Technology Overview
The CMF system uses a drum or disc assembly mounted on a central hollow shaft, coated with a specialised Polstoff filtration fabric (cloth media), providing a filtration depth of 4–5 mm. The Polstoff cloth media consists of free fibres (fibre length 10 to 12 mm and diameter of 13 to 27 µm) that are fastened to a woven fabric that serves as support. The Polstoff media is available in several nominal pore sizes to suit all applications. The discs (or the drum) are completely immersed in the water to be treated. The Cloth Media Filters are equipped with an onboard cloth backwashing system. During filtration the discs (or the drum) are stationary and only rotate when backwashing (or cleaning of the cloth media) is required.
Gravity-driven filtration occurs continuously with backwashing automatically triggered when a water level differential is reached. During the filtration phase, solids in the effluent contact and are removed by the Polstoff cloth media. As deposition of solids on the cloth media increases, the hydraulic resistance of passing liquid through the cloth media increases, which results in a water level differential. When a differential of about 200 mm is reached, it automatically activates the cleaning process of the cloth to restore its filtering capacity, called a backwash sequence.
During backwashing, the filter slowly rotates and a pump with suction nozzles draws filtered effluent through cloth media. This process causes the free fibres of the cloth media to straighten and release the solids particles retained therein. As the discs (or drum) continues to rotate, the contact between the suction nozzles and cloth media recompresses the free fibres which returns the cloth media to its filtering state, thus restoring its filtering capacity.
With treatment capacities ranging from 10 m³/h to over 800 m³/h, the CMF system offers a reliable, low-energy, and low-maintenance solution in a compact footprint.
Advantages
- Available as packaged filters in steel tanks, or fitted into concrete tanks
- Gravity filtration with low headloss (max 500 mm)
- Continuous operation with backwashing on demand without standby units
- Low energy consumption and minimal space requirements
- Fully automated on-board backwash system
- High-strength, Polstoff cloth media for robust filtration
- Simple, reliable operation with very low maintenance costs
- Flexible design to handle variable hydraulic and solids loads
Applications include tertiary treatment for municipal and industrial wastewater, phosphorus reduction, pre-filtration for UV disinfection, downstream filtration of chemical-physical treatments, secondary sedimentation in attached growth processes, membrane pre-filtration (UF/RO), and surface water pre-filtration.
Applications
Real-world examples
A regional wastewater treatment plant was suffering problems with key equipment in their process train. Equipment was either operating inefficiently or was regularly out of service, due to the variability in the quality of onsite washwater. Treated effluent from the plant was discharged into a pond, then pumped into two storage tanks, before being reused for site reticulation and washwater for equipment. Spray nozzles on the inlet screens and on the sludge dewatering equipment were blocking frequently due to solids in the washwater, causing equipment downtime and impacting overall plant operation. The water authority decided to install a filtration system to treat pond effluent before it is stored for reuse. The filtration system had to meet the site’s tight hydraulic and footprint constraints and installation required minimum interruption to normal operations.
Western Australia
Water Filtration Systems
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