Case Study
Award winning water treatment system protects SSSI conservation site
Construction, Infrastructure & DevelopmentClient
Advance JV on behalf of United Utilities
Location
Lake District
Objective
Construction of a state-of-the-art water treatment works in West Cumbria
Challenge
Addressing water treatment and pollution risks during five year construction
The challenge
United Utilities 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.
The solution
Before our involvement, muddy surface water was directed into a lagoon to stop silty runoff from reaching local rivers. From there, the water was pumped and transported off-site for disposal – a method that was neither cost-effective nor sustainable for the duration of the project.
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.
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.
Long-term silt capture
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.
Innovative water treatment
A 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®.
Slowing the flow
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.
Easy to install and monitor
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.
Managed in-house
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.
Adaptive design to suit dynamic site
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 results
TSS (Total Suspended Solids)
Reduced from 310mg/l to 37mg/l
Turbidity
Reduced from >3000 NTU to just 25 NTU
Phosphorus
Reduced fivefold (0.1 mg/l → 0.02 mg/l)
COD (Chemical Oxygen Demand)
Dropped from 69 mg/l to <10 mg/l
Heavy metals
Significant reductions in arsenic, iron, nickel, and zinc
pH levels
Remained stable throughout treatment
Acrylamide
Peaked well below the drinking water standard (0.017 vs. 0.1 µg/l)
The products
Gel Flocculant for Silt Control
- Can be deployed passively in flowing water or in pumped systems (Pipe Reactor & Clearflow GFR)
- Long lasting, low maintenance silt control devices
- Supplied with site review service to ensure correct site-specific deployment and efficacy
- The most cost effective method to manage fine suspended solids on site
Pipe Reactor
- Portable unit for dosage of Gel Flocculant blocks
- Quick and simple to set up
- Treats water at up to 1,800 litres per minute
- Highly cost-effective method of managing clayey water on site
Floc Mat®
- Low cost, low carbon way to treat clay-impacted water run-off
- Can be used on land and in ditches
- 100% biodegradable for easy disposal or seed onsite
- Simple to deploy and highly effective at controlling fine particle silt pollution
Silt Capture Channel
- Captures silt and flocculated fine silt particles
- Unique design utilising Frog Environmental products
- Standard design polishes up to 900 litres per minute
- Supplied with site review service to ensure correct placement on site
Silt Mat™
- Cost effective silt pollution control on site
- 100% biodegradable for easy disposal or seed onsite
- Can be used on land, in ditches, streams or rivers
- Unique heavy-weight design delivers longevity on site
Silt Wattle
- Traps sediment, slows runoff and captures soil
- Flexible enough to work on slopes and uneven ground
- Quick to install, lightweight and easy to place
- Offers a cost-effective silt and erosion control option
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