| Affiliation: | (1) CSIR, Water, Environment, and Forestry Technology, PO Box 395, Pretoria, 0001, South Africa;(2) BCL, PO Box 3, Selebi Phikwe, Republic of Botswana;(3) Thuthuka Project Managers, Midrand, PO Box 6013, Halfway House, 1685, South Africa;(4) Golder Assoc Africa, PO Box 6001, Halfway House, 1685, South Africa;(5) School of Chemical and Minerals Engineering, North West Univ, Potchefstroom, 2531, South Africa |
| Abstract: | Abstract. Design criteria were developed for the construction of a full-scale limestone neutralization plant to treat leachate from the waste rock of a nickel mine, using data from laboratory studies, pilot-scale studies, and operation of a full-scale limestone handling and dosing facility. We learned that: limestone powder can be slurried to a constant slurry density of 60 g/L; Fe (II) can be oxidised at low pH (2.5) at a rate of 16.1 g/(L/d) using geotextile as a medium; and that the integrated Fe (II)-oxidation and limestone neutralization process allows neutralization, Fe (II)-oxidation, and gypsum crystallization to take place at the same time, provided that the solids concentration is high (greater than 30 g/L). A full-scale plant with a capacity of 50 m3/h was designed and constructed. The plant consists of the following stages: biological Fe (II)-oxidation, a fluidised-bed limestone neutralization reactor, a complete-mix gypsum crystallization reactor, and a clarifier. |
