<p>The application of engineered nanomaterials in wastewater treatment has improved pollutant removal efficiency but has also introduced concerns related to secondary solid waste generation, regeneration requirements, and environmental persistence. In response to these limitations, transient inorganic nanomaterials have emerged as a sustainable alternative for advanced water remediation. Magnesium based and calcium-based nanomaterials, including magnesium oxide, magnesium hydroxide, calcium oxide, and calcium carbonate, represent a distinctive class of treatment agents that undergo controlled dissolution into environmentally benign ionic species after contaminant removal. This self-dissolving behavior enables genuinely zero waste treatment systems while maintaining high reactivity and process efficiency. Their inherent alkalinity, pH-responsive solubility, and controlled ion release support diverse removal mechanisms such as adsorption of dyes and pharmaceutical residues, precipitation and immobilization of toxic metals, catalytic activation of oxidants, and enhanced coagulation and flocculation processes. Despite their environmental compatibility and practical advantages, the role of these materials as intentionally transient nanosystems remains insufficiently explored. This review provides a comprehensive assessment of their material characteristics, dissolution driven mechanisms, pollutant removal pathways, and environmental fate in aquatic systems. Applications in industrial effluents, acid mine drainage, textile wastewater, and decentralized treatment units are discussed along with safety considerations related to water chemistry, alkalinity, and ecotoxicological impacts. This review positions magnesium and calcium based transient nanomaterials as a promising platform for sustainable and zero-waste wastewater treatment.</p> Graphical abstract <p></p>