Climate change has fundamentally transformed water patterns, with rainfall becoming evermore unpredictable, prolonged droughts, and rising pressures on freshwater supplies. Water reclamation and wastewater reuse have shifted from a desirable option to a necessary measure. This chapter discusses how climate change impacts wastewater networks, such as fluctuations of flow and composition of the influent, reduced efficiency of treatment, and greater exposure of the network’s components to extremes such as weather and sea-level rise. Rising temperatures also intensify public health risks, accelerating the spread of waterborne diseases such as cholera, typhoid, and other enteric infections. Addressing these interconnected risks requires a One Health approach that recognizes the highly linked ways that human health, disease vectors among animals, and environmental pollution interact with one another. We review the science of climate-driven hydrological changes and their implications for wastewater treatment, public health risks, and opportunities, with emphasis on the effects of heat waves, storm events, and droughts. Innovative technologies, such as membrane bioreactors, microbial fuel cells, and predictive models based upon AI, are making possible responses to such challenges. Case studies highlight the policy and technological barriers with which many communities are still struggling, most of all at low-resource scales, where it is difficult to do so, even though needs are great. By integrating advanced treatment technologies with evidence-informed policy reforms, this chapter outlines pathways toward wastewater systems that remain resilient under climate stress. It concludes with overriding priorities for future research and policy, intended to foster equitable, efficient, and sustainable water reuse in a warming world.