6C Water quality modelling

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Collaborative

Laura Monteiro

Chair:

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Dynamics of pipe walls material detachment under flushing conditions in a full scale drinking water laboratory system

Artur Sass Braga

Presenter:

Authors:

Artur Sass Braga, Rain Saulnier, Alexandria Cushing and Yves Filion

Discolouration events in drinking water distribution systems (DWDS) are caused by a systematic detachment of accumulated materials from pipe walls during high flowrates. The phenomena are characterized by complex turbidity profiles in response to flushing, where still poorly understood detachment mechanisms contribute to shape the turbidity output. In this study, a set of discolouration experiments were realized in the Drinking Water Distribution Laboratory (DWDL) focused on reproducing the accumulation and mobilization of materials in pipe-walls of a full-scale laboratory system. Experiments of 40, 80 and 120 days were realized using two different conditioning wall shear stress (0.02 and 0.08 Pa) and two temperatures (8°C and 16°C). In the end of each experiment, a series of three sequential flushing steps at wall shear stresses of 1.2, 3.2 and 5.2 Pa were realized to mobilize the material from the pipe-walls to investigate detachment mechanisms using high-resolution turbidity data. Results shown that higher detachment rates for the start of flushing where the water is being accelerated than for steady-states immediately after the acceleration. Moreover, material layer shear strength distribution was consistent for different accumulation periods, and tests with 16°C had a significant higher detachment rates, indicating fewer cohesive layers. However, additional experiments with enhanced monitoring capabilities are needed to verify these new aspects of discoloration mechanics.

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Sediment Transport in Sewer Pipes: An Experimental Approach to Bedload Transport

Carlos Montes

Presenter:

Authors:

Carlos Montes, Zoran Kapelan and Juan Saldarriaga

Sediment transport is an important process for the design of self-cleansing sewer systems. Traditionally, minimum velocities and shear stress values have been suggested in different publications and industry manuals with the aim to avoid deposition and accumulation of material at the bottom of pipes. Several authors have shown that the use of these traditional criteria and threshold values leads to overdesigning the slope for small diameter pipes (i.e., D < 500 mm). To address this issue experimental investigations were carried out. These studies focused on estimating the self-cleansing conditions and developing corresponding predictive models where minimum self-cleansing velocity is a function of several parameters such as the Darcy friction factor, the hydraulic radius, the specific gravity of sediments, the dimensionless grain size or the volumetric sediment concentration. This work aims to test the performance of these self-cleansing models by using an experimental approach. In addition, a new model has been developed for bedload transport with the same experimental data collected.

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Discolouration Modelling

Stewart Husband

Presenter:

Authors:

Stewart Husband, Joby Boxall and Manar Al-Saffar

Using managed flow increases to condition pipes in distribution systems is a proven method to mitigate the risk of discolouration and improve resilience. Operational interventions such as flow conditioning require risk assessments, and these can be supported by the freely available EPANET PODDS model that allows turbidity responses to be predicted simply from proposed flow changes. However, as an empirical model there are concerns over the transferability of the model parameters, and because site specific calibration to the range of pipes that comprise distribution networks is not practical. Flow and turbidity data from 76 independent flow conditioning exercises conducted by Yorkshire Water since 2017 has been used to populate PODDS EPANET models. For all datasets an acceptable calibration was achieved, highlighting universal and predictable behaviour with a limited range in parameter values required demonstrating viable business application such as for risk assessments or assessing network impact to flow changes.

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Dynamic Water Quality Sensor Placement in Water Distribution System Using an Evolutionary Algorithm

Essa Q Shahra

Presenter:

Authors:

Essa Q. Shahra and Wenyan Wu

The optimal placement of water quality sensors for detecting contamination events and determining their source is an active research topic. This is mainly because of the costs associated with the type and number of sensors required, which implies that the few sensors that can be placed need to be at optimal locations. The deployment and maintenance of sensors, which require significant financial investments, also need to be accounted for in this context. This paper proposes an EA-based placement method for dynamic water quality sensors, which adapts the sensor locations based on the number of suspected contamination sources. The proposed method aims at quickly and reliably detecting the occurrence of contamination events while minimising the number of sensors required.

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Long-Term Discolouration Modelling for Cast Iron Mains

Manar Al-Saffar

Presenter:

Authors:

Manar Al-Saffar and Stewart Husband

Yorkshire Water, who supply over 5 million customers in the north of the UK, has put a very important target to reduce the number of discolouration contacts by promoting innovative maintenance strategies to support aging water distribution systems. One of the practices identified that can be conducted on a larger scale within the business is self-conditioning of trunk mains through frequent business-as-usual flow increases. Managed flow increases in distribution systems has been proven as a method to mitigate the risk of discolouration and improve resilience. Although a major component of the trunk main network is recognised as a potential discolouration risk, little understanding of cast iron mains has been recorded, compared to studies such as on ductile iron pipes. In these, the Variable Condition Discolouration Model (VCDM) has been used successfully to predict turbidity responses and subsequently plan long term maintenance strategies to manage discolouration. Using long term data from a cast iron main, this work investigates for the first time if extended period VCDM simulations can be calibrated to describe the behaviour of discolouration material in these critical assets. Turbidity data was collected from a 15 km, 18” cast iron main during a long-term investigation of self-conditioning potential. The initial improved resilience was achieved by conditioning with an increase in daily peak flow from 80 l/s to 100 l/s over one week, then this daily peak was maintained at 100 l/s. The simulation results indicate the VCDM is a viable tool to predict the turbidity and explain the behaviour of discolouration material over long periods.

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Numerical Simulation of Solute Migration and Flow Characteristics at Dead-End Branch Pipe in Water Distribution System

Shiyuan Hu

Presenter:

Authors:

Shiyuan Hu, Jinliang Gao, Wenyan Wu, Yuanzhe Li, Shuhe Zou and Chenhao Ou

Water distribution network is an intricacy and essential part of the infrastructure, and these networks are pivotal for public health. The existing water quality models ignore the deterioration of water quality caused by the migration of contaminants accumulated in the dead-end branch pipes, such as the fire hydrant and cut-off pipes, resulting in inaccurate water quality models. The method of computational fluid dynamics (CFD) is used in this paper. A 3-D geometrical model of Tee-pipe structure with no outlet for the flow in the dead-end branch pipe was established to simulate the flow state by using the k-ε model. This model is combined with cavity theory for analysis the variation of velocity distribution, streamline distribution and contaminants concentration with time. The causes of the migration of contaminant in the dead-end branch pipes were investigated. The study found that contaminant in dead-end branch pipes of water distribution network will periodic flow into the main pipes under pressure wave. Large quantities of contaminants will migrate into the main pipe when the water flow state of the network changes abruptly and a significant disturbance occurs in the dead-end branch pipe. This study aims to reduce the errors caused by dead-end branch pipes and improve the accuracy of water quality model.

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Peter Chalk Centre

University of Exeter

Stocker Road

Exeter

EX4 4QD

Tel: +44 (0)1392 263637

E-mail: CCWI2019@exeter.ac.uk 

17th International Computing & Control for the Water Industry Conference

1st - 4th September 2019
University of Exeter, UK
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