The following is based upon an article about the latest Enviros designed and commissioned Leachate Treatment Plant, published in the July 2009 Edition of the Community Newsletter published by Barr:
Rain falling on the waste in a landfill is held within the plastic lining the waste sits on, which is intended to stop the rainfall entering the soil and rock beneath.
As site operator Barr Environmental needs to pump it out of the waste and treat it as per their SEPA waste permit. Till last year the leachate from the waste at Garlaff was treated in an open lagoon system close to the site entrance. While this plant still worked it was built many years back and wasn't able to treat the leachate to the highest standards now feasible. This old plant has been substituted by a state of the art treatment system beside Cell two of the rubbish heap.
The new plant is one of the most recent systems in the United Kingdom and was designed by leading leachate professionals Enviros. The consultants have designed over one hundred plants around the globe to treat this kind of waste water and have advised the UK govt and in particular the DEFRA government department in the Best Available Techniques (BAT) available for this kind of leachate treatment.
The plant is entirely automated and computer controlled and can nicely treat all of the leachate the landfill site produces every day. The system was built by Barr Surfacing & Civil Engineering and largely invisible from outside of the site as four fifth's of the plant is built below ground, rather like a below ground multi-storey car park.
The leachate is pumped from the rubbish heap from a series of wells in the waste to an large holding tank in the plant. There were some concerns about odour from this tank. So, all the tanks have been sealed at the top to stop any smells entering the air round the site before the leachate starts to be dealt with.
The main treatment tank is aerated and the leachate treated using the natural microbes in the sludge in the tank in the same way a sewage plant works. These microbes are specifically evolved to treat the ammonium rich liquid to provide a clean liquid that is fit for discharge to the brook.
The plant has been engineered to the most recent standards with a high efficiency energy rating that's achieved by insulating the tank with earth around it and transferring the heat from the aerators into the treatment liquid. Keeping up the leachate temperature through the winter at about 25 degrees C creates the ideal conditions for fast decrease in the pollutants within the aeration tank.
Still working with nature the final part of the treatment process uses natural reedbeds on site to shine and take away the last traces of solids and nitrogen.
The reedbeds have proven to be a helpful habitat as well to wildlife. They will quickly become home to many insects and the tiny birds that eat them.
Barr have been so happy with this new leachate plant that they have just built its twin at their other landfill site, at Auchencarroch in West Dunbartonshire, Scotland. Together these plants are the biggest and most modern leachate plants to ever be built in Scotland and controlled by one company.
The plants will operate for no less than the next 30-40 years till the leachate has been fully treated on the site and no longer is required to be removed.
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