The lagoons on a former colliery tip next to Grassmoor Country Park contain tar and contaminated liquid from the former Avenue Coke Works run by British Coal.
A project to remove the toxins was launched in 1995. And following detailed environmental assessments, trials and drainage, specialist equipment has now been imported from America to start a process called bioremediation.
A windrow turner, thought to be the largest in Europe, will mix 50,000 cubic metres of contaminated soil − the equivalent of 25 Olympic-sized swimming pools − with shale and compost which will work with the bacteria naturally present in the soil to break down the contaminants.
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The machine lays out the mixture on-site in long rows called windrows, turning it regularly for up to eight weeks to break down the toxins.
All the treated soil will be reused in landscaping the site which will be turned into a park open to the public.
Councillor John Allsop, cabinet member for technology and recycling, said: "Grassmoor lagoons have been a blight on the local landscape for more than 15 years.
"We're pleased we've reached this key stage in the process to bring the site back into use and look forward to eventually being able to open it up as a safe country park area which the whole community can enjoy."
Derby-based Remedx is carrying out the clean-up and landscaping which is expected to be complete by summer 2016.
(CD/GK)
