GRAVITY FILTER BED CLEANING
Replacing media and fittings in Rapid Gravity Filters is expensive. In-situ cleaning is quicker and improves performance for a fraction of the replacement costs
Following successful development work and trials, an innovation in the cleaning of gravity filter beds is now set to become common place in the water industry.
Panton McLeod has now completed another successful trial, this time working in partnership with Scottish Water to clean gravity filter beds while the filter media remains in place. This dramatically reduces the costs and time involved in current methods which means the filter media is removed and often replaced and aeration nozzles and pipework is replaced rather than being maintained.
Panton McLeod has been using its own proprietary cleaning solution to clean and disinfect services reservoirs for over 20 years now. This is a proven and well-established cleaning technique for drained down water storage assets that is used across the industry in the UK.
The team at Panton McLeod are always exploring new ways of using this same product to address different and common problems faced by the water industry
This resulted in a recent successful trial using the product to clean a rapid gravity filter bed with the filter media in place. The filter nozzles and aeration lines were blocked with biofouling and the build-up of pressure during the backwash was causing the pumps to trip before completing the backwash cycle.
Iain Ross, Capital Liaison Engineer with Scottish Water explains “We were experiencing issues with some filters having an extremely violent backwash and through investigation work we found that the nozzles in the filter floors were choked with a sort of biological film. Rather than remove all of the media and remove all the nozzles we were investigating to see if we could do something with the media still in place.”
Iain came across the new technique while watching EddyVision, an online media channel aimed at providing water industry information to the sector. In the episode, Yorkshire Water were facing significant costs to replace media, nozzles and aeration lines of one of their gravity filter beds. Yorkshire Water were also considering a reasonably sized capital project to bring in a different source water for the treatment works in the hope that this would slow the build-up of biofouling in the future. The episode highlighted that Yorkshire Water now have another, much more cost effective, option to call upon after a cleaning trial there enabled normal operation of the filter bed once again without the significant cost of replacing all the media and filter bed fittings.
Iain Ross continues “I saw the episode of EddyVision and it immediately sparked a light bulb moment. I got in touch with Panton McLeod to see what we could achieve. They came up with a methodology to do a clean using PM77, with the media still in place. They developed a methodology to use dosing lances which were used to spray the chemical throughout the filter bed quite evenly allowing us to control it. We filled the plenum up with water so that it held the chemical in the exact area where the nozzles were.”
There were many challenges facing the project, but the main objective was always clear; to save money, time and reduce the environmental impact of cleaning gravity filter beds.
Everything from volumes to dilution rates to contact time, waste management and scaffolding set up had to be precise, effective and efficient to ensure the team were successful. If it didn’t meet this criteria the team would rethink and come up with another solution.
Simon Jefferson, Commercial Director at Panton McLeod said “Scottish Water are a forward-thinking organisation, meaning we could work well together. Our teams developed a process that was not only effective but unlocked significant efficiencies that we could pass on directly to our clients.
Simon continues “We work closely with our clients across the country and through listening to them we realised that the cleaning of gravity filter beds was a costly and time-consuming challenge. A challenge where long standing, traditional solutions were not being reviewed in a creative way to try and drive increased value for the customer. We wanted to address this for Scottish Water and are now developing that into a long-term water quality package that water companies can choose that will realise even more cost savings.”
Following the successful clean the gravity filter bed is now performing a uniform backwash which has reduced the amount of media that is lost during the cycle, leading to additional savings over the lifetime of the asset. The team at Panton McLeod are now looking at an additional six gravity filter beds with a view to completing one every month.
Iain Ross added “It’s vital for Scottish Water to explore new ways of dealing with old challenges because it leads to cost savings as well as efficiencies, time savings, health and safety reasons along with environmental impacts. If we were to replace the media it would include the cost of lorries running up and down the road, the quarrying costs and large amounts of labour, not to mention the increase in downtime. There’s a whole raft of benefits.”
This has now led to a much broader discussion with stakeholders across the water industry and academia to explore further uses of the PM solution and enhanced cleaning techniques, including membrane filter cleaning, utilising the cleaning solution to address common industry problems in a different and more cost-effective way
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