Using earthworms to process hazardous materials containing heavy metals

After pollinating insects, worms are probably the gardener's best friend and they have been encouraged to process garden waste and soil for generations. The common earthworm, Eisenia fetida, could also become a useful tool in the processing and safe management of hazardous solid and liquid wastes with high metal content, according to chemist Lué Merú Marcó Parra of the Universidad Centro Occidental Lisandro Alvarado in Cabudare, Venezuela, and colleagues there and in Argentina.

The team has carried out two feasibility studies on the use of worms in treating waste. The team first used compost produced by worms, vermicompost, as a successful adsorbent substrate for remediation of wastewater contaminated with the metals nickel, chromium, vanadium and lead. The second used earthworms directly for remediation of arsenic and mercury present in landfill soils and demonstrated an efficiency of 42 to 72% in approximately two weeks for arsenic removal and 7.5 to 30.2% for mercury removal in the same time period.

Earthworms could offer an inexpensive and effective bioremediation alternative to complex and costly industrial cleanup methods, the team suggests. Given that the accumulation of solid wastes in landfills causes high risk for soils, underground and surface water contamination, so an effective remediation method is increasingly important as toxic metals in a wide range of waste products from obsolete computers to portable electronic devices are discarded in landfill.