Uncertainty assessment of deterministic water quality model for a combined sewer system with the GLUE method

The research project ‘Real Time Control of a Combined Sewer System by Radar estimates of Precipitation’ seeks to improve the water quality of a stream by reducing quantitative and qualitative discharges of combined sewage overflow (CSO). The complex monitoring and simulation system that has been set up for control purposes is described. Two advanced real time control (ARTC) strategies have been developed. First a pollution based real time control (PBRTC) strategy, and second a water quality based real time control (WQBRTC) strategy. The PBRTC strategy is already implemented, the WQBRTC strategy will be implemented during the course of the project. For the PBRTC an off-line analysis is presented to show the effectiveness of the strategy.

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Combined sewer system versus separate system – a comparison of ecological and economical performance indicators

Water Science & Technology ◽

10.2166/wst.2007.116 ◽

2007 ◽

Vol 55 (4) ◽

pp. 255-264 ◽

Cited By ~ 12

Author(s):

S. De Toffol ◽

C. Engelhard ◽

W. Rauch

Keyword(s):

Water Quality ◽

River Water ◽

River Water Quality ◽

Sewer System ◽

Effect Analysis ◽

System A ◽

Combined Sewer ◽

Combined Sewer System ◽

Separate System ◽

The Cost

This paper aims at comparing the cost-effectiveness of the two main types of urban drainage systems, that is, the combined sewer system and the separate sewer system, based on the analysis of simulations. The problem of which of the two systems is better was heavily discussed over the years and the answer given to the question was usually: ‘it depends’. In this work, specific impacts are investigated in terms of a cause–effect analysis. The results are subsequently summarized and can help in the choice of the system to be implemented. Despite earlier reasoning, studies on river water quality strongly indicate that the separate system is not always the preferable solution because the polluted runoff from the street, containing e.g. different heavy metals, is discharged directly into the river. This analysis aims to compare the two different sewer systems on the basis of literature data and simulation of specific cases. The results are evaluated, as suggested in the EU-Water Framework Directive, on the basis of different assessment criteria: river water quality and morphology impacts, emissions and costs.

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River Water Quality Model no. 1 (RWQM1): Case study I. Compartmentalisation approach applied to oxygen balances in the River Lahn (Germany)

Water Science & Technology ◽

10.2166/wst.2001.0247 ◽

2001 ◽

Vol 43 (5) ◽

pp. 41-49 ◽

Cited By ~ 12

Author(s):

D. Borchardt ◽

P. Reichert

Keyword(s):

Water Quality ◽

Water Column ◽

River Water ◽

Water Quality Model ◽

River Water Quality ◽

Combined Sewer Overflows ◽

Quality Model ◽

Combined Sewer ◽

Sewer Overflows

A case study on the application of the River Water Quality Model No. 1 (RWQM1) is presented in order to illustrate the importance of modelling a sediment compartment for an ecologically meaningful assessment of the impact of wastewater effluents and combined sewer overflows. The focus of this case study is on the compartmentalisation approach of the RWQM1 that makes such a description possible. In contrast to this, a strongly simplified biochemical submodel is used that considers only oxygen and dissolved substrate. The object of the case study is the River Lahn, a moderately polluted 5th order stream in Germany, for which the connectivity of surface/subsurface flows and mass fluxes within river sediments have been intensively investigated. The hyporheic flow between a downwelling and upwelling zone of a riffle-pool sequence has been studied with the aid of tracer experiments and continuous records of water constituents. High diurnal fluctuations of oxygen travelled to considerable depth of the sediment and oxygen in the interstitial water decreased considerably while travelling through the riffle. Starting with the implementation of a strongly simplified version of the biochemical part of the RWQM1, but with the consideration of a sediment pore water compartment in addition to the water column compartment, a calibration procedure is performed using tracer data from the water column and the sediment. The calibrated model is then used to study the system response to wastewater treatment plant effluent and combined sewer overflow emissions. The modelling approach makes it possible to quantify the sediment oxygen demand and the spatial and temporal extent of sediment zones with oxygen depletion. However, the spatially averaged approach does not account for inhomogeneities in the sediment. It is shown that for this river with its alluvial coarse sediments even moderate emissions from sewerage systems may be high enough to drop sediment oxygen concentrations to low levels while those in the surface flow remain close to saturation. Similarly, it is demonstrated that combined sewer overflows may cause anoxic sediment oxygen conditions for extended time periods. The implications for ecologically sound river water quality modelling and for specific quality objectives are discussed.

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