Phytoremediation project redditch

[Rt400]

PHYTOREMEDIATION PROJECT REDDITCH

 

Acorn Environmental Management Group (AEMG) the Midlands based Tree Maintenance, Arboricultural Consultancy and Landscape Management Group has recently completed the first commercial project using Trees for Phytoremediation in the UK in conjunction with URS/Scott Wilson.

 

The project involved:

 

• Removal of exiting scrub and vegetation using Multi task land clearance machine

• Site preparation and planting of 600 Willow sets using deep planting techniques

• Liaise with Environment Agency and Local Authority

• On site establishment maintenance and aftercare.

 

The site, the former BA Tubes site located to the southeast of Redditch town centre, covers an area of approximately 6.5 hectares, with the general topography sloping gently from west to east towards the River Arrow.

In 1940 site operations involved the re-melting of aluminium and subsequent cutting, extrusion and drawing to form aluminium tubes. As part of these manufacturing operations, the site handled large quantities of chemicals such as caustic soda, TCE and various other hydrocarbon-based fuels and oils.

 

There are a number of water courses, surface water features and underground surface water drains located within a close proximity to the site. All of which could be at risk of contamination.

 

Previous investigations at the site and in the surrounding area have identified the presence of the chlorinated solvents TCE and its degradation products in shallow groundwater. This contamination is believed to have originated from historical activities at the site.

 

A number of methods of reducing the impact to the River Arrow are being implemented, including the use of Phytoremediation to reduce the contaminant mass that is entering the river via groundwater baseflow.

 

The Phytoremediation technique involved the planting of appropriate phreatophytic tree species in selected on-site and off-site areas to reduce over the medium and long term the contaminant flux toward the river Arrow. Phreatophytes are plants that can obtain water from the water table rather than just the unsaturated zone. Therefore, such plants are capable of creating zones of hydraulic containment, by effectively acting as solar-driven “biological pumps” that draw down water levels and create a barrier effect. Phreatophytic species include

 

 

 

• Salix (willow),

• Populus (poplar, aspen),

• Alnus (alder)

• Fraxinus (ash)

 

 

Willow and Poplar are the most commonly used species for Phytoremediation purposes, due to their:

 

• ability to take up large quantities of water through transpiration;

• fast growth rates;

• ability to take up and phytovolatilize certain contaminants (e.g. chlorinated hydrocarbons); and ease of planting and maintenance.

 

Furthermore, the zone of soil around the tree roots (the rhizosphere) provides an environment that is conducive to the growth and activity of microorganisms. These enhanced populations can typically cause increased contaminant degradation in this zone through both aerobic and anaerobic processes.

 

As such, the key natural processes that will be exploited by the proposed scheme will include:

 

• hydraulic containment by drawing down groundwater levels and creating a barrier

effect;

• the removal of contaminant mass through:

• enhanced contaminant degradation in the rhizosphere; and

• the removal of contaminant mass through up-take and metabolism of contaminants in the trees as well as subsequent phytovolatilisation to the atmosphere.

 

The trees will require a number of years to reach maturity. Once mature, it is envisaged that the trees would act as a form of hydraulic barrier through transpiration-driven removal of groundwater and enhance natural degradation of the contamination within the root zone.

[David Humphries]

Very interesting.

 

Appreciate the posting.

 

 

Has Mycorrhizal activity been factored in to how it may effect the rhizospherical system?

 

 

.

[sloth]

Sounds like a very interesting job thanks for posting, a few questions if I may...

You say this is first project of its kind in the UK; how much success has it had elsewhere? With the same contaminants?

Are deep planting techniques as self explanatory as they sound? To get roots in the ground water sooner?

What is currently growing on site, and is any of it seen as beneficial and to be left?

What is TCE?

A number of other methods are being implemented to reduce the impact to the river arrow; any more info?

Just a couple more...

Please could you further explain how hydraulic containment works/helps?

How do you expect the contaminants to affect what tree related mycorrhizal species will be present? I'd be curious about Gerrits view on this

Sorry for all the questions! Just to be clear I don't mean to pry or question the validity of this method, I'm simply interested in its detail

Edited January 15, 2012 by sloth

[sloth]

Thought this was related enough to add here: http://www.thedailygreen.com/environmental-news/latest/pollution-eating-tree-47011201

This would suggest trees must be 'modified' to be effective, is that true? What would the TCE be broken down into?

Are the trees being used expected to 'store' the contaminants in any way, if so might they be released as the trees themselves decay?

Oh, and no need to fear, they WILL be cut down before seed is allowed to spread.... why do I doubt this!