Bristol Water addresses water quality

Summary

Bristol Water has provided clean, fresh drinking water to its customers since 1846. Today, Bristol Water serves over 1 million people in the city of Bristol and surrounding areas in the west of England. As part of its business plan, Bristol Water undertook its largest-ever program of customer engagement by inviting customers to participate in the decisions made about the future of its water services. Leveraging hydraulic modelling and simulation software, Bristol Water was able to address critical improvement projects and increase customer satisfaction.

Reverse trace analysis. Image courtesy of Bristol Water.

Putting the customer at the forefront

Bristol Water’s customers enjoy excellent water quality, and the company's commitment to meeting customer demand is written into its business plan. The goal for Bristol Water is to improve the appearance of the water it supplies, measured by reducing the number of negative customer complaints by 10%.

Achieving the target involves people from all areas of the company, not least the hydraulic modellers who model the network and run simulations to show what happens to supply when conditions change. By using a calibrated model of the water supply network an engineer can determine the likely outcome at a customer’s address if something higher up the network happens. That could be a change in pressure, a pipe burst, or even the introduction of a contaminant. Kevin Henderson, Network Asset Modelling Manager for Bristol Water explained, "When you know the source, you can follow the network to the endpoint, where the water comes out of the tap. Tracing activity from the customer's address back to its source is more of a challenge."

Water quality data over a 5 year period. Image courtesy of Bristol Water.

Bristol Water focuses on water quality

If you know that a customer is experiencing a problem with water quality, it makes sense to look at the reverse journey on the network to determine the root cause. However, mapping the network from an individual house back to the source is not straightforward. There are so many possible starting points and a myriad of potential pathways along the supply network to be analyzed to get to a common point. With that in mind, Bristol Water undertook a 'Reverse Trace Analysis' project to see how advanced water supply modelling software could help locate the source of contaminants affecting the appearance of water.

"The modelling approach allowed us to carry out a detailed analysis of our dataset to target investment in those areas to provide the greatest benefit to our customers. It is a simple, transparent, evidence-based process making use of the latest data."

—Jon Scott, Senior Water Quality Scientist, Bristol Water

Reverse trace analysis to identify customer problems

The project team coupled data from periodic random water quality samples that are sent for analysis with the last five years of customer complaints about discoloured water. This information was put into the InfoWorks WS Pro model and analyzed using SQL queries. The team developed queries to create a spatial layer showing data from customers with water quality issues. They then mapped the associated pipes from a specific snapshot in time, for example, 1 p.m., and used this to run SQL queries to trace water supply back to a common point.

The team ran the trace back to create a matrix identifying the main pipes that were common to the premises the complaints came from. The queries searched for pipes that met three water quality criteria:

0% of samples downstream >200 micrograms total iron
5% of samples downstream >100 micrograms total iron
0.64% of customers downstream reported discoloured water

A thematic review of pipes based on these criteria filtered out results until the most likely source of the contamination was identified. This analysis enabled Bristol Water to decide which larger diameter ferrous mains are good candidates for renovating (the likely source of downstream increased iron levels and discolouration complaints). Flushing is impossible for large-diameter pipes as the velocities required to resuspend sedimentation cannot generally be achieved. So, working in collaboration with Bristol University, Bristol Water developed an innovative approach to pipe cleansing using sludge-ice in non-ferrous pipes. This is where ice slurry is propelled through a pipe to sweep away debris and sediment. Ice slurry takes less water than ﬂushing and once the ice has done its job, it melts away and is easy to dispose of.

InfoWorks WS Pro supports detailed analysis of water distribution networks

The success of the project has led to the adoption of InfoWorks WS Pro to review mains pipes and determine which pipes to consider for lining or replacement. The project outcomes were used to inform the company's AMP 5 trunk mains relining/replacement program and the associated systematic ﬂushing of the distribution mains supplied from these trunk mains. The renovation of 60 km of trunk mains reduced the amount of corrosion debris within the network and the systematic ﬂushing program has removed historic corrosion debris. Bristol Water's customers now enjoy a cleaner network and a reduced risk of discoloured water complaints when there is any disturbance to ﬂows caused by burst mains.

The project's success is reﬂected in the number of negative customer complaints regarding water quality. In 2017/18 against an Outcome Delivery Incentive (ODI) target of 2,322 complaints, the company actually received 1,711 – 25% lower than expectations, and down 20% from the previous year. Kevin Henderson said, "Water quality has significantly improved and the use of InfoWorks WS Pro has enabled us to take informed action to line or replace the right pipes. This has not only contributed greatly to customer satisfaction, but it also ensures that we get the maximum return on the resources we invest in the network."

Kevin Henderson and his team are continually exploring the boundaries of how to use technology to improve the performance of Bristol Water. Water technology solutions are widely used to underpin decisions that aﬀect not just the network, but ultimately the lives of customers and the community served by Bristol Water.

"Water quality has significantly improved and the use of InfoWorks WS Pro has enabled us to take informed action to line or replace the right pipes. This has not only contributed greatly to customer satisfaction, it also ensures that we get the maximum return on the resources we invest in the network."

—Kevin Henderson, Network Asset Modelling Manager, Bristol Water

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