Using gypsum for the treatment of mine water

• Main Author: Green, Collen
• Format: Others
• Language: en
• Published: 2003
• Online Access: http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001042

Thesis (MTech. degree in Metallurgy)--Tshwane University of Technology. === Premier Mine’s current slimes dam is nearing the end of its operational life. This is aggravated by a large volume of poor quality water in the dam that is not being recycled back into the process. The poor quality of water is the result of a stable colloidal suspension formed from the dominant clay species present in the kimberlitic ore body. Phosphogypsum has been identified as an alternative coagulant to clarify the slimes dam water at a relatively low cost. Laboratory and plant scale test work showed that gypsum has the ability to successfully destabilise the colloidal suspension. However, poor settling rates were achieved. This improved when the gypsum was added in a slurry form in two stages. The addition of flocculants to aid in settling did not have the desired effect, with resultant high consumptions and operating costs. Diamond recovery efficiencies deteriorated when a clarified gypsum solution were used as wash water on the grease belts. However, the coatings formed on the diamond surfaces could be easily removed by a proper scrubbing cycle using clean potable water. An Ecological and Hygiene Impact Assessment indicated that low levels of radiation exist, but that the radiation levels are below the standards set by the NNR. Toxicity tests indicated no lethality to Daphnia organisms and showed a positive growth in the Algae test. The establishment of a monitoring programme will assist in determining the long-term effects of gypsum on the environment.