August 21, 2012 by desertrose
Crossroads News : Changes In The World Around Us And Our Place In It
The Beauty Of Nature : Bio-remediation
Earthworms soak up heavy metal
by Staff Writers
London, UK (SPX)
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Earthworms could be used to extract toxic heavy metals, including cadmium and lead, from solid waste from domestic refuse collection and waste from vegetable and flower markets, according to researchers writing in the International Journal of Environment and Waste Management.
Swati Pattnaik and M. Vikram Reddy of the Department of Ecology and Environmental Sciences, at Pondicherry University, in Puducherry, India, explain how three species of earthworm, Eudrilus eugeniae, Eisenia fetida and Perionyx excavates can be used to assist in the composting of urban waste and to extract heavy metals, cadmium, copper, lead, manganese, zinc, prior to subsequent processing.
With rapid increases in urban populations particularly in the developing world, there is a growing problem of how to manage organic waste and to find alternatives to landfill disposal particularly for domestic food waste and that from vegetable markets.
According to the research team, it is an unfortunate fact of life that much of this waste is currently dumped on the outskirts of many towns and cities and is causing serious pollution, disease risk and general ecological harm.
It also represents a considerable wasted resource, whereas the organic matter might be exploited usefully in growing food crops.
The process of vermicomposting in this way allows such waste materials to be remediated and the compost used subsequently for use in growing human food without the risk of accumulating heavy metals in crops.
The team says that up to about three-quarters of the various heavy metals can be removed by the worms from solid waste.
The E. eugeniae species was the most effective worm at remediating solid waste and producing rich compost. The team’s tests on vermicomposting reveal that the heavy metal content of such waste can be reduced to levels significantly below the permissible safe limits.
The worms’ digestive system is apparently capable of detaching heavy metal ions from the complex aggregates between these ions and humic substances in the waste as it rots.
Various enzyme-driven process then seem to lead to assimilation of the metal ions by the worms so that they are locked up in the organism’s tissues rather than being released back into the compost as worm casts.
The separation of dead worms from compost is a relatively straightforward process allowing the heavy metal to be removed from the organic waste.
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Comments
Quite right. There are microorganism that are capable of breaking down heavy metals. These are in the soil. This experiment has been done in the USA. It is a combination of using earthworms and microorganism from the soil. By feeding the microorganism with fertilizers, the heavy metals are broken down into particles that are not taken or up taken by plants. The draw back is the need for a large piece of land and machinery to turn the soil when the soil temperature goes below 150 F.
Yes this is very true. But the way I viewed this article was more on a stand point of what they can accomplish in our compost piles. Removing heavy metals from the soil in our compost piles to make it safe for us to grow organically. The amounts of heavy metals would be dependent on the environment and the earthworms would still be in the soil so we are not exposing them to any thing that they would not encounter otherwise. But it makes us aware that they do provide a very valid and important function for us.
Therefore, giving us the knowledge and understanding that earthworms are vital not only for their production of worm casting but in their uptake of heavy metals from the environment as they also occur naturally not just from pollution..
It is too easy that is why it is not apply. The only thing that bugs me is that the heavy metal are in the body of the earthworms.