Contamination and Pollution

Bioremediation is the process by which microbes (generally bacteria) or plants transform a harmful water contaminant into a non-harmful substance, much as we turn sugar into carbon dioxide
Methane is a gas composed of carbon and hydrogen. It has the chemical formula CH4. Methane originates from several different sources. 
The U.S. Geological Survey is responsible for providing the reliable and impartial scientific information on geologic and hydrologic processes affecting mineral deposits, mine lands, and water quality.
Methane gas – whether microbial or thermogenic -- can migrate into water wells along with the groundwater if underground conditions are favorable for it.
The concerns about high concentrations of methane in water wells focus on the potential of this colorless and odorless gas to accumulate in confined spaces and act as an asphyxiant or become flammable or explosive in confined spaces containing oxygen a
USGS has several ongoing efforts to monitor methane in groundwater, we have completed several others, and we are doing basic research into detecting methane in streams as a tool to map methane leaking from underground.
Mine drainage is formed when pyrite, an iron sulfide, is exposed and reacts with air and water to form sulfuric acid and dissolved iron.
Problems that can be associated with mine drainage include contaminated drinking water, disrupted growth and reproduction of aquatic plants and animals and the corroding effects of the acid on parts of infrastructures such as bridges. 
Our USGS Mine Drainage Activities website has a lot of good information on this topic, including links to USGS programs, activities, and featured articles.