Award winning water treatment system using Gel Flocculant protects conservation site with SSSI status

An award winning and unique water treatment system was implemented to protect a nationally important river during the five year construction of a state-of-the-art water treatment works in West Cumbria.

Frog Environmental’s technical team supported United Utilities and their construction delivery partner, Advance JV, with proactive environmental site planning and mitigation to include the design of a highly effective water treatment solution at Williamsgate Water Treatment Works.

Our simple yet effective solution is estimated to have saved close to £1 million* over the five year period compared with alternative options available on the market, and most importantly, mitigated silt pollution throughout the project, protecting water and aquatic life in the nearby River Derwent, a Site of Special Scientific Interest.

Our achievements at a glance:

  • Total Suspended Solids were reduced from 310mg/l to 37mg/l.
  • Turbidity reduced from >3000NTU to an average of 25NTU.
  • Phosphorus decreased from 0.1mg/l to 0.02mg/l.
  • Chemical Oxygen Demand decreased from 69mg/l to <10mg/l.
  • Heavy metal reduction included Arsenic, Iron, Nickel, Zinc.
  • There was no change in pH.
  • Acrylamide levels peaked at 0.017 µg/l – this is a fraction of the drinking water standard set at 0.1 µg/l.

Our solution enabled the discharge of treated site dewatering upstream of the River Derwent SSSI and gave our client and the regulators full confidence in knowing the environment was protected in doing so.

Furthermore, our water treatment systems were adopted at both new service reservoir sites created at High Leys and Moota Hill as a result of the success of our work at Williamsgate.

The project won a Green Apple Award for innovation in water treatment in 2019.

SSSI project challenges and background

United Utilities recently concluded the West Cumbria Water Supplies Project to end the abstraction of raw water from precious local water bodies including Crummock Water, Chapelhouse Reservoir, Overwater and Ennerdale Water in order to protect the Freshwater Pearl Mussel population in the River Ehen and secure a more sustainable water supply for West Cumbria.  

The scheme involved the construction of a 100km of pipeline from Thirlmere Reservoir, two service reservoirs and Williamsgate Water Treatment Works.

In preparation for obtaining planning consent, United Utilities identified that the construction of the infrastructure had the potential to impact on the water quality of the local rivers, including the River Derwent, designated as a Site of Special Scientific Interest for its salmonid populations.

Silt pollution from surface water runoff was identified as a major environmental risk to these rivers as the contractors had to move around 400,000 tonnes of soil before they could begin building the water treatment works.

Ineffective and expensive methods led to effective chemical-treatment silt control

Before Frog Environmental came on the scene, to prevent silty water entering local rivers from the site, a lagoon received the muddy surface waters and from there, water was pumped and transported off site for disposal. This was not a cost effective or sustainable option for the length of project which led United Utilities and Advance JV to consider other alternatives.

We were engaged to provide silt control advice including the specification of a low maintenance long-term water treatment system for the construction phase that would deliver a cost efficiency against more conventional tank-based systems, without risking the high water quality standards that would allow the site to discharge into the River Derwent.

Advance JV, in partnership with United Utilities, initiated chemical-treatment silt control trials using our Gel Flocculant. Offering a bespoke, market-leading system, Gel Flocculant utilises a patented synthetic anionic polyacrylamide flocculant developed by Clearflow Group to bind fine clay and silt particles together so it can be separated and removed from the water.

Without our innovative flocculant solution, Advance JV shared that construction would have been delayed at a cost of around £70k/week until either a better period of weather, or until all waters had been tankered off-site.

Regulator approved solution

Gel Flocculant has been a game-changer worldwide in the construction industry. We have championed their use in the UK by developing new ways to manage surface waters using practical ‘Rain Ready’ gravity treatment systems or pumped systems that optimise on-site surface water features during temporary works as well as helping to reduce site silt management product and operational costs and carbon footprint.

Regulatory stakeholders, including the Environment Agency, were closely involved with the initial trial process, which ran from November 2017 until April 2018, to check that the legally-acceptable chemical discharge parameters would have no long-term detriment to the environment.

