Historical trends in occurrence and atmospheric inputs of halogenated volatile organic compounds in untreated ground water used as a source of drinking water

Analyses of samples of untreated ground water from 413 community-, non-community- (such as restaurants), and domestic-supply wells throughout the US were used to determine the frequency of detection of halogenated volatile organic compounds (VOCs) in drinking-water sources. The VOC data were compiled from archived chromatograms of samples analyzed originally for chlorofluorocarbons (CFCs) by purge-and-trap gas chromatography with an electron-capture detector (GC-ECD). Concentrations of the VOCs could not be ascertained because standards were not routinely analyzed for VOCs other than trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113). Nevertheless, the peak areas associated with the elution times of other VOCs on the chromatograms can be classified qualitatively to assess concentrations at a detection limit on the order of parts per quadrillion. Three or more VOCs were detected in 100% (percent) of the chromatograms, and 77.2% of the samples contained 10 or more VOCs. The maximum number of VOCs detected in any sample was 24. Modeled ground-water residence times, determined from concentrations of CFC-12, were used to assess historical trends in the cumulative occurrence of all VOCs detected in this analysis, as well as the occurrence of individual VOCs, such as CFC-11, carbon tetrachloride (CCl(4)), chloroform and tetrachloroethene (PCE). The detection frequency for all of the VOCs detected has remained relatively constant from approximately 1940 to 2000; however, the magnitude of the peak areas on the chromatograms for the VOCs in the water samples has increased from 1940 to 2000. For CFC-11, CCl(4), chloroform and PCE, small peaks decrease from 1940 to 2000, and large peaks increase from 1940 to 2000. The increase in peak areas on the chromatograms from analyses of more recently recharged water is consistent with reported increases in atmospheric concentrations of the VOCs. Approximately 44% and 6.7% of the CCl(4) and PCE detections, respectively, in pre-1940 water, and 68% and 62% of the CCl(4) and PCE detections, respectively, in water recharged in 2000 exceed solubility equilibrium with average atmospheric concentrations. These exceedences can be attributed to local atmospheric enrichment or direct contaminant input to ground-water flow systems. The detection of VOCs at concentrations indicative of atmospheric sources in 100% of the samples indicates that untreated drinking water from ground-water sources in the US recharged within the past 60 years has been affected by anthropogenic activity. Additional inputs from a variety of sources such as spills, underground injections and leaking landfills or storage tanks increasingly are providing additional sources of contamination to ground water used as drinking-water sources.     

Identification and significance of sulphonamides (p-TSA, o-TSA, BSA) in an urban water cycle (Berlin, Germany)

Because of the nature of the water cycle in Berlin, a number of persistent wastewater residues are present in the surface water and may potentially reach the groundwater via bank filtration and artificial recharge. The occurrence and behaviour of the wastewater residues para-toluenesulphonamide (p-TSA), ortho-toluenesulphonamide (o-TSA) and benzenesulphonamide (BSA) through wastewater treatment, surface water, bank filtration and drinking water treatment was studied. In addition, groundwater below a former sewage farm was investigated. All three compounds are ubiquitous in the aquatic environment of Berlin. p-TSA concentrations are much higher than those of o-TSA and BSA. p-TSA was found in high concentrations in the wastewater influent (2 to 15microg/L), in the wastewater effluent (<0.15 to 2.34microg/L) and in sewage farm groundwater (<0.05 to 20microg/L) and in lower concentrations in the surface water (<0.05 to 1.15microg/L), bank filtrate (<0.05 to 0.30microg/L) and drinking water (<0.05 to 0.54microg/L). p-TSA is considerably depleted during waste- and drinking water treatment ( approximately 90% reduction each). The concentration ranges for o-TSA and BSA in wastewater influents were 0.11 to 8microg/L and <0.05 to 0.64microg/L, respectively, while the values for wastewater effluents were 0.14 to 4microg/L for o-TSA and 0.25 to 0.49microg/L for BSA. Wastewater treatment and drinking water treatment do not reduce the concentrations of o-TSA and BSA. The behaviour of o-TSA during wastewater treatment varies largely between different wastewater treatment plants where concentrations increase, remain constant or decrease. BSA forms during treatment. The concentrations measured in surface water, sewage farm groundwater, bank filtrate and drinking water were <0.05 to 1.74microg/L for o-TSA and <0.05 to 0.53microg/L for BSA.     

