28 March 2024

Reed beds protect the environment from landfill leachate water

Aberdeenshire Council completed improvements to a reed bed system in Banchory that ensures any leachate water draining from its landfill site is clean and leaves the environment unharmed.

Water can enter a landfill through rain or surface drainage. As the water moves through the waste, it becomes something known as leachate and needs to made safe for the environment before it can be released.

Banchory was one of the last landfills in Aberdeenshire to be closed and so still produces significant gas and leachate.

The leachate is first cleaned by large underground tanks in which a rotating aerator engine stirs leachate among a special activated sludge and water to cleanse the mixture.

The cleaned water is then decanted into the reed bed lagoons. In the lagoons, bacteria and other organisms eat up the remaining pollutants to a standard higher than is required by the Scottish Environment Protection Agency.

As the landfill was lined before any waste entered it, should any rain or surface water enter the waste, it can only travel through the leachate-treatment tanks and then into the reed beds before leaving the site as clean water.

The capacity of a reed lagoon reduces over time as the reeds overtake the lagoon space. The improvement works replanted two lagoons to return the site to optimum working conditions. This refurbishment work also reduces the need for tankers to transport excess leachate water away from the site.

Chair of the council’s Infrastructure Services Committee Councillor Alan Turner said: “There is far more to the recycling and waste service than bin collections and this is an excellent project to highlight that. Even in this most unlikely of places, work is ongoing to make things more sustainable and better for our environment.”

Vice-chair Councillor Isobel Davidson said: “Decades of waste management goes into a landfill site long after it has closed. The waste doesn’t just disappear, and we have to deal with it. Doing so in a way that minimises our impact on the environment is always the goal."

These refurbishment works are not the only sustainability improvements on the Banchory landfill site. Landfills generate gas as the waste decomposes. The gas builds up inside the landfill and must be flared off to avoid environmental damage, odour, or other pollution.

In Banchory, this gas buildup is instead utilised in an active landfill gas extraction system where a ground flare and micro generator converts the gas into green electricity. The energy generated goes to the national grid but can also help to power some of the facilities in the landfill, neighbouring household recycling centre, and waste transfer station when needed.

A landfill recovers over time as the material inside decays and less gas and leachate are produced.

The typical lifespan of a landfill can be 50 years or more, depending on the content and overall volume of the waste tipped. Landfills must be maintained and monitored for all that time. Banchory was closed and began to be professionally restored in 2011, so the land is not likely to recover within the next few decades.

Today, non-recyclable waste from Aberdeenshire, Aberdeen City, and Moray Councils goes to the NESS Energy from Waste facility located in East Tullos instead of being sent to landfill.