Water & Wastewater Treatment

ADVERTORIAL AMP6 brings new challenges to achieve outcomes more efficiently, with a particular focus upon whole life cost (WLC) and carbon footprint. In addition, quality standards continue to improve so processes require high performance and reliable operation. e water industry has historically relied upon sand filters for water treatment and tertiary treatment of wastewater. But sand filters are expensive to build, occupy a large footprint and increasingly are unable to achieve the tighter standards now required for some tertiary treatment applications. e development of continuous backwashing filters (CBFs) in the 1990s offered some advantages over traditional rapid gravity filters in terms of a smaller footprint and reduced construction costs for small sites, but CBFs have high operating costs and are seldom the lowest WLC solution. FilterClear takes media filtration into the 21st century, applying sound engineering principles to achieve a higher filtrate quality than a sand filter within a smaller footprint. Indeed a FilterClear plant is compact enough to treat up to 50 l/s on a single skid, bringing project cost and programme savings as well as providing operators and maintenance teams with a plant which has been designed, built and tested offsite with their needs in mind. A Better Filter One of the biggest drawbacks of a conventional rapid gravity sand filter is that, during backwashing, large grains of sand migrate to the bottom of the filter bed whilst small grains are lied to the top. e effect is that most filtration occurs in the top layers of a sand filter, leading to rapid fouling and frequent backwashing. FilterClear overcomes this by using up to four media layers of different density such that the layers re-form aer each backwash. Layers are arranged with coarse grains at the top of the filter and the finest layers at the bottom, so solids are removed progressively as water passes through the filter. e entire bed depth is utilised, giving a higher solids holding capacity and longer filter runtimes. e bottom layers are much finer than a conventional sand filter without risk of blockage, so FilterClear achieves a far better filtrate quality. Anglian Water verified FilterClear's performance in trials at Cambridge Water Recycling Centre, and FilterClear is now one of their framework solutions for tertiary solids removal. ree full-scale FilterClear plants were installed in Anglian Water during AMP5 to achieve stringent BOD consent limits. FilterClear was selected because of reliable high effluent quality, low WLC and low carbon emissions. Small Footprint FilterClear uses enclosed filter vessels made of GRP, epoxy coated or rubber-lined steel depending on the application. By pumping the flow to the filter at pressures of 0.2 – 1.0 bar (less than the typical pressure required by a CBF), FilterClear can operate at filtration rates of 25 m/h and more. is equates to a filter area roughly one third the size of a conventional sand filter, so FilterClear needs fewer, smaller filters and occupies less space. Keeping it Clean e key to successful long- term operation of a filter is an effective backwash. FilterClear uses a four-phase backwash comprising a pre-wash, partial drain-down, air scour and main wash. During the wash phases, clean water is pumped in reverse through the media bed at 60 m/h, expanding all layers by 30-40%. e air scour, again at 60 m/h, helps to remove any biofilm growth, allowing FilterClear to operate successfully with flows containing a high BOD concentration. Other features of FilterClear, such as the design and distribution of floor nozzles, contribute to an extremely effective backwash using a minimal amount of water. Multipurpose anks to FilterClear's highly efficient backwash, it can be used for a wide range of applications from fresh water or seawater filtration, through rainwater harvesting to tertiary filtration of wastewater and industrial water treatment. FilterClear can even be used for high-load applications such as downstream of septic tanks, or for concentration of backwash water. DWI-Approved versions are available for potable water. Offsite Assembly anks to the small footprint of FilterClear, it is well-suited to off-site construction as a skid- mounted package plant. Off-site assembly and testing allows significant savings to be made in duration and cost of a project. A FilterClear skid can be delivered, installed and connected within a week, and factory pre- testing means a reliably quick commissioning phase. Offsite assembly and testing reduces project risks, and the associated cost. Programme risks are reduced because FilterClear is delivered as a single package, meaning construction progress is less dependent upon the weather and the coordination of different contractors. Health and safety risks are reduced because the complex work to assemble the package plant takes place in a dry, well-lit factory environment, which also assures the quality of the finished product. A New Generation FilterClear brings together proven filtration principles within a compact package, ideally suited to upgrading both water and wastewater treatment plants. Offsite assembly and testing result in low overall project costs and quick installation. By moving away from conventional sand filters, water companies and industrial users can benefit from a reliably good quality of filtered water and low whole life costs. For further information contact jeremy.biddle@bluewaterbio.com or visit www.bluewaterbio.com Offsite Assembly sOlutiOns fOr WAter filtrAtiOn Project costs can be reduced substantially by offsite fabrication and testing. Bluewater Bio's Engineering Director, Jeremy Biddle, explains how their advanced filtration system, FilterClear™, offers benefits to projects in water and wastewater treatment. www.wwtonline.co.uk | WWT | sepTember 2015 | 31

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