The invention disclosure is a method of bioremediation of wastewater, particularly groundwater, by utilizing coupled anaerobic and aerobic biological treatment, more specifically, methanogenic (strictly anaerobic) and methanotrophic (strictly aerobic) microbial populations, in combination with a supply of in-situ generated water-dissolved oxygen and hydrogen. Water electrolysis is used to produce water-dissolved oxygen and hydrogen. The immediate advantage of using H2 from the electrolysis is to provide electron donors to methanogens to reductively dechlorinate the chloroaliphatics, and to reduce the water carbonates and generate methane which is used as energy and carbon source for the methanotrophic bacteria. Oxygen is used as electron acceptor by the aerobic bacteria, including the methanotrophs. The addition of an organic carbon source can be minimized or even eliminated, so as to diminish the competition between methanotrophic bacteria and heterotrophic bacteria for oxygen.