<p>Carbon emissions from the water and wastewater treatment sector account for about 2% of global carbon emissions, calling for the integration of sustainable energies to decrease carbon footprints. Here we review the use of hydrovoltaic technologies in water and wastewater treatment, with emphasis on the hydrovoltaic effect, self-powered sensors, and pollutant removal. The hydrovoltaic effect can be obtained using moisture-induced hydrovoltaic generators and water evaporation-induced hydrovoltaic generators. Strain, pressure, humidity, gas, and liquid sensors can be powered by hydrovoltaic generators. Remarkably, the hydrovoltaic technology-driven liquid sensors can reach a detection limit of 1 femtomolar. The hydrovoltaic technology reduces pollution in two ways, first by generating electricity from environmental moisture and evaporation, thereby reducing fossil fuel dependency. Second, it takes advantage of the photocatalytic properties of materials to decompose organic matter during water treatment, thus minimizing the usage of chemical reagents. Applications comprise wastewater power generation, seawater desalination and organic matter degradation.</p>