System disgnosis using flow data: quantifying sources and opportunitites for performance improvement

Abstract

Foul sewer systems often show functional problems as a result of significant proportion of the total flow originating from infiltration, storm water inflows and industrial effluents. Quantification of the components that do not originate from domestic sources is an essential step both to assess the magnitude of the problem and for setting a plan aiming at detection and reduction of the excessive flows. This is particularly important when bathing water quality is to be protected and operation costs are significant. The paper presents a methodology that was used for differentiating and quantifying the different flow sources mainly by processing existing flow data currently obtained from a large network of flow meters, in a case study where mathematical modelling has limited application. Additionally, evaluation of systems performance was carried out and compared with design conditions when appropriate. Other sources of pollution are identified and difficulties associated with their location and quantification emphasised. Results are critically analysed and some actions to improve systems performance suggested.