Control of mercury in effluents from chlorine plants.

Background information as to the environmental effect of discharges of mercury is provided. The information has justified a programme, outlined in the paper, for reducing mercury in products, waste waters and vented air from chlorine plants using the mercury process. The strict separation of the waste waters and certain technical measures creates possibilities of reducing the discharges effectively. An 80 per cent reduction of the mercury in effluents was achieved, for example, by substituting indirect forced cooling of the hydrogen for the traditional direct cooling and returning the condensate to the head of the amalgam decomposers. The major cause of discharge of mercury with vented air was found to be leaking hot hydrogen in the cell room. Different principles for the polishing of the final effluent and for the removal of mercury from the caustic soda produced are described.