Contribution of the FPA tasting panel to decision making about drinking water treatment facilities.

The flavour profile analysis (FPA) panel of Aigües de Barcelona has participated in three engineering projects initiated to improve both the quality of the water supplied and the use of the scarce resources available. The information provided by the panel enables a solid evaluation of the organoleptic quality of the water produced in the facilities, which is very useful in making decisions concerning the development of the projects. The first project refers to the Besòs full scale nanofiltration pilot plant. The study includes characterisation of the organoleptic quality of the water obtained and the behaviour of blends in different proportions with water from the Ter river. Secondly, this article presents the results obtained in El Papiol pilot plant for the reduction of trihalomethanes in water from the Abrera WTP, situated by the Llobregat river. The tasting results indicate that the stripping treatment slightly improves the quality of water, whereas the improvement is more remarkable with carbon filtration. The third project was the reverse osmosis pilot plant installed in the Sant Joan Despi WTP, which also collects water from the Llobregat river. A gradual improvement of the water treated was clearly observed when increasing amounts of reverse osmosis treated water were added. Some trends were also observed according to the characteristics of the feed water to the reverse osmosis facilities.

Managing an odour episode in Barcelona's water supply: strategies adopted, the causative agent (diacetyl) and determination of its organoleptic properties.

The Llobregat River is a basic drinking water resource for the city of Barcelona, meeting 40% of the demand. The river runs through a densely populated industrial area, so that it has in its history experienced various episodes due to industrial spills. The present work deals with a recent episode involving diacetyl. To the best of our knowledge this episode is the first time that this compound has been identified as an odour-causing compound in water. In a previous work the analytical method used for the identification of the compound causing the episode was described. The present work focuses its attention on how the episode was handled: action taken at the Sant Joan Despi water treatment plant and the sampling strategy on the river that led to the identification of the company responsible for the spill, a paper mill. It also deals with the role played by the FPA panel in the resolution of the episode: organoleptic description of samples of the problem in the initial phase of the episode (from the treatment plant, distribution network and customer complaints) and, once the compound responsible was identified, the determination of its organoleptic characteristics (odour threshold, odour descriptors, Weber-Fechner curve).

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.

Determination of odour threshold concentrations and dose-response relations in water of several minor disinfection by-products: aldehydes and alkyl nitriles.

The odour threshold concentrations (OTCs) levels of aldehydes and alkyl nitriles, two groups of disinfection by-products of water treatment, have been studied in order to know if some of these compounds can be associated with off-flavour events. For aldehydes, as a result of the values obtained, which are in the low microg/L range, it is possible that they are related to these events. This is not the case for the other group, alkyl nitriles, with very high OTC values.

Effect of blending two treated waters on the organoleptic profile of Barcelona's supply.

Barcelona's drinking water has two distinct origins: the Ter and Llobregat rivers supply the city in a ratio of 35/65. The organoleptic quality of the two waters is very different. Treated water from the Llobregat sometimes has organoleptic problems, whereas the quality of treated water from the Ter is much better. The aim of this paper is to study the effects of blending the two types of water and to determine the best blend of the Ter and Llobregat treated waters in terms of flavour and odour, using the A/not A test and the Flavour Profile Analysis. The optimum blend of Ter and Llobregat water is the blend that contains the highest percentage of Llobregat water without any appreciable loss of the characteristics of Ter water.

Taste and odor profiles (off-flavors) in the drinking waters of the Barcelona area (1996-2000).

The Aigües de Barcelona laboratory systematically monitors the organoleptic quality of the water it supplies. The water comes mainly from the Llobregat and Ter rivers, with the two sources having cleary differentiated chemical characteristics. Water is monitored by the tasting panel, which works according to FPA (Flavor Profile Analysis) principles. This paper reports the results from the period 1996-2000: characteristic organoleptic profiles, evolution of descriptors and the overall organoleptic evaluation of the water. The results show that in Llobregat water the descriptors chlorinous, medicinal, rubbery and salty are the most relevant, whereas in Ter water fresh nature/grassy and metallic are. The Aesthetic Quality Index drawn up by our laboratory confirms that Ter water has better organoleptic quality than Llobregat water. Monitoring also found that neither water lost quality significantly within the distribution network.

The panel of Aigües de Barcelona: 15 years of history.

The Aigües de Barcelona Laboratory has been working on odour and taste research in water for 15 years. During the entire period its basic tool has been the FPA (Flavour Profile Analysis) standard method, used by a group of trained tasters. This paper reports the main activities of the panel in recent years, such as the recruitment and training of panellists, the wheel of descriptors used, the Aesthetic Quality Index (AQI) developed for the quality control of water supplies, various research studies, and taste and odour episodes in which it has helped.

Removal of radionuclides in drinking water by membrane treatment using ultrafiltration, reverse osmosis and electrodialysis reversal.

