A plant was designed, built and operated to remove Hg from waste water and sludge produced by a mercurycell chlor-alkali plant. Mercury content of the waste water ranged from 300 - 18,000 ppb mercury while mercury content of the brine sludge ranged from 150 to 1500 ppm Hg. Other sludges processed include sludges from the waterway near our plant outfall with a Hg content of 10 - 25 ppm Hg. From a variety of removal techniques tried in the lab, the methods selected were sulfide precipitation for the water treatment and high temperature roasting for the sludge treatment. The sulfide precipitation consists of collecting the various water streams, adjusting the pH from 5 - 8 with spent sulfuric acid, settling the large solid particles in a surge tank, adding sodium sulfide to a 1-3 ppm excess, adding diatomaceous earth at the rate of 0.07 gpl in an R.P. Adams pressure filter. The effluent Hg levels range from 10-125 ppb with an average of 50 ppb Hg for an 87-99% removal, averaging 96.8%. The sludge system contains a collection system, 3.7 m diameter thickener, 1.8 m diameter rotary vacuum filter, 1.37 m i.d. multiple hearth furnace, and 3 stainless steel condensers 21 sq m each. Processing rate for the sludge is 140-320 kg/hr, dry basis. Capital costs were $364,500 and operating costs were $32 per m ton of dry sludge treated.

Report prepared by Georgia-Pacific Corporation, Bellingham Division. Prepared for National Environmental Research Center, Office of Research and Development, U.S. Environmental Protection Agency under project 12040 HDU, program element 1BB037, ROAP/TASK no. 21 AZX/022. Includes bibliographical references (pages 76-80).