Seasonal Variation of Iron Removal in Coal Mine Water Discharge Lagoons and Constructed Wetlands

Abstract Passive Mine Water Treatment Schemes (MWTS) have been developed to remove iron from coal mine drainage before discharge into the environment to prevent potential ecological environmental problems caused by coal mine drainage. The performance of these MWTS vary across distinct climatic conditions, based on variations in temperature and rainfall patterns. Therefore, this study analysed monthly iron concentrations of 10 settlement lagoons and 5 constructed wetlands (CWs) in 5 full-scale MWTS to assess the influence of varying seasons on the MWTS lagoons and CWs treatment performance using removal efficiency (R.E.). The comparative performance of monthly records of Ferric Iron (Fe 3+ ), Ferrous Iron (Fe 2+ ) and pH over a period of 12 years were conducted using comprehensive statistical analysis of Fe 3+ R.E. Fe 3+ R.E. obtained for the 5 MWTS ranged from 50.97 to 98.98% and is in the order Site A > Site C > Site B > Site E > Site D. pH increased from slightly acidic to neutral while Fe 3+ and Fe 2+ concentrations decreased. The MWTS achieved an average Fe 2+ R.E. of 46.66–98.16%. Seasonal variation affected iron removal from the schemes, i.e., Fe 3+ R.E. in the lagoons and wetlands was in the order summer > spring > autumn > winter. Due to increased rates of sedimentation, filtration and absorption in warmer seasons, treatment performance of the schemes was better compared to colder seasons. The experimental results obtained provide a scientific basis for MWTS operators, research scientists, policy makers to improve R.E. and ensure consistent treatment performance in different seasons throughout the year.