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Biocides are included in organic building façade coatings as protection against biological attack by algae and fungi but have the potential to enter the environment via leaching into runoff from wind driven rain. The following field study correlates wind driven rain to runoff and measured the release of several commonly used organic biocides (terbutryn, Irgarol 1051, diuron, isoproturon, OIT, DCOIT) in organic façade coatings from four coating systems. During one year of exposure of a west oriented model house façade in the Zurich, Switzerland area, an average of 62.7 L/m(2), or 6.3% of annual precipitation came off the four façade panels installed as runoff. The ISO method for calculating wind driven rain loads is adapted to predict runoff and can be used in the calculation of emissions in the field. Biocide concentrations tend to be higher in the early lifetime of the coatings and then reach fairly consistent levels later, generally ranging on the order of mg/L or hundreds of μg/L. On the basis of the amount remaining in the film after exposure, the occurrence of transformation products, and the calculated amounts in the leachate, degradation plays a significant role in the overall mass balance.

The removal of natural organic matter (NOM) from lake water was studied in two pilot-scale adsorbers containing granular activated carbon (GAC) with different physical properties. To study the adsorption behavior of individual NOM fractions as a function of time and adsorber depth, NOM was fractionated by size exclusion chromatography (SEC) into biopolymers, humics, building blocks, and low molecular weight (LMW) organics, and NOM fractions were quantified by both ultraviolet and organic carbon detectors. High molecular weight biopolymers were not retained in the two adsorbers. In contrast, humic substances, building blocks and LMW organics were initially well and irreversibly removed, and their effluent concentrations increased gradually in the outlet of the adsorbers until a pseudo-steady state concentration was reached. Poor removal of biopolymers was likely a result of their comparatively large size that prevented access to the internal pore structure of the GACs. In both GAC adsorbers, adsorbability of the remaining NOM fractions, compared on the basis of partition coefficients, increased with decreasing molecular size, suggesting that increasingly larger portions of the internal GAC surface area could be accessed as the size of NOM decreased. Overall DOC uptake at pseudo-steady state differed between the two tested GACs (18.9 and 28.6 g-C/kg GAC), and the percent difference in DOC uptake closely matched the percent difference in the volume of pores with widths in the 1-50 nm range that was measured for the two fresh GACs. Despite the differences in NOM uptake capacity, individual NOM fractions were removed in similar proportions by the two GACs.

Hintergrund, Ziel und Zweck Die Anwendung von Nanosilber nimmt zwar stetig zu, doch die Kenntnisse zum Vorkommen nanoskaligen Silbers in Abwassern und zum Verhalten in Klaranlagen sind gering. Untersuchungen unter realen Betriebsbedingungen fehlen sogar vollstandig. In der vorliegenden Studie wurde Nanosilber mit folgenden Zielen untersucht: 1) Hemmung der Nitrifikationsleistung im Belebtschlamm einer Klaranlage, 2) Erstellung einer Massenbilanz fur Nanosilber in einer Pilotklaranlage und 3) Verifizierung der Bilanz durch eine Untersuchung in einer realen kommunalen Klaranlage, in die durch einen Indirekteinleiter partikulares Silber eingetragen wird. Methoden Der Einfluss von vier marktublichen Nanosilberadditiven auf die Ammoniumoxidation im Belebtschlamm wurde in Batchreaktoren bei zwei Konzentrationen (1, 100 mg/L Ag) und zwei Expositionszeiten (2 h, 6 Tage) untersucht. In einer Pilotklaranlage in der Grose von 70 Einwohnerwerten wurde partikulares Silberchlorid und metallisches Nanosilber jeweils fur die Dauer zweier Schlammalter (25 Tage) dosiert und weitere zwei Schlammalter bilanziert. Als Grundlage wurden die Abwassermengen und die Silberkonzentrationen erfasst. Zudem wurde die Anlagerung von Nanosilber an Feststoffen durch elektronenmikroskopische Untersuchungen erfasst. Auf einer Klaranlage (60 000 Einwohnerwerte) wurden der Zu- und Ablauf sowie der Faulschlamm im Rahmen von vier Messkampagnen beprobt und wiederum auf Silber chemisch und Nanosilber mikroskopisch analysiert. ErgebnisseDie Zugabe von 1 mg/L Ag in Form von Silbernitrat, metallischem Nanosilber, partikularem Silberchlorid und Mikrokomposit-Silber bleibt ohne Wirkung auf die Nitrifikationsleistung. Dagegen resultieren 100 mg/L Ag fur alle Silberformen in einer Hemmung, welche zwischen 100 % fur Silbernitrat und 20–30 % fur kolloidales Nanosilber liegt. In der Massenbilanzstudie wird deutlich, dass nach Zugabe von partikularem Silberchlorid 96 % des Silbers mit dem Schlamm und 4 % uber das Nachklarbecken – also das gereinigte Abwasser – ausgetragen werden. Die Massenbilanz fur metallisches Nanosilber fallt ahnlich aus. Diese Bilanzen aus der Pilotklaranlage decken sich mit derjenigen von einer realen Klaranlage. Der Silberaustrag korreliert mit dem Feststoffaustrag im Schlammabzug und Nachklarbeckenablauf. Die Jahresfracht zum Vorfluter durfte bei 4–40 mg/a Ag pro Einwohnerwert liegen. Mit Elektronenmikroskopie lasst sich zeigen, dass das Nanosilber in und an die Belebtschlammflocken gebunden vorliegt. Diskussion Chlorid ist im Abwasser in groseren Mengen verfugbar, sodass Silberionen praktisch vollstandig zu Silberchlorid ausfallen. Silberionen binden auch an organischen Komplexbildnern und reduzierten Schwefelgruppen. Deshalb ist eine hemmende Wirkung auf Nitrifikanten selbst fur Silbernitrat bei 1 mg/L Ag (250 mg Ag/kg TS) nicht zu beobachten. Bei der sehr hohen Dosierung von 100 mg/L Ag stellt sich nicht genugend schnell ein Losungsgleichgewicht zwischen freien Silberionen und Bindungsstellen ein. Die Massenbilanz uber die Klaranlage unterstreicht, dass Nanosilber sehr gut an Partikeln bindet und effizient aus dem Abwasser eliminiert wird. Verglichen mit problematischen organischen und anorganischen Mikroverunreinigungen ist die Eliminationsrate mit uber 95 % hoch. Mit der Reduktion der ungelosten Stoffe (GUS) lasst sich auch die Silberfracht im Ablauf vermindern. SchlussfolgerungenNanosilber liegt in der Regel gebunden vor, wird dadurch effizient eliminiert und kann allenfalls mit einer Abwassernachbehandlung in Form einer Raum- oder Flachenfiltration weiter reduziert werden. Der Schlamm stellt die wichtigste Senke fur Nanosilber dar. Silberpartikel >100 nm Grose binden tendenziell weniger gut als Nanosilber im engeren Sinne. Alle analysierten Silberpartikel im Zulauf, Ablauf und Schlamm deuten darauf hin, dass das Silber vor allem sulfidisch (als Ag2S) die Klaranlage verlasst. Aufgrund der vernachlassigbaren Wasserloslichkeit dieser Silberform werden keine Silberionen freigesetzt. Empfehlungen und Ausblick Die Forschung ist auf Prozessmechanismen und die Oberflachenmodifikation von Nanosilber zu konzentrieren, die die Speziierung und das Bindungsvermogen unter Umweltbedingungen beeinflussen. Verglichen mit anderen organischen Spurenstoffen zeigt sich kein dringender Handlungsbedarf bezuglich Nanosilber im Bereich von Klaranlagen. Masnahmen zur Emissionsminderung sollten dennoch dem Vorsorgeprinzip folgend entwickelt werden.

