New application of a traditional analytical method--arsenic removal from water works sludge during iron(III) chloride coagulant production.
The Marsh Test, the original means of determination of arsenic by hydride generation, has been modified to remove arsenic from water works sludge, with iron used instead of zinc as the main agent. Water works sludge (main compound iron(III) oxyhydrate) generated during groundwater treatment can be enriched in arsenic up to several gkg(-1). Acidic dissolution of this sludge to produce FeCl3 coagulant liberates the arsenic. Addition of elemental iron reduces this dissolved As(V) mainly to dispersed elemental As(0) particles, which can be removed by filtration. If the reaction temperature is kept below 50 degrees C, more than 99% of the arsenic can be removed from the coagulant solution and less than 10% will escape as gaseous arsine (AsH3). Severe foaming and silicic acid gel formation occurs during the acidic dissolution, however. For technical and economic reasons the use of the water works sludge for FeCl3 coagulant production is not competitive when compared with other recycling methods.
Maier
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Stadtwerke Karlsruhe GmbH, Germany.
Maier
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Oberacker
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F
D001151:Arsenic / Q000737:chemistry*; D002712:Chlorides; D005290:Ferric Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000379:methods*
D002712:Chlorides; D005290:Ferric Compounds; D012722:Sewage; D014874:Water Pollutants, Chemical; D001151:Arsenic; C024555:ferric chloride