Scottish Water has partnered with Zero Waste Scotland to turn grit that is found in the wastewater system into a valuable raw building material for the construction industry.
A trial project has successfully shown that the grit, which would otherwise be sent at a cost to landfill, can potentially be recovered and converted into aggregate for use in products such as kerbstones.
The project is an example of the circular economy in action as a waste product is transformed into something of value. In this case the grit is collected during the filtration process and recycled into a valuable material instead. The process also displaces the need to dig up virgin materials through energy intensive quarrying – resulting in an estimated carbon saving of more than 70%.
Grit enters the wastewater system from road runoff into sewerage catchments and then passes into wastewater treatment works. As part of the Circular Economy Business Support Service, Zero Waste Scotland supported three Scottish SMEs from the aggregates production and recycling sector to determine the commercial viability of recycled grit.
Assessments by Levenseat, Thompsons Quarries and Brewster Brothers showed clear cost and carbon savings through resource efficiency, particularly in the form of transportation and landfill.
The next step will be physical trials where wastewater grit will be put through a series of physical and chemical tests to determine whether it meets strict ‘end of waste’ criteria. The overall aim of the project is to design a process whereby all business can take advantage of grit recovery.
Scottish Water environment program manager in research and innovation Tamsyn Kennedy said, “Scottish Water is committed to reducing the impact we have on the environment and finding innovative ways to reuse our waste products to support a flourishing Scotland.
“Grit from wastewater treatment is a great example of something we routinely remove during our treatment processes that can have a valuable second life. Repurposing it will also save waste from landfill and contribute to meeting our net zero emissions target.
“This ongoing project has been a great opportunity to work with Zero Waste Scotland and SEPA towards Scotland’s Circular Economy goal, as well as collaborate across teams within Scottish Water such as research & development, regulation, and waste management.
“We hope this is the first of many products we can recover from our day to day operations that can be safely and beneficially used in other Scottish industries.”