In this study we investigate the release of metallic silver nanoparticles (Ag-NP) from paints used for outdoor applications. A facade panel mounted on a model house was exposed to ambient weather conditions over a period of one year. The runoff volume of individual rain events was determined and the silver and titanium concentrations of 36 out of 65 runoff events were measured. Selected samples were prepared for electron microscopic analysis. A strong leaching of the Ag-NP was observed during the initial runoff events with a maximum concentration of 145 micro Ag/l. After a period of one year, more than 30% of the Ag-NP were released to the environment. Particles were mostly15 nm and are released as composite colloids attached to the organic binders of the paint. Microscopic results indicate that the Ag-NP are likely transformed to considerably less toxic forms such as Ag2S.

The impact of membrane fouling by natural organic matter (NOM) on the behavior of micropollutants during ultrafiltration (UF) was investigated. Batch experiments with radioactively labeled estradiol and ibuprofen in the presence of NOM model compounds (alginate, Nordic aquatic and Aldrich humic acid) were performed using a hydrophilic and a hydrophobic membrane. The results indicate that the impact of the NOM fractions studied on micropollutant retention correlated with the fouling mechanism of the individual NOM fractions. NOM substances of high molecular weight such as alginate and Aldrich HA that foul the membrane by pore blocking and cake/gel formation had a greater impact than the Nordic aquatic humic acid of lower molecular weight. The effect of cake formation was attributed partly to micropollutant-NOM partitioning and subsequent NOM retention and partly to the effect of the fouling layer itself acting as a kind of second membrane. Fouling by NOM cake/gel formation led to a significantly increased retention of estradiol, whereas the impact Of fouling on ibuprofen retention was negligible due to significantly lower log K-oc values of ibuprofen compared to estradiol. Moreover, NOM adsorption on the membrane can lower the adsorption of hydrophobic micropollutants. Membrane adsorption of estradiol was in the order of mg/m(2) and was largely reversible with caustic solutions. The results of this study may prove useful for predicting the mass flow of micropollutants in UF applications. (c) 2009 Elsevier B.V. All rights reserved.

Hintergrund, Ziel und Zweck Die Belastung von Flieβgewassern durch organische Mikroverunreinigungen wirft haufig die Frage der Quellenzuordnung auf. Baumaterialien als Quellen problematischer Spurenstoffe finden in der Gewasserbeurteilung bisher wenig Beachtung, obwohl bereits heute biozide Wirkstoffe aus Materialschutzanwendungen zu einer Belastung des Regenwasserabflusses fuhren. In der vorliegenden Untersuchung wurden (1) die okotoxikologischen Kenngrosen fur typische Biozide in Fassadenbeschichtungen ermittelt, (2) die Auswaschung von besonders problematischen Bioziden aus Fassaden quantifiziert und (3) das Belastungsrisiko fur Gewasser mittels Stofftransportmodellierung abgeschatzt. Methoden Acht Biozide wurden untersucht, die in kunstharzgebundenen Fassadenbeschichtungen verwendet werden. Dazu gehoren auch Wirkstoffe, deren Umwelteintrag bisher eher der Landwirtschaft zugerechnet wurde, z. B. Diuron, Carbendazim und Terbutryn. Fur jedes Biozid wurden okotoxikologische Qualitatskriterien fur aquatische Organismen bestimmt. Die Auswaschung von vier Bioziden aus einer verputzten Fassade wurde im Laborversuch unter Berucksichtigung von UV-Bestrahlung untersucht, wobei die Temperatur variiert wurde. Uber 80 Beregnungsintervalle in 28 Tagen wurden Proben des Fassadenabflusses entnommen, die Wirkstoffkonzentrationen gemessen und die ausgewaschenen Wirkstoffmengen berechnet. Basierend auf einem Austragsszenario wurde das mogliche Belastungsrisiko im Gewasser durch das Biozid Cybutryn mit einer Stofftransportmodellierung abgeschatzt. Die ermittelten wirkstoffspezifischen Qualitatskriterien und die Auswaschcharakteristik wurden darin berucksichtigt. Ergebnisse Die akuten und chronischen Kriterien sowie vorhergesagten Konzentrationen ohne Effekt weisen auf eine hohe Okotoxizitat der betrachteten Biozide hin. Die Ergebnisse zum Auswaschungsverhalten von vier Bioziden (Diuron, Terbutryn, Cybutryn und Carbendazim) zeigen, dass die Wirkstoffe im Fassadenabfluss vorkommen und die Belastung unter den gewahlten experimentellen Bedingungen exponentiell abnimmt. Dabei fuhrt eine Temperaturerhohung wieder zu einem Konzentrationsanstieg. Die ausgewaschenen Stoffmengen liegen zwischen 7 % und 29 %. Bereits innerhalb der ersten 15 min wurde mehr als die Halfte der gesamten Stoffmenge wahrend der 60 min Beregnungsdauer ausgewaschen. Die Stofftransportmodellierung zum Eintrag des Biozids Cybutryn aus Fassaden ins Gewasser deutet auf ein hohes Belastungspotential fur kleinere Gewasser hin. Diskussion Die Ergebnisse zur Auswaschung von Bioziden, deren potentielle okotoxische Effekte und Stabilitat in der Umwelt zeigen, dass von einigen Wirkstoffen fur Gewasser ein hohes potentielles Belastungsrisiko, von anderen aber nur ein geringes Risiko ausgehen durfte. Belastetes Fassadenwasser muss fur einige Biozide sehr deutlich durch unbelastetes Regenwasser verdunnt werden, damit die Qualitatskriterien im Gewasser eingehalten werden. Diuron und Carbendazim werden auch in anderen Materialschutzanwendungen verwendet oder in der Landwirtschaft ausgebracht. Cybutryn wird oft als Antifouling-Wirkstoff in Bootsanstrichen eingesetzt, so dass eine Belastung im Gewasser erst unter Berucksichtigung aller Eintragswege beurteilt werden kann. Schlussfolgerungen Kritische Konzentrationsbereiche im Fassadenabfluss sind an neuen Gebaudefassaden zu erwarten, in der Regel vor allem an warmegedammten Fassaden. Angesichts der niedrigen vorhergesagten Konzentrationen ohne Effekt im Bereich von wenigen ng/L und den hohen Anwendungsmengen in Fassaden sollte die Auswaschung und das Umweltverhalten wirkstoffspezifisch abgeschatzt werden. Masnahmen an der Quelle und die jeweils nachhaltigste Regenwasserentsorgung sollten evaluiert werden. Empfehlungen und Ausblick Bei der Beurteilung der Qualitat von Regenwasserabflussen, der Entsorgungswege und Boden- und Gewasserbelastung sollte dem zunehmenden Einsatz von Bioziden und anderen Additiven in Baumaterialien als mogliche Belastungsquelle verstarkt Beachtung geschenkt werden. Ein ganzheitliches Management von Baumaterialien und der Regenwasserbewirtschaftung ist gefordert. Die noch laufenden Labor- und Feldstudien werden weitere Ergebnisse zur Auswaschung von Bioziden und Additiven aus Fassadenfarben und -putzen sowie Dachmaterialien liefern.

