A stochastic sewer model to support sewer design under water conservation measures

There is a need to reduce household water use and many countries are making the transition to separated sewer networks. Both the actions will reduce the wastewater that enters the sewage system. As part a PhD project at the University of Bath, UK, Olivia Bailey is developing a model that will help to better understand the effects that water conservation could have on sewer networks. SIMDEUM® and SIMDEUM®_WW are being used in combination with InfoWorks ICM® to produce this stochastic wastewater flow and quality model.

Sewer models are typically generated assuming continuous household discharge patterns obtained through measurements and scaled to the average household occupancy and water use of the area. Introducing stochastic discharge patterns greatly enhances the accuracy of the sewer model. The figure below shows the superiority of the stochastic model at predicting the peaks and troughs in wastewater flow within the sewer network. Both models have been compared to the 95% confidence interval of data obtained from a flow monitor in the catchment. Modelling the sewer with stochastic discharge patterns (produced using SIMDEUM_WW®) allows investigation into the effects that specific water saving appliances and changes in consumer habits could have on the sewer system. To conduct this type of analysis with a continuous model would involve applying a factor to the discharge patterns, producing inaccurate results. SIMDEUM_WW® has been very useful for reproducing the dynamic nature of the sewer within the model and will be further used to explore future water use scenarios on an appliance specific basis. The SIMDEUM®_WW tool has been particularly useful for this research application as it can be easily developed to suit a specific application, e.g. to synchronise with InfoWorks ICM® or create hypothetical wastewater scenarios.

This project is funded as part of the Centre for Doctoral Training in Water Informatics: Science and Engineering (WISE CDT) within the Water Innovation and Research Centre (WIRC) at the University of Bath, UK. It has been primarily supervised by Prof. Jan Hofman and Dr. Tom Arnot of WIRC with additional industrial supervision has been provided by Dr. Mirjam Blokker (KWR, NL), Prof. Zoran Kapelan (TU Delft, NL) and Dr. Jan Vreeburg (Evides Water Company, NL). Collaborations have been established with Wessex Water, UK who provided data for the development of the flow model.