The circular economy (CE) is a concept in which goods, materials (including raw materials), and waste are viewed as secondary raw materials that can be recycled for processing and re-use. This sets it apart from a linear economy based on the 'take-make-use-dispose' paradigm, in which waste is often the product's last step cycle of life.
What is circular economy?
CE is a concept that encourages sustainable material and energy management by minimising waste, the amount of waste produced and its potential for re-use as a secondary material.The main reasons for implementing a circular economy are limited raw material availability, the economy's reliance on raw material imports (high prices, market volatility, and uncertain political situations in certain countries), and the economy's decreasing competitiveness in global economies.
The reuse of treated wastewater from WWTPs for agriculture and land irrigation, industrial purposes, toilet flushing, and groundwater replenishment is a key component of the current strategy aimed at releasing freshwater for domestic use, improving the effluent quality of WWTPs, and, as a result, improving the quality of river waters used for drinking water abstraction.
For many years, it has been known that using treated wastewater for irrigation in agriculture can help to replace farm demand while also reducing local water stress. Furthermore, nutrients found in wastewater lessen the requirement for commercial fertiliser application. Secondary treatment effluent should be used to irrigate non-food crops, while tertiary treatment effluent should be used to irrigate food crops.
Planned (direct or indirect) or unplanned (potable) reuse of urban wastewater is most commonly associated with non-potable uses, however there are instances of unplanned potable reuse. Residential irrigation and business fire prevention, car washes, toilet flushing, and other uses of urban water reuse are the most common. The main issues with urban reuse are the dangers to human health and the expensive cost of multiple systems for delivering reclaimed water.
Indirect potable reuse involves discharging high-quality WWTP effluent directly into groundwater or surface water sources to supplement drinking water supply. Direct potable reuse (pipe to pipe) is another option, which involves introducing treated wastewater directly into a water distribution system. However, due to the high effluent quality requirements, direct potable reuse significantly increases operational costs. It's also vital to consider the absence of social acceptance.
What is the ultimate goal?
The goal of circular economy is to optimise circle system functions by reducing resources exiting the system. Moving toward greater circular economycan assist in meeting the resource efficiency goals set out in theStrategy for smart, inclusive, and sustainable growth.
For optimal sustainable development, smart cities concept is a pragmatic and balanced blend of social, economic, ecological, and other key fields. The purpose of ecological cities around the world is to "improve citizens' and society's well-being through integrated urban planning and management that fully utilises the benefits of ecological systems while protecting and nurturing these assets for future generations."