This study focused on the mechanistic effects of molecular interactions between inorganic particles (kaolinite) and the two main NOM fouling fractions of polysaccharides (alginate) and humics (humic acids) in ultrafiltration. Fouling effects were studied during the dead-end filtration of individual and mixed compounds as well as during the subsequent filtration of individual compounds. SEM analyses were performed to further study the fouling-layer structure. A significant synergistic effect was observed during combined particle-NOM fouling, which was considerably greater than the sum of particle and organic fouling alone. Synergistic fouling could be explained by NOM-particle interactions in the feed solution and during the fouling process. Kaolinite alone formed a fouling layer of particle aggregates, whereas humic acid adsorption onto kaolinite resulted in a fouling layer of stabilized colloids of humic acid and kaolinite. In the case of alginate, simultaneous pore-blocking and cake-layer formation of NOM and kaolinite dominated the fouling. In both cases, incorporation of the organics in the kaolinite fouling layer resulted in a fouling cake of significantly reduced porosity compared to individual particle filtration. Irreversible fouling by NOM could not be prevented by kaolinite. SEM images showed patches of the particle-fouling layer remaining on the membrane surface after backwashing, which can be linked to particle-membrane associations by NOM bridging.

There is increasing concern about environmental pollution by diffuse emissions of various environmental hazards emitted by transportation activities. For the first time substances released by railways to the environment were investigated. We considered the significant sources and the amounts emitted by regular operation within the Swiss Federal Railways (SBB) network (7200 km tracks). The main substances are about 2270 t y−1 metals, 1357 t y−1 hydrocarbons and 3.9 t y−1 herbicides. Most of the released metals are particles emitted by friction processes with iron, followed by copper, zinc, manganese, chromium, nickel, vanadium and lead. Only a small amount of metals is expected to be leached in dissolved phase. The emission of hydrocarbons may be diffusive (e.g. operational losses) or at point-sources (e.g. track-switch). The wooden sleepers seem to be the most important sources of hydrocarbons, followed by lubricants from track-switches and wheel flanges. The emissions reflect a spatial and temporal exposure pattern. The assessment is valuable for regulatory authorities working on soil and water protection as well as for railway companies determining their necessity of water and soil protection measures. Based on the results, selected studies may establish an understanding on relevant processes and environmental risk of railway imissions to soil, drainage water and groundwater.

Pilot tests were performed with a process combination of electrodialysis and ozonation for the removal of micropollutants and the concentration of nutrients in urine. In continuous and batch experiments, maximum concentration factors up to 3.5 and 4.1 were obtained, respectively. The desalination capacity did not decrease significantly during continuous operation periods of several weeks. Membrane cleaning after 195 days resulted in approximately 35% increase in desalination rate. The Yeast Estrogen Screen (YES), a bioassay that selectively detects oestrogenic compounds, confirmed that about 90% of the oestrogenic activity was removed by electrodialysis. HPLC analysis showed that ibuprofen was removed to a high extent, while other micropollutants were below the detection limit. In view of the fact that ibuprofen is among the most rapidly transported micropollutants in electrodialysis processes, this result indicates that electrodialysis provides an effective barrier for micropollutants. Standardised plant growth tests were performed in the field with the salt solution resulting from the treatment by electrodialysis and subsequent ozonation. The results show that the plant height is comparable to synthetic fertilisers, but the crop yield is slightly lower. The latter is probably caused by volatilisation losses during field application, which can be prevented by improved application technologies.

Granular activated carbon (GAC) filtration is used during drinking water treatment for the removal of micropollutants such as taste and odour compounds, halogenated hydrocarbons, pesticides and pharmaceuticals. In addition, the active microbial biomass established on GAC is responsible for the removal of biodegradable dissolved organic carbon compounds present in water or formed during oxidation (e.g., ozonation and chlorination) processes. In order to conduct correct kinetic evaluations of DOC removal during drinking water treatment, and to assess the state and performance of full-scale GAC filter installations, an accurate and sensitive method for active biomass determination on GAC is required. We have developed a straight-forward method based on direct measurement of the total adenosine tri-phosphate (ATP) content of a GAC sample and other support media. In this method, we have combined flow-cytometric absolute cell counting and ATP analysis to derive case-specific ATP/cell conversion values. In this study, we present the detailed standardisation of the ATP method. An uncertainty assessment has shown that heterogeneous colonisation of the GAC particles makes the largest contribution to the combined standard uncertainty of the method. The method was applied for the investigation of biofilm formation during the start-up period of a GAC pilot-scale plant treating Lake Zurich water. A rapid increase in the biomass of up to 1.1 x 10(10)cells/g GAC dry weight (DW) within the first 33 days was observed, followed by a slight decrease to an average steady-state concentration of 7.9 x 10(9)cells/g GAC DW. It was shown that the method can be used to determine the biomass attached to the GAC for both stable and developing biofilms.

Urine contains nutrients which can be applied usefully as a fertiliser in agriculture, but the relatively high pH can lead to ammonia evaporation. Electrodialysis with bipolar membranes was combined with an additional mass transfer unit in order to render a product containing ammonium and phosphate at a low pH. In one case, the additional mass transfer unit consisted of bubble columns placed in acid and basic concentrate streams, connected with a circulating gas phase. In the other case, the unit consisted of a gas-filled (hydrophobic) membrane placed in between the circulating acid and basic concentrate streams. The results showed that ammonia was transferred through the gas phase, but also carbonate, which is present in stored urine originating from the hydrolysis of urea. Although the pH in the product stream decreases initially, it rises above pH 7 at longer operation times. This pH increase can be attributed to a combination of proton compensating effects. The use of ammonia-selective membranes for the transfer into the acid concentrate could provide a solution to generate an ammonium phosphate product at low pH and high recoveries.

