In 2015 OIS Ltd was instructed by FRS to investigate a Leachate Treatment Plant (LTP). The client was concerned that the LTP was not treating the leachate to the permitted discharge requirements. It was a closed landfill site that was used for the disposal of municipal waste from the 1950s to the mid 1990s. A leachate treatment plant was installed in the 1980s to treat leachate to a standard that enabled discharge into a nearby water course.

Investigations by OIS established that the LTP was continuously shutting down as a result of the failing treatment process. To address this in the immediate term, the client arranged for leachate to be tankered off site for treatment at a third party facility, at a daily cost of up to £1200.

Investigation by OIS established that the leachate arising from the former landfill site had passed the methanogenic phase and consequently, the existing treatment process was no longer appropriate or effective. OIS also found that the collection system and drainage was hydraulically unbalanced, the entire drainage system that collects and feeds the leachate under gravity to the collection lagoon was below the discharge point in the collection lagoon. This meant that land surrounding the LTP was constantly flooded with leachate.

Furthermore, the contaminated water from this area passed into the surface water drainage system prior to discharge into the adjacent water course. To address this issue, OIS recommended the installation of a pumping station at the final drainage chamber and the permanent sealing of the pre-existing discharge line from the final chamber. This work was carried out by OIS following instruction by the client. The pumping station now prevents the field from flooding and prevents the leachate entering the surface water system and discharging to the Tiel Burn.

In order to ensure that leachate produced at the site could be effectively treated on site, OIS recommended that a nitrification treatment process should be installed to replace the original treatment technology. Following instruction by FRS, this work was carried out by OIS. Leachate lagoonThis included installing a media designed and owned by OIS. The instruction from FRS also provided for OIS assuming responsibility for the management, maintenance and operation of the LTP and the site's extensive drainage systems, covering 45 hectares of land. Since carrying out this duty the LTP has operated successfully, has never experienced any downtime and has enabled the site to obtain an "Excellent" rating under SEPA's Compliance Assessment Scheme.

An additional benefit of the works carried out by OIS is that 3rd party leachate can now be treated there. The LTP can treat up to 90m3 per day of third party leachate from April to October, and 330m3 per day of third party leachate from November to March.

“OIS were engaged to investigate the causes of poor performance of a leachate treatment plant (LTP) at a closed landfill site at Balbarton, near Kirkcaldy. The site had been used for the disposal of municipal waste from the 1950s until 1998. The LTP was installed in the 1980s to treat leachate to a standard that enabled discharge to a local burn. However, by 2015 the LTP was no longer operating effectively, and as a result leachate was being tankered off site for treatment elsewhere at substantial cost.

Investigations by OIS revealed that the landfill site had passed the methanogenic phase, resulting in significant changes to the characteristics of the leachate. Those changes meant that the original LTP was no longer capable of treating leachate to the standard specified in Fife’s discharge consent.

OIS’ report included recommended actions to resolve the issue on site, with which we agreed. Consequently, OIS were engaged to implement their recommendations and to assist in the submission of an application to the Scottish Environment Protection Agency (SEPA) to secure a modification to the environmental permit insofar as it relates to leachate treatment.

The improvements initiated by OIS have been a complete success. Principal outcomes are the production of a treated effluent that is once again suitable for discharge into a local burn and a substantial saving in off-site treatment costs. The improvements have also contributed to ensuring that the site has secured an “Excellent” rating under SEPA’s Compliance Assessment Scheme.”

John Conaghan, Service Manager (Resources Recovery), Resource Efficient Solutions