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Water 2017, 9(11), 906;

Impact of Combined Sewer Overflow on Wastewater Treatment and Microbiological Quality of Rivers for Recreation

Institute for Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, 8020 Graz, Austria
Author to whom correspondence should be addressed.
Received: 20 October 2017 / Revised: 15 November 2017 / Accepted: 16 November 2017 / Published: 22 November 2017
(This article belongs to the Special Issue Recent Advances in Water Management: Saving, Treatment and Reuse)
PDF [635 KB, uploaded 23 November 2017]


Within the framework of a one-year study the treatment capacity of a municipal wastewater treatment plant (WWTP) was evaluated, with regard to fecal indicator bacteria (FIB) and to their influence on the recipient. The logarithmic reduction rates for fecal coliforms (FC), Escherichia coli (EC) and intestinal enterococci (IE) were 2.84, 2.90 and 2.93. In the investigated period of time, the tested treatment plant released 4.3% of the total annual load flow volume as combined sewer overflow (CSO), that is, when the influent into the combined sewer exceeds the capacity of the treatment plant and coarsely cleaned wastewater arrives at the recipient. This CSO discharge increased the number of FIB significantly by 1.2 × 102 MPN/100 mL for EC, and by 1.8 × 101 MPN/100 mL for IE. For the Styrian part of the Mur River (1.6 million inhabitants), a calculation of FIB of all sewage treatment plants estimating the same ratio of CSO (4.3%) and a given mean flow rate (QM) results in a significant increase of the FIB load in the recipient: 3.8 × 103 MPN/100 mL for EC and 5.8 × 102 MPN/100 mL for IE. On the basis of these values the standards of water quality for recreational purposes cannot be met. View Full-Text
Keywords: combined sewer; wastewater treatment; microbiological quality; surface water; river combined sewer; wastewater treatment; microbiological quality; surface water; river

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Mascher, F.; Mascher, W.; Pichler-Semmelrock, F.; Reinthaler, F.F.; Zarfel, G.E.; Kittinger, C. Impact of Combined Sewer Overflow on Wastewater Treatment and Microbiological Quality of Rivers for Recreation. Water 2017, 9, 906.

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