Automatic backwash filters protect membranes

Cross automatic water filters have helped Northumbrian Water improve filtration at a remote, unmanned water treatment plant, restoring continuous operation and avoiding supply interruptions

Cross automatic water filters have helped Northumbrian Water improve filtration at a remote, unmanned water treatment plant.

The plant at Birch Tree treats shallow well spring water collected from the surrounding fells at a rate of up to 1000 cubic metres per day to supply nearby communities and the town of Haltwhistle.

Approximately two years ago, membrane filtration was introduced at the plant to protect against the threat of cryptosporidium.

Fluctuating raw water quality placed a heavy workload on the inlet strainers fitted to the membranes, leading to excessive membrane backwashing and supply interruptions, necessitating excessive manual attendance at the site to ensure continuity of supply.

Northumbrian Water acceptance manager Tony Bell takes up the story: "Securing a dramatic improvement in inlet filtration performance - within the limited space confines of the existing building - was the vital requirement at Birch Tree.

Filtration specialists John Morfield were called in and designed a compact and successful solution based on the use of Cross zero-gravity filtration technology.

Cross Phoenix filters have been fitted behind the original strainers to permanently filter out all particles that are above 50 microns, after which cartridge filters capture any residual smaller solids before the water reaches the membranes".

Cross zero-gravity filter coils backwash automatically to a completely clean condition on a preset differential pressure signal with a time lapse back-up.

Backwashing is performed without any interruption to the flow and therefore without any impact on the operation of the membrane systems.

The efficiency of the Cross filters in removing the offending solids has been confirmed by the extended life of the cartridge filters, which are inspected during routine maintenance schedules.

Tony Bell concludes: "The introduction of the Cross filters has improved the situation at Birch Tree, saving us the inconvenience and expense of responding to alarm signals by enabling the plant to run more effectively and economically.".

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