Circular Water Economy
In our current economic model, manufactured capital, human capital, and natural capital all contribute to human welfare by supporting the production of goods and services in the economic process, where natural capital — the world’s stock of natural resources (provided by nature before their extraction or processing by humans) — is typically used for material and energy inputs into production and acts as a ‘sink’ for waste from the economic process.
This economic model can be best described as ‘linear’ which typically involves economic actors harvesting and extracting natural resources, using them to manufacture a product, and selling a product to other economic actors, who then discard it when it no longer serves its purpose.
The circular economy, in contrast to the linear ‘take-make-consume-dispose’ economy, aims to decouple economic growth from resource use and associated environmental impacts. The notion of decoupling is that economic output shall continue to increase at the same time as rates of increasing resource use and environmental impact are slowed, and in time brought into decline.
Circular water economy
In the context of water resources management, the circular economy aims to:
- Reduce water consumption through water conservation and water use efficiency and management
- Reuse water for another purpose without treatment
- Recycle water for various potable and non-potable uses
- Recover materials from wastewater, including generating renewable energy and recovering materials
- Regenerate natural capital by reducing consumptive and non-consumptive uses of water
Sludge to fertiliser
At Ryaverket Wastewater Treatment Plant in Gothenburg, Sweden, sludge goes into the biogas plant where it lies in a 37-degree oxygen-free environment for around three weeks and is digested. After digestion, the sludge is centrifuged to remove additional water. Afterwards, the sludge contains around 70% water and looks like moist soil, part of which is composted and used as plant soil. More than a third of the sludge is sanitised and used as a fertiliser. The sludge is certified according to REVAQ, which is operated by the Swedish Water and Wastewater Association, the Federation of Swedish Farmers, the Swedish Food Federation, and the Swedish food retailer’s federation, in close cooperation with the Swedish Environmental Protection Agency. The goals of REVAQ are to avoid the unacceptable accumulation of metals or undesired organic sub-stances on agricultural land in the long term, have no accumulation of cadmium taking place from 2025, and reduce the accumulation of non-essential substances to a maximum of 0.2% from 2025.
The take-out
The circular water economy maximises water while turning waste into resources.
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