Engineering programmable floating wetlands: synthetic biology, sensing, and AI control for water quality

Floating treatment wetlands (FTWs) are increasingly used as nature-based water infrastructure, but their performance is often limited by oxygen transfer, hydrodynamic variability, and unstable microbiomes. This review synthesizes bioaugmentation evidence from FTWs and related wetlands for nutrients, metals, hydrocarbons, pharmaceuticals, antibiotics, microplastics, and emerging contaminants like per- and polyfluoroalkyl substances (PFAS), noting that destructive transformation is rarely demonstrated for some compounds. Separating contaminant removal from confirmed degradation, we review mechanisms, robustness, and scale. This review compares liquid consortia with carrier-immobilized or encapsulated inoculum and extract-based practical design criteria for plant-microbial partnerships, rhizosphere engineering, and biofilm development and persistence under shear, seasonality, and pulse loading. Targeted aeration, supportive media, and electrochemical augmentation, such as wetland microbial fuel cells and electrochemical oxidation (electro-oxidation) and coagulation-based processes (e.g., conventional chemical coagulation or electrocoagulation), can boost performance and stabilize new functions. Mechanistic sections map attenuation pathways to catalytic modules, including oxygenases, reductases, and hydrolases, as well as to biosorption and biomineralization, and identify dominant failure modes that hinder translation, including washout, community reversion, inhibitory intermediates, and uncertain long-term ecological effects. Building on this evidence base, we outline a testable translational roadmap toward more programmable FTWs, emphasizing near-term decision support rather than fully automated control, and specifying validation needs for multi-omics-guided strain selection, division-of-labor consortia, safety-by-design containment, and model-informed monitoring and operation under climate variability. Finally, we propose reporting and governance metrics, including effect sizes versus controls, persistence, ecological risk monitoring, and life-cycle trade-offs, to support responsible field deployment and water reuse.