Characteristics of Water Quality in Abandoned Coal Mines

Abstract

Coal is a combustible dark hard rock utilized as fossil fuel and mostly comprised of 65-95% carbon with hydrogen, Sulphur, oxygen and nitrogen. India is the third largest coal producing country in a world after china and USA with total production of 526 metric tons as per Coal India Limited 2016. Report of the ministry of coal released in March 2015, states that India as a total of 246 abandoned coal mines. The extraction of coal is normally done by means of opencast as well as underground mining. In India maximum coal production is through opencast mining process. Abandoned mines are those mines with not in operation status or closed one after coal extraction. Abandoned mine due to coal mining normally fills with surface runoff, as well as water nearby sources depending on the geology of the area. The water quality of abandoned coal mine contaminated with sulphur which gives rise to formation of acid and responsible for acid mine drainage (AMD). The presence of AMD gives rise to heavy metals dissolution. During heavy rainfall, these contaminated mine water of abandoned coal mines may overflow and pollute nearby streams and ground water. In the present research, the water quality of some of the abandoned opencast coal mines was investigated and the parameters were compared with prescribed Indian drinking water quality standard and effluent standards. Four mines were selected for the study, three from WCL (Rawanwada Khas Opencast, Kukurmunda OCP and Haran Bhatta OCP) in Chindawara district in the State of Madhya Pradesh and one from MCL (Basundhara East abandoned coal mine) in Sundergarh district of Odisha, India. Total 10 water samples were collected from different abandoned coal mines and were analyzed for pH, Conductivity, Turbidity, Dissolved Oxygen(DO), Biological Oxygen Demand(BOD), Total Dissolved Solids(TDS), Total Suspended Solids(TSS), Total Hardness, Total Alkalinity, Chloride, Nitrate, Magnesium, Calcium, as per APHA(1998), using multi-parameter water test kit. The trace elements like Cadmium (Cd), Copper (Cu), Chromium(Cr), Zinc(Zn), Lead (Pb), Nickel(Ni) etc. were analyzed using ICP-MS, Ion Chromatography. From the experimental investigations and results, the following conclusions can be derived at: Water samples from all the abandoned mines were in general acidic in nature so not suitable for drinking purpose as per Indian drinking water quality standard and need to be treated before discharge/use. Water quality parameters such as electrical conductivity, BOD, DO, TDS and hardness were within the standard limit in respect of both drinking water and effluent standards. Chloride and nitrate levels were also within the standard limit for all the samples. In some of the water samples (R1, R2, K, BS1) the TSS values were above permissible limits. The water from Kukurmunda (K-259.15 mg/L) and Basundhara (BS1-47.4 mg/L, BS2-71.1 mg/L, BS3- 47.4 mg/L) were having Mg value more than the permissible limit (30 mg/L), whereas samples from all other locations are within the limit. The heavy metals viz., Ni, Cu, Zn, Cr and Pb concentrations were within the Indian standard for drinking water at all the locations. Water of all the locations were having some traces of Cd in samples of which may be harmful to the environment or the eco-system of nearby area. Cd was not detected for Basundhara mine water. Based on the water quality index (WA-WQI), the water quality of samples drawn from R1 & R2 and BS3 were of C-type (poor water quality), whereas water quality of R3, K and BS2 were of D-type (very poor). Samples from two locations of HB1 and BS1 were of B type (good water quality). Water quality at HB2 was of excellent grade (A-type). The HB3 had the highest WQI value of 314.39 and is horribly contaminated and is most unsuitable for drinking purpose coming under grade E. One location from Basundhara East OCP (BS1) showed good quality of water (B-type) whereas at other two locations the samples were poor-very poor in grade. From the above study, it can be suggested that water from the abandoned mines can be used only after proper treatment for objectionable parameters at different locations.