ERS wins at the Remediation Innovation Awards

An innovative treatment plant to remove hexavalent chromium

ERS was commissioned to build a treatment plant to remove hexavalent chromium from contaminated drainage water and groundwater at Summerford Park, an 8 hectare public space owned by Falkirk Council. The innovative solution effectively removes contamination by means of a hi-tech but cost-effective groundwater treatment system designed for long-term unmanned operation.

Background

Falkirk Council discovered that hexavalent chromium was leeching into local rivers and streams from contaminated dranwater from Summerford Park an 8 hectare public space located on a former industrial site near to the Falkirk Wheel.

Arriving at an appropriate solution

After careful nalaysis of the underlying hydro-geology, ERS proposed installing a chemical reduction treatment system that operated via an in-house optimised reagent was selected as the most cost effective approach. Water is pumped into an intermediate holding tank to enable the designed plant to operate at a constant flow. The system also features a passive overflow system in place fortimes of excessive rainfall overflow.

Collected groundwater is chemically treated to reduce the hexavalent chromium to trivalent chromium, which is relatively insoluble and precipitates out as a fine gelatinous hydroxide. This precipitate is mechanically separated by means of a Dissolved Air Floatation unit, a pressurised air and water mix which produces a better floatation of suspended solids. These are then mechanically recovered using scrapers.

The treated water is discharged to the local waterway (the Mungal Burn and eventually the River Carron) and the sludge is dewatered and disposed of. The plant is designed to operate unmanned with a telemetry system allowing the engineer to receive information. The system is capable of treating up to 200m³ per day and reducing chromium concentrations from between 8-30mg/1 to < 0.1mg/1.

A cost-effective, long-term solution

The primary goal of this remediation solution was to prevent contamination of local watercourses. Disposal to landfill would have been economically unfeasible, whilst capping would not have prevented leaching from below. The total cost of the treatment was £1.2m – approximately £15/m3, which for a site this size is both environmentally and cost effective. The system has been designed to operate over a 20 year period. A passive system using sorbant or reductive media over this timescale would prove more costly due to the need for frequent regeneration and replacement: it would also require a much larger area  Thee active system in place is capable of taking chemical deliveries without downtime.

Gaining public support for the project

The drainage system was incorporated in to re-landscaping of the area, and the land used safely as an amenity space, ensuring little impact on the surrounding environment.

It was important to gain public support for and understanding for the ERS solution. Public consultation and publicity for the project were advertised through the local press, leaflet drops and posters. Workshops, interviews and questionnaires were used to ensure that local views were properly represented.

Minimising the risk to site personnel

Health and safety issues were of paramount importance to this project since it employs potentiallly hazardous chemical reagents. The risk of exposure to site personnel is minimised by the automated unmanned operation of the plant 

Detailed method statements were prepared for regular works, including chemical deliveries, which represent the highest risk of exposure to chemicals. To minimise risks ERS designed an external delivery point, with large bunded concrete are isolating the delivery point form the soil and water environment.

NOTE TO EDITORS: ERS are one of leading land remediation companies in Scotland. ERS works with companies, local authorities and individuals to help realise the value of their land by solving contamination problems with the least intervention and cost through innovation and an open, collaborative approach. Led since 1994 by Andrew Mackenzie ERS operates from bases in Glasgow and Inverness and employs over 40 people.