Particles in lake water samples originating from the Swiss lakes of Zurich and Constance were analysed, showing an exponential increase of particle number with decreasing particle size down to the detection limit (350 nm). Investigation of nanoparticles in Lake Zurich by microscopic methods showed that relatively large numbers of clay particles are present with different Al/Si composition and sizes. The small-sized clay particles (ca. 80 nm) tend to build aggregates with a size of 500–1,000 nm. In karstic spring water, the particle count and size distribution is strongly dependent on the precipitation rate. At high precipitation rates, channel flow occurs in the subsoil, leading to high particle counts among the whole size range and a larger average particle size. In membrane treatment by microfiltration and ultrafiltration this leads to membrane fouling due to pore blocking and cake formation, the latter being associated with the presence of organic compounds.

Runoff monitoring of six rainfall events was carried out in a highway, Winterthur, Switzerland focusing on first flush (runoff volume up to 2.88 mm). Six runoff events were used to investigate the characteristics of particle-associated PAHs in first flush. The fine fraction (

Ozonation membrane contact was carried out with a tubular membrane module to study the effects of the flow rates and the temperatures of the liquid phase on ozone transfer and on the enhancement of mass fluxes. Changes in liquid temperature gave both positive and negative effects on the ozone fluxes for the nitrite solutions. The increase of the ozone fluxes with temperature was observed until the temperature approached approximately 40 degrees C. Ozonation membrane contact was also applied to decolorize Norwegian natural organic matter (NOM) at typical color concentrations in the range of 15-20 mg Pt/L. The ozone consumption for NOM decolourization tended to decrease with the liquid flow rates. A simple mass transfer model was proposed for the ozonation membrane contactor for the NOM decolourization studied here. The model was developed based on the concepts of the ozone consumption and the enhancement factor and can be used to describe the influence of mass transfer on the effluent colour concentration of the NOM. The experimental results validated the proposed model with deviations in the range of -9 to + 7%. The decolourization rate constants obtained from the concentration-time (C-tau) model for the ozonation membrane contactor were found to be in the range of 139.44-298.81 M-1 s(-1). Simple concept to design ozonation membrane contactor for NOM decolourization was proposed. The kinetic characteristics for the NOM decolourization in ozonation membrane contactor are discussed in this paper. (c) 2005 Elsevier B.V. All rights reserved.

Continuous runoff quality monitoring was conducted for one month at urban highway drainage with an area of 8.4 ha. Dynamic change of suspended solids and heavy metal concentrations were investigated during first flush periods, taking the particle size distribution into consideration. Except for Pb, the concentrations of TSS and heavy metals in runoff were within the range of the EMC reported in recent highway runoff research. Particle-bound heavy metals (Zn, Pb, and Cu) accounted for more significant pollutant loads than soluble fractions. Their content decreased with increasing total SS concentration in runoff samples. The results of particle size distribution (PSD) analysis of runoff samples indicate that high TSS concentration samples contained coarser particles. Based on the PSD results, a stepwise wash-off phenomenon of TSS under varying runoff rate conditions was explained by the different washoff behavior of fine (< 20 mm) and coarser particles.

Copper washed off from roofs and roads is considered to be a major contribution to diffuse copper pollution of urban environments. In order to guarantee sustainable protection of soils and water, the long-term strategy is to avoid or replace copper containing materials on roofs and façades. Until achievement of this goal, a special adsorber system is suggested to control the diffuse copper fluxes by retention of copper by a mixture of granulated iron-hydroxide (GEH) and calcium carbonate. Since future stormwater runoff concepts are based on decentralised runoff infiltration into the underground, solutions are proposed which provide for copper retention in infiltration sites using GEH adsorption layers. The example of a large copper façade of which the runoff is treated in an adsorption trench reveals the first full-scale data on façade runoff and adsorber performance. During the first year of investigation average façade runoff concentrations in the range of 1-10 mg Cu/l are reduced by 96-99% in the adsorption ditch.

Water production technology for the treatment of karstic springs hasto cope with high fluctuations of various water quality parameters, in particular with high turbidity peaks. In addition, natural and manmade dissolved contaminants such as NOM, pesticides and chlorinated hydrocarbons require complex multistage treatment schemes applying conventional process trains like flocculation, granular media filtration, ozonation, granular activated carbon filtration and final disinfection. Several alternatives using membrane processes are proposed in order to simplify the plant schemes and to reduce treatment costs. A cost assessment of existing conventional treatment plants and following membrane systems of the same size is presented: micro-, ultrafiltration with and without powdered activated carbon (PAC) and the integrated system ultrafiltration—nanofitration (MF, UF, MF/PAC, UF/PAC, UF/NF). Based on full- and pilot-scale experience with karstic spring water, capital as well as operating and maintenance costs (O&M) for conventional and membrane plants are evaluated. Detailed cost analysis reveals that compared to conventional systems, membrane treatment leads to a substantial relative increase of O&M fraction. Especially, the dosing of PAC to MF or UF increases energy consumption and costs for PAC renewal. A comparison of the overall specific production costs shows that for the studied plant capacity in the range of 30–300 m3/h, the costs for simple membrane treatment with MF or UF are 5% less than for conventional process schemes whereas the costs in combination with PAC are 20% higher. Integrated systems using UF/NF combinations may not compete with conventional and UF/PAC plants.

The assumption that roof runoff can be considered as non-polluted stormwater that can be discharged directly into natural water bodies without impairing their quality and use was examined in a field study. Concentrations of major ions; total C, N, and P; heavy metals (Cu, Zn, Pb, Cd, Cr, Mn, Fe) and pesticides (triazines, acetamides, phenoxy acids) were measured in runoff from an inclined tile roof, an inclined polyester roof and a flat gravel roof. Runoff from the first two roofs showed initially very high concentrations declining rapidly to lower constant levels. This first-flush effect was modelled using a first-order rate law (wash-off function). For most constituents, concentrations were in the range of the wet deposition after the first few mm runoff depth and total loads in the runoff corresponded approximately to the total (dry and wet) atmospheric deposition load. The flat gravel roof depicted a different behaviour. Rainwater was first retained before it overflowed. Consequently gravel will be weathered and most pollutants were partially retained in the gravel layer. However, corrosion of Cu in drains (rate about 5 g m −2 y −1 ) produced such high Cu concentrations that direct disposal of runoff is questionable.

