Environmental technologies aim to reduce negative environmental impacts and promote resource use efficiency, including green energy sources like solar, wind, geothermal, and water energy. These technologies are increasingly applied also in urban wastewater treatment processes to address challenges in pollutant removal, resource recovery, and energy efficiency. Reducing energy costs using green energy (e.g. solar panels) is starting to resonate also in urban wastewater treatment processes and technologies. However, diverse pollutants in wastewater require advanced treatment technologies that integrate biological, physical, and chemical processes. With the ongoing amendment of EU legislation on urban wastewater treatment, stricter requirements for pollutant removal are expected, driving the need for innovative environmental technologies. However, implementing these technologies may raise energy costs, necessitating the development of sustainable solutions. This special issue will provide a platform for researchers, practitioners, and policymakers to share their latest findings, experiences, and perspectives on technologies for urban wastewater treatment. It is expected to contribute to the knowledge and innovation in this field and promote sustainable solutions for wastewater treatment that align with the principles of resource use efficiency, green and renewable energy production, and environmental protection.