A pilot plant had been built to test the behaviour of ultrafiltration (UF), reverse osmosis (RO), and electrodialysis reversal (EDR) in order to improve the quality of the water supplied to Barcelona metropolitan area from the Llobregat River. This paper presents results from two studies to reduce natural radioactivity. The results from the pilot plant with four different scenarios were used to design the full-scale treatment plant built (SJD WTP). The samples taken at different steps of the treatment were analysed to determine gross alpha, gross beta and uranium activity. The results obtained revealed a significant improvement in the radiological water quality provided by both membrane techniques (RO and EDR showed removal rates higher than 60%). However, UF did not show any significant removal capacity for gross alpha, gross beta or uranium activities. RO was better at reducing the radiological parameters studied and this treatment was selected and applied at the full scale treatment plant. The RO treatment used at the SJD WTP reduced the concentration of both gross alpha and gross beta activities and also produced water of high quality with an average removal of 95% for gross alpha activity and almost 93% for gross beta activity at the treatment plant.

Distribution of uranium isotopes in surface water of the Llobregat river basin (Northeast Spain).

A study is presented on the distribution of (234)U, (238)U, (235)U isotopes in surface water of the Llobregat river basin (Northeast Spain), from 2001 to 2006. Sixty-six superficial water samples were collected at 16 points distributed throughout the Llobregat river basin. Uranium isotopes were measured by alpha spectrometry (PIPS detectors). The test procedure was validated according to the quality requirements of the ISO17025 standard. The activity concentration for the total dissolved uranium ranges from 20 to 261mBqL(-1). The highest concentrations of uranium were detected in an area with formations of sedimentary rock, limestone and lignite. A high degree of radioactive disequilibrium was noted among the uranium isotopes. The (234)U/(238)U activity ratio varied between 1.1 and 1.9 and the waters with the lowest uranium activity registered the highest level of (234)U/(238)U activity ratio. Correlations between uranium activity in the tested water and chemical and physical characteristics of the aquifer were found.

All-solid-state potentiometric sensors sensitive to nonionic surfactants based on ionophores containing ethoxylate units.

Earlier work of potentiometric Ion-selective electrodes (ISEs) sensitive to nonionic surfactants of the polyethoxylate type is further extended. The ISEs constructed were all-solid-state sensors with plasticized PVC membranes. The sensing material was a tetraphenylborate salt of the barium complex with a polyethoxylate nonionic surfactant. As membrane component, the combinations of two polyethoxylates of the nonylphenoxy type, which differed in the number of oxyethylene units (5 or 12), and two different plasticizers, (o-nitrophenyloctyl ether and o-nitrophenylphenyl ether), were tested. The response of these electrodes to different nonionic surfactants and the interference effect of several species has been evaluated. For all the types of tested electrodes, the sensitivities shown were ca. 30.0 mV dec(-1) and the limit of detection, ca. 10(-5) M, when a nonylphenoxyde with 12 oxyethylene units was used as standard. The membrane with the best response characteristics was then applied in potentiometric titrations of this kind of surfactants in the presence of Ba(2+) ion and using tetraphenylborate as the titrant.

Gas chromatographic-mass spectrometric characterization of volatile organic compounds in Barcelona tap water.

Barcelona's tap water is supplied by the Llobregat and Ter rivers, which have significant differences in raw water quality. Volatile organic compounds (VOCs) from Barcelona tap water were isolated by closed-loop stripping analysis (CLSA) and identified and determined by gas chromatography-mass spectrometry. The results showed that the Ter river gives the better quality tap water. VOCs, in particular solvents, phosphates, hydrocarbons, C3 and C4 alkylbenzenes and surfactant-related compounds such as C10-C13 alkylbenzenes and non-ionic compounds such as polyethoxylated nonylphenols and their brominated derivatives are present at the ppb level. The last two types of compounds have not previously been reported using the CLSA technique.

Determination of trace levels of anionic surfactants in river water and wastewater by a flow injection analysis system with on-line preconcentration and potentiometric detection.

The authors present an automated flow injection analysis (FIA) system for the determination of low levels of anionic surfactants in river water and wastewater. The system uses especially constructed tubular flow-through ion-selective electrodes (ISEs) as potentiometric sensors and on-line preconcentration techniques. The anionic surfactant ISEs employed are of the all-solid-state type with a plasticized PVC membrane. They show a general response to anionic surfactants with a lower limit of linear response of ∼10(-)(5) M, when used in direct determinations. However, their specificity is limited, which hampers their direct use with environmental samples. Therefore, the FIA system presented here includes a solid-phase extraction procedure for purification and preconcentration of analytes. Breakthrough curves were constructed to characterize different sorbents and different eluents were tested to optimize the preconcentration process. The FIA system was first applied to the determination of different types of anionic surfactant standards. Potentially interfering substances such as chloride, nitrate, and nonionic surfactants were checked to verify that they did not interfere on the response of the system. Concentrations of ∼10(-)(7) M (0.03 ppm) of sodium dodecyl sulfate could be detected in the nonlinear response region when 3 mL of sample was preconcentrated and eluted with 50 µL of a 75% acetonitrile/water (v/v) solution. Precision was 2% RSD (n = 31) for a 1 × 10(-)(6) M sodium dodecyl sulfate standard solution and the sample throughput was 10 h(-)(1). The FIA system was then used for the determination of total anionic surfactants in river water and wastewater.