Karstic springs are characterized by their unsteady behaviour of quantitative and qualitative parameters. The irregular and unpredictable increases of turbidity, natural organic matter (NOM), particles and solutes require a flexible and reliable treatment to ensure save drinking water quality at any time. In this study, results of a microfiltration (MF) and an ultrafiltration (UF) pilot plant are presented based on 15 and 12 months on-site experience. The investigations were focused on the optimization of the operation conditions of the membranes (maximum flux, dead-end mode, cross-flow mode) in order to guarantee drinking water production at any raw water quality. The results strongly support that MF performance is mainly influenced by submicron particles contained in the raw water suspension at higher turbidity peaks and that UF membrane permeability is affected by NOM during storm weather events. Additional quality problems in some springs caused by the presence of micropollutants (trichlorethene, tetrachlorethene, atrazine) gave rise to experimentally assess the combination of powdered activated carbon (PAC) with membrane filtration. The adsorption characteristics of the solutes on different PACs were tested in laboratory and pilot scale. In the on-site experiments, removal rates of 80–90% could be achieved by adopting the necessary contact time to the previously determined kinetic data. Additionally, NOM adsorption by PAC addition could substantially improve UF performance.

The complex nature of particulate matter in natural water resources and in waste waters is characterized by the heterogeneous distribution of particle size, shape, density, and shear strength. Among these parameters, floc strength is most important in the last stages of flocculation. Experimental data on floc strength based on different methods are assessed and correlated with shear gradients in different aquatic environments. The analysis of turbulent motion reveals that the energy which affects particle agglomerates is only a small portion of the totally dissipated energy. Among the different flow fields in turbulent motion, converging/diverging flow cause strain forces which prove to be critical with respect to floc rupture. Model calculations of the surface forces on ellipsoidal particles in pure shear and strain flow fields and corresponding experiments confirm the importance of converging flow. A comparison of modeled and measured rupture forces allows to establish relationships between floc size, strain and shear rates and resulting surface forces leading to probable floc break-up. Flocs of appreciable size (200 - 2000 μm) prepared for settling are likely to be ruptured under moderate velocity gradients occurring in flocculation tanks, whereas smaller agglomerates (< 200 μm) may withstand strain forces much higher than found under practical conditions. An example of model application shows the particle stress in the entrance to porous media filters where typically high strain gradients may easily lead to a breakup of flocs larger than 200 μm.

A surface and a sub-surface infiltration system that received runoff water from trafficked roads for several decades was dug up and the contamination with heavy metals, PAH and AOX was investigated. Most measured solid phase concentrations exceeded background concentrations in nearby surface soils and sub-surface sediments and some even exceeded guidelines fixed to preserve the fertility of soil. However, the contamination decreased rapidly with depth. None of the measured metal concentrations in simulated soil solutions exceeded defined drinking water quality standards. Surprisingly, the surface and the sub-surface infiltration system seemed to be equally good at retaining pollution. This indicates that the runoff sludge found in such infiltration systems plays an important role both as a source and a sorbent for stormwater contaminants. The study does not point at a considerable risk for groundwater contamination due to stormwater infiltration, but highlights that well absorbable contaminants readily available in urban stormwater runoff eventually build up in surface soils and sub-surface sediments to environmentally critical concentration levels. Thus, on the one hand stormwater infiltration systems may act as effective pollution traps and on the other, they may pose a potential solid waste disposal problem that future stormwater management based on local infiltration will have to face.

In seven wastewater installations in the area of Zürich, Switzerland, four different filtration systems for tertiary wastewater treatment (deep bed, cloth drum, continuous up-flow and cell filters) were investigated with special attention to particle size distributions in the in- and outflow of the flocculation and the filtration step. Flocculation and filter performance was characterised by the shift of particle number curves. For each filter, particle number, surface and volume removal as a function of particle size was determined and revealed to be an excellent tool to evaluate the filter plants under practical conditions. The number removal efficiency for small particles in the colloidal size range proved to be the most sensitive parameter and could be related to operating parameters such as flocculant dose and filtration rate. The results of the particle analysis were compared to quality parameters related to small particles such as micro-organism and heavy metal concentrations. A good agreement between the removal of small size particles (< 8 μm) and bacteria counts as well as copper was found in the different filter systems. The filters were finally classified according to their particle removal performance.

Biofilters for secondary treatment, tertiary nitrification and tertiary denitrification were investigated with regard to solids and gas accumulation. Biomass growth, solids capture by filtration and gas entrapment were quantified for the three different applications. In biofilters for COD-removal or denitrification heterotrophic growth dominates solids accumulation. In tertiary nitrifying biofilters the biomass remaining attached to the media after backwash and suspended solids deposits are the main fractions responsible for filter clogging. Depth profiles of solids accumulation indicate that top layers cause the main headloss in biofilters. As a consequence of solids accumulation increasing gas entrapment in countercurrent and denitrifying biofilters lead to a sudden headloss increase and terminate the filter runs.

In different pilot experiments with tertiary trickling filters, rotating biological contactors, aerated biofilters and other fixed bed reactors, the effects of transient NH4-loading rates, transient oxygenation capacities, short- and long-term organic loading on nitrification performance were studied. Operating tools and mechanisms are shown to enhance NH4- and O2-limited nitrification rates. Periodic flow reversal in trickling filter and rotating contactor series and the use of pure oxygen in biofilters are possibilities to increase the nitrification capacity of tertiary biofilm reactors. Due to O2-competition and heterotrophic overgrowth, the presence of biodegradable organics may lower or completely stop the nitrification activity of tertiary biofilms. In this respect frequently backwashed biofilters and other fixed beds are superior to conventionally operated trickling filters or rotating biological contactors with stationary biofilms. Frequent removal of the top biofilm layers by backwashing is shown to offer the advantage of enhanced O2-supply into the depth of the biofilm and the possibility to maintain thin and fully aerobic multispecies biofilms with elevated nitrification potential.

Heavy metals such as cadmium, copper, lead and zinc are the critical metals in domestic wastewaters. Based on mass flow studies, the runoff from roofs and streets contribute 50-80% of these metals to the total mass flow in domestic sewage. Depending on the sewerage concept, the metals accumulate in different environmental compartments. Witt the combined sewer system, most commonly applied, the major part of the metals is bound to the sludge during sewage treatment. If the sludge is used in agriculture, the metals are enriched slowly in the top soils. With separate sewer systems, the metal loads to the receiving waters are increased, finally leading to accumulation in the sediments. If the new concept for the infiltration of runoff waters is applied, rapid and concentrated accumulation at the infiltration sites will occur. As a short term measure, new adsorptive elements in infiltration facilities would allow us to control the accumulation. The deposition of heavy metals in the environment cannot be avoided as long as no further efforts are made to reduce metal emission at the source. New partnerships between environmental/sanitary engineers and other professional groups such as architects, plumbers, car engineers, material technologists have to be established in order to minimize diffuse longterm deposition of hazardous substances and to be able to realize sustainable small water cycles without negative side-effects.

