Michèle Prévost

LIVE/DEAD® BacLight: application of a new rapid staining method for direct enumeration of viable and total bacteria in drinking water

A rapid epifluorescence staining method using the LIVE/DEAD Bacterial Viability Kit (BacLight) was applied to estimate both viable and total counts of bacteria in drinking water. BacLight is composed of two nucleic acid-binding stains: SYTO 9 and propidium iodide. SYTO 9 penetrates all bacterial membranes and stains the cells green, while propidium iodide only penetrates cells with damaged membranes, and the combination of the two stains produces red fluorescing cells. Optimal incubation conditions were found to be 15 to 20 min, at room temperature in the dark. Total (red + green) and viable (green) cells can hence be counted simultaneously. Factors affecting the staining procedure were tested (addition of glutaraldehyde, staining time, chlorine impact). In the absence of stress, BacLight viable counts were comparable and to 5-cyano-2,3-ditolyl tetrazolium (CTC) counts. BacLight total counts were comparable to acridine orange counts (differing by <0.1 log/ml). However, the increase in environmental stresses (chlorine, growth rate or temperature) induced a decrease in viability that was more pronounced for CTC and plate counts than for BacLight viable counts.

A prospective epidemiological study of gastrointestinal health effects due to the consumption of drinking water

The objective of this study was to assess if drinking water meeting currently accepted microbiological standards is the source of gastrointestinal illnesses and to attempt to identify the source(s) of these illnesses. A randomized prospective study was conducted over a period of 16 months (September 1993-December 1994) in a middle class suburban community served by a single water filtration plant. A representative sample of 1400 families were selected and randomly allocated in four groups of 350, to the following regimens: (1) tap water; (2) tap water from a continuously purged tap; (3) bottled plant water; (4) purified bottled water (tap water treated by reverse osmosis or spring water). The water treatment plant produced wather that met or exceeded current North American regulations for drinking water quality. The distribution system was found to be in compliance for both coliforms and chlorine. Using the purified water group as the baseline, the excess of gastrointestinal illness associated with tap wa...

Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH)

Relatively limited information is available regarding the impacts of temperature on the adsorption kinetics and equilibrium capacities of granular ferric hydroxide (GFH) for arsenic (V) and arsenic (III) in an aqueous solution. In general, very little information is available on the kinetics and thermodynamic aspects of adsorption of arsenic compounds onto other iron oxide-based adsorbents as well. In order to gain an understanding of the adsorption process kinetics, a detailed study was conducted in a controlled batch system. The effects of temperature and pH on the adsorption rates of arsenic (V) and arsenic (III) were investigated. Reaction rate constants were calculated at pH levels of 6.5 and 7.5. Rate data are best described by a pseudo first-order kinetic model at each temperature and pH condition studied. At lower pH values, arsenic (V) exhibits greater removal rates than arsenic (III). An increase in temperature increases the overall adsorption reaction rate constant values for both arsenic (V) and arsenic (III). An examination of thermodynamic parameters shows that the adsorption of arsenic (V) as well as arsenic (III) by GFH is an endothermic process and is spontaneous at the specific temperatures investigated.

Ozone oxidation of pharmaceuticals, endocrine disruptors and pesticides during drinking water treatment.

This study investigates the oxidation of pharmaceuticals, endocrine disrupting compounds and pesticides during ozonation applied in drinking water treatment. In the first step, second-order rate constants for the reactions of selected compounds with molecular ozone (k(O3)) were determined in bench-scale experiments at pH 8.10: caffeine (650+/-22M(-1)s(-1)), progesterone (601+/-9M(-1)s(-1)), medroxyprogesterone (558+/-9M(-1)s(-1)), norethindrone (2215+/-76M(-1)s(-1)) and levonorgestrel (1427+/-62M(-1)s(-1)). Compared to phenolic estrogens (estrone, 17beta-estradiol, estriol and 17alpha-ethinylestradiol), the selected progestogen endocrine disruptors reacted far slower with ozone. In the second part of the study, bench-scale experiments were conducted with surface waters spiked with 16 target compounds to assess their oxidative removal using ozone and determine if bench-scale results would accurately predict full-scale removal data. Overall, the data provided evidence that ozone is effective for removing trace organic contaminants from water with ozone doses typically applied in drinking water treatment. Ozonation removed over 80% of caffeine, pharmaceuticals and endocrine disruptors within the CT value of about 2 mg min L(-1). As expected, pesticides were found to be the most recalcitrant compounds to oxidize. Caffeine can be used as an indicator compound to gauge the efficacy of ozone treatment.

