M. Burkhardt*, T. Kupper*, S. Hean**, R. Haag**, P. Schmid** , M. Kohler** and M. Boller* *Department of Urban Water Management, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Ueberlandstrasse 133, Duebendorf, Switzerland (E-mail:
[email protected];
[email protected];
[email protected]) **Laboratory for Road Engineering/Sealing Components and Laboratory for Analytical Chemistry, Swiss Federal Institute for Materials Science and Technology (Empa), Ueberlandstrasse 129, Duebendorf, Switzerland (E-mail:
[email protected];
[email protected];
[email protected];
[email protected]) Abstract 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 1051w and its metabolite exceeded the Swiss water quality standard of 0.1 mg/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. Keywords Biocides; measures; separated sewer system; storm water; transport behavior
Water Science & Technology Vol 56 No 12 pp 63–67 Q IWA Publishing 2007
Biocides used in building materials and their leaching behavior to sewer systems
Introduction
There is increasing concern about diffuse pollution of surface and ground water by organic compounds used in rural and urban areas. Leaching of pesticides used for agricultural purposes, their occurrence and impact in the aquatic environment have been studied to large extent. In contrast, knowledge on the high diversity of substances applied in urban areas and their transport behavior to receiving soil or waters bodies is still a new issue. Substances of particular interest include biocides acting against fungi, algae, and bacteria. Active ingredients might be harmful to aquatic organisms if natural weather conditions cause their release from applications such as coatings. As a typical example, building envelopes treated with preservatives may release biocides diffusely to the aquatic environment. Similar applications of additives are known for plastic and bitumen membranes on flat roofs. The number of biocides exceeds those of pesticides in agriculture (Lassen et al., 2001; Sattelberger, 2001). In the group of preservatives (product type 7) (Biocidal Product Directive, 98/8/EC), 139 active substances are listed as in-can preservatives and 89 as film preservatives. A first estimation for annual use of biocides in Switzerland shows that considerable quantites have to be considered, e.g. terbutryn and carbendazim 26 t /a each, IPBC 68 t /a, and dichlofluanid and OIT 100 t /a each (Bu¨rgi, pers. comm.). On a European level it is estimated that in 2005, about 3.9 mio t biocides are applied for coatings in buildings (Paulus, 2005). Besides biocides, other additives are used for material protection, e.g. UV-filters, doi: 10.2166/wst.2007.807
63
M. Burkhardt et al.
flame retardants or root protection agents. The annual consumption of the root protection agent mecoprop used in bitumen sheets for water proofing reached between 40 and 50 t in Switzerland. This additive was originally registered as a plant protection product. The annual consumption of mecoprop in agriculture is nowadays about three times lower than use in bitumen sheets. Next to mecoprop, biocides such as carbendazim, terbutryn, and diuron are also used for both plant protection and material protection. Additives and biocides, respectively, used in building envelopes are found in urban sewer systems (Clark et al., 2005). Diuron, terbutryn and carbendazim used in paints and plaster of facades were detected in effluents of waste water treatment plants (WWTPs) (Gerecke et al., 2002). Nevertheless, most information on the leaching of biocides from facades and plastic roofs is based on laboratory studies (Cadmus and Brophy, 1982; Lindner, 1997; Schoknecht et al., 2003). Elution of mecoprop from bitumen roofs and its transfer to surface water has been reported almost ten years ago (Bucheli et al., 1998). To our knowledge, investigations on the fate of biocides in urban drainage systems have not been carried out yet. With regard to most sensitive pathways, separated sewer systems and rainwater infiltration systems might be of increasing concern due to direct discharge of storm water to natural water bodies (Figure 1). Due to the lack of knowledge on the fate of biocides in urban areas, an assessment of their environmental impact on soil, ground and surface water is difficult. Within the ongoing project URBIC (Biocides in urban water systems; www.eawag. ch/urbic) we investigate the release of biocides and additives, respectively, from building materials for facades and flat roofs and determined their occurrence in the storm water sewer and the receiving water. Investigations under field conditions are completed by a laboratory study on leaching from flat roof sheets. Initial results are presented here. The aim of this study is to examine the transport behavior of individual biocides with potential impacts on storm and surface water quality and to evaluate measures for source control.
