological aspects of fish grown in treated wastewater

Tilapia, common carp and silver carp were reared in treated domestic wastewater. The most sensitive to this environment was the silver carp, followed by common carp and tilapia. In healthy clean fish, bacteria were not found in the blood or the muscles. They were present in small numbers in various organs and in concentrations of 10⁶–10⁷ g⁻¹ in the digestive tract content. In fish exposed to treated wastewater for the entire growing period, bacteria were found in the muscles. The number of bacteria recovered from various organs ranged between 10⁴–10⁶ g⁻¹ and their concentration in the digestive tract content was 10⁸–10⁹ g⁻¹. The number of bacteria in the pond water determined the presence and concentration of bacteria in the fish. The number of bacteria that caused their appearance in the muscles of fish has been named the “threshold concentration”. Considering the public health aspects, fish can be reared in treated wastewater provided the bacteriological quality of the water is compatible with the “threshold concentration” levels of the fish grown in the ponds. The suitability of E. coli (fecal coliform bacteria) as indicators for the bacteriological quality of fish grown in wastewater-fed ponds is examined.     

Bacterial community dynamics in horizontal flow constructed wetlands with different plants for high salinity industrial wastewater polishing

This study is focused on the diversity of bacterial communities from two series of horizontal subsurface flow constructed wetlands (CW) polishing high salinity tannery wastewater. Each series was planted with Arundo donax or Sarcocornia sp. in a substrate composed by expanded clay and sand. Chemical and biochemical oxygen demand removal efficiencies were similar in each series, varying between 58 and 67% (inlet COD 218 ± 28 mg L⁻¹) and 60 and 77% (inlet BOD₅ 37 ± 6 mg L⁻¹), respectively. High numbers of culturable bacteria were obtained from substrate and root samples - 5.75 × 10⁶-3.95 × 10⁸ CFU g⁻¹ recovered on marine agar and 1.72 × 10⁷-8.46 × 10⁸ CFU g⁻¹ on nutrient agar. Fifty bacterial isolates were retrieved from the CW, related phylogenetically to Firmicutes, Actinobacteria, Bacteroidetes, α-, β-, and γ-Proteobacteria. Changes in the bacterial communities, from roots and substrate of each series, related to the plant species, hydraulic loading rates and along CW operation were examined using denaturating gradient gel electrophoresis (DGGE). The clustering analysis suggested that a diverse and distinct bacterial community inhabits each series, which was related to the type of plant present in each CW.     

Occurrence, molecular characterization and antibiogram of water quality indicator bacteria in river water serving a water treatment plant

Water pollution by microorganisms of fecal origin is a current world-wide public health concern. Total coliforms, fecal coliforms (Escherichia coli) and enterococci are indicators commonly used to assess the microbiological safety of water resources. In this study, influent water samples and treated water were collected seasonally from a water treatment plant and two major water wells in a Black Belt county of Alabama and evaluated for water quality indicator bacteria. Influent river water samples serving the treatment plant were positive for total coliforms, fecal coliforms (E. coli), and enterococci. The highest number of total coliform most probable number (MPN) was observed in the winter (847.5 MPN/100 mL) and the lowest number in the summer (385.6 MPN/100 mL). Similarly E. coli MPN was substantially higher in the winter (62.25 MPN/100 mL). Seasonal variation of E. coli MPN in influent river water samples was strongly correlated with color (R² = 0.998) and turbidity (R² = 0.992). Neither E. coli nor other coliform type bacteria were detected in effluent potable water from the treatment plant. The MPN of enterococci was the highest in the fall and the lowest in the winter. Approximately 99.7 and 51.5 enterococci MPN/100 mL were recorded in fall and winter seasons respectively. One-way ANOVA tests revealed significant differences in seasonal variation of total coliforms (P < 0.05), fecal coliforms (P < 0.01) and enterococci (P < 0.01). Treated effluent river water samples and well water samples revealed no enterococci contamination. Representative coliform bacteria selected by differential screening on Coliscan Easygel were identified by 16S ribosomal RNA gene sequence analysis. E. coli isolates were sensitive to gentamicin, trimethoprim/sulfamethazole, ciprofloxacin, vancomycin, tetracycline, ampicillin, cefixime, and nitrofurantoin. Nonetheless, isolate BO-54 displayed decreased sensitivity compared to other E. coli isolates. Antibiotic sensitivity pattern can be employed in microbial source tracking.     

Discomfort due to Vertical Thermal Gradients

Abstract Abstract When 207 subjects wearing their own clothing were randomly assigned to 9 conditions, consisting of 3 levels of vertical thermal gradient (nominally 0, 2 & 4 K/m), and 3 levels of estimated whole-body heat loss (40, 48 & 56 W/m² as measured on a similarly-clothed and seated thermal manikin, corresponding to warm, neutral and cool conditions respectively, “warm” being 1.4 K above neutral in terms of operative temperature, and “cool” being 1.4 K below) and exposed for 1 hour, local thermal discomfort was reported by 45% of the group. Local and whole-body discomfort sensations were unaffected by thermal gradient (P>0.30), but were strongly affected by operative temperature (P<0.001). Discomfort due to dry air was unaffected by thermal gradient (P>0.30), but increased significantly with operative temperature (P<0.001). Discomfort due to dry eyes increased significantly above 2 K/m (P<0.01), but was unaffected by operative temperature (P>0.80). Individual differences in thermal and air quality requirements are shown to be sufficient to cause the thermal discomfort associated with thermal gradients up to 4 K/m.