Developing a Stochastic Sewer Input Model to Support Sewer Design Under Water Conservation Measures

Population growth and climate change place a strain on water resources. There is growing motivation to reduce household water use. UKWIR (2016) have stated the aim to halve water abstraction by 2050. This will significantly reduce inflow to the sewer and drive up wastewater concentration. How will our sewers respond to this and could changes in design lead to a more efficient system in the future? This work presents the development and calibration of a stochastic sewer input model that will predict both hydraulic and pollutant loading for various water saving scenarios. For the first time the stochastic water demand model SIMDEUM® will be integrated with InfoWorks ICM (Sewer Edition), software for hydraulic sewer modelling. This enables accurate time dependent predictions of water, BOD and nitrogen loads from household discharges to the sewer under dry weather conditions. Calibration has been carried out using two sets of sewerage data from small residential catchments in the Wessex Water region of the UK. The model gives an accurate prediction of the diurnal patterns of sewage discharge at a household level. This will be used as an input to future sewer simulation models to accurately predict changes to flow velocity and pollutant concentration as a consequence of water conservation.