10.4122/1.1000001666 Rueedi, J. Cronin, A.A. Morris, B.L. Daily patterns of micro-organisms in the foul sewer system of Doncaster, United Kingdom DTU Library, Technical University of Denmark (DTU) 2005 Urban water Daily pattern Micro-organisms Sewage Seasonal trend Enterovirus University of Surrey, Robens Centre for Public and Environmental Health Cronwnmarsh Guifford, British Geological Survey en Conference full text 10.4122/1.1000001665 application/pdf 1 Much is known about short-term changes in sewage volumes because they are often measured in pipeline design studies. Usually, sewage volumes peak in the morning and again in the evening, and leakage rates are expected to change correspondingly. To assess the contaminant load leaking into the subsurface, however, it is important to know the daily evolution of contaminant concentrations. These data are scarce, particularly for pathogenic micro-organisms. This study describes results of raw sewage sampling at three pumping stations for total coliforms, faecal coliforms, faecal streptococci, sulphite-reducing clostridia, coliphage and enteric viruses. The results show that all analysed micro-organisms follow a similar daily pattern, namely high concentrations during the morning, dropping around noon, rising again during the afternoon and then falling again in the evening and nighttime. Concurrent measurement of sewage volumes enabled assessment of total contaminant loads leaving the urban area, estimation of likely daily patterns of toilet/grey water contribution to raw sewage and calculation of daily average loads for urban mass balance modeling. The paper shows how important it is to measure not only daily patterns of sewage volumes but also sewage concentrations because both vary significantly during the day due to different household usage patterns.