Non-interuptive water quality sampling

ATi recently worked in partnership with Panton McLeod and one of the UK’s largest water utilities, to facilitate a sampling survey, as part of two service reservoir water quality inspections.

Several samples were required from different parts of the reservoir and at various depths. The construction of the reservoirs and lack of access meant any kind of meaningful dip-sampling would not be adequate for providing enough samples and the spread would not be representative of the reservoir content. It was apparent that a submersible ROV (remotely operated vehicle) would be required that could be used or adapted to travel to the different parts and depths of the reservoir.

In order to provide the best service for this bespoke project, ATi worked closely with Panton McLeod, renowned inspection, cleaning and water asset performance specialists who provide innovative products and solutions, particularly for the cleaning and inspection of service reservoirs.

During the planning and preparation for this project, a consultative workshop took place at Panton McLeod’s headquarters in Tweedbank, Galashiels, where a working mock-up was configured to test the Panton McLeod ROV with an attached umbilical cord to ATi’s SiteBox portable water quality monitoring and control unit.

This test unit gave an accurate prototype of what would happen on site, with the successful development and testing giving high levels of confidence that this bespoke, collaborative solution would provide reliable and consistent results onsite.

Workshop trial

After the successful workshop trial, discussions were opened up with the water company, showcasing this new option of internal reservoir water quality testing. Foremost, it was recognised that not all samples being taken would be equivalent to regulatory samples taken and tested in a laboratory.

It was considered that chlorine monitoring was the most essential using the SiteBox and its industry-leading M-Node digital sensors, with turbidity, dissolved oxygen and pH being beneficial for an indicative quality of the reservoir content. These samples would highlight areas of concern within the reservoir. Other samples could be taken for laboratory testing via the umbilical pipe feeding the SiteBox.

SiteBox water quality control unit

Planning for the onsite sampling included consultation with all parties for risk assessment and RAMS (Risk Assessment Method Statement) preparation. Hygiene was of priority concern as the reservoirs were in use with potable water. No contamination would be allowed and all parties had to provide RAMS to confirm no risks were being taken. Even the risk of open hatches had to be mitigated, even for rain (see picture with tent over hatch). RAMS were to include all aspects of undertaking the task for all parties i.e. ATi and Panton McLeod both presented to the water company, who also had to comply with their own operational rules and standards.

A methodology was developed by the water company’s technical team and with consultation with the Reservoir Operational Section. ATi and Panton McLeod were also involved to confirm the methodology proposal would work. A map of the reservoir was split into grid-like sections and the number of points for sampling were determined by location and also at what depth. Each location would have a sample at the bottom, middle and near top of the level of water in the reservoir. The depth of this reservoir and water contained at the time of the testing determined that three samples should be taken at the chosen depths. Shallower reservoirs or emptier reservoirs may only require one or two depth related samples.

Panton McLeod operators set up the ROV and also the site, so safe access to the water space could be achieved. All equipment was sanitised for access to potable water. Preparation of site and deployment of ROV with ATi’s SiteBox portable water quality monitor.

Continuous monitoring for hygiene purposes was maintained for the duration of the exercises, as more than one site and two visits to each site on different days was accomplished. At each occasion the ROV was deployed into the reservoir and moved to the pre-determined sample points. Once at a sample point, the ROV remained stationary for 10 to 15 minutes to allow for the water from that point to travel down the length of the umbilical tube to the SiteBox.

At the ATi SiteBox, the position, time and the readings were noted. Regular chlorine checks by manual testing were also taken to confirm sensor accuracy. Some ‘bottle’ samples were also taken for laboratory testing. The lab results were not shared with ATi or Panton McLeod, however no detrimental results were found. Chlorine levels within the reservoirs identified various chlorine strengths across the reservoir’s areas and depths. All were within acceptable levels. Areas of reduced chlorines were identified but, in these instances, did not generate any actions but did identify areas of concern. They also indicated some differences, though not detrimental, of water quality in different areas and depths of the reservoirs

Conclusion

This new concept of implementing condition checks of a reservoirs content to completion of sampling, utilising a bespoke water quality monitoring approach was a resounding success. The research and trials conducted indicated that ATi’s SiteBox was the most suitable solution, in collaboration with Panton McLeod’s specialist ROV, due it it’s modular monitoring, control and policing nature. With the ability to monitor live readings, SiteBox provided the customer with clear and consistent data throughout the operation, along with taking samples, demonstrating that the reservoirs met company and regulatory standards. The data would assist in assessing future issues and enable predictive maintenance for specific needs identified.

This innovative ‘Lift & Shift’ method of water quality monitoring was vital in identifying and assessing issues within the service reservoirs, along with asset performance. Being proactive at this early stage can prevent shutting down reservoirs, saving on unnecessary and costly project work in the future. The water company were pleased with the results, the interpretation of the data recorded and what it told them about their reservoirs. Future use of the equipment and collaboration between ATi and Panton McLeod with other water companies will certainly provide an accurate and beneficial insight into the condition of any potable water reservoir surveyed.

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