Occurrence and seasonal variations of Giardia in wastewater and river water from Al-Jinderiyah region in Latakia,Syria

ABSTRACT

This study investigates the occurrence and concentration of Giardia cysts in wastewater and river water samples in Al-Jinderiyah region, Latakia, Syria. A total of 120 samples were collected between October 2016 and October 2017 from influent and effluent of Al-Jinderiyah Waste Water Treatment Plant (WWTP) and from three contaminated river water sites. Samples were concentrated and subjected to microscopic examination. The results show that the concentrations of cysts ranged from 0 to 297 cysts/L in wastewater samples. The overall removal efficiency of cysts in the activated sludge WWTP was 84.35%. The concentrations of cysts ranged from 0 to 128.52 cysts/L in river water samples. The highest concentration in river water was recorded near the raw wastewater discharge point. Seasonal variations of Giardia cysts concentration were significant, and the highest concentrations were recorded in the rainy season. The results suggest that Giardia may pose a public health risk in the studied region.     

A survey of organic contaminants in household and bottled drinking waters in Kuwait

Chemical analysis of volatile organic compounds (VOCs) and semivolatiles (SVs), including pesticides, was performed on 623 and 568 samples, respectively, of household drinking water, as well as on 113 samples from 71 brands of bottled water available in Kuwaiti markets. The analysis was performed according to United States Environmental Protection Agency (US-EPA) Methods 524.2 and 525.2. Nine VOCs and eight SVs were found in household water. Furthermore, between one and seven of 12 VOCs were detected in 93% of the bottled water brands. All bottled waters were found to be completely free of SVs. Styrene was the main pollutant found in all brands packaged in polystyrene containers of sizes 200-mL and 250-mL, with levels generally higher than the WHO guideline value of 20 µg/L. The levels of styrene, toluene, ethyl benzene and xylenes were found to increase with storage time, which indicates that these VOCs were migrating from the container material. No effect was detected due to changes in the storage temperature. All detected VOCs and SVs in household and bottled waters, except styrene, were found at concentrations much lower than those established as safe by WHO guidelines and US-EPA maximum contaminant levels (MCLs), respectively.     

Perfluorinated alkylated substances in the aquatic environment: An Austrian case study

Perfluorinated alkylated substances (PFAS) are of global interest due to their occurrence and persistency in the environment. This study includes surface waters and sediments for the analysis of eleven PFAS. The PFAS studied can be grouped in perfluoroalkyl carboxylates (PFCAs), perfluoroalkyl sulfonates (PFS) and perfluoroalkyl sulfonamides (PFSA). The two most important compounds are perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). These two substances showed the most significant values for surface water samples with maximum concentrations of 21 ng l⁻¹ for PFOA and 37 ng l⁻¹ for PFOS. Sediment samples from seven Austrian lakes and the river Danube were studied. Whereas PFSA and PFS were not detected in any sediment sample PFCAs were detected in most of the lake samples in concentrations up to 1.7 μg kg⁻¹ dry wt. PFOA, perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA) were detected in all Danube river sediment samples in concentrations varying from 0.1 up to 5.1 μg kg⁻¹ dry wt. For the various sampling points the proportional mass flows deriving from wastewater discharges were calculated. Whereas only up to 10% of the average flow is discharged wastewater up to more than 50% of the PFAS mass flows in the rivers can be attributed to wastewater discharges. Besides wastewater different other pathways as emissions from point sources, further degradation of precursor products, runoff from contaminated sites or surface runoff as well as dry and wet deposition have to be considered as relevant sources for PFAS contamination in surface waters.     

