Determination of radionuclides in discharged water from gold processing plant

Abstract

The levels of radionuclides concentrations in discharged water from gold processing into the environment of Bogoso (Ghana) were determined using radioanalytical techniques. Radioactivity screening was first carried out to identify physical and chemical processing stages that might be concentrating the radionuclides. Water samples collected from each processing stage were screened for gross alpha-beta using Quantulus 1220 Wallac Liquid Scintillation Counter. The physical processing steps relatively concentrated alpha emitting radionuclides compared to that of beta. In the chemical processing stages of the oxide and sulphide ores treatment plants, alpha and beta emitting radionuclides were most concentrated in the first carbon-in-leach tank. Long-lived radionuclides from the Uranium-, Thorium- and Actinium-decay chains in the discharged water into the environment were radiochemically separated and the activity concentrations determined for ²³⁸U-series ranged from 3.8 ± 1.5 to 178 ± 19 mBqL^-1, ²³²Th-series ranged from < 2.0 to 47.8 ± 7.3 mBqL^-1 and ²³⁵U-series ranged from 0.4 ± 0.1 to 11.4 ± 4.5 mBqL^-1. The concentrations were lower than global derived released limits for diffuse naturally occurring radionuclide materials which ranged from 1 to 10 BqL^-1 for the three decay chains. Thus the discharged water was not expected to pose any radiological threat to the environment.