FILTRATION AND SEPARATION
Faster cleaning delivered T
he installation of a new media in a Welsh water treatment works has paid back in wash water and energy savings, says
Stuart Watson of AMTSystems. To reduce the frequency of filter washing and the volume of water used, AMT Filtration has installed 0.8 - 1.6 mm Filtralite at Sluvad Water Treatment Works (WTW) in Wales, the media is being used as an alternative to 0.6 – 1.18mm sand. One filter had 900mm of new sand installed as a comparator. The other filters had 900mm Filtralite installed. The Filtralite filters have consistently exhibited much slower headloss build up, giving greatly extended filter runs. The filters are post clarification with a turbidity on to the filters of 0.7NTU and a typical turbidity off the filtralite of 0.045NTU.
Initially the operators were cautious and ran the sand filter to a headloss of 1.8m, but washed the Filtralite filters on time, as they never reached the wash initiating headloss. Once confident, they pushed the wash times further and further until they have extended to 90 hours, still
Sluvad WTW has successfully trialled Filtralite
without washing on headloss. They intend to extend to 100 hours, but extrapolating the trends, agree that the Filtralite would typically take 120 hours to reach 1.8m headloss, compared to only 40 hours for the sand. Once the Filtralite had been in for a few weeks it had also shown better filtered water turbidities than those achieved by the sand. Elsewhere, one client has been testing Filtralite against anthracite.
Again they have found that the headloss build up is slower. In addition they have been testing the volume of water required to wash the media. The dirty backwash water was tested for turbidity. The Filtralite cleaned up faster, initially giving dirtier backwash water but quickly cleaning up resulting in shorter wash times, saving significantly on the volume per wash as well as the number of washes per annum.
Algal blooms One UK water company which suffers from seasonal algal blooms has also found that very significant increases – in the region of 300% – were achieved in filter run times during this critical period when using Filtralite in their roughing filters instead of sand/anthracite. These three advantages – longer run times,
fewer washes and less water per wash give significant savings on power, water usage, size of clean and dirty backwash tanks, number of filters. These savings can result in a payback period of significantly less than one year when changing to Filtralite, Watson says. ■■■
September 2010 Water & Wastewater Treatment 27
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