COMPARATIVE STUDY OF SURFACE AND SUBSURFACE FLOW CONSTRUCTED WETLANDS FOR TREATMENT OF GOLD MINE WASTE ROCKS LEACHATE WATER
Alexander Marwa
Alexander Marwa: School of Engineering and Environmental Studies, Ardhi University, P. O. Box 35176, Dar-es-Salaam, Tanzania.
ABSTRACT
The mining industry poses significant environmental challenges, particularly in relation to the generation of mine waste rocks and leachate water. These waters contain low pH and elevated metals, making them difficult to manage. Constructed wetlands (CW) have emerged as a promising technology for the treatment of industrial wastewater due to their cost-effectiveness, low energy consumption, and minimal maintenance requirements. This study aimed to investigate the use of surface flow (SFCW) and subsurface flow (SSFCW) for potentially treating mine waste rock leachate water from gold mines. Both types of CW were planted with Pennisetum purpureum, and the results showed that the SSFCW had better performance in terms of metal removal, reduced the levels of metals such as Fe, Zn, and Cu from 48 mg/L to 8.16 mg/L (Fe), 9 mg/L to 2.52 mg/L (Zn), and 3.5 mg/L to 0.99 mg/L (Cu), respectively. This translates to a removal efficiency of 83%, 72%, and 71.7%, respectively. On the other hand, the SFCW achieved a removal efficiency of only 31%, 36%, and 22%, respectively. These results clearly show that the use of SSFCW planted with P. purpureum is a promising technology for treating gold mine waste rock leachate water during and after mine closure.
Keywords: Constructed wetland, mine leachate water, metals, surface and subsurface flow constructed wetland, mining