An acute taste and odour episode solved by olfactory GC-MS.

This paper details the analytical strategy that was used to understand the origin of an acute taste and odour episode that induced the temporary shutdown of a plant serving several million customers in South America. The odour of the drinking water was described by local people as "olive odour". The odour of a first sample was described as green apple, fruity and olive oil by CIRSEE panellists. LLE and CLSA-GC/MS showed that the sample contained high levels of 2,4-ditertbutylphenol. When submitted to olfactory-GC/MS, the LLE extract revealed the presence of an intense sweet-fruity odour that did not match any of the MS peaks. Investigation of a second, more concentrated sample collected during the peak of the episode finally revealed that this main odour was due to 2-ethyl-5,5-dimethyl-1,3-dioxane (2EDD). The cis and trans isomers of 2-ethyl-4-methyl-1,3-dioxolane (2EMD) were also identified, together with a variety of plastic additives or oligomers. These compounds had been spilled by a polyester resin manufacturing plant. The characteristics of these episodes are compared with the rare similar episodes previously reported in the literature.     

Off flavours in large waterbodies: physics, chemistry and biology in synchrony.

The Laurentian Great Lakes of North America are a drinking water source for millions of Canadian and US consumers. These waterbodies have undergone extensive change over the past century as a result of widespread degradation and remediation. Many of the Lakes are prone to taste and odour (T&O), and although these outbreaks have been poorly monitored, evidence suggests that they are increasing in frequency. Tracing and controlling T&O in such large systems presents a challenging task, due to their physical size and complexity. This paper presents an overview of recent investigative and management approaches to T&O in Lake Ontario and its outflow, the St. Lawrence River. We have identified three distinct patterns of T&O in these source-waters, caused by geosmin and 2-methylisoborneol and differing in their planktonic and benthic sources, and temporal and spatial dynamics. Each pattern has required a different approach by scientists and management, in partnership with the water industry. We have shown these T&O outbreaks are caused and moderated by physical, chemical and biological mechanisms over a spectrum of spatial and temporal scales. Canadian municipalities affected by these outbreaks have been key to the investigation of the links between T&O and ecosystem processes with the aim to develop more proactive water treatment and long-term management.     

The Ontario Water Works Consortium: a functional model of source water management and understanding.

With an historical onus on reactive water treatment in North America, most taste and odour (T&O) outbreaks and other water quality issues have been unanticipated and difficult to control. Recent severe outbreaks of these drinking water issues have prompted wider advocacy of a more proactive "source-to-tap" approach, with greater focus on multidisciplinary partnerships among utilities, scientists and management/policy-makers. However, the practical application of this management model is faced with fragmented drainage basins, waterbodies and jurisdictions, and often requires a common issue such as T&O to initiate its development. This paper presents an example of a successful cooperative approach to drinking water management, the Ontario Water Works Research Consortium (OWWRC), consisting of the six major water utilities drawing water from Western Lake Ontario, scientists from the Canadian and Ontario governments and universities, and several other agencies. Established in 1999 following severe T&O outbreaks, the OWWRC has since operated as a highly effective model, employing a science-based approach to T&O management, supporting research on source-water and treatment issues, public outreach and utility surveys. The paper describes this partnership and summarises the results of an OWWRC T&O survey as one of the significant steps towards source-water characterisation undertaken by this cooperative.     

The implications of point source phosphorus management to potable water treatment

The Vaal River Barrage reservoir is an important source of raw water for Rand Water which supplies at least 10 million people with drinking water daily. Return effluents from waste water treatment works, industries and informal urban settlements in the catchment has resulted in algal problems in the raw water and treatment process.In order to attempt to reduce the effect of eutrophication of South African inland water quality the Department of Water Affairs implemented in 1985 a 1 mg/l ortho-phosphate standard for waste water treatment works effluents.The amount of phosphate originating from the waste water treatment works decreased significantly over the 10 years after the standard was implemented even though 40% of the time the works do not comply to the standard. This has resulted in no significant change in the chlorophyll values at Rand Water Intake No. 1. The algal species composition has changed with blue-greens becoming more dominant which has resulted in a higher incidence of algal related problems. The stabilizing of the chlorophyll values is not only as a result of lower ortho-phosphate levels but also due to residence times, turbidity and conductivity.To further reduce the algal concentrations at Rand Water Intake No. 1 the 1 mg/l ortho-phosphate standard will have to be enforced, the standard possibly reduced and diffuse sources managed on a catchment basis.     