Size density relationships for aggregated particulates in suspension are transferred into a model describing the accumulation of particulate deposits in the pore space of granular media filters. Using data from several shallow filter layer experiments, the deposit density and the actual pore volume occupied by the captured particulates were estimated for solids of different characteristics. Based on extension of existing headloss models, the effects of particulate size, particulate density, filtration rate, and media grain size on headloss development during particle deposition were evaluated.

Organic architectural coatings require the use of biocides to prevent microbial defacement of building facades. The biocides are meant to slowly release to the surface, but they can still potentially enter the environment via runoff during rain events. Accurate source emissions estimates are necessary for risk assessments, and knowledge of the release mechanism can aid both regulators and producers alike. In this study, several biocides and several market and reference coating systems were subjected to regular irrigation and drying cycles with varying temperature conditions. The results were compared to other studies and models from the controlled release literature, demonstrating diffusion controlled release with dependence on the experimental conditions. The role of wetting and drying cycles in accelerating release is highlighted.

Three different types of internally aerated pilot scale biofilters were operated as tertiary nitrification systems. Long-term performance of the three aerated biofilters was tested under various operating conditions. The maximum volumetric nitrification rates under non NH4-limiting conditions for the three aerated biofilter systems were investigated. Based on measured temperature dependencies, an exponential relationship was established enabling the prediction of the nitrification rates at desired temperatures. Based on a temperature of 10°C, the results allow a comparison between the surface and volume specific nitrification rates in the tested biofilters as a function of the NH4 effluent concentration. As shown by experiments, nitrification performance depends on water as well as air velocities in the filter. Higher velocities of both air and water increase the nitrification rate. However, they also increase the head loss and thus decrease the filter run time. Therefore, the optimal operating conditions depend also on the filter media and the required effluent quality. Compared to fully O2-limiting operating conditions, nitrification performance during a period under partially NH4-limiting conditions clearly decreased in all tested biofilters.

The variables affecting nitrification in biofilms are identified on a theoretical basis. The influence of various design and operational parameters which affect the resulting substance fluxes into and out of the biofilm and the biomass activity regarding nitrification are illustrated with the help of experimental investigations with plastic media trickling filters, rotating biological contactors and different aerated biofilters. The results of experiments with these systems in tertiary nitrification applications reveal process limitations and technical measures to enhance nitrification performance in each system. In a case study, a comparison between the different biofilm processes and activated sludge alternatives showed that biofilm systems may lead to remarkably smaller reactor volumes, but high energy consumption due to unfavorable oxygen utilization.

Indigenous bacteria are essential for the performance of drinking water biofilters, yet this biological component remains poorly characterized. In the present study we followed biofilm formation and development in a granular activated carbon (GAC) filter on pilot-scale during the first six months of operation. GAC particles were sampled from four different depths (10, 45, 80 and 115 cm) and attached biomass was measured with adenosine tri-phosphate (ATP) analysis. The attached biomass accumulated rapidly on the GAC particles throughout all levels in the filter during the first 90 days of operation and maintained a steady state afterward. Vertical gradients of biomass density and growth rates were observed during start-up and also in steady state. During steady state, biomass concentrations ranged between 0.8 – 1.83 x 10 −6 g ATP/g GAC in the filter, and 22% of the influent dissolved organic carbon (DOC) was removed. Concomitant biomass production was about 1.8 × 10 12 cells/m 2 h, which represents a yield of 1.26 × 10 6 cells/μg. The bacteria assimilated only about 3% of the removed carbon as biomass. At one point during the operational period, a natural 5-fold increase in the influent phytoplankton concentration occurred. As a result, influent assimilable organic carbon concentrations increased and suspended bacteria in the filter effluent increased 3-fold as the direct consequence of increased growth in the biofilter. This study shows that the combination of different analytical methods allows detailed quantification of the microbiological activity in drinking water biofilters.

Pre-ozonation altered removal of organic matter during bench or full-scale water treatment through two main effects. First, pre-ozonation directly removed organic matter by mineralization, volatilization and/or stripping reactions, improving removal in comparison to unozonated systems. On the other hand, pre-ozonation decreased the surface charge of floc formed after coagulation with hydrolyzable metal salts, hindering adsorptive removal of the anionic organic molecules by floc surfaces and/or inducing stabilized floc formation; changes that decrease removal in comparison to unozonated systems. The relative importance of the two effects determined whether pre-ozonation enhanced or hindered removal of organic matter. In most water treatment plants pre-ozonation is predicted to have an adverse effect on physical removal of organic matter at ozone doses above about 0.7 mg O3/mg TOC, while enhanced removal may occur if relatively high concentrations of volatile organic matter are present. In ancillary results, pre-ozonation hindered turbidity removal and increased the concentration of coagulant metal residuals in finished drinking water at low coagulant doses.

Solids separation, adsorption onto participates and volatilization are the main physico-chemical mechanisms responsible for the removal of organic matter in wastewater treatment plants. In addition, solids separation as well as adsorption performance may be enhanced by chemical flocculation/precipitation with hydrolyzing metal salts. With the help of particle size distributions and other characteristics of the particulates at different treatment stages, more insight can be gained into the interactions between paniculate properties and solids separation performance. Significant removal of trace organics is achieved by adsorption onto paniculate surfaces and stripping in aeration tanks. Examples illustrate the adsorption of the relatively large quantities of substances contained in detergents and reveal the effect on water and sludge quality. Octanol/water partition coefficients of trace organics may be used together with oxygen transfer characteristics to determine the potential of volatilization into the air. The effect of flocculants on paniculate and dissolved organics removal in wastewater treatment is illustrated when Fe-salts are dosed to raw sewage, to the biological stage or to tertiary filters.

Laser-induced breakdown detection (LIBD) is a promising method to detect trace amounts of nanoparticles (NP,100 nm) in aqueous suspensions. Based on available systems, we developed a mobile LIBD, designed for on-site and on-line measurements. We used the energy ratio of every laser pulse before and after passing the laser beam through the aqueous sample as a new method to detect laser-induced plasma events. The particle size and the particle number density are derived from recorded energy curves. Our LIBD is operated with a Nd:YAG laser at 100 Hz significantly reducing the measurement times compared to other LIBD systems operated at 20 Hz and increasing the capabilities for monitoring purposes. Long-term experiments on water samples revealed losses of NP up to 75% in 15 mL and 35% in 5 L sample containers after 3 months. The size of the particles remained constant (5 L) or slightly decreased (15 mL) indicating significant adsorption of NP to the walls of the sampling containers. Furthermore, we monitored the NP content of water after different purification steps at a drinking water plant (Maennedorf, Lake Zurich, Switzerland). Activated carbon filtration resulted in an increase of the particle size from approximately 20 nm to approximately 75 nm possibly caused by the release of organic fragments derived from the biology within the activated carbon tank. After the final ultrafiltration step the particle size was around 10 nm in agreement with the nominal cutoff of 100 kDa of the membrane. The results underline the strength of a fast-screening LIBD to detect relative changes in NP size and concentration.

