This chapter examines the evolution of smart nanomaterials and integrated systems engineered for real-time environmental monitoring and water treatment. It highlights advanced materials capable of sensing, detecting, and removing pollutants within unified platforms that enable autonomous and continuous purification. Emphasis is placed on responsive photocatalytic and adsorptive nanomaterials, hybrid systems that couple pollutant detection with remediation, and multifunctional materials suited for complex water matrices. A comprehensive overview of advanced sensing technologies—including resistive, capacitive, electrochemical, optical, piezoelectric, acoustic, field-effect transistor (FET)-based, and nanoparticle-enabled sensors—is provided, focusing on their mechanisms, sensitivity, and applicability in field settings. This chapter also explores real-time data processing, feedback-controlled systems, and their integration into municipal and industrial infrastructures. Key practical considerations such as reusability, operational stability, light-harvesting efficiency, and pollutant selectivity are analyzed. Also, this chapter discusses integrated adsorption–photocatalytic processes, major performance bottlenecks, and overarching environmental challenges, offering guidance for designing scalable, durable, and adaptable smart treatment technologies.