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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Solubility equilibrium models and/or adsorption models enable the prediction of phosphorus residuals in an effluent of a wastewater treatment plant over a wide range of operating conditions. A generally valid model cannot be given because the model parameters depend on wastewater composition, e.g. on dissolved and particulate water constituents, above all on phosphorus speciation. Chemical precipitation is able to bind ortho-phosphates proportionally to added chemicals and polyphosphates to a great extent. The P-residuals consist mainly of organically bound phosphorus and some residual polyphosphate. In wastewater treatment plants with enhanced biological phosphorus removal (EBPR), an extensive use of precipitation chemicals could suppress the EBPR-ability of the sludge. In EBPR-plants a part of the phosphorus can also be eliminated by chemical precipitation without added chemicals. In experiments with inactivated sludge derived from a wastewater treatment pilot plant, a pH-sensitive and partly reversible precipitation of calcium phosphates was observed at pH values below 8.0. A dynamic model was formulated on the basis of these observations. It contains the following reactions: – Fully reversible precipitation of hydroxydicalcium phosphate (Ca 2 HPO 4 (OH) 2 , HDP) as an intermediate, with a solubility product of 10 −22.6 (kmole m −3 ) 5 (20°C). – Formation of hydroxyapatite (Ca 5 (PO 4 ) 3 OH, HAP) from HDP. HAP is regarded as a kinetically stable endproduct. If the solubility of HDP is exceeded, then 15.5 gpm −3 d −1 of inorganic calcium phosphate (HAP) is fixated irreversibly in the sludge.