Enrichment and application of sewer-derived aerobic methanotrophs to enhance gaseous methane removal in sewers.

Methane emission from sewer systems persists as a dual environmental threat, combining explosion risks with potent greenhouse gas impacts. Current methane removal strategies have primarily targeted biofilm and wastewater phases by chemical dosing; however, microbial adaptation and fluctuating water quality often reduce the control efficiency, incurring high chemical costs. Here we propose and demonstrate a novel microbial approach that utilizes aerobic methanotrophs for direct gaseous methane oxidation. Sewer-derived microbes was discovered to exhibit a high methane oxidation capacity of 0.30 μmol/(h·g). The sewer-derived methanotrophs were then successfully enriched, with a high methane oxidation rate of more than 200 mg CH4/(g DCW·d). Leveraging the enriched aerobic methanotrophs, an innovative in-situ gaseous methane control strategy was developed. Methane emission reduction reached 85.6 % in a sewer reactor under prolonged operation, and microbial activity could be restored following easy and flexible reactivation treatment. Notably, hydrogen sulfide could be eliminated in this reactor, attributed to biochar-mediated adsorption and subsequent chemolithotrophic oxidation, which demonstrates the multifunctionality of the hybrid system. High-throughput sequencing and metagenomic sequencing further revealed Methylocystis (15 %-20 % relative abundance) and Methylophilus (17 %-46 % relative abundance) as core functional species that exhibit significant potential for carbon emission reduction in sewer systems. These results can demonstrate an economical and environmentally friendly solution to both gaseous methane and hydrogen sulfide removal in sewers.