TECHNOLOGY
treatment process . Like arsenic , selenium is present in two oxidation states , selenite ( Se4 +) or selenate ( Se6 +). Two methods are commonly used for its removal , either chemical reduction of selenate to selenite followed by co-precipitation with iron , or biological reduction to precipitate it as insoluble selenium . The biological process has found favour particularly where the raw mine water concentrations are relatively low . Other options include ionic exchange and reverse osmosis . Again , the challenge is to develop selenium removal systems that minimise cost and maximise sustainability .
Treatment standards for sulphate vary both nationally and on the level of dilution possible in the receiving watercourse . Typical values , particularly in more arid regions , are less than 200mg / l , making treatment challenging for more heavily contaminated mine waters . The addition of lime to neutralise acidity and precipitate dissolved metals also helps reduce the sulphate concentration by the formation of gypsum . However , depending on the method of metal removal used
Siltbuster Process Solutions water treatment system at the world ’ s 4th largest tungsten site
22 December 2017