Climate change and urban wastewater infrastructure: There is more to explore J.G. Langeveld a,b,⇑ , R.P.S. Schilperoort b , S.R. Weijers c a Delft University of Technology, Sanitary Engineering, PO Box 5048, 2600 GA Delft, The Netherlands b Royal HaskoningDHV, Urban Drainage Group, PO Box 151, 6500 AD Nijmegen, The Netherlands c Waterboard De Dommel, PO Box 10.001, 5280 DA Boxtel, The Netherlands article info Article history: Received 30 March 2012 Received in revised form 15 October 2012 Accepted 17 October 2012 Available online 1 November 2012 This manuscript was handled by Geoff Syme, Editor-in-Chief, with the assistance of Paul Jeffrey, Associate Editor Keywords: Climate change Sewer systems Wastewater treatment plant Monitoring Data mining summary Climate change is one of the main challenges to the urban wastewater systems in the next decades. In literature, the focus has primarily been on impacts of singular climate changes, such as the impact of more intense storm events in summer or prolonged wet periods in winter. The impact of these expected climate changes on wastewater system performance has been studied extensively by applying the expected climate change as input for urban drainage, sewer or wastewater treatment models. The model-based analysis of the impact of climate change has an important drawback: applied models can only represent the processes incorporated in the model and typically have a limited universality, if at all calibrated, due to the limited information available in the time series used for model calibration. Lit- erature describing possible climate change impacts on performance of the urban wastewater infrastruc- ture based on the analysis of monitoring data is hardly available. Recent developments in continuous monitoring have resulted in an increased availability of high qual- ity data sets. These data sets allow assessment of the impacts of climate change by scrutinizing the data sets searching for meteorological conditions that resemble expected climate changes. The potential of applying data analysis to study climate change effects is illustrated for the case of the Eindhoven waste- water system, for which an extensive database is available. The results of this study show that, due to the limitations of state of the art sewer water quality models as well as WWTP models, model based assess- ment of climate change impacts does not properly address all possible impacts of climate change. Con- sequently, the impact of climate change is underestimated. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Climate change is one of the main challenges to the urban wastewater infrastructure, requiring new design criteria for urban drainage systems (Mailhot and Duchesne, 2010), more appropriate drainage systems (Faram et al., 2010), innovative, decentralized strategies (Smith, 2009) or adaptation strategies (Arnbjerg-Nielsen and Fleischer, 2009). Most of these strategies build on the per- ceived impact of climate change on wastewater system perfor- mance, mainly focusing on the effect of increased rainfall intensities. The impact of increased rainfall intensities has been studied by many authors. Kleidorfer et al. (2009) simulate the im- pact of higher rainfall intensities on combined sewer overflow (CSO) discharges and flood risk. Butler et al. (2007) evaluated the impact of climate change on sewer storage tank performance and Sharma et al. (2011) on treatment efficiencies of stormwater reten- tion ponds. Climate change, however, is not limited to increasing rainfall intensities only. According to the Royal Netherlands Meteorologi- cal Institute (KNMI), The Netherlands will be facing a temperature rise due to which mild winters and hot summers will become more common. In addition, winters will become wetter and extreme pre- cipitation amounts over a time span of a couple of days will in- crease. In summer, the intensity of extreme rain showers will increase coupled with a decrease in the number of rainy days (Klein Tank and Lenderink, 2009). The impact of a combination of climate changes has hardly been studied. Only a few descriptions are available. Parry et al. (2007) show that the combination of higher temperature, increased precipitation intensity and longer periods of low flows are likely to exacerbate many forms of water pollution, impacting water system reliability and operating costs (Parry et al., 2007). Patz et al. (2008) describe that due to climate change, the Great Lakes Region of the US will likely be facing a combination of an increase of CSO discharges due to heavy rainfall, warmer lake waters and lowered lake levels. These three aspects increase the risk of waterborne diseases. Plósz et al. (2009) describe the impact of a temperature rise in the winter period in Norway. They show that not the increase in average winter temperature but rather the variation of tempera- ture during the winter period proves to be the determining factor 0022-1694/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhydrol.2012.10.021 ⇑ Corresponding author at: Delft University of Technology, Sanitary Engineering, PO Box 5048, 2600 GA Delft, The Netherlands. E-mail addresses: j.g.langeveld@tudelft.nl, jeroen.langeveld@RHDHV.com (J.G. Langeveld), remy.schilperoort@RHDHV.com (R.P.S. Schilperoort), sweijers@ dommel.nl (S.R. Weijers). Journal of Hydrology 476 (2013) 112–119 Contents lists available at SciVerse ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol