Biosolids industry ready for bigger things
Australia is already a world leader in biosolids reuse rates but innovative utilities are pushing for new solutions for more effective resource recovery.
The nation’s leaders in the sector will be gathering today and tomorrow at the 2016 Biosolids and Source Management Conference in Melbourne, offering an opportunity for debate, networking and collaboration.
Currently, almost 90% of all biosolids are beneficially reused in Australia but much of the regulation covering it dates to the 1990s, ignoring advances in technology and experience since then, slowing innovation.
AECOM Water Supply and Wastewater Treatment Sector Leader Peter Hillis said there had been few major changes in biosolids management from a utility perspective in recent years.
“What drives biosolids management is external factors, so because Australia has historically been blessed with having plenty of land, we’ve had low-tech solutions for biosolids,” he said.
However, Hillis said a number of emerging factors were driving more high-intensity and innovative biosolids management practices.
“Whether that be encroachment of development on sewage works meaning utilities have to start dealing with odour issues, storage space or a general drive to recover resources from biosolids,” he said.
Barwon Water, for example, built Australia’s first thermal drying plant to produce biosolids pellets after running out of on-site storage space.
“Benefits are the small footprint required … it’s fully-enclosed so we can control things like noise, odour and dust,” said Infrastructure Services General Manager Paul Northey.
“Biosolids in the form of pellets are more easily re-used. Because we’ve got a high-quality product, we don’t have the same restrictions that more traditional treatment methods have. Then there are environmental benefits, including a 40% reduction in greenhouse gas emissions compared to long-term storage and air-drying [Barwon Water’s previous management approach].”
The plant began operating in 2013 and was delivered through a public-private partnership aimed at selling a product, rather than treating biosolids in the most convenient way for the utility.
“We got in partners who had the experience and capabilities to not only deliver a biosolids treatment facility, but also develop the market,” Northey said.
The product is now sold to farmers across Victoria, New South Wales and South Australia, but the venture is yet to turn a profit. “Revenue is certainly not outstripping our expenses at this stage; however, it is going some way to offsetting the cost,” he said.
South East Water (SEW) was also facing storage restrictions when it gained Environment Protection Authority approval in December 2015 to slash the minimum three-year drying and storage period to just one year at two of its treatment plants.
The utility had been processing its sewage sludge in an aerobic digester and sludge lagoon, then drying solids in open drying pans or closed solar driers, before stockpiling them in the open for three years.
“We didn’t change our management process; we just proved that one year was sufficient to achieve the pathogen reductions required to meet Treatment Grade T1,” said SEW Product Quality Scientist Dr Aravind Surapaneni.
And the storage period could be reduced even further, according to preliminary testing of biosolids treated using SEW’s solar driers. Surapaneni noted that SEW’s experience suggested pathogen management controls may be too conservative.
“The regulations are too stringent but, having said that, regulators are more than happy to engage with the water industry to look for other options – our EPA is very proactive in that.”
Click here for more information on the 2016 Biosolids and Source Management Conference.