Turn Waste into Wealth: The Reuse of Recycled Water Shapes a New Urban Ecosystem

Water is the source of life and a fundamental condition for human survival. The application of recycled water has become an effective approach to addressing water resource scarcity.

Recycled water refers to water resources that are collected from rainwater, industrial wastewater, and domestic sewage, then treated appropriately to meet specified requirement standards for reuse. The whole process is akin to nirvana and rebirth of sewage. For example, domestic sewage such as flushing water, bathing water, and vegetable-washing water can undergo secondary treatment at sewage treatment plants and then be reused for groundwater recharge, non-potable applications in various industries, and landscape irrigation. 

Typically, sewage undergoes three treatment stages to become clear and reusable water.

1. Primary Treatment: The sewage passes through processes such as screening, aerated grit chambers, and primary sedimentation tanks, removing about 20% of pollutants.

2. Secondary Treatment: The sewage is directed into biological tanks, where bacteria and microorganisms break down pollutants into harmless substances like water and carbon dioxide, followed by sludge-water separation.

3. Tertiary Treatment (Advanced Treatment): This stage includes processes like bio-filtration, de-colorization, and disinfection. Pollutants are further removed, while chlorine, ultraviolet light, or ozone is applied to eliminate persistent harmful bacteria and pathogens, ensuring the safety of the treated sewage.

After a series of treatments, the wastewater is officially transformed into recycled water: one portion can be used for road cleaning, toilet flushing, industrial cooling, landscaping, and farmland irrigation, while another portion flows into urban water systems.

Recycled water facilitates green development in ecological environments. For instance, with the surge of visitors to Mount Tai, sewage from catering and accommodation services has increased dramatically, leaving the scenic area grappling with dual challenges of “difficult wastewater treatment and insufficient water supply.” To address this issue, Mount Tai Scenic Area has adopted decentralized treatment systems and recycled water reuse initiatives, actively preserving the mountain’s ecological environment.   

Moreover, recycled water plays a positive role in urban development. In Beijing, recycled water has become a “second water source”, extensively utilized in scenic areas and urban construction. A prime example is Zhongshan Township in Tonglu County, Zhejiang Province. Recycled water is not only beneficial to the local environment but also facilitates a remarkable transformation, turning “pale waters and ashen mountains” into thriving “lucid waters and lush mountains.”

The reuse of recycled water will be of value to economic, social, and environmental benefits. It not only conserves substantial amounts of clean water resources and alleviates urban water scarcity, but also helps reduce pollutant discharge while enabling sustainable utilization of wastewater resources. In addition, the cost of reusing recycled water is relatively low, which is much lower than long-distance water diversion. For these reasons, the reuse of recycled water contributes to reducing carbon emissions in China and advances the realization of a circular economy.