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Reed beds provide alternative treatment for distillery headache

CONTRACT

SITE WORKERS have installed sludge treatment reed beds (STRB) as a sustainable alternative to spreading waste from one of the oldest working distilleries in Scotland on to agricultural land.

The Blair Athol Distillery is in picturesque Pitlochry and produces whisky - including a 12-year-old single malt - for its owner Diageo.

As part of its commitment to improve environmental performance, the company contracted ARM to build a series of six STRB to treat sludge produced as a result of the distilling process.

ARM contracted Enviroseal to install lining material in the beds.

STRB operate by passing untreated ef uent through sand and gravel beds in which reeds have been planted. Beds are typically either horizontal w systems, suitable for reducing biochemical oxygen demand (BOD) and suspended solids in low-strength efuent, or vertical ow systems for stronger ef uent, capable of removing higher BOD levels and reducing ammonia.

This system differs from conventional reed beds because it has deeper basins that hold and provide advanced treatment of sludges. It consists of a number of cells used sequentially to allow for de-watering.

Sludge is pumped on to the reed bed basin through a series of distribution pipes.

The majority of sludge water content ows vertically through the sludge residue and lter layer.

This leaves the dry solid content of the sludge on the reed bed surface as sludge residue - this is called sludge cake.

Over time, sludge reduces through a number of physical and biological processes. It takes an estimated 10 years before basins reach capacity and need emptying.

The basins are comprised of gabion baskets lled with site-won material. Site workers used Geofabrics' HPS6 as a protection layer before installing its 1mm LLDPE membrane to help with containment.

Reed beds treat contaminated groundwater or polluted efuent through a number of physical and bioengineering processes without using chemicals.

Work to install the STRB was completed in mid March.

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