An appraisal of the water related contaminants as they affect the environment around the Enugu coal mines of Enugu state, southeastern Nigeria

Abstract

Enugu metropolis is within the Anambra basin, which comprises mainly sedimentary rocks of sandstone, siltstone, mudstone and shales in the Lower Benue trough and as the capital of Enugu state in Nigeria and also as one of the major municipal and industrial centers in southeastern Nigeria experiences much groundwater contamination due to coal mining activity. The Area is richly endowed with sub-bituminous three-coal seams within the Mamu Formation. It also lacks prolific and potable groundwater due to the thinning-out of the Ajali sandstone aquifer through Udi town and Ninth-mile into Enugu metropolis. Generally, the specific discharge of Ajali sandstone (17.5 m2/day) is higher than that of Mamu Formation (14.5 m2/day). This appraisal becomes necessary to acquaint the Enugu city developers on the need for the prediction and understanding of the Environmental Impact Assessment (EIA) on the future development, management and maintenance of the mine water. The study also aims at identifying various contaminants, sources, level of concentrations, effects and control measures. Many springs, streams and seepages exist on the foot of most of the hills and ridges. The springs form the headwaters of the major streams and rivers like Ekulu, Iva and Nyaba at the base of the escarpment. Out of the streams and rivers in Enugu coal city, Ekulu River is the largest and thus very important for industrial and agricultural purposes. However, the coal mines discharge their effluents and waste waters directly into the Ekulu River with toxic heavy metals like As, Cd, Cr, Fe, Mn, Ni and Pb that contaminate the water and sediments. At the mines, most of the seepages, springs and streams rise directly from the perennial flood water from the mines. The water from the coal mines with special treatment for pH and iron contents can be employed in augmenting the present inadequate water supply that comes from the Ninth Mile borehole network and Ekulu River reservoir. The pH can be treated with hydrated lime, while iron (Fe2+) can be treated with aeration and filtration. Key words: Groundwater, coal mine, Ajali sandstone, sub-bituminous, coal, rivers, seepage.