Pre-mining water quality prediction from non-weathered sulphide ores along the Ashanti metallogenic belt in Ghana using Acid-Base accounting procedure

Abstract

The prediction of pre-mining water quality from non-weathered sulphide ores using the Acid-Base accounting (ABA) procedure was studied at the Anglogold-Ashanti, Obuasi mine and located on the Ashanti metallogenic belt in Ghana. The purpose of the study was to establish database for use during preliminary mining project evaluation, mining project permitting, and tailings waste management planning and implementation. Total Sulphur (TS) was determined by hightemperature furnace combustion using the LECO sulphur analyzer, while carbonate was determined by gravimetric method. Average TS % and Neutralization Potential (NP) due to calcium carbonate were 1.46% and 4.34 kg CaCO3/ton respectively. The average TS% multiplied by the constant 31.25 yielded Maximum Potential Acidity (MPA) value of 45.63 kg CaCO3/ton. Also, Net Neutralization Potential (NNP), defined by NNP=NP-MPA, yielded the value -41.29 kg CaCO3/ton and NP: MPA ratio of 0.095. Multiple regression statistics on NP and MPA gave Rsquare value as 0.0005 and indicated a poor predictive neutralization model. From the NNP and NP: MPA values, it was concluded that the non-weathered sulphide ores at the AnglogoldAshanti, Obuasi mine are likely to generate high acidic waters. Adequate alkaline amendment is therefore required during ore treatment.