Robust water and wastewater defences are required as Australia dries out under the effects of El Nino and Climate Change.
By Michael Bambridge*, Managing Director, CST Wastewater Solutions
As Australia’s weather patterns turn drier with the arrival of the El Nino forecast by the Weather Bureau to arrive by the end of this year, our water and wastewater treatment plants are going to have to work harder than ever before.
They will be asked to efficiently process throughputs over a wider range of flow rates, without clogging and environmental spills – and continue to do it with less on-site maintenance, because local authorities today can typically afford fewer specialist operations and engineering staff – or are too far away to get them on-site immediately when they are needed.
This scenario applies particularly the smaller operators among our 300 urban water authorities, as well as and remote community and industry-specific plants, such as mining, chemical and petrochemical plants, pharmaceutical plants, abattoirs and canneries, and food and beverage processing.
Headworks, the front line of defence
The problem is compounded by the trend over the last 20 or more years to use cheaper one-size-fits all engineering solutions, including typically imported headworks (the subject of this article) which are less flexible, less durable and not built to cope with the demands of the driest inhabited continent on Earth. And when things do go wrong, engineering support and parts are far away along stretched supply lines.
So as we move into 2024 the country’s approx. 4,000 water and wastewater plant operators will likely be called upon to do more with less in dealing with increasingly challenging scenarios – muddier, nutrient-rich and more solids-intensive throughputs, As they did in 2019, when Australia experienced one of the worst droughts in the last 100 years.
That drought had a particularly severe impact on the areas of the southern coast of Australia, the west coast of Western Australia, northeastern New South Wales, and the greater southeast of Queensland. The arid interior of Australia and most of the Northern Territory also experienced even drier conditions than in previous years as Climate Change took hold.
This task of managing climate change is growing more demanding and unpredictable, particularly during cycles of drought, flood, and irregular loads, which are increasingly common in these days and erratic conditions affecting different areas in different ways. The problem is worldwide, but especially prevalent in the notoriously variable conditions of Australasia and the broader Asia-Pacific, where regulators are intensely concerned about water quality, environmental spills, and water tables.
Headworks are the first line of defence to help prevent such issues. It is true that pumps and dewatering systems are engineered to handle some impurities and variations, but, beyond a certain level, debris and irregular feeds can lead to equipment failures and faster component wear.
Unless solids are efficiently separated out from wastewater at the start of the purification process, you are inviting trouble into the system. This can cost dearly in terms of downtime, environmental risk, clean-up costs and OH&S hazards for the operator teams involved.
This means ease of maintenance of headworks is a key consideration in preventing trouble, especially for those municipalities and smaller industrial concerns operating on tight budgets.
Flexibility is also key to ongoing efficiency in handling diverse inputs and flows, regardless of the location and input. Headworks that are efficient over diverse conditions are vital to all the downstream purification and recycling process stages in a properly engineered wastewater treatment plant.
As a result of our experience over more than 30 years of wastewater installation and operational experience throughout the Asia-Pacific region, we have taken a different path to many in producing our different headworks designs for municipal and industrial applications to prepare for a future that is already arriving.
A different approach
Our engineering approach is not one-size-fits-all, because one size (or type) does not. Our horizontal in-channel rotary drum screening technology is built from the outset to be both robust and adaptable, not to be cheaper up front, or to transfer cost and problems down the line.
This whole-of-lifespan value, as distinct from a race to the bottom on sticker price, is a mature engineering approach in meeting and continuing to meet users’ tasks that vary from place to place, day-to-day and week-to-week as loads on the system change.
Some non-technical people, who don’t have to live with the results of their decisions, might say “So what?”, we are not addressing them. We believe the guys on the front line, the operators, and engineers, will have a different view. That’s why we present our engineering and operational principles for a mature and timely discussion.
There are common features we embrace that are universally beneficial to WWTP’s expected to perform and keep on performing.
Compared with typical traditional screening at wastewater treatment plants, for example, our in-channel technology has lower fluid head loss at peak flows to increase solids removal efficiency.
When dealing with fine screening of larger flows, this technology has the advantage of mechanical simplicity, self-cleaning and high efficiency screening. This results in reduced maintenance and cheaper whole-of-life costs compared with other types of screens, such as band and inclined drum screen designs.
Key to delivering this functionality is the configuration of the design, in which the screening drum is installed horizontally semi-submerged in line with the incoming wastewater. The plate at the back of the drum re-directs flow radially through the mesh to optimise solids separation and self-cleaning. This back plate prevents bypassing.
The rotary drum is manufactured from either self-cleaning wedge wire for primary screening, or perforated plate for fine pre-membrane bioreactor (pre-MBR) screening. It is washed by a system of spray nozzles at a moderate pressure.
Our screening technology approach provides for optimal adjustment of screen gap widths and sieve hole diameters for the most appropriate screening result when matched to individual installations’ characteristics, such as the application flow and local site conditions.
An internal hopper collects the screenings, which are flumed out to the integral lifting and dewatering screw, to efficiently dewater and reduce screenings volume.
The lifting screw is shaftless to avoid any blockages, even in the presence of fibrous products, and includes screen and screening washing. Lifting and screenings handling can also be conducted outside the channel, which increases options for additional washing and dewatering, according to individual applications. Alternatively, collected solids can be flumed away.
The horizontal drum design lowers operating depth and range to reduce average screen velocities for higher removal efficiencies and easier cleaning than alternative screens.
The benefits of an efficient engineering concept and detailed engineering have combined to produce exceptionally low whole-of-life costs when compared with most other screens, with servicing required only every four to six years.
The last word
One final way in which we have a different approach is our move to local manufacture closer to the place of use throughout the Asia-Pacific, taking advantage of Australia’s high quality manufacturing capabilities.
This move comes as intensifying supply chain issues interrupt, delay and lessen the supply of some of vital wastewater treatment technology, which is key to the sustainability and environmental performance of industrial and municipal wastewater treatment plants and key to their overall reliability in delivering services.
Not only does local manufacture deliver a more robust and low-maintenance product – and better whole-of-lifecycle value – but it places the customer next to the source of supply for spare parts, future extensions, and retrofits to boost performance long-term.
The switch to local production also enables us to offer full stainless-steel products with world-respected standards of Australasian metals engineering, replacing carbon steel components and further improving corrosion resistance in harsh local environments.
So if you are interested in the future, If our different engineering approach attracts you, we would value your observations and experience. Good engineering is an ongoing discussion, which we are keen to extend and develop in the light of real experience and vision.
*Michael Bambridge BE, ME, is Managing Director of CST Wastewater Solutions. His experience over more than 30 years in Australasia and Asia spans hundreds of municipal and industrial WWTP’s throughout Australasia and internationally, particularly into Asia and China.
CST offers the latest in specialised mechanical and process equipment, built from our ‘hands-on’ experience in the industry and a clear understanding of our clients’ needs. Beyond equipment supply, we have the ability to design, install, maintain, and in specific cases, operate premium wastewater treatment systems. For clients who require a more comprehensive solution, CST constructs complete wastewater treatment plants in partnership with major specialist companies.
