As the world human population and industrialization keep growing, the water availability issue has forced scientists, engineers, and legislators of water supply industries to better manage water resources. Pollutant removals from wastewaters are crucial to ensure qualities of available water resources (including natural water bodies or reclaimed waters). Diverse techniques have been developed to deal with water quality concerns. Carbon based nanomaterials, especially carbon nanotubes (CNTs) with their high specific surface area and associated adsorption sites, have drawn a special focus in environmental applications, especially water and wastewater treatment. This critical review summarizes recent developments and adsorption behaviors of CNTs used to remove organics or heavy metal ions from contaminated waters via adsorption and inactivation of biological species associated with CNTs. Foci include CNTs synthesis, purification, and surface modifications or functionalization, followed by their characterization methods and the effect of water chemistry on adsorption capacities and removal mechanisms. Functionalized CNTs have been proven to be promising nanomaterials for the decontamination of waters due to their high adsorption capacity. However, most of the functional CNT applications are limited to lab-scale experiments only. Feasibility of their large-scale/industrial applications with cost-effective ways of synthesis and assessments of their toxicity with better simulating adsorption mechanisms still need to be studied.

Enteric viruses in wastewater remain a persistent public health threat. Conventional treatments often achieve only modest viral log₁₀ reductions and can generate toxic disinfection byproducts, but high-energy advanced processes are often unaffordable. Antiviral phytoremediation, which involves virus removal mediated by plants and their rhizosphere microbiota, offers a low-cost, low-energy alternative; however, it has scarcely been studied. A bibliometric analysis of ~23,000 wastewater treatment studies (1976–2025) identified only 30 virus-targeted records within plant-based treatment branches, representing ~0.13% of the total corpus. This critical review structures antiviral phytoremediation into a four-barrier framework: (i) sorption/filtration, (ii) rhizosphere-mediated inactivation, (iii) plant internalization, and (iv) intracellular degradation. Pilot and full-scale studies provide strong support for the first two barriers, whereas evidence for internalization and intracellular degradation is limited, mainly laboratory-based, and often inferred from molecular rather than infectivity assays. Standalone constructed wetlands typically achieve ~1–3 log₁₀ virus reductions, but hybrid configurations that combine wetlands with complementary processes achieve ~3–7 log₁₀ reductions, with performance varying between enveloped and non-enveloped viruses and across climates. This review distills design principles for cost-effective hybrid systems and identifies methodological and governance priorities, positioning rigorously designed phytoremediation as a scalable part of climate- and pandemic-resilient wastewater infrastructure.