Improving bioremediation

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Courtesy of Newzeye Ltd

Sustainability is becoming a benchmark for the quality of companies who offer remediation solutions, the technologies that they develop and offer commercially, as well as the entire projects where they are used. It is, in essence, not something that can be simply ignored in the months and years ahead if standards are to continue to improve, says Tom Hayes of Ecologia.

The sustainability associated with various types of remediation processes is a current and important topic. The complexity and necessity of the investigation into the sustainability of our industry and been highlighted by recent work by the Sustainable Remediation Forum (SuRF).

The role of organisations who are involved in developing innovative technologies as well as improving existing processes have, until now, been focused on the reduction of treatment costs. This has been encouraged and aided by measures such as the abolition of the landfill tax exemption in October 2008. However, the increasing awareness of sustainability within our industry has provided a new impetus to not only the development of new technologies, but the improvement of exiting techniques, which are considered to be mature in terms of the design, scope of use and cost.

A technique that Ecologia has been working to improve is ex-situ bioremediation. Bioremediation is a technique with good sustainability credentials. Ex-situ bioremediation comes in several guises and the specific form of ex-situ bioremediation that we use is biopiles; engineered piles of soil that include active aeration of the soil using a vacuum blower, collection of leachate and allow the abatement of VOCs by capturing the extracted gases. Biopiles operate very quietly with comparatively little operation and maintenance required, so one might wonder how we can improve this.

Bioremediation

One important aspect we have focused on is the use of energy to aerate the soil. Aeration of the soil biopile can require a great deal of energy. Commonly the aeration blowers are left running 24 hours a day, seven days per week, or, in the case of windrows and large turners are often driven up and down the site burning diesel and releasing VOCs into the atmosphere from the soil. The approach we have studied and successfully used is to only aerate the soils when it is required.

We have been monitoring gases within biopiles for many years to provide data on the health and effectiveness of the biopile. Respiration tests can be undertaken by switching the aeration system off line and measuring the rate of oxygen depletion and carbon dioxide production to assess the rate of contaminant breakdown associated with biological activity. This method not only produces data to demonstrate to a sceptical client that there is something actually going on in the ‘heap of muck’, but it also provides valuable data on the progression of the process and when validation soil samples should be taken.

Recently, we began to use automated gas analysis and to record the concentrations of oxygen and carbon dioxide every minute by using multiple gas sampling ports and devices within the Biopile. Our fully telemetrically controlled systems allow us to access this data from our office and remotely run respiration tests to see the health of the biopile without the need to get in a van (or an aeroplane) and actually go to site.

It was a relatively short leap to link the automated gas analysis to the process logic controller for the biopile plant and switch the blowers to come on line only when the carbon dioxide builds up above a certain level. This idea was tested, with our equipment which was designed and built in Kent, at the former gasworks in Verona, Italy. The project in Italy involved the construction of two identical 3,500m3 biopile batches, one after another, on the same treatment pad. The first was run in the traditional manner and the second was aerated automatically.

The two batches of material were treated in the same time but the key difference was that the second batch using the automated system used only 20% of the electrical power that the first batch did. The very large reduction in energy use is combined with the possibility of using smaller equipment in the future, reduced visits to site, and lower running costs due to decreased wear and tear of the equipment, making the process more environmentally and economically sustainable.

The example of our work in Verona shows that continued improvement of what we do can be the key to improvement of all aspects of sustainability and does not necessarily rely solely upon brand new technologies, but can also include innovation of important aspects of existing techniques.

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