Bristol Water has provided clean, fresh drinking water to its customers since 1846. For almost 200 years, the health and environment of their communities has remained at the forefront of their values. Today, Bristol Water supplies over 1 million people within Bristol, England, across an area of almost 2,400 square kilometres. Bristol Water’s operations include the abstraction, storage, treatment, and distribution of water to homes, businesses, and other premises. They focus exclusively on water, not wastewater.
As part of Bristol Water’s routine monitoring of Clevedon Well a sample collected in January 2018 was reported to contain a single Cryptosporidium (Crypto) oocyst. Cryptosporidium is a fecal-oral pathogen, this is caused because of poor hygiene, food, or animal waste. If it is ingested it can cause symptoms of diarrhea, nausea, vomiting and stomach pain. Upon hearing this news, Bristol Water notified the operations team immediately and Clevedon Treatment Works was shutdown.
The two most important challenges for water engineers and operators are the requirement to supply adequate drinking water and to maintain its quality. There is also a significant emphasis on maintaining levels of service so that Bristol Waters customers are always protected and get accurate information as quickly as possible.
Solution:
Clevedon Well draws from a confined aquifer that was assessed as low risk for crypto and there had been no history or signs of Crypto in the past. Following the report of this incident, half of Clevedon Treated Water Tank was taken out of service and drained to reduce the treated water volume stored in the system. The Drinking Water Inspectorate, Public Health England and the local authority environmental health team were alerted and kept fully informed throughout the incident.
The treated water tank also had an inlet from Backwell Hill Service Reservoir, so flows were increased from this reservoir to ensure supplies to Clevedon were maintained. Next, a “Boil Water Notice” was put in place for all local customers as a precautionary measure to minimise the risk to health. Although Crypto was found in the untreated raw water, the potential significance meant that Bristol Water took the treatment works out of supply with immediate effect.
To restore water quality as quickly as possible, the engineers calculated how much quicker freshwater could move through the network using InfoWorks WS Pro. This required the standby cover Network Asset Modelling Engineer to evaluate network options to find the best solution for service restoration in the fastest possible way while maintaining system integrity. The analysis and output from the hydraulic model showed that if one compartment was taken out of service this would allow the system to be purged within 24 hours. Then water quality, systematic flushing programmes were initiated to remove any remaining “Clevedon” water from the downstream network.
InfoWorks WS Pro enabled Bristol Water’s engineers to quickly model solutions to the incident. In parallel samples were taken for Crypto from the network. With the networked purged and all samples returning negative results for Crypto the Boil Water Notice was lifted after consultation and advice from Public Health England.
In total 17,036 people and 7,375 properties were impacted by the incident. To protect the health of the local population Clevedon Treatment Works has been kept out of service until further notice. Bristol Water received a 70% customer satisfaction score for its management of the incident.
InfoWorks WS Pro enabled Bristol Water to act fast to model solutions to resolve the incident. To learn about how you can respond faster, more accurately and confidently, visit: InfoWorks WS Pro