Material and methods
The fate and behavior of nine biocides used for material protection of building envelopes was studied (Table 1). Paints and plasters of facades and roof waterproofing membranes for flat
64
Figure 1 Pathways of point and diffuse pollution in urban areas. Waste water enters surface water mainly as a point-source via waste water treatment plants
Table 1 Characteristics of substances investigated on field scale of the URBIC study (Paulus, 2005) CAS number
Application
Water Solubility (mg/L)
BIT Carbendazim CMIT Diuron IPBC Irgarol 1051w - Descyclopropyl Mecoprop OIT (Octhilinone) Terbutryn
2634-33-5 10605-21-7 26172-55-4 330-54-1 55406-53-6 28159-98-0
broad spectrum antimicrobial fungicide, herbicide broad spectrum antimicrobial algicide, herbicide fungicide algicide metabolite of Irgarol 1051w additive, herbicide algicide, fungicide algicide, herbicide
1000 8 5000 42 190 7 no data 700 480 25
7085-19-0 26530-20-1 886-50-0
M. Burkhardt et al.
Substance name
roofs (bitumen and plastic sheets) are considered as potential sources. Ongoing experiments cover different scales from laboratory, small-scale model systems to watershed level. The storm water catchment investigated nearby Zu¨rich is well defined and maintained (Figure 2). Buildings connected to the storm water system are characterized by residential and commercial buildings mainly with flat roofs. The biocidal ingredients of all coatings and roof materials have been assessed and the initial biocides stock calculated. Currently, leaching of biocides from facades coating is investigated at new and aged buildings (Figure 2: sampling site 1, 2). Their dynamic occurrence is tracked by flow proportional sampling in the storm water sewers at two sites. Analysis of carbendazim, terbutryn, Irgarol 1051w (including metabolite), diuron, mecoprop, IPBC, and isothiazolinones (OIT, BIT, CMIT) (Table 1) is performed with online-SPE coupled to HPLC-ESI-MS/ MS for. Isotope-labeled internal standards were added for each biocide (except BIT and CMIT) to account for matrix suppression. For leaching experiments with bitumen sheets we considered 16 different bitumen sheets. All sheets were delivered by the market leaders in Switzerland and have different material characteristics such as surface modification, thickness, concentration of root protection agent,
Figure 2 Discharge of storm water to receiving waters in the studied urban catchment regarding runoff from building envelopes and paved surfaces, respectively. 1,2: sampling of facades runoff at new and aged coatings, 3: storm water sampling of five buildings; 4: Sampling of a defined catchment with known building materials; 5: Sampling of discharge to the brook of the entire separated sewer system catchment
65
M. Burkhardt et al. 66
and root protection agent product. Three root protection products have been studied containing two different active ingredients based on mecoprop (polyethylene glycol ester, ethylhexyl ester). Additionally, two agents based mainly on the enantiomerically pure species (R)-mecoprop which is the active form of mecoprop. Regarding the root protection products and their concentrations in bitumen sheets, all samples represent the past, present and future market. Material samples were leached three times successive (E1, E2, E3) each lasting 7 days. In between, two artificial ageing steps were conducted in a weather simulation chamber (12.5 days). Analysis of mecoprop was performed with solid phase extraction (SPE) and HPLC-UV. Results and discussion
The sub-catchment of sampling site 4 encloses an area of about 14 ha and is clearly structured (Figure 2). Residential and commercial buildings as well as paved streets and parking covers roughly one-third of that area each. 80% of the buildings are not older than five years (Figure 2: building 1–7). It is estimated that nearly 95% of the rainfall discharges directly to the storm water system or via drainage systems of buildings and underground parking. Generally, both in-can and film preservatives for facades protection consist of 5 to 8 biocides. In the catchment investigated plasters and paints of a single building complex contained 7 active ingredients, i.e. BIT, OIT, CMIT/MIT, Irgarol 1051w, zinc pyrithione, zinc oxide, as well as a formaldehyde releasing compound. In most buildings, contents range between 0.03 and 0.6 g/m2 for each biocide. Hence, for a single building complex with a surface of about 4500 m2 base area, up to 5 kg of Irgarol 1051w were applied in paints and plasters. However, not all parts of facades are exposed to rain and facades runoff, respectively, and an unknown proportion may evaporate directly from the coatings. The most persistent biocides, such as terbutryn, diuron, carbendazim, irgarol, and mecoprop, were determined at sampling site 5, representing a catchment of about 30 ha. It has been shown that the entire pathway from the building envelope to receiving surface water is traceable, e.g. for Irgarol 1051w which is exclusively applied on facades. Furthermore, our initial results indicate that water quality standards of 0.1 mg/L are exceeded up to ten-fold after the first flush of storm water runoff. In general, the first flush exhibits even higher concentrations. Nevertheless, it seems plausible that after rainfall the tailing of the concentration curve might be extended over a few days. The laboratory results for mecoprop exhibit leaching rates varying over two orders of magnitude in 16 roof sealing membranes. For example, the current concentrations applied in bitumen cause higher leaching rates than these designed for the future (Figure 3, left).