Analysis of natural and synthetic estrogenic endocrine disruptors in environmental waters using online preconcentration coupled with LC-APPI-MS/MS.

This paper describes a fully automated online method for solid-phase extraction coupled with liquid chromatography and tandem mass spectrometry using atmospheric pressure ionization (LC-LC-APPI-MS/MS) to simultaneously detect selected dissolved natural and synthetic hormones at concentrations as low as 5 ng/L from aqueous matrices. The method shows excellent performance for the direct analysis of water and wastewater with respect to calibration curve linearity, analytic specificity, sensitivity, and carryover, as well as overall method accuracy and precision. With a runtime of 15 min, a minimum of 200 samples were analyzed using a single online solid-phase extraction (SPE) column without noticeable differences in system performance. Because of the ruggedness and simplicity of this system, generic methods can be easily developed and applied for the high-throughput analysis of a wide variety of compounds without the need to resort to laborious offline SPE sample preparation.

Toxic cyanobacterial breakthrough and accumulation in a drinking water plant: A monitoring and treatment challenge

The detection of cyanobacteria and their associated toxins has intensified in recent years in both drinking water sources and the raw water of drinking water treatment plants (DWTPs). The objectives of this study were to: 1) estimate the breakthrough and accumulation of toxic cyanobacteria in water, scums and sludge inside a DWTP, and 2) to determine whether chlorination can be an efficient barrier to the prevention of cyanotoxin breakthrough in drinking water. In a full scale DWTP, the fate of cyanobacteria and their associated toxins was studied after the addition of coagulant and powdered activated carbon, post clarification, within the clarifier sludge bed, after filtration and final chlorination. Elevated cyanobacterial cell numbers (4.7 × 10(6)cells/mL) and total microcystins concentrations (up to 10 mg/L) accumulated in the clarifiers of the treatment plant. Breakthrough of cells and toxins in filtered water was observed. Also, a total microcystins concentration of 2.47 μg/L was measured in chlorinated drinking water. Cyanobacterial cells and toxins from environmental bloom samples were more resistant to chlorination than results obtained using laboratory cultured cells and dissolved standard toxins.

Impact of temperature on nitrification in biological activated carbon (BAC) filters used for drinking water treatment

The impact of temperature on nitrification in biological granular activated carbon (GAC) filters was evaluated in order to improve the understanding of the nitrification process in drinking water treatment. The study was conducted in a northern climate where very cold water temperatures (below 2 degrees C) prevail for extended periods and rapid shifts of temperature are frequent in the spring and fall. Ammonia removals were monitored and the fixed nitrifying biomass was measured using a method of potential nitrifying activity. The impact of temperature was evaluated on two different filter media: an opened superstructure wood-based activated carbon and a closed superstructure activated carbon-based on bituminous coal. The study was conducted at two levels: pilot scale (first-stage filters) and full-scale (second-stage filters) and the results indicate a strong temperature impact on nitrification activity. Ammonia removal capacities ranged from 40 to 90% in pilot filters, at temperatures above 10 degrees C, while more than 90% ammonia was removed in the full-scale filters for the same temperature range. At moderate temperatures (4-10 degrees C), the first stage pilot filters removed 10-40% of incoming ammonia for both media (opened and closed superstructure). In the full-scale filters, a difference between the two media in nitrification performances was observed at moderate temperatures: the ammonia removal rate in the opened superstructure support (more than 90%) was higher than in the closed superstructure support (45%). At low temperatures (below 4 degrees C) both media performed poorly. Ammonia removal capacities were below 30% in both pilot- and full-scale filters.