Mutagenic and clastogenic effects of organic extracts from the Athenian drinking water

Organic extracts of chlorinated drinking water collected from the water distribution system of Athens, Greece, were tested in parallel for their ability to cause mutations in the Salmonella His+ reversion system and sister chromatid exchanges (SCE) and chromosomal aberrations in CHO cells. They were found to induce His+ revertants in frequencies similar to those detected previously with drinking water extracts from other areas around the world. We observe that organic samples from surface drinking water induce SCE and chromatid type abnormalities in CHO cell cultures while samples collected from ground drinking water did not. These findings confirm that chlorinated surface drinking water contains substances which are mutagenic and clastogenic and may be carcinogenic in humans.     

Fate of aromatic hydrocarbons in Italian municipal wastewater systems: An overview of wastewater treatment using conventional activated-sludge processes (CASP) and membrane bioreactors (MBRs)

We studied the occurrence, removal, and fate of 16 polycyclic aromatic hydrocarbons (PAHs) and 23 volatile organic compounds (VOCs) in Italian municipal wastewater treatment systems in terms of their common contents and forms, and their apparent and actual removal in both conventional activated-sludge processes (CASP) and membrane bioreactors (MBRs). We studied five representative full-scale CASP treatment plants (design capacities of 12 000 to 700 000 population-equivalent), three of which included MBR systems (one full-scale and two pilot-scale) operating in parallel with the conventional systems. We studied the solid-liquid partitioning and fates of these substances using both conventional samples and a novel membrane-equipped automatic sampler. Among the VOCs, toluene, ethylbenzene, xylenes, styrene, 1,2,4-trimethylbenzene, and 4-chlorotoluene were ubiquitous, whereas naphthalene, acenaphthene, fluorene, and phenanthrene were the most common PAHs. Both PAHs and aromatic VOCs had removal efficiencies of 40-60% in the headworks, even in plants without primary sedimentation. Mainly due to volatilization, aromatic VOCs had comparable removal efficiencies in CASP and MBRs, even for different sludge ages. MBRs did not enhance the retention of PAHs sorbed to suspended particulates compared with CASPs. On the other hand, the specific daily accumulation of PAHs in the MBR’s activated sludge decreased logarithmically with increasing sludge age, indicating enhanced biodegradation of PAHs. The PAH and aromatic VOC contents in the final effluent are not a major driver for widespread municipal adoption of MBRs, but MBRs may enhance the biodegradation of PAHs and their removal from the environment.     

Spatial and temporal variations in the occurrence of cocaine and benzoylecgonine in waste- and surface water from Belgium and removal during wastewater treatment

Estimates of cocaine consumption are currently resulting from population surveys, consumer interviews and crime statistics. A new approach (“sewage epidemiology”) based on the analysis of cocaine (COC) and its metabolite, benzoylecgonine (BE), in water samples was applied to 10 river sites and 30 wastewater treatment plants (WWTPs) in Belgium. Each river site was sampled twice, during the summer of 2007 and the winter of 2007-2008, while each WWTP was sampled on a Sunday and a Wednesday, during the summer-autumn of 2007 and the winter of 2007-2008. This sampling strategy allowed for the evaluation of spatial and seasonal variations in the occurrence of COC and BE in waste- and surface water. WWTP Brussel-Noord was sampled for 19 consecutive days to evaluate daily and weekly variations in the presence of COC and BE in wastewater. For 7 WWTPs, influent and effluent water samples were collected to investigate the removal of COC and BE during the wastewater treatment process. Analysis of water samples was performed using solid-phase extraction and liquid chromatography coupled to tandem mass spectrometry. Measured concentrations were further converted into an amount of used cocaine, called cocaine equivalents, as previously described in the literature. Results showed no significant difference in cocaine use between the investigated seasons. A constant cocaine consumption was observed during the week (Monday-Friday) with peaks during the weekend for WWTP Brussel-Noord. The COC/BE ratio in water samples was significantly higher during winter, most probably due to a slower hydrolysis of cocaine in low-temperature water. COC and BE were removed in the investigated WWTPs with a removal efficiency of >93%.     