Settlement and flocculant validation tests were undertaken to illustrate the behaviour of the sediments on site and match the flocculant to the site’s soil and water chemistry. This helped our technical team to advise on the best water treatment system design and which Gel Flocculant blocks to use as part of their set up for optimal performance. 

Glenn Entwistle, Senior Environmental Advisor at Advance JV was impressed with the outcome, stating:

“Frog Environmental were knowledgeable, helping to establish a workable, cost-effective and low maintenance solution for site approved by the regulator.

They really understood the water management issues we had on site and worked with us to develop a solution which works, as well as engaging with our operatives to ensure that they could effectively manage the system.

It was a long regulatory process, but we understand the risks associated with working in such sensitive areas, especially with new and different products and the concerns Stakeholders may have, and they were brilliant in helping provide the necessary data to satisfy Regulator requirements.

We are delighted to have found a solution that prevents pollution and protects the environment, and ultimately allows us to continue with construction.”

Treated clear water running over captured silt
Treated clear water running over captured silt

Easy, low maintenance and cost effective design

Our technical team designed and implemented a Silt Capture Channel with a Pipe Reactor containing Gel Flocculant to cope with the sheer volume of silty water on the construction site.

The lagoon was used as a primary sedimentation basin from which water was pumped at a rate of 900 L/min through a Pipe Reactor containing Gel Flocculant.

The treated water then passed into an open channel lined with a combination of our 100% biodegradable silt capture mats, Silt Mat™ and Floc Mat™.

To increase the efficiency of the channel, a diffuser was used at the inlet and our Silt Wattles were placed at intervals down the channel to further slow the flow of water and encourage further deposition.

Our solution led to an easy site set up which was simple and easy to monitor, with no risk of overdosing, and none of the risks traditionally associated with storing liquid treatment chemicals.

Following our support with implementation and training, the Advance JV team managed the water treatment system on site including monitoring. We provided remote technical support when needed, and replenished stocks such as Gel Flocculant and other materials used in their Silt Capture Channels.

Our water treatment system was in situ throughout the duration of construction to allow for intermittent pumping following rainfall events. Following the results of our flocculant trials in year one, the Environment Agency granted the permit to discharge into nearby rivers in August 2018.

Adaptations were made to scale the system as the project evolved, increasing treatment capacity by adding an additional Pipe Reactor and Silt Capture Channel and improving the design of the sedimentation pond to reduce the resuspension of the accrued material before scaling down the treatment in the final phases of build.

The ongoing performance of the water treatment system protected the environment and delivered significant cost savings across the whole project.

  • The total spend on the water treatment solution was c.£40k over 5 years.
  • *A cost saving of over £1 million is estimated should a hire tank-based solution have been adopted.  
Silt capture channels form part of a water treatment system
FlocMat™and SiltMat™ laid in a Silt Capture Channel
The Pipe Reactor is quick and simple to deploy and highly versatile

Crystal clear water

The treatment performance was validated with the initial trial and ongoing monitoring:

  • Turbidity reduced from >3000NTU to an average of 25NTU
  • Total Phosphorous decreased from 0.1mg/l to 0.02mg/l
  • Chemical Oxygen Demand decreased from 69mg/l to <10mg/l
  • Heavy metal reduction included Arsenic, Iron, Nickel, Zinc
  • No change in pH
  • Acrylamide levels peaked at 0.017 µg/l, significantly lower than the drinking water standard of 0.1 µg/l.

Are you considering Gel Flocculants for your next project? Contact Us for technical support and a no-obligation quote.

Frog Environmental are silt control & water quality specialists working with contractors, regulators and consultants within construction, utilities, marine and coastal and public sector industries across the UK and Europe.

Bringing our water quality and silt control specialist team of consultants on board early allows you to prevent issues arising; through training up your staff, offering technical design and site preparation support, as well as products that are engineered to meet needs across a wide range of industries.

Follow our news and updates, find out more about our products, or contact us for technical support.