Efficient taste and odour removal by water treatment plants around the Han River water supply system.

Seven major water treatment plants in Seoul Metropolitan Area, which are under Korea Water Resources Corporation (KOWACO)'s management, take water from the Paldang Reservoir in the Han River System for drinking water supply. There are taste and odour (T&O) problems in the finished water because the conventional treatment processes do not efficiently remove the T&O compounds. This study evaluated T&O removal by ozonation, granular activated carbon (GAC) treatment, powder activated carbon (PAC) and an advanced oxidation process in a pilot-scale treatment plant and bench-scale laboratory experiments. During T&O episodes, PAC alone was not adequate, but as a pretreatment together with GAC it could be a useful option. The optimal range of ozone dose was 1 to 2 mg/L at a contact time of 10 min. However, with ozone alone it was difficult to meet the T&O target of 3 TON and 15 ng/L of MIB or geosmin. The GAC adsorption capacity for DOC in the three GAC systems (F/A, GAC and O3 + GAC) at an EBCT of 14 min is mostly exhausted after 9 months. However, substantial TON removal continued for more than 2 years (>90,000 bed volumes). GAC was found to be effective for T&O control and the main removal mechanisms were adsorption capacity and biodegradation.     

Prevalence of human adenoviruses in raw and treated water.

Human adenoviruses (HAds), of which there are 51 antigenic types, are associated aetiologically with gastrointestinal, respiratory, urinary tract and eye infections. The clinical importance of HAds and the potential health risks constituted by HAds in water environments are widely recognised. This study was conducted to assess the use of an optimised integrated cell culture molecular-based technique to determine the prevalence of HAds in raw and treated drinking-water supplies in South Africa. Selected supplies were monitored weekly for the presence of adenoviruses over a one-year period (July 2001 to June 2002). Drinking-water supplies were derived from acceptable quality surface water sources using treatment processes that conformed to international standards for the production of safe drinking water. Adenoviruses were detected by amplification in cell cultures, followed by amplifying the extracted nucleic acids using molecular techniques (nested PCR). HAds were detected in 29.8% (59/198) of the treated drinking water, 16% (8/50) of dam water and 44% (22/50) of river-water samples tested. The results of this study confirmed the presence of HAds in some raw and treated drinking water supplies in South Africa.     

Daphnia behavioural responses to taste and odour compounds: ecological significance and application as an inline treatment plant monitoring tool.

Continuous monitoring of volatile organic compounds (VOC) in raw water is highly desirable for taste and odour management, but in most treatment plants this capacity is lacking. We used a bbe Daphnia toximeter installed in the Zurich water treatment plant to determine if Daphnia magna could be used to monitor odour compounds in source-water. Trace levels of two widely distributed biogenic VOCs in freshwater: P-cyclocitral and 2(E),4(E),7(Z)-decatrienal were added to the raw water inflow to chambers containing test animals and their behaviour was recorded using a high resolution camera. We observed that each compound elicited a marked short-term increase in Daphnia swimming velocity, but the effect was brief and an acclimation to the compounds was observed after a time period or with repeated additions. The results demonstrate that the toximeter has considerable potential as a tool to monitor certain VOCs in water, and that Daphnia perceive and react to 2(E),4(E),7(Z)-decatrienal and P-cyclocitral at concentrations between 2.5 and 25 microM.     

Comparison between ozone and ferrate in oxidising geosmin and 2-MIB in water.

