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removal efficiencies and easier cleaning than alternative screens. The benefits of an efficient engineering concept and detailed engineering have combined to produce low ‘whole of life’ costs when compared with most other screens, with servicing required only every 4-6 years.
CONCLUSION CST’s approach is to move local
manufactures closer to the place of use throughout Asia-Pacific as intensifying supply chain issues interrupt, delay and lessen the supply of wastewater treatment technology. This is key to the sustainability and environmental performance of industrial and municipal WWTPs and key to their overall reliability in delivering services. Not only does regional manufacture deliver a more robust and low-maintenance product, but it also 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 CST to offer full stainless-steel products with world standards of metals engineering, replacing carbon steel components and further improving corrosion resistance in harsh local environments.
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are important. This can cost in terms of downtime, environmental risk, clean-up costs, and occupational safety and health (OHS) hazards for the operator teams involved.” A DIFFERENT APPROACH “We have taken a different path to many in producing our different screen designs for municipal and industrial applications to prepare for a future that is already arriving,” Bambridge said. “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, which is a false economy that can transfer cost and problems down the line. “This ‘whole of lifespan’ value 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.” Compared to typical traditional screening at WWTPs, for example, CST’s in-channel technology adapted to local conditions reportedly 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 redirects flow radially through the mesh to optimise solids separation and self-cleaning. The rotary drum is manufactured from either self-cleaning wedge wire for primary screening, or perforated plate for fine pre-MBR screening. It is washed by a system of spray nozzles at a moderate pressure. CST screening technology approach is said to 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. If the site allows it, a flumed system can be used. The horizontal drum design lowers operating depth and range to reduce average screen velocities for higher
Images: CST
Michael Bambridge Managing director, CST
48 Water & Wastewater Asia | September-October 2024
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