Turning Wastewater into Resourcewater
In the circular water economy, wastewater treatment plants are resourcewater plants that recover valuable resources, with multiple environmental and economic benefits. Read how Scottish Water is recovering grit from wastewater for the construction industry.
In the traditional linear economy, the sole role of wastewater treatment plants is to protect downstream users from health risks. In contrast, the circular water economy views wastewater treatment plants as a source of resources that can be recovered, including organic matter, phosphorous, nitrogen, heavy metals, thermal energy, cellulose, and recycled water. In addition to the environmental benefits of recovering resources from wastewater, adopting circular water economy principles can transform the treatment of wastewater from a costly service to one that is self-sustaining with financial returns able to provide a revenue stream to cover operational and maintenance costs as well as fund future plant upgrades.
Wastewater typically contains grit that can interfere with treatment processes or cause mechanical wear and increased maintenance on wastewater treatment equipment. Grit includes sand, gravel, cinder, or other heavy solid materials that are heavier than the organic biodegradable solids in the wastewater. Grit can also include eggshells, bone chips, seeds, coffee grounds, and large organic particles, such as food waste. Typically, collected grit is removed, dewatered, washed, and conveyed to a disposal site.
Scottish Water recovering grit from wastewater
Scottish Water has partnered with Zero Waste Scotland to turn grit into valuable raw building material for the construction industry. A trial project recently completed has shown that grit — generally disposed of in a landfill — can potentially be recovered and converted for use in products such as kerbstones. In addition to transforming waste into a resource, the process reduces the need to dig up virgin materials through energy-intensive quarrying, reducing carbon emissions by more than 70%. As part of the project, Zero Waste Scotland’s Circular Economy Business Support Service supported three Scottish SMEs from the aggregates production and recycling sector to determine the commercial viability of recycled grit. The next steps will involve physical trials with the recovered grit being put through a series of physical and chemical tests to determine whether it meets strict end of waste criteria, specifically if it ceases to be waste and obtains a status of a product (or secondary raw material).
The take-out
The circular water economy views all types of waste as a resource.
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