Eutrophication driven by excessive phosphorus discharge threatens global aquatic ecosystems. Enhanced biological phosphorus removal (EBPR) is a sustainable, widely deployed wastewater treatment technology, yet it often requires optimization to meet increasingly stringent global phosphorus emission standards. Conventional chemical supplements can achieve deep phosphorus removal, but they require excessive dosing, generate large volumes of sludge, and can inhibit the essential polyphosphate-accumulating organisms (PAOs) that drive biological treatment. Here we show that a low-dose, slow-release lanthanum aerogel (LZGA) activates PAO metabolism, enabling deep biological phosphorus removal with a near-zero chemical footprint. By releasing La³⁺ into sequencing batch reactors, the LZGA platform reduced effluent total phosphorus from 0.85 mg L⁻¹ to 0.14 mg L⁻¹ at an optimal dose of 15 mg L⁻¹. This represents a two-order-of-magnitude reduction in chemical consumption compared to conventional precipitation methods, requiring 0.7 g of lanthanum to treat one ton of wastewater. Proteomic and microbial analyses reveal that trace La³⁺ stimulates potassium channels, upregulating key energy metabolism pathways and driving an order-of-magnitude increase in the protein expression of the core PAO Candidatus Accumulibacter. Furthermore, the system enhances extracellular polymeric substance (EPS) production, and improves the phosphorus absorption capacity of EPS. These findings demonstrate that targeted trace-metal activation of microbial metabolic pathways offers a strategy to upgrade existing bioreactors. This strategy provides a versatile paradigm for global wastewater management and advanced eutrophication control.