Fouling is one of the most critical aspects of membrane technology and is strongly influenced by natural water characteristics.This studyfocuses on a mechanistic understanding of the impact of interactions between natural organic matter (NOM) and particles on fouling. The model substances used were humic acid, alginate (polysaccharide), and kaolinite. NOM-kaolinite adsorption experiments, particle characterization, and dead-end ultrafiltration (UF) batch experiments were performed. The adsorption experiments indicated particle stabilization at low NOM equilibrium concentrations, whereas calcium induced significant aggregation, especially with alginate. UF experiments implicated a synergistic fouling effect of particle-NOM combinations, which was greatly reduced by calcium. Moreover, irreversible NOM fouling was only prevented by particles in the presence of calcium. On the basis of our results, we present a mechanistic model suggesting that synergistic fouling effects occur due to particle stabilization by NOM adsorption, especially shown for HA, and antagonistic effects due to particle destabilization by calcium. However, synergistic fouling can also be based on sterical interferences between larger NOM in the form of polysaccharides and particles during simultaneous pore blocking and cake formation. A heterogeneous NOM-particle fouling layer is ultimately formed with membrane associations dominated by NOM. The combined fouling is conclusively determined bythe type of NOM, its specific fouling mechanisms, and its particle interactions prior to and during the filtration process.

We present direct evidence of the release of synthetic nanoparticles from urban applications into the aquatic environment. We investigated TiO(2) particles as these particles are used in large quantities in exterior paints as whitening pigments and are to some extent also present in the nano-size range. TiO(2) particles were traced from exterior facade paints to the discharge into surface waters. We used a centrifugation based sample preparation which recovers TiO(2) particles between roughly 20 and 300nm. Analytical electron microscopy revealed that TiO(2) particles are detached from new and aged facade paints by natural weather conditions and are then transported by facade runoff and are discharged into natural, receiving waters. Microscopic investigations are confirmed by bulk chemical analysis. By combining results from microscopic investigations with bulk chemical analysis we calculated the number densities of synthetic TiO(2) particles in the runoff.

In Switzerland, the installation of small treatment plants in rural areas is being and will be intensified. In order to remove the numerous small pollution sites, new guidelines have been established in which basic information is given on the procedure of how to consider local circumstances of wastewater characteristics and of how to integrate local quality requirements of the receiving water into the design of small plants. The statistics on small treatment plants show a preferential application for extended aeration, RBCs and trickling filters. Due to the lack of skilled operation and maintenance, the performance of small treatment plants is not always satisfactory. New economic, reliable and less service-demanding methods are increasingly studied and applied.

The primary objective of this investigation has been to compare layered upflow carbon adsorption (LUCA) with conventional fixed-bed adsorbers for removing chlorinated hydrocarbons from drinking water sources. During LUCA operation, the granular activated carbon (GAC) is added in thin layers, with a new layer being added whenever the maximum allowed effluent concentration of the contaminants is reached. Thus, the time of exposure of the GAC to dissolved organic carbon, which is known to reduce GAC's adsorption capacity for organic contaminants, is reduced. This mode of operation has been found to produce approximately 50 percent longer operating times and correspondingly higher throughputs.

The addition of rotating biological contactors (RBC) to existing treatment plants for tertiary nitrification showed many advantages over conventional one-stage RBC's. Compared to tertiary trickling filters, the nitrification rates could be doubled. In extended pilot experiments, it was demonstrated that nitrification can additionally be enhanced by a periodic change of the flow direction in a series of RBC's, by filtration of the wastewater between the first and the second biological stage (pre-filtration) and by the control of the rotational speed. The experimental findings were confirmed in a full scale two-stage RBC-plant with intermediate filtration.

A mathematical model for aerobic and anoxic degradation of organic components as well as nitrification in RBC systems is developed and verified against experimental experience after primary, secondary and tertiary treatment. The model considers biomass distribution within the biofilm as well as along a reactor chain. The simulation program is not yet ready for practical application but may well prove to become a design tool in the future.

There is increasing concern about diffuse pollution of aquatic systems by biocides used in urban areas. We investigated sources and pathways of biocides significant for the pollution of storm water runoff. Main sources seem to be building envelopes, i.e. facades (paints, plasters) and roof sealing membranes. First results from a defined urban catchment drained by a separated sewer system without any agricultural activities reveal a substantial occurrence. Even after the first flush, concentrations of terbutryn, carbendazim, mecoprop as well as Irgarol 1051® and its metabolite exceeded the Swiss water quality standard of 0.1 μg/L. In laboratory experiments, leaching of mecoprop used as a root protection agent in bitumen sheets for roof waterproofing was determined. The concentrations differed in 16 different sheets two orders of magnitude, depending on the product composition. Using optimized products, it is expected to be the most efficient and sustainable way to reduce the environmental impact. To understand transport dynamics and environmental risk, further storm water events will be analyzed. Based on the ongoing project URBIC, first measures will be proposed to limit the release to surface and ground water.

In this paper we comprehensively characterized particles in drinking water originating from a lake water source. We focused on particles smaller than a few hundred nm. Several analytical techniques were applied to obtain information on number concentration, size distribution, morphology and chemical composition of the particles. Morphological information was obtained by atomic force microscopy (AFM) analysis. Two types of particles, spherical aggregates up to a few tens of nm and elongated fibers were identified. Similar structures were also observed in transmission electron microscope (TEM) images. A size distribution of the particles was obtained by applying image analysis (IA) tools on the TEM images. IA results showed an exponential increase of the particle number concentration down to 40 nm, which is the lower detection limit of our setup. The total number of particles down to 10 nm and the average particle diameter were determined with the laser-induced breakdown detection (LIBD) method. The results were in good agreement with the TEM-IA data and showed a total number concentration of roughly 108 particles/mL in the purified water. The carbon of the particles was investigated with scanning transmission X-ray microscopy (STXM), which revealed that most particles were organic matter; the C-1s spectra were typical for dissolved organic matter. The methods were applied to characterize the particles from two different drinking waters treated with different methods (conventional vs. ultrafiltration (cut-off 100 kDa)). The results showed that the particle number density following ultrafiltration was lower by a factor of 5–10, compared to conventional treatment. However, the average particle diameter in the finished water of both treatment trains was roughly the same.

