What it is:
- Chemical symbol: CH4
- Methane is the simplest of the alkanes, a family of 100-plus compounds, each of which consists only of carbon and hydrogen atoms. Other common alkanes include propane (C3H8), butane (C4H10) and octane (C8H18).
- Colorless, odorless. Common form is a gas (boils at -161 degrees C, or -258 F).
- Dissolves in water, but does not ionize. Solubility in water at 10 degrees C (50 F) is 42 mg/L. As water temperature increases, CH4 solubility decreases.
- Less dense than air at room temperature.
- Methane is common in nature, resulting from anaerobic digestion of plant and animal matter. Also called "swamp gas," "biogas," or, in coal mines, "fire-damp" or "coal-gas."
- Naturally dissolved in some groundwaters, especially near petroleum deposits or coal seams.
- It is principal constituent (75 percent or more) of natural gas used for heating, etc. Odor is added to natural gas to make it detectable.
- Can be manufactured, and is used in some industrial processes.
- Non-toxic, but can produce suffocation by replacing oxygen in confined air space. Can be absorbed into the body by inhalation.
- Flammable and potentially explosive when mixed with air.
- Can cause "water hammer" in plumbing systems or "fizzing" of water drawn from taps.
- When dissolved in water, it can give water a milky look, or "swampy" odor and taste.
- The US Environmental Protection Agency (EPA) does not regulate the methane content of drinking water.
- Safety: To avoid fire or explosion, gaseous methane should be kept away from sparks, flames or spark-producing tools, and should be vented out of buildings. Follow all applicable OSHA, fire-safety and other rules.
Aeration in an atmospheric tank is effective. Methane is not filterable or removable chemically.Recommendations for aeration:
- Prefilter to avoid particle or precipitate blockage of spray nozzles.
- Disinfection (typically chlorination) of aeration-system feedwater is recommended to avoid biofouling/contamination, especially in warmer climates.
- Aeration-released methane must be ventilated from tank to the outdoors with spark-free air blower fan, preferably operating 24/7.
Discussion and more information.
Wells that contain methane are often located in areas where gas and oil wells are common.
Atmospheric aeration is essentially the only treatment for methane in well water. Atmospheric aeration involves allowing the methane gas to escape to the atmosphere. Pressurized aeration tanks, though vented, will not work well for methane. Exposing the water in an atmospheric tank means that water pressure will be lost and a repressurization system consisting of a pump and usually a pressurized pump tank will be needed.