Occurrence and suitability of sucralose as an indicator compound of wastewater loading to surface waters in urbanized regions

Urban watersheds are susceptible to numerous pollutant sources and the identification of source-specific indicators can provide a beneficial tool in the identification and control of input loads, often times needed for a water body to achieve designated beneficial uses. Differentiation of wastewater flows from other urban wet weather flows is needed in order to more adequately address such environmental concerns as water body nutrient impairment and potable source water contamination. Anthropogenic compounds previously suggested as potential wastewater indicators include caffeine, carbamazepine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, primidone, sulfamethoxazole, and TCEP. This paper compares the suitability of a variety of anthropogenic compounds to sucralose, an artificial sweetener, as wastewater indicators by examining occurrence data for 85 trace organic compounds in samples of wastewater effluents, source waters with known wastewater point source inputs, and sources without known wastewater point source inputs. The findings statistically demonstrate the superior performance of sucralose as a potential indicator of domestic wastewater input in the U.S. While several compounds were detected in all of the wastewater effluent samples, only sucralose was consistently detected in the source waters with known wastewater discharges, absent in the sources without wastewater influence, and consistently present in septic samples. All of the other compounds were prone to either false negatives or false positives in the environment.     

Rainwater harvesting, quality assessment and utilization in Kefalonia Island, Greece

The quality of harvested rainwater which is used for domestic and drinking purposes in the northern area of Kefalonia Island in SW Greece and the factors affecting it were assessed through 3-year surveillance. In 12 seasonal samplings, 156 rainwater and 144 ground- or mixed water samples were collected from ferroconcrete storage tanks (300-1000 m3 capacity), which are adjacent to cement-paved catchment areas (600-3000 m2). Common anions and major cations as well as the metals Fe, Mn, Cd, Pb, Cu, Cr, Ni and Zn were tested. The presence of three major groups of organic compounds, polycyclic aromatic hydrocarbons (PAHs), organochloride pesticides (OCPs) and volatile organic compounds (VOCs), was screened by common analytical techniques. All of the rainwater samples were within the guidelines for chemical parameters established by the 98/93/EU directive. As far as microbiological quality is concerned, total coliforms, Escherichia coli and enterococci were detected in 80.3%, 40.9% and 28.8% of the rainwater samples, respectively, although they were found in low concentrations. Chemical and microbiological parameters showed seasonal fluctuations. Principal component analysis revealed that microbiological parameters were affected mainly by the cleanness level of catchment areas, while chemical parameters were influenced by the sea proximity and human activities. Disinfection should be applied into the tanker trucks which distribute the water to the consumers and not into the big storage tanks in order to avoid by-products formation. Due to the lack of fluoride in rainwater samples, the consumers must become aware of the fact that the supplementation of this element is needed.     

The electronic nose as a rapid sensor for volatile compounds in treated domestic wastewater

An electronic nose consisting of 12 metal oxide sensors was used to monitor volatile compounds in effluent of a domestic wastewater treatment plant. Effluent and reference (deionized water) samples were heated to 60 and 90 degrees C to promote the volatilization and to increase the sensitivity. An effluent measuring campaign of 12 weeks was conducted and the repeatability and reproducibility of the procedure and the apparatus were determined. Processing the obtained fingerprints with principal component analysis (PCA) allowed interpretation and differentiation of the samples in terms of origin and quality, relative to the reference. To minimize the variance due to sensitivity fluctuations of the apparatus and to detect effluents with deviating qualities, two new concepts were defined, i.e. the relative sensorial odour perception (in short: rSOP) and the relative fingerprint. Correlations between the relative overall electronic nose output, expressed as rSOP, and selected routine parameters were weak except for the parameter "volatile suspended solids" (VSS), indicating adsorption of volatile organic compounds (VOCs) onto the organic particles. The results clearly demonstrate the possibility to use the electronic nose as a rapid alarm generator towards volatile compounds, e.g. in specific advanced treatment processes to produce reclaimed water from effluent of the domestic wastewater treatment plant under scrutiny.     