Seasonal variations in the occurrence and fate of basic and neutral pharmaceuticals in a Swedish river–lake system

The seasonal variations in the occurrence of carbamazepine, atenolol, metoprolol, sotalol, and acebutolol were studied at seven sites along River Fyris from December 2007 to December 2008. Samples were collected from the effluent of a waste water treatment plant (WWTP), at one upstream site, and five downstream sites of the WWTP. During one occasion in May 2008, water samples were collected at different locations and depths in the recipient lake. All analytes except of acebutolol were present in both the river and the lake at quantifiable amounts at all sampling occasions. Carbamazepine was found in similar concentrations (about 90 ng L(-1)) at all sampling sites and all studied depths (0.5-40 m) in the lake, indicating high environmental persistence of this compound. A clear seasonal pattern was observed for the natural attenuation of the beta-blockers in the river, with the highest attenuation occurring in summer and the lowest in winter. The loss of beta-blockers on a distance of 1320 m reached up to 75% during summer time but was insignificant during winter. The seasonal variations in the loss followed the seasonal variations in water temperature and chlorophyll a mass flow suggesting that biotransformation and adsorption are the main processes responsible for the loss of the studied pharmaceuticals in River Fyris downstream the WWTP.

Fate of toxic cyanobacterial cells and disinfection by-products formation after chlorination

Drinking water sources in many regions are subject to proliferation of toxic cyanobacteria (CB). Chlorination of source water containing toxic cyanobacterial cells for diverse treatment purposes might cause cell damage, toxin release and disinfection by-products (DBP) formation. There is limited information available on chlorination of different toxic CB cells and DBP formation potentials. This work: (1) determines the extent of lysis and toxins/taste and odor compound release in chlorinated natural water from CB cells (Anabaena circinalis, Microcystis aeruginosa, Cylindrospermopsis raciborskii, and Aphanizomenon issatsckenka) from laboratory cultures and natural blooms; (2) assesses the rates of oxidation of toxins by free chlorine under environmental conditions; (3) studies the DBP formation associated with the chlorination of CB cell suspensions. With chlorine exposure (CT) value of <4.0 mg min/L >60% cells lost viability causing toxin release. Cell membrane damage occurred faster than oxidation of released toxins. Kinetic analysis of the oxidation of toxins in natural water revealed significant differences in their susceptibility to chlorine, saxitoxins being the easiest to oxidize, followed by cylindrospermopsin and microcystin-LR. Furthermore, concentrations of trihalomethanes and haloacetic acids (<40 μg/L) and N-nitrosodimethylamine (<10 ng/L) as chlorination by-products were lower than the guideline values even at the highest CT value (220 mg min/L). However, the DBP concentrations in environmental bloom conditions with very high cell numbers were over the guideline values.

Evaluating pharmaceuticals and caffeine as indicators of fecal contamination in drinking water sources of the Greater Montreal region.

We surveyed four different river systems in the Greater Montreal region, upstream and downstream of entry points of contamination, from April 2007 to January 2009. The studied compounds belong to three different groups: PPCPs (caffeine, carbamazepine, naproxen, gemfibrozil, and trimethoprim), hormones (progesterone, estrone, and estradiol), and triazine herbicides and their metabolites (atrazine, deethylatrazine, deisopropylatrazine, simazine, and cyanazine). In the system A, B, and C having low flow rate and high TOC, we observed the highest detection frequencies and mass flows of PPCPs compared to the other compounds, reflecting discharge of urban contaminations through WWTPs and CSOs. However, in River D, having high flow rate and low TOC, comparable frequency of detection of triazine and their by-products and PPCPs, reflecting cumulative loads of these compounds from the Great Lakes as well as persistency against natural attenuation processes. Considering large differences in the removal efficiencies of caffeine and carbamazepine, a high ratio of caffeine/carbamazepine might be an indicative of a greater proportion of raw sewage versus treated wastewater in surface waters. In addition, caffeine appeared to be a promising indicator of recent urban fecal contaminations, as shown by the significant correlation with FC (R(2)=0.45), while carbamazepine is a good indicator of cumulative persistence compounds.