Municipal　wastewater　treatment　that　mainly　performed　by　conventional　activated　sludge　(CAS)　process　faces　the　challenge　of　intensive　aeration-associated　energy　consumption　for　oxidation　of　organics　and　ammonium,　contributing　to　significant　directly/indirectly　greenhouse　gas　(GHG)　emissions　from　energy　use,　which　hinders　the　achievement　of　carbon　neutral,　the　top　priority　mission　in　the　coming　decades　to　cope　with　the　global　climate　change.　Therefore,　this　article　aimed　to　offer　a　comprehensive　analysis　of　recently　developed　biological　treatment　processes　with　the　focus　on　reducing　discharge　and　CO2　footprint.　The　biotechnologies　including　＂Zero　Carbon＂,　＂Low　Carbon＂,　＂Carbon　Capture　and　Utilization＂　are　discussed,　it　suggested　that,　by　integrating　these　processes　with　energy-saving　and　carbon　recovery,　the　challenges　faced　in　current　wastewater　treatment　plants　can　be　overcome,　and　a　carbon-neutral　even　be　possible.　Future　research　should　investigate　the　integration　of　these　methods　and　improve　anammox　contribution　as　well　as　minimize　organics　lost　under　different　scales.