Among the chemicals causing taste and odour (T&O) in drinking water, the most commonly identified and problematic ones are geosmin and 2-MIB (2-methylisoborneol). Since the reported odour thresholds of geosmin and 2-MIB are as low as 4 and 8.5 ng/L, respectively, they are not readily removed by conventional water treatment processes. In this study, ozone (O3) and ferrate (Fe(VI)) were applied to oxidise geosmin and 2-MIB. Their performances were compared in terms of removal efficiency of geosmin and 2-MIB. In the case of O3, removal efficiency of geosmin and 2-MIB ozonation at different initial O3 doses, H2O2/O3 ratios and water temperatures were evaluated. The oxidation rates of geosmin and 2-MIB by Fe(VI) were measured within pH 6-8. The effect of H2O2 addition was also evaluated. In summary, O3, especially with H2O2, could almost completely oxidise geosmin and 2-MIB, while Fe(VI) could not oxidise them more than 25% at any pH that was considered in this study. This was attributed to the structure of the organics and high reaction selectivity of Fe(VI). Further study should be conducted to find the reason of inhibition of oxidation by Fe(VI).     

Treatment of taste and odor material by oxidation and adsorption.

Massive blooms of blue-green algae in reservoirs produce the musty-earthy taste and odor, which are caused by compounds such as 2-MIB and geosmin. 2-MIB and geosmin are rarely removed by conventional water treatment. Their presence in the drinking water, even at low levels (ng/L), can be detected and it creates consumer complaints. So those concentrations have to be controlled as low as possible in the drinking water. The removals by oxidation (O3, Cl2, ClO2) and adsorption (PAC, filter/adsorber) were studied at laboratory and pilot plant (50 m3/d) to select suitable 2-MIB and geosmin treatment processes. The following conclusions were derived from the study. Both of the threshold odor levels for 2-MIB and geosmin appeared to be 30 ng/L as a consequence of a lab test. For any given PAC dosage in a jar-test, removal efficiencies of 2-MIB and geosmin were increased in proportion to PAC dosage and were independent of their initial concentration in raw water for the tested PAC dosages. In comparison of geosmin with 2-MIB, the adsorption efficiency of geosmin by PAC was superior to that of 2-MIB. The required PAC dosages to control below the threshold odor level were 30 mg/L for geosmin and 50 mg/L for 2-MIB at 100 ng/L of initial concentration. Removal efficiencies of odor materials by Cl2, ClO2, and O3 were very weak under the limited dosage (1.5 mg/L), however increased ozone dosage (3.8 mg O3/L) showed high removal efficiency (84.8% for 2-MIB) at contact time 6.4 minutes. According to the initial concentrations of 2-MIB and geosmin, their removal efficiencies by filter/adsorber differed from 25.7% to 88.4%. For all those, however, remaining concentrations of target materials in finished waters were maintained below 30 ng/L. The longer run-time given for the filter/adsorber, the higher the effluent concentration generated. So it is necessary that the run-time of the filter/adsorber be decreased, when 2-MIB or geosmin occurs in raw water.     

A nose for trouble--the role of off-flavours in assuring safe drinking water.

A detailed review of drinking water disease outbreaks over the past 30 years in 15 affluent countries produced over 70 case studies, some involving fatalities, which revealed a number of common factors in these disasters. Some of these outbreaks involved off-flavours, either as a driver for reducing disinfection and making the system vulnerable to pathogenic contamination or as an early warning of contamination that was not responded to with sufficient urgency or efficiency to avoid a disease outbreak. The characteristics of these outbreaks are recounted and the important link they reveal between aesthetically pleasing drinking water and safety is documented. Our analysis of common features in drinking water outbreaks also supports an argument that the failure of a water utility to be concerned about aesthetic factors makes such water supplies an inherently greater health risk for their consumers.     

Removal of geosmin and 2-methylisoborneol by biological filtration.

