Ensuring access to clean water remains a global challenge, while conventional contaminant detection and treatment demand high energy. Here, multifunctional metallic nanotube arrays (MeNTAs) engineered with tunable compositions and wettability are reported, enabling self-powered sensing and thermocatalytic remediation. Ni-W-Ni MeNTAs, generating the highest triboelectric voltage, are integrated into droplet-mode liquid-solid triboelectric nanosensors (DLS-TENSs) for detecting Cr6+, Pb2+, and Hg2+, achieving rapid responses within 20 ms. For biological sensing and remediation, superhydrophilic W-SS MeNTAs are employed. Functionalization with Au nanoparticle-aptamers allowed highly sensitive E. coli detection, while Bi2Te3 coatings facilitated thermocatalytic H2O2 generation, leading to efficient bacterial inactivation (97%) and Cr6+ (95%) reduction. To demonstrate practical utility, a wireless sensing bottle is developed for real-time detection of heavy metals and bacteria in wastewater. Integration of sensing and treatment modules enables simultaneous on-site monitoring and purification. This work introduces a cost-effective, portable, and self-powered platform for advanced water treatment, highlighting the versatility and real-world potential of MeNTAs.