Ockleston, Grant (1998) A novel approach to combined sewer overflow & sewer monitoring. (MPhil thesis), Kingston University, .

Abstract

This thesis is presented on the development of a novel combined sewer overflow (GSO) and sewer volumetric flow monitoring system based principally upon the angular measurement of displaced engineering structures. The thesis plots the technological development from initial prototype, which established the frequency, duration and indicated discharge magnitude, through to the establishment of a robust series of instruments capable of producing both volumetric hydrographs and discharge water quality information using automatic sampling systems. The TEMS[sup]TM CSO monitor records the angular displacement of flap gates, commonly installed to protect the sewerage system from river ingress, as an integral part of the technology. The TEMS[sup]TM angular measurement system has operated maintenance free at one of London's largest sewage pumping stations for a period of 4 years. The instrument has recorded storm sewage discharges, dry weather crude sewage discharges caused by operational failures and pump malfunctions. Further research and development has enhanced system capabilities to include flow prediction, based upon the conservation of angular momentum, which has been shown accurate to ± 30% for gate inclinations < 20[sup]O and ± 20% for inclinations> 20[sup]O. The TEMS[sup]TM system successfully employs robust angular measurement technology in combination with in-sewer and river depth measurement to enable long-term assessment of CSO discharges on surface water quality. The Flowstick[sup]TM monitoring system removes the dependency for installation at sites with flap gates by employing a specially designed stick suspended from the crown of the culvert. The system provides the capability of long-term deployment at CSO, surface water outfalls (SWO) and general sewer flow surveys. A flow predictive model based upon the principle of drag has been successfully developed to enable production of volumetric hydrographs with accuracy generally to ± 15%. In addition, the system utilises an automatic sampling system, triggered by the displacement of the stick, to obtain water quality information. Full-scale trials of both technologies over a period of 18 months at the Pymme's Brook, East Barnet, have shown the TEMS[sup]TM and Flowstick[sup]TM systems suitable for long-term deployment. Opportunities now exist for the determination of actual CSO and SWO causing poor surface water quality. Key words: Combined sewer overflow, surface water outfall, sewage, sewerage, pollution, monitoring, assessment, long-term, water quality, foul flush.

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