The quality of drinking water is sometimes diminished by the presence of certain compounds that can impart particular tastes or odours. One of the most common and problematic types of taste and odour is the earthy/musty odour produced by geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol). Taste and odour treatment processes including powdered activated carbon, and oxidation using chlorine, chloramines, potassium permanganate, and sometimes even ozone are largely ineffective for reducing these compounds to below their odour threshold concentration levels. Ozonation followed by biological filtration, however, has the potential to provide effective treatment. Ozone provides partial removal of geosmin and MIB but also creates other compounds more amenable to biodegradation and potentially undesirable biological instability. Subsequent biofiltration can remove residual geosmin and MIB in addition to removing these other biodegradable compounds. Bench scale experiments were conducted using two parallel filter columns containing fresh and exhausted granular activated carbon (GAC) media and sand. Source water consisted of dechlorinated tap water to which geosmin and MIB were added, as well as, a cocktail of easily biodegradable organic matter (i.e. typical ozonation by-products) in order to simulate water that had been subjected to ozonation prior to filtration. Using fresh GAC, total removals of geosmin ranged from 76 to 100% and total MIB removals ranged from 47% to 100%. The exhausted GAC initially removed less geosmin and MIB but removals increased over time. Overall the results of these experiments are encouraging for the use of biofiltration following ozonation as a means of geosmin and MIB removal. These results provide important information with respect to the role biofilters play during their startup phase in the reduction of these particular compounds. In addition, the results demonstrate the potential biofilters have in responding to transient geosmin and MIB episodes.     

The anatomy of odour wheels for odours of drinking water, wastewater, compost and the urban environment.

In the drinking water and air pollution fields, odour quality characterisation and intensity of each odour characteristic needs to be developed to evaluate the causes of the odours present. Drinking water quality characterisation has matured to the point where an "odour wheel" is described and the primary chemicals producing the odour are known and therefore a potential treatment can be defined from the odours reported. Sufficient understanding of the types of odorous compounds that can arise from wastewater and compost treatment processes and odours in the urban environment are starting to emerge. This article presents the anatomy of the odour wheels. It is hoped that the foundation of odour wheels will evolve as odour quality data are reported and linked with chemical causation. The compost and urban odour wheels are presented in print for the first time.     

The effect of white or grey PVC pipe and its joint solvents (primer and cement) on odour problems in drinking water distribution systems.

A study of the production of odour-causing compounds was conducted from the leaching of polyvinylchloride (PVC) pipe and its joints, primer and cement, into drinking water distribution systems. Flavour Profile Analysis (FPA), closed-loop stripping analysis--gas chromatography/mass spectrometry (CLSA-GC/MS) and sensory-GC analysis of white or grey PVC alone found no odour-causing compounds produced during the leaching experiments. FPA analysis of the PVC's primer and cement leached alone and/or when applied to grey or white PVC pipes produced a glue/varnish odour. A sweet/phenolic odour replaced the glue/varnish odour after the leached media were diluted with Milli-Q water to threshold odour intensity. Three compounds were responsible for the sweet/phenolic odour and were observed by sensoryGC analysis. The leaching study of the PVC pipe with its joint solvents (primer and cement) concluded that the original solvent compounds, and their reaction products that formed during the bonding process on the PVC pipe, were a primary source of the glue/varnish odour. The original compounds of the PVC primer and cement were not detected by CLSA-GC/MS, due to their high volatility during the CLSA extraction method and/or these compounds appeared in a solvent peak of the GC/MS analysis. However, the original primer and cement chemicals (acetone, tetrahydrofuran, methyl ethyl ketone, and cyclohexanone) had a glue/varnish odour. A total of nine odorous GC peaks were produced as reaction products from leaching of primer in water and white or grey PVC pipe with primer and cement, and white or grey PVC with primer only. None of these compounds were among the chemical ingredients in the original primer or cement. Four GC peaks with a sweet/phenolic odour were present due to the reaction products of the cement leached with white or grey PVC. None of these compounds were positively identified.     

A review of taste and odour events in Barcelona's drinking water area (1990-2004).

The main, relevant, solved problems associated with taste and odour incidents in Barcelona's drinking water area in the last 14 years are reviewed. Events produced by creosote, dioxanes and dioxolanes, dicylopentadiene, and diacetyl, among the anthropogenic compounds; geosmin, MIB and iodinated trihalomethanes and chlorobromoanisoles as examples of compounds of natural origin are exemplified. The determination of the odour threshold concentrations of selected odorous compounds is also shown as a tool to gain a better knowledge of future taste and odour events.     

