The Problem

Willacy Oil were commissioned by a national utility supplier to carry out the desilting of a settlement pond situated on an industrial water clarification lagoon in Scotland. Over time, sludge and sediment had built up in a settlement pond where gravitational separation takes place. This reduced the overall efficiency of the site’s treatment process, meaning that water from the site was at serious risk of failing its discharge consent. Complicating matters further, the site could only be accessed via a very narrow country lane. This ruled out the usual types of equipment we might deploy, such as a centrifuge system.

In addition to this, the site’s reed-bed had become overgrown and required cutting back to ensure it could act as an effective filter.

Above: An empty geo-bag shown before the treatment process. The visqueen sheeting prevents the contamination of the site.

Above: A full geo-bag, shown after the treatment process. The geo-bag contains the solid whilst the liquid is released through the bag’s pores.

The Willacy Solution

Firstly, we utilised our specialised sonar system to identify the quantities and locations of the sludge that had built up. Once this was completed, we were able to tailor bespoke solutions for the cleansing of the pond, the separation of sediment from the water and the cutting of the reeds.

Amphibious equipment was used to pump the sludge from the pond, directly into a geo-bag. The porous geo-bag bag then acted as a filtration system for the sludge, allowing water to escape via the pores leaving a solid cake to be dug out when dry and transported away from the site. The geo-bags, normally used for such purposes as preventing the erosion of riverbanks, proved to be an excellent light-weight solution to the problem of not being able to transport larger equipment to the site. We protected the site against contamination by spills, isolating the settlement pond from the reed-bed and covering the area around the geo-bags with visqueen sheeting.

A liquid grade polymer was added to the geo-bags as required throughout the process, to help ensure the dryness of the cake and clarity of the filtrate. Samples were taken beforehand in order to assess the amount of polymer required.

Using the same amphibious equipment used during the pumping process, we were able to access and cut the reed-bed down to size. Having used the same equipment for both the pumping and cutting processes, we were able to work around the difficulties of narrow access and limited space on the site.

Once the settlement pond had been cleared of excess sludge and the reed-bed cut back, they were able to more effectively filter the sediment meaning that water from the site met the required discharge consent.

Above: Amphibious equipment used for both the pumping and reed-cutting processes.

Above: Amphibious equipment and operator in action, carrying out the reed-cutting.

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