Thermal hydrolysis, improved aeration and digestion processes, and better tertiary treatment practices are all part of the drive to find smarter ways to treat larger quantities of wastewater. Patricia Moore looks at a growing waste-not culture.
The current boom in population growth is all good news for New Zealand’s economy. What’s perhaps not so good is the pressure it puts on managing the infrastructure in our major cities and larger urban centres.
Finding smarter ways to deal with larger quantities of wastewater is one of these issues, says Timothy Phelan, water sector leader – water and wastewater treatment with Opus. On the plus side, he says that’s driving innovation.
“Granular sludge technology innovations immediately spring to mind. These make the whole process more efficient, meaning more waste can be processed without increasing the size of the facility.
“Another interesting area is around energy capture; using the methane and carbon dioxide produced as a by-product of sludge digestion to heat boilers or for power or to put back into the grid.
“These technologies include thermal hydrolysis, pH hydrolysis and electro-magnetic hydrolysis, which increase the energy recovery from waste while reducing its mass.
“They’ve been proven in Europe and are on the rise in North America and elsewhere but are just starting to take off here, with Watercare in Auckland pioneering thermal hydrolysis.”
And, he says, the technology has matured to a point where New Zealand can avoid some of the earlier obstacles and simply purchase off-the-shelf technology.
FILTEC’s managing director Matt Ewen reports several key trends. First up he points to the drive for energy efficiency in order to reduce a carbon footprint and – for a lot of water authorities – a drive towards energy-neutrality for the entire organisation.
“The first process that gains a lot of attention when addressing this is the aeration process,” he says, “which can consume up to 60 percent of the energy required to run a wastewater treatment plant. The next are the digestion processes where innovation is enabling greater power production.”
Matt also highlights increased awareness of the environmental impact of wastewater discharge, and a consequent tightening of requirements on solids and nutrients allowed to be discharged.
“This is leading to tertiary treatment processes being added to existing systems and lending itself towards the membrane bioreactor [MBR] processes in many greenfields builds,” he says.
Matt says there is an increasing focus on the treatment of bio-solids. “This is leading to innovation in drying processes, thermal and solar: the latter assisting in the drive for energy efficiency.”
Traditional thinking is changing as bio-solids become a resource in several different ways. “A wastewater treatment plant is now seen as a resource recovery centre with the potential to generate power and produce resources that are of value.”
At AECOM, Peter Hillis, sector leader – water supply and wastewater treatment, also highlights a need for change.
“The current approach to treatment of wastewater is based on 20th century technologies and needs to change. Rather than a problem to be solved by treating and discharging, we should instead regard wastewater as a value-creating resource – an energy resource or potential nutrient recovery resource. That’s the direction research and technologies are taking us.”
Rocketing energy costs, greenhouse gas emissions, drought and flood, tightening regulations, finite resources, and the push to do more for less, are all pointing to this, he says.
Meanwhile, GHD principal water / wastewater engineer Bradley Rudsits says local authorities are thinking innovatively by adopting risk-based assessment for level of service definition.
“We’ve worked with Hamilton City Council in the development of their Long Term Plan for Wastewater Management which includes the adoption of risk-based assessment to inform the level of service.
“This directly feeds into the prioritisation of infrastructure projects for the short, medium and long term: all aligned with the increased growth from residential, commercial and industrial developments.”
Brad says innovative approaches are also demonstrated in work to develop Sydney Water’s System Blueprint for the Malabar Wastewater Catchment where each blueprint seeks to ensure short- and medium-term investment is aligned with wide-ranging objectives, regulations and strategies, while taking into account all relevant issues, opportunities and risks.
He also points to work at Melbourne’s Fisherman’s Bend, a previously heavy industrial area on the CBD fringe currently undergoing redevelopment.
“The outcome of a study to look at servicing 120,000 new residents for potable, non-potable, stormwater and wastewater services, was the recommendation of a macro pressure sewer system in conjunction with a wastewater recycling plant to offset peak wastewater flows and offer potable water replacement.”
Innovative online and mobile products are also revolutionising the sector. Pingstreet, for example, allows local authorities to receive immediate consumer interactions and reporting of faults. And information from apps, that can be configured to utilise smart phone features for user-generated content, can be analysed to help local authorities identify trends and ongoing management issues.
Says Brad, “Use of Internet of Things devices for increased resolution, and Software as a Service [SaaS] as part of wastewater management, will allow local authorities to increase response times for incidents, such as network blockages, in upper catchment reaches not typically covered by traditional monitoring stations.”
But, he says, local authorities will need to be adaptive and flexible to change, in both data collection and resolution, and how this information is used as an input to infrastructure investment decisions.
AECOM’s Peter Hillis notes that the water industry is being pushed harder to deliver services within tight financial constraints.
“The need to develop and apply technologies for the recovery of energy and nutrients will continue to evolve as the needs of the industry become more apparent.”
The adoption of technology will be driven by this necessity, he says.
“The exciting news is that the wastewater plant of the future is destined to be a closed loop system that is at least energy neutral and more likely, energy positive.
“This will result in a zero net carbon footprint and reduced waste management issues, and a positive impact on society. The future is now within our grasp – and it’s a future we can achieve.”
This article was first published in the September 2017 issue of NZ Local Government Magazine.