Developing a stochastic sewer model to support sewer design under water conservation measures

Abstract

Developing a stochastic sewer model to support sewer design under water conservation measures Bailey, O.; Arnot, T. C.; Blokker, E. J.M.; Kapelan, Z.; Vreeburg, J.; Hofman, J. A.M.H. Abstract: Population growth and climate change place a strain on water resources; hence, there are growing initiatives to reduce household water use. UKWIR (2016) have a stated aim to halve water abstraction by 2050. This will significantly reduce inflow to sewer systems and increase wastewater concentration. This work presents a new stochastic sewer model that can be used to predict both hydraulic and pollutant loading for various water saving scenarios. The stochastic sewer model is based on integration of the stochastic water demand model SIMDEUM® with the InfoWorks ICM® (Sewer Edition) hydraulic model and software. This model has been developed using foul sewer networks, i.e. where household discharges are the dominant inflow; however, it could also be used in combined sewage systems where rainwater flows would add to © 2019 Manuscript version made available under CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/ 2 the stochastic dry weather flow (DWF). The stochastic sewer model was tested and validated on several real catchments in the Wessex Water area of the UK. Calibration was carried out using metered consumption data. The stochastic sewer model gives an accurate prediction of the diurnal patterns of sewage discharge at a household level and was validated using real flow measurements within the catchment. The results obtained indicate that this model can be used to accurately predict changes in flow velocity and pollutant concentrations because of water conservation. A preliminary study for the impact of low water use on this validated network model has been conducted and it was found that overnight and daytime flow was reduced by up to 80 % whereas evening flows remained largely similar. Extended stagnation times were observed in the street scale pipes (150 mm) in the low water use scenario.

Real-time foul sewer hydraulic modelling driven by water consumption data from water distribution systems

“…In this study, a transfer factor i k is used to represent the proportion of water consumption used by node i that has been collected by its corresponding manhole. Such a factor can vary as a function of the properties of the water users, such as user types (commercial users or common resident users) and habits of water usages (Bailey et al, 2019). Therefore, the transfer factor needs to be calibrated for each demand node based on the nodal water consumption data and the sewer observations (e.g., sewer flow rates or water depth in the manholes) in the FSS.…”

“…Collected wastewater is transported then downstream to wastewater treatment plants (WWTPs) or released directly into rivers (Bailey et al, 2019). These sewer networks are often called combined sewer systems (CSSs), which have been widely used in large cities around the world (Li et al, 2014).…”

“…More recently, Bailey et al (2019) presented a new FSS model, where the stochastically simulated water demands were imported into the sewer network model. While these limited previous studies have made great contributions in assimilating water use records into FSS modelling (mainly used for FSS design purpose), the water consumption data used are either collected manually at a very low time resolution (e.g., monthly, Bruke et al, 1986) or provided by a stochastic simulator (Bailey et al, 2019). Consequently, these data cannot represent the true underlying temporal and spatial variations of the manhole inflows.…”

A Stochastic Model to Predict Flow, Nutrient and Temperature Changes in a Sewer under Water Conservation Scenarios

“…InfoWorks ® ICM incorporates both hydraulic and wastewater quality modelling components. The hydraulic component was validated by Bailey et al [12] using measured flow, depth and velocity data. Saint-Venant equations govern hydraulics in InfoWorks ® ICM.…”

“…Bailey et al [12] developed a stochastic flow model to assess the impact of water conservation on the sewer. This model utilised stochastic household discharge patterns (generated with SIMDEUM WW ® ) as input to a sewer network model based in InfoWorks ® ICM.…”