The fate of wastewater-derived NDMA precursors in the aquatic environment

To assess the stability of precursors of the chloramine disinfection byproduct N-nitrosodimethylamine (NDMA) under conditions expected in effluent-dominated surface waters, effluent samples from four municipal wastewater treatment plants were subjected to chlorination and chloramination followed by incubation in the presence of inocula derived from activated sludge. Samples subjected to free chlorine disinfection showed lower initial concentrations of NDMA precursors than those that were not chlorinated or were disinfected with pre-formed chloramines. For chloraminated and control (unchlorinated) treatments, the concentration of NDMA precursors decreased by an average of 24% over the 30-day incubation in samples from three of the four facilities. At the fourth facility, where samples were collected on three different days, NDMA precursor concentrations decreased by approximately 80% in one sample and decreased by less than 20% in the other two samples. In contrast to the low reactivity of the NDMA precursors, NDMA disappeared within 30 days under the conditions employed in these experiments. These results and measurements made in an effluent-dominated river suggest that although NDMA may be removed after wastewater effluent is discharged, wastewater-derived NDMA precursors could persist long enough to form significant concentrations of NDMA in drinking water treatment plants that use water originating from sources that are subjected to wastewater effluent discharges.     

Distribution of 1,4-dioxane in relation to possible sources in the water environment

The distribution of 1,4-dioxane was investigated in surface and groundwater in relation to possible sources. Water samples from river, coastal sea, and groundwater were collected and examined in Kanagawa Prefecture, Japan, from 1995 to 1998. Almost all samples were contaminated by 1,4-dioxane. On annual changes, the concentrations did not vary significantly in river water. However, some samples were still heavily polluted in groundwater. The highest correlation was between the concentration of 1,4-dioxane and 1,1,1-trichloroethane in the polluted groundwater samples. Soil and groundwater that was polluted by 1,1,1-trichloroethane in the past is still a possible source of 1,4-dioxane. In regard to a survey of other sources, effluents from the combined collection treatment from apartment houses, river basin sewage systems, and chemical plants were examined. The load unit of 1,4-dioxane from the treated effluent of domestic wastewater was assumed to be approximately 0.25 mg/person/day. This was derived from commonly used household chemicals, which contained 1,4-dioxane as a by-product. In river basin sewage systems, the concentrations in effluents varied significantly. High concentration inflows were probably not degraded and released. Although 50-60% of removal was recognized in acclimatized activated sludge from a chemical plant, 1,4-dioxane was easily desorbed with water from sludge.     

Monitoring of opiates, cannabinoids and their metabolites in wastewater, surface water and finished water in Catalonia, Spain

The occurrence of several opiates and cannabinoids in wastewaters and surface waters has been investigated. Most of the compounds (8 out of 11) were identified in both influent and effluents of fifteen wastewater treatment plants (WWTPs). Codeine, morphine, EDDP and methadone were detected in almost all samples with median values of 69 ng/L; 63 ng/L; 28 ng/L and 18 ng/L, respectively, whereas the main cannabinoid metabolite THC-COOH presented a median value of 57 ng/L in influents. A rough estimate of heroin and cannabis consumption was performed from the analysis of target urinary metabolites in wastewater influents. Data obtained from influents of rural and urban WWTPs gave 0.07% of heroin consumption (0.67% for the largest urban WWTP) and 4% consumption of cannabinoids, respectively for the population aged between 15 and 64 years old. The presence of opiates and cannabinoids in surface waters used for drinking water production showed the presence of the same compounds identified in wastewater effluents at concentrations up to 76 ng/L for codeine; 31 ng/L for EDDP; 12 ng/L for morphine and 9 ng/L for methadone at the intake of the DWTP. A complete removal of all studied drugs present in surface water was achieved during the potabilization process except for methadone and EDDP (91% and 87% removal, respectively).     

