Trials and tribulations of wastewater flow monitoring

Local Authorities today are relying more and more on hydraulic models to assist in the planning of infrastructure upgrades and assessing the performance of their existing networks. They are also continually faced with the challenges of providing the most cost effective solution for reticulated sewerage infrastructure and ensuring that the systems are also optimised for performance. The basis for any hydraulic model is the input data put into the model such as asset data, flow data and rainfall data. The asset data can be easily verified as with the rainfall data as this is obtained from the metrological service.

The flow data component for modeling is usually collected ‘in-house’ or by specialist flow monitoring contractors, typically both using engineering technicians or often staff with limited or no tertiary hydraulics or hydrographics training. Hydrographics training is usually for rainfall and open stormwater channels, therefore not always directly applicable to the unique world of piped and pumped wastewater networks. Engineering training provides theoretical training, but also lacks the hands on training required for installing, operating and calibrating specialist flow and rainfall gauge instrumentation.

This paper will outline the various different gauge types that can be utilized to capture flow data within wastewater systems along with the various different monitoring technologies and their relative strengths and weaknesses. It is well known that budgetary considerations are a significant driver for the amount of flow monitoring undertaken.

The paper will discuss how you can ensure suitably trained staff and appropriate equipment and gauging methods is provided to undertake accurate and comprehensive flow gauging studies for completing requirements of network model calibration and inflow / infiltration (I/I) assessment. Alternatively the information from this paper may allow you to assess perceived or real accuracy issues from former monitoring studies from an understanding of the issues associated with wastewater flow measurement.

This paper shall discuss these issues in more detail and provide Local Authorities with a comprehensive overview of current issues associated with flow monitoring in the 21st century.