ABSTRACT

Charlie and Frederik were unloading rail tank cars filled with inorganic waste from a metal plating factory. The acid waste from pickling (cleaning) steel would be neutralised with slaked lime in a large lined concrete tank. The cyanide waste would be detoxified with sodium hypochlorite (similar to household bleach but more concentrated). Charlie was in the control room. Having received two tanker loads of acid, he observed that the correct amount of fluid had been transferred and that the pump had stopped. He contacted Frederik, who was in the rail yard, by mobile radio: ‘Send up another bucket full’. (This sounds more fluent in the original language.)

Frederik disconnected the unloading hose, connected it to the next tank car and started the pump. About 6 cubic metres of cyanide waste had been pumped to the acid tank, before the release of hydrogen cyanide gas was registered and the pumping shut down. (The gas detectors were mounted on and around the cyanide tank, as required by the design, and not on the acid tank, where there was ‘no apparent need’.) No one was hurt, but the company was embarrassed, this incident being one in a fairly long series.