Electrodialysis was investigated for the separation of micropollutants from nutrients in anthropogenic urine. In a continuously operated process, the nutrients were concentrated up to a factor of 3.2. The concentration factor was limited by water transport across the membrane. Water transport was caused by osmosis and electroosmosis, and a model was developed to describe these phenomena. The removal of several spiked micropollutants was investigated in continuous electrodialysis experiments. Ethinylestradiol was removed completely during the whole operating period. Diclofenac and carbamazepine were initially retained, but limited permeation (5-10%) occurred after longer operating times (90 days). Retentions of propranolol and ibuprofen were also high initially, but substantial breakthroughs occurred during extended operation. Considerable adsorption on the membranes was observed for all compounds. The permeation mechanism of several compounds appears to depend on the adsorbed amount on the membrane, which indicates that partitioning and diffusion mechanisms play an important role in the permeation transport. Partial desorption occurred in leaching experiments with polarity reversal, and almost quantitative desorption was observed after incubation of the membranes with Filter Count Gel Solution. Because environmental concentrations are much lower than the concentrations spiked here, it can be anticipated that operation without significant permeation is possible in practice during extended periods of time.

Large, uncoated copper and zinc roofs cause environmental problems if their runoff is infiltrated into the underground or discharged into receiving waters. Since source control is not always feasible, barrier systems for efficient copper and zinc removal are recommended in Switzerland. During the last few years, research carried out in order to test the performance of GIH-calcite adsorber filters as a barrier system. Adsorption and mass transport processes were assessed and described in a mathematical model. However, this model is not suitable for practical design, because it does not give explicit access to design parameters such as adsorber diameter and adsorber bed depth. Therefore, for e.g. engineers, an easy to use design guideline for GIH-calcite adsorber systems was developed, mainly based on the mathematical model. The core of this guideline is the design of the depth of the GIH-calcite adsorber layer. The depth is calculated by adding up the GIH depth for sorption equilibrium and the depth for the mass transfer zone (MTZ). Additionally, the arrangement of other adsorber system components such as particle separation and retention volume was considered in the guideline. Investigations of a full-scale adsorber confirm the successful application of this newly developed design guideline for the application of GIH-calcite adsorber systems in practice.

During rain events, copper wash-off occurring from copper roofs results in environmental hazards. In this study, columns filled with granulated ferric hydroxide (GFH) were used to treat copper-containing roof runoff. It was shown that copper could be removed to a high extent. A model was developed to describe this removal process. The model was based on the Two Region Model (TRM), extended with an additional diffusion zone. The extended model was able to describe the copper removal in long-term experiments (up to 125 days) with variable flow rates reflecting realistic runoff events. The four parameters of the model were estimated based on data gained with specific column experiments according to maximum sensitivity for each parameter. After model validation, the parameter set was used for the design of full-scale adsorbers. These full-scale adsorbers show high removal rates during extended periods of time.

The potential of nanofiltration for the separation of pharmaceutical and estrogenic compounds from salts in urine was investigated with the aim of producing a micropollutant-free nutrient solution that can be used as a fertilizer. A fresh urine solution and a synthetic solution of similar inorganic composition were tested at different pH values in order to investigate their separation behavior. These solutions were spiked with the micropollutants propranolol, ethinylestradiol, ibuprofen, diclofenac and carbamazepine. Among the membranes tested, NF270 showed the best performance with respect to the retention of micropollutants. The optimum retention of micropollutants was obtained at values of around pH 5. At this point, the retention of all micropollutants in non-hydrolysed urine was above 92%, while the corresponding value for the synthetic urine solution was above 73%. From the results, it can be concluded that the retention mechanism is determined by steric and electrostatic effects as well as by the partitioning of the micropollutants in the membrane. The nutrients urea and ammonia were well permeated, but phosphate and sulfate were almost completely retained. Nanofiltration can consequently be used to produce a permeate which contains most of the nitrogen and a greatly reduced proportion of micropollutants.

Due to their large specific surface and their abundance, micro and nano particles play an important role in the transport of micropollutants in the environment. Natural particles are usually composed of a mixture of inorganic amorphous or crystalline material (mainly FeOOH, FexOy, MnxOy and clays) and organic material (humics and polysaccharides). They all tend to occur as very small particles (1-1,000 nm in diameter). Most natural amorphous particles are unstable and tend to transform with time towards more crystalline forms, either by aging or possibly, by dissolution and re-crystallization. Such transformations affect the fate of sorbed micropollutants and the scavenging properties are therefore changed. As these entities are sensitive to dehydration (aggregation, changes in the morphology), it is highly important to observe their morphology in their natural environment and understand their composition at the scale of the individual particles. Also for the understanding and optimization of water treatment technologies, the knowledge of the occurrence and behavior of nano-particles is of high importance. Some of the possible particle analysis methods are presented: aggregation processes, biomineralization, bacterial adhesion, biofilms in freshwaters, ferrihydrite as heavy metals remover from storm water. These examples demonstrate the capabilities and focus of the microscopes. Atomic Force Microscopy (AFM) allows to analyze the particles in their own environment, meaning in air or in the water. Thus, native aspects of particles can be observed. As well, forces of interactions between particles or between particles and other surfaces such as membranes will be highly valuable data. Scanning Electron Microscopy (SEM) and for higher lateral resolution, Transmission Electron Microscopy (TEM) allow measurement of the morphology and composition. Especially, TEM coupled with Electron Energy Loss Spectroscopy (TEM-EELS) is a powerful technique for elemental analysis. Finally, general guidelines for the effective use of microscopic techniques are provided.

A long-term continuous runoff monitoring was carried out in a highway in Winterthur, Switzerland. The total suspended solids (TSS) samples were fractionated into fine (45 μm) fraction and their washoff behavior was studied. The fine and coarse fraction showed different washoff behaviors. During the runoff the concentration of the fine fraction was less fluctuated compared to coarse. The fluctuation of the coarse fraction was more influenced by TSS concentration. The PAH content measurement in fine fraction showed less fluctuation compared to the coarse fraction. The PAH content in the coarse fraction was found decreasing with increasing the coarse fraction contribution to TSS. © 2005 Elsevier Ltd. All rights reserved.

Advanced oxidation has proven to be an efficient process to increase micropollutant removal compared to conventional ozonation and to lower considerably the load to subsequent activated carbon treatment. Laboratory tests to determine the most important reaction rate constants involved in conventional and advanced oxidation and the OH radical/ozone ratio in the specific water to be treated can provide the basic parameters to simulate direct ozone and OH radical reactions. The combination of tracer based hydraulic reactor and chemical reaction modelling made it possible to simulate full-scale reactor performance. Model extrapolations used to optimise the peroxide dosing point for maximum micropollutant removal showed that disinfection for Cryptosporidium may severely be impaired.