Continuous monitoring in sewer networks an approach for quantification of pollution loads from CSOs into surface water bodies

Abstract

Different approaches for quantification of pollution loads discharged from combined sewer networks into surface water bodies have been observed over the last few years and decades, but a large number of unresolved problems still remain. Many monitoring campaigns have been based on manual or automated spot sampling - with the long known limitations of this method such as sampling errors and errors due to sample conservation, transport and preparation. On the other hand, only recently have sensors became available which are suitable for continuous application in sewer networks. A large number of practical problems still have to be solved before continuous monitoring in sewer networks will be successful. Additionally, most of the applicable sensors are based on surrogate methods which results in a considerable effort for reference measurements for sensor calibration. Finally, it has to be considered that, depending on the sewer network topography, deposition and remobilisation of pollutants varies considerably, which limits the generality of monitoring results and, subsequently, their applicability as a base for the design of storm water tanks or combined sewer overflows (CSO). A monitoring station for continuous monitoring of load discharges from a CSO has been installed and operated for more than one year. The design and equipment of the measurement station, operational experiences and results are given in this paper.

Using data from monitoring combined sewer overflows to assess, improve, and maintain combined sewer systems

“…Gruber et al, 2005;Tetzlaff et al, 2005). Simultaneously monitoring all of the structures within one system would provide more useful information about the performance of the CSS as a whole but was until today cost prohibitive.…”

Monitoring of rain events with a submersible UV/VIS spectrophotometer

“…For these tests the device has been implemented on the pre-treatment stage of the NancyMaxé ville wastewater treatment plant (350,000 PE) which receives wastewater from a combined sewer network. In previous work using UV/VIS submersible spectrophotometers on CSOs it has been reported difficulties concerning calibration due to the fast changing composition of the wastewater composition (Stumwö hrer et al 2003;Gruber et al 2005).…”

Potential and limitations of modern equipment for real time control of urban wastewater systems

“…The high flow variability demands innovative concepts for the installation of the sensors; the surrounding condition in combined or sanitary sewer with its often corrosive atmosphere and ingredients like solid matter, faecal and colloidal dissolved substances causes serious maintenance problems. Some pilot installations indicate that operating online measurement stations over a long period is in principle possible (Gruber et al 2005); however, depending on the kind of used sensors considerable maintenance efforts are needed. As already mentioned in Section 3, promising developments have taken place regarding online water quality sensors.…”