Methane emission and methanotrophic activity in groundwater fed drinking water treatment plants

Abstract: Groundwater for drinking water production may contain elevated concentrations of methane that is vented to the atmosphere during aeration at drinking water treatment plants (DWTPs). This study summarizes emission of methane from 1004 DWTPs in Denmark including data from 3068 groundwater wells. Fate of methane and occurrence of methane oxidizing bacteria in DWTPs was examined including a potential role in ammonia removal. Methane emission from Danish DWTPs corresponded to 0.05-0.11 % of the national anthropogenic emission of this important greenhouse gas. Traces of methane remained in water after primary aeration and entered sand filters as a microbial substrate. Methanotrophic bacteria and active methane oxidation was always detected in sandfilters at groundwater-fed DWTPs. Methanotrophic consortia in sandfilters facilitated removal of inorganic constituents such as ammonia via assimilation and co-oxidation activity.