Occurrence of emerging contaminants, priority substances (2008/105/CE) and heavy metals in treated wastewater and groundwater at Depurbaix facility (Barcelona, Spain)

The presence of 170 pharmaceuticals, personal care products, priority substances according to the 2008/105EU Directive and four metals (Cd, Ni, Hg, Pb) have been investigated at the Llobregat delta, south of Barcelona (Spain). In the area, reclaimed water is destined to satisfy environmental uses, irrigation and the construction of a hydraulic barrier against seawater intrusion in the deep aquifer of the delta. A monitoring survey was undertaken of water samples from a tertiary wastewater treatment plant (Depurbaix), treated waste water with an additional treatment of ultrafiltration, reverse osmosis, and UV disinfection (WWATP, for the hydraulic barrier injection). Groundwater samples from the aquifer receiving recharge were also investigated. The pharmaceutical group of substances was detected in sampled waters at concentrations rarely exceeding a few μg/L, among the compounds Caffeine, Nicotine and Galaxolide (musk fragrance) were found to be present in more than 60% of the samples. Diuron was the only priority substance detected. The four metals were always present in a variable concentration. After the WWATP treatment the majority of analytes are removed from tertiary treated wastewater or their concentration is reduced below 0.1 μg/L. Monitoring revealed a widespread occurrence of analysed compounds in groundwater. Among them Codeine (analgesic), Ibuprofen (anti-inflammatory), Iopamidol, Iopromide (contrast agent) and Paraxanthine (metabolite of caffeine) have only been detected in groundwater, and are not present in water currently being injected in the deep aquifer.     

A field study on 8 pharmaceuticals and 1 pesticide in Belgium: Removal rates in waste water treatment plants and occurrence in surface water

Only recently, attention has been drawn towards the occurrence of pharmaceuticals in the environment. In recent years many reports have been made on the occurrence of the large, differentiated group of pharmaceuticals in waste water, surface water, ground water and in soil. In this study, we demonstrate the applicability of a previously developed LC-MS/MS method by evaluating in waste water and surface water samples from Belgium the occurrence of 8 pharmaceuticals and 1 pesticide (flubendazole, pipamperone, rabeprazole, domperidone, ketoconazole, itraconazole, cinnarizine, miconazole and propiconazole). Removal rates in five public waste water treatment plants were assessed. Introduction of several compounds into the aquatic environment by discharge of effluent could be demonstrated. For several compounds, the highest concentrations (up to 35.6 μg/l for pipamperone) were observed in the effluent of a WWTP receiving water from chemo-pharmaceutical and other industrial companies. The occurrence of these compounds in the aquatic environment was assessed by analyzing 16 surface water samples, taken from various locations. Four pharmaceuticals (flubendazole, pipamperone, domperidone and cinnarizine) could be detected in at least one sample at low concentrations (up to 26.4 ng/l). The pesticide propiconazole was found in comparable concentrations (up to 85.9 ng/l) as in effluent, suggesting potential introduction by direct seepage of water from rural grounds. The highest concentrations of flubendazole, pipamperone, domperidone, propiconazole and cinnarizine (up to 961.3 ng/l) were observed in a sample, taken near the discharge of a WWTP receiving water from chemo-pharmaceutical and other industries. An initial environmental risk assessment was done based on these results.     

Part I. Identifying anthropogenic markers in surface waters influenced by treated effluents: a tool in potable water reuse

In potable water reuse, treated wastewater becomes part of the drinking water supply. An important question associated with this practice is whether or not the organic quality of the treated wastewater is chemically different from that of non-human impacted water. This question was addressed in a case study of indirect potable water reuse where the organic matrix of the South Platte River was analyzed upstream and downstream of the discharge of treated wastewater effluent using conventional water quality parameters combined with pyrolysis-GC/MS. Effluent-derived organic material (EfOM) was found to be more aliphatic and had higher organic nitrogen and halogen content compared to organic material derived from "natural" (non-anthropogenic) sources (NOM). Seasonal changes that resulted from the change in the contributions of aquatic and terrestrial sources were not observed in EfOM; but they were strongly observed in NOM under the control of natural processes. Using principal component and factor analyses, the pyrolysis fragments of phenol, alkyl-phenols, and acetic acid were identified as the seasonal indicators for the NOM set of samples. In contrast, benzaldehyde, benzonitrile, chlorobutanoic acid, furancarboxaldehyde, and methylfurancarboxaldehyde were identified as the indicators for wastewater inputs for the EfOM set of samples. Overall, the results from conventional water quality parameters and pyrolysis-GC/MS revealed that: (1) EfOM bears a chemical signature distinct from NOM and (2) under the conditions of this study, EfOM discharged to the South Platte River persisted and controlled organic quality at downstream points.     