Figure 3 Leaching of mecoprop (E1) from bitumen sheets with input-concentrations (1.0% vs. 0.5%) representing the present and future market (left). The root protection product is the same. Leaching behavior of bitumen sheets coated by shale and talcum-sand (right), with E1, E2, and E3 representing three successive leachates (each 7 days). The input-concentrations are different, but the root protection agent is the same
A similar reduction effect was observed between surface coatings based on shale and talcum sand due to their different effective coverage of the bitumen surface (Figure 3, right). Material properties have an impact on the leaching rate of mecoprop. These results show that source control is a successful approach to limit the runoff pollution. Such measures are most efficient and sustainable for protecting aquatic systems.
We demonstrated that appropriate building materials may reduce the environmental impact at the source, as illustrated for mecoprop. The reduction is dependent on material properties, such as the type of root protection agent and surface modification. To minimize the environmental impacts, other main sources at building envelopes will be evaluated. Initial storm water analysis has shown significant concentrations, although most biocides are potentially adsorbing and degradable. The results on facades runoff monitoring and on the occurrence of biocides in the storm water underline the importance of urban sources for the diffuse water pollution of aquatic systems. Thus, with regard to sustainable water protection, it is important to account for both rural and urban sources. This may lead to a substantial reduction of contaminants in surface and ground waters.
M. Burkhardt et al.
Conclusions and outlook
Acknowledgements
We thank Sylvia Jaus, Heinz Singer, and Alfredo Alder for analyzing the initial water samples from the field study. Highly acknowledged is the funding of the URBIC project by the Cantonal Office for Waste, Water, Energy and Air Zurich (AWEL), the Cantonal Office for Environment and Energy Lucerne (uwe), the Swiss Federal Office for the Environment (FOEN), and the Swiss Federal Institute of Aquatic Science and Technology (Eawag). We thank for fruitful collaboration with several companies producing biocides and products for facades and roofs.
References Bucheli, T.D., Mu¨ller, S.R., Heberle, S. and Schwarzenbach, R.P. (1998). Bituminous roof sealing membranes as major sources of the herbicide (R,S)-mecoprop in roof runoff waters: potential contamination of groundwaters and surface waters. Environ. Sci. Technol., 32, 3465– 3471. Cadmus, E.E. and Brophy, J.F. (1982). Diffusion von Bioziden aus weichmacherhaltigen PVC-Folien. Kunststoffe, 72, 233 –235. Clark, S.E., Lalor, M. M., Pitt, R. and Field, R. (2005). Wet-weather pollution from commonly-used building materials. 10th International Conference on Urban Drainage, Copenhagen/Denmark, 21 – 26 August 2005 Gerecke, A.C., Scharer, M., Singer, H.P., Muller, S.R., Schwarzenbach, R.P., Sagesser, M., Ochsenbein, U. and Popow, G. (2002). Sources of pesticides in surface waters in Switzerland: Pesticide load through waste water treatment plants-current situation and reduction potential. Chemosphere, 48, 307 – 315. Lindner, W. (1997). Studies on film preservatives: Retention of DCMU in outdoor paints. Biofouling, 11, 179 –189. Lassen, C., Skarup, S., Mikkelsen, S.H., Kjolholt, J., Nielsen P.J. and Samsoe-Petersen, L. (2001). Inventory of biocides used in Danmark. Report, Environmental Project No 585 2001. Danish Environmental Protection Agency. Paulus, W. (2005). Directory of Microbicides for the Protection of Materials - A Handbook, Springer, Dordrecht, The Netherlands. Sattelberger, R. (2001). Einsatz von Pflanzenschutzmitteln und Biozid-Produkten im nicht-land- und ¨ sterreich, Wien. forstwirtschaftlichen Bereich. Monography, Vol. 146, Umweltbundesamt O Schoknecht, U., Wegner, R., Horn, W. and Jann, O. (2003). Emission of biocides from treated materials Test procedures for water and air. Environ. Sci. Pollut. Res., 10, 154 – 161.
67