再生水回用于景观水体磷营养盐对叶绿素a和藻密度的影响研究

以北京市某再生水厂出水为研究对象,人工配制各浓度梯度的营养盐,试验研究补给再生水后景观水体水质指标的变化,重点考察磷对叶绿素a和藻密度的影响情况.试验结果表明叶绿素a和藻密度主要受水体中氮磷比和磷酸盐浓度的影响.在磷酸盐保持在1 mg/L以下,氨氮在2 mg/L以下,硝酸盐氮在8 mg/L以下,将再生水一次性补给景观水体是完全可行的,不会产生藻类暴发;当磷酸盐浓度增加至1.5 mg/L,藻密度将显著增加.     

饮用水处理工艺出水对雄性生殖系统的生物活性

饮用水水源中内分泌干扰物(EDCs)的存在引起人们的广泛关注。以大鼠睾丸支持细胞为对象,研究了饮用水常规处理工艺各处理单元出水对于雄性生殖系统的生物活性。结果表明,原水受到一定程度的污染,可以诱导睾丸支持细胞的增殖。各工艺单元出水对睾丸支持细胞均没有增殖作用,说明常规水处理工艺有效地降低了原水中EDCs的生物活性。原水诱导睾丸支持细胞增殖的作用机制主要是通过改变细胞周期中的S期和G2期,使其明显升高。水样对波形蛋白的表达具有抑制作用,尤其是龙头水,表明管网输送过程中可能引入了新的物质,细胞周期分析也显示管网运输过程对于出水生物活性的改变与水厂内处理环节不同。     

A fast stir bar sorptive extraction method for the analysis of geosmin and 2-methylisoborneol in source and drinking water.

The presence of unpleasant taste and odour in drinking water is an ongoing aesthetic concern for water providers worldwide. The need for a sensitive and robust method capable of analysis in both natural and treated waters is essential for early detection of taste and odour events. The purpose of this study was to develop and optimise a fast stir bar sorptive extraction (SBSE) method for the analysis of geosmin and 2-methylisoborneol (MIB) in both natural water and drinking water. Limits of detection with the optimised fast method (45 min extraction time at 60 degrees C using 24 microL stir bars) were 1.1 ng/L for geosmin and 4.2 ng/L for MIB. Relative standard deviations at the detection limits were under 17% for both compounds. Use of multiple stir bars can be used to decrease the detection limits further. The use of 25% NaCl and 5% methanol sample modifiers decreased the experimental recoveries. Likewise, addition of 1 mg/L and 1.5 mg/L NaOCI decreased the recoveries and this effect was not reversed by addition of 10% thiosulphate. The optimised method was used to measure geosmin concentrations in treated and untreated drinking water. MIB concentrations were below the detection limits in these waters.     

再生水回用于景观水体氮营养盐对叶绿素a和藻密度的影响研究

再生水回用于景观水体是否会带来严重的生态风险,尚需广泛而深入的研究。以北京市某再生水厂出水为研究对象,人工配制各浓度梯度的营养盐,试验研究补给再生水后景观水体水质指标的变化,重点考察氮营养盐(氨氮、硝酸盐氮)对叶绿素a和藻密度的影响情况。试验结果表明叶绿素a和藻密度主要受水体中氮磷比和磷酸盐浓度的影响,与单独的硝酸盐氮浓度增加并无直接的关系。当磷酸盐浓度保持在1mg/L以下,氨氮浓度在4mg/L以下,硝酸盐氮浓度在16mg/L以下,将再生水一次性补给景观水体是可行的,不会产生藻类暴发。     

Taste and odour issues in South Korea's drinking water industry.

This paper reviews taste and odour (T&O) issues of South Korea's water industry. For this purpose, an overview of the water supply systems and drinking water standards is presented and some results from citizen surveys for customer satisfaction are included. A case study is presented in which the water intake was shifted from inside a main reservoir to a downstream location due to T&O problems. It is true that the South Korean water industry has long relied on the tolerance of consumers for periodic T&O events. Recently the South Korean water industry has become aware that the T&O problems are at the centre of consumers' concerns and has taken several positive approaches. These include monitoring T&O events using sensory and instrumental methods, installation of a baffled-channel PAC contactor and application of advanced water treatment processes.