Microbiological investigations for sanitary assessment of wastewater treated in constructed wetlands

Microbiological investigations into the occurrence and fate of pathogens in wastewater were carried out in a multi-annual measurement programme, using samples from three artificial wetlands equipped with pre-treatment systems (multi-chamber septic tanks, lagoons) and predominantly treating domestic wastewater. In this study, the concentrations of indicator organisms and pathogenic or potentially pathogenic microorganisms were determined in the various components or stages of the systems. The evaluation of data from some 3.600 microbiological analyses and a comparison with older data from a plant which has already been operation for 18 y made it possible for the first time ever to include operational factors in the assessment. Average removal of all major indicator organisms and pathogens is 1.5-2.5 log units for one-stage systems and increases to 3-5 log units for multi-stage systems. Significant differences between horizontal and vertical filters were not found. If no clogging problems arise during their operation, multi-stage systems can meet the requirements of the EU bathing water and irrigation water directives. Influent concentration, wastewater temperature, and hydraulic loading rate were found to be major factors of influence. The performance of constructed wetlands in removing microorganisms is clearly superior to that of conventional biological activated sludge systems.     

Distribution and potential significance of a gull fecal marker in urban coastal and riverine areas of southern Ontario, Canada

To better understand the distribution of gull fecal contamination in urban areas of southern Ontario, we used gull-specific PCR and qPCR assays against 1309 water samples collected from 15 urban coastal and riverine locations during 2007. Approximately, 58% of the water samples tested positive for the gull-assay. Locations observed to have higher numbers of gulls and their fecal droppings had a higher frequency of occurrence of the gull marker and a higher gull marker qPCR signal than areas observed to be less impacted by gulls. Lower gull marker occurrence and lower qPCR signals were associated with municipal wastewater (7.4%) and urban stormwater effluents (29.5%). Overall, there were no statistically significant differences in gull marker occurrence at beach sites for pore water, ankle, and chest-depth samples, although signals were generally higher in interstitial beach sand pore water and ankle-depth water than in chest-depth water samples. Overall, the results indicated that gull fecal pollution is widespread in urban coastal and riverine areas in southern Ontario and that it significantly contributes to fecal indicator bacterial loads.     

Spatial and temporal variability of priority volatile organic compounds in the Scheldt estuary

The occurrence and spatial-temporal variability of 25 volatile organic compounds (VOCs) was studied from May 1998 to November 2000 in the Scheldt estuary. Target VOCs were selected from lists of priority pollutants to the North Sea, and included chlorinated short-chain hydrocarbons (CHCs), monocyclic aromatic hydrocarbons (MAHs) and chlorinated monocyclic aromatic hydrocarbons (CMAHs). Samples were taken between Vlissingen and Temse over a 95 km trajectory, and analysed by purge-and-trap and high resolution gas chromatography-mass spectrometry. Data were attended by analyses deemed 'in control' by a rigorous quality assurance/quality control program, as proposed by Quality Assurance of Information for Marine Environmental Monitoring in Europe (QUASIMEME). CHCs were among the most commonly found VOCs in the estuary, ranging from a few ng l(-1) to several microg l(-1). Most analytes were traceable to a single input source in the upper part of the estuary, which is densely populated and highly industrialized. By contrast, the occurrence of MAHs resulted from contributions of a wide spectrum of sources. The CMAHs were less abundant in the water column, and were mainly detected as chlorobenzene and 1,4-dichlorobenzene. Concentrations of several priority VOCs have markedly decreased since 1995 owing to emission reduction efforts within international frameworks for the protection of the North Sea.