BTS | HARDING PRIZE COMPETITION 2025


tender through enquiries and to contract award. This gave me insight into the commercial and contractual requirements at the early inception of construction. I then worked with the chosen subcontractor, vesting the materials on a fortnightly basis to secure a cashflow prior to the overseeing of both factory and on-site acceptance tests. The timescale for the project was a key consideration in awarding the contract and the plant went from tender award to treating water in under six months. The installation of this plant, pictured in Figure 7, has allowed Align to treat water at 250m3


/hr to the quality Above, figure 9:


Graph of recycled water usage and anticipated demands


This was a vital stage in allowing the innovation


to be replicated across other HS2 sites and also in the recycled water initiative at Align, enabling the JV to move and treat the water further. It has added a host of other opportunities as well as being self-reliant through the environmental discharge permit.


3.3 Innovation 2 – New WTP The success of the above report, stakeholder engagement and production works at the STP led to an expansion of my interests as to the next steps for the water treatment process. From this interest I also expanded my role to incorporate the WTP. The original WTP at Align could treat for pH


correction and removal of suspended solids, although not meeting the stringent requirements for discharge to the environment as detailed in the Table. Initially, a series of on-site trials were undertaken,


primarily using a reverse osmosis (RO) container to further treat the original WTP discharge. This successfully removed most contaminants but raised the pH. Changes were made to reduce the pH through the original WTP and add oxygenation methods to the treated water storage pond to remove the nitrites to acceptable levels. However, the oxygenation wasn’t realised and therefore an ion exchange unit was added to the RO, which successfully treated the water to the required quality for discharge. I was involved throughout this trial-and-error approach as the production lead, exploring the technical possibilities with different subcontractors, liaising with the onsite environmental team and a specialist consultant. With the concept proven, it was then needed to be


established at production scale. While following the trials, I had built up a portfolio of information and so I volunteered to produce a specification for a new WTP, capable of meeting the discharge criteria (including waste feed to sewer) based on the measured inlet water quality measured on site. This was to accommodate both - water from production activities and the anticipated surface water run-off from rainfall events. From this work, I then presented the package to various potential bidders taking the specification to


22 | May 2025


parameters required for discharge. This means the plant can discharge all site water to the environment, bypassing the reliance on a public sewage treatment works. Due to the stringent environmental constraints, the water produced from the project is of such a high quality that there was a potential to be reused on site. This would alleviate the requirement on the potable water network thus securing sustainable consumption and production, and thereby reducing impact on water availability for local inhabitants achieving SDG’s 6 and 12 in the process.


3.4. Water Recycling At the outset, site recycled water was considered an important factor for optimisation and efficiency. A storage tank was installed at the WTP connected to a pressurised main running throughout the site, as seen in the process flow diagram on Figure 8. However, due to the length of time passed between its installation to the point of use, methods had already been standardised and the network was then seldom in use. Here, I used the installation drawings to track


where the connections surfaced, which allowed me to champion the use of the water for tunnel cooling and the batching plants. This work led to three new connections being made in the pressurised main network to support cleaning of the concrete MSVs and for use in the batching plants. I monitored all points of the recycled network and


its potable counterparts, taking regular readings from production aspects across the project, including, but not limited to, concrete batching, the tunnel segment precast factory, STP, WTP, tunnel works and TBM production, and dust suppression. With these datasets collected, I compared them to the calculations for water consumption made at the outset of the project, shown in Figure 9. These innovations vastly reduced the reliance on the potable water network; the recycled water on average provided 85% of the water consumption. It should be noted that these recycled water figures


were achieved despite running the plant in a sub- optimal way for production. The plant had to be run to maintain a low water level in the pond storage network, generating capacity against rainfall scenarios. In retrospect, it would have been beneficial to run the plant to accommodate demand for the recycled water thus preventing overflows to environment close to predicted dry spells, reducing the recycled resource.


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