The sand granulometries, referred to as G1 (fine: effective diameter--[D.sub.10] = 0.55 mm and uniformity coefficient--UC = 1.34), G2 (medium: [D.sub.10] = 0.77 mm and UC = 1.28) and G3 (coarse: [D.sub.10] = 1.04 mm and UC = 1.36), were used with a fixed filter bed height of 0.35 m, according to the recommendations of the manufacturer.
After the filtration step, backwash trials were performed in each filter individually and the procedure consisted in applying a flow rate from the fourth filter of the module (FR) in the opposite direction of the filtration process, in order to generate a filter bed expansion of 25%, according to the guidelines of Brouckaert (2004), which corresponded to the height of 0.44 m.
Backwash was evaluated based on the collection of sand samples at different depths inside the filter bed (four sampling points in the filter bed profile).
1 and, based on its sum, the total mass of solids present in the filter bed ([MS.sub.Ftotal]) was estimated.
[MS.sub.Fi]--mass of solids present in the filter bed after filtration trial (degree of soiling) in each fraction of volume of the filtering layer i (g); and
2 was used to determine the mass of solids removed in each backwash trial in the filter bed individual layers ([MS.sub.Ri]) and, based on its sum, the total mass of solids removed in the backwash process ([MS.sub.Rtotal) was estimated.
As one of only a handful of large filter bed
systems planted across the country, the pounds 255,000 FORE filter bed
will dramatically enhance the water quality of the River Blythe running through Solihull, Monkspath and Shirley, according to the company.
Based on the successful performance of the first seven Accutronix MX actuators, the city of Bismarck added 107 more actuators, with plans for more than 150, and a second DDC-100 network to serve new filter beds
that will treat an additional 40 million gallons per day.