Is it possible to transform highly toxic hexavalent chromium into trivalent chromium, which is harmless? It would appear so. The removal of hexavalent chromium is possible thanks to whey and ferrous sulphate which seem to work well.
In Brescia, a city included in the Caffaro site of national interest in which thousands of tonnes of PCBs (polychlorinated biphenyls) have been produced, an experiment run by geologist Claudio Leoncini from Verona to try to restore the polluted water-bearing stratum with whey was started up in 2014. The first encouraging results are starting to appear although it is too early to say how much longer chromium removal operations will have to continue.
Let’s go into more detail. Whey deriving from cow’s milk is used as a reagent to oxidise the hexavalent chromium in the first water-bearing stratum and transform it into harmless trivalent chromium (activities have been agreed upon with the supervisory authorities from the municipality of Arpa). Approved by the Italian Ministry of the Environment, the project involves the use of whey powder, whilst maintaining the function of the existing hydraulic barrier, in order to have even greater guarantees that contamination within the site is under control.
The results obtained over the last five years speak clearly. In 2008 the land had a concentration of hexavalent chromium equal to 200,000 microgrammes per kilo (40,000 times higher than the legal limit); after three years it dropped to 20,000 microgrammes per kilo and is currently decreasing further, towards 2,000 microgrammes per kilo. In certain areas the chromium has entirely disappeared, whereas in other areas a considerable number of interventions are required. The cost of the operation is more than one million euros and has been paid by Baratti Inselvini in line with the ‘polluter pays’ principle, which in truth is rarely respected in Italy.
When the first biological reagents deriving from whey were injected into the land, the level of chromium initially increased. However, this was due to an uncontrolled oxidated reaction which then subsided.