A pilot study was conducted to evaluate the Atlantic City
Municipal Utilities Authority's (ACMUA) existing filtration facilities to
determine the potential for increasing filtration capacity. The ACMUA has
established a goal of upgrading their filtration facilities to allow for: additional capacity (increase from 18 MGD to 22 MGD); the ability to
remove filters from service to perform maintenance; and, to meet a turbidity
goal of 0.1 NTU at their filtration plant.
Filtration theory, particularly the L/d (bed depth divided by the media diameter)
and L/d<sup>3</sup> ratios, was examined in order to design alternative filter media
configurations. Traditionally, the L/d ratio has been on the order of 1,000 to
1,200. Recent filtration theory has shown particle removal is a function of the
L/d<sup>3</sup> ratio which is more dependent on media size (ES). The higher the L/d<sup>3</sup>
ratio the lower the initial filtered water turbidity.
The pilot study tested three alternative media configurations along with a control
column that was identical to the existing filter media configuration:
control - 36" Filtrasorb 300 (0.9 mm ES) and 4" sand (0.5 mm ES);
Alternative 1 - 36" Filtrasorb 300 (0.9 mm ES) and 12" sand (0.5 mm
ES);
Alternative 2 - 48" Filtrasorb 816 (1.4 mm ES) and 12" sand (0.5 mm
ES); and,
Alternative 3 - 48" Filtrasorb 820 (1.1 mm ES) and 12" sand (0.5 mm
ES). The three alternative media configurations and the control were tested at a
loading rate of 5.5 gpm/sf. The tests were conducted with four 4-inch diameter
filtration columns operating in parallel. The flow treated by the filtration
columns was taken from the top of the existing filters. Data recorded included
turbidity, particle counts and headloss.
The control filter column mimicked the full-scale plant. All three alternative
configurations outperformed the control filter - that is, they produced filtered
water with lower turbidity and particle counts, but longer filter run times.
The pilot study results demonstrated that additional capacity could be achieved
without constructing new filtration facilities. Renovation of the existing filters
saved ACMUA millions of dollars in capital costs. The design of the upgrade of
the existing filters was based on the configuration of the pilot filter system with
the optimum filtered water turbidity, particle count and unit filter run volumes.
The selected media configuration was 36 inches of 1.1 mm ES GAC over 12
inches of 0.5 mm ES sand. The new filters have a higher L/d<sup>3</sup> ratio, thicker sand
layer, new underdrain and upgrade in the backwash scheme including air scour
and increased backwash rate. The first of six filter upgrades was placed in
service in March 2007. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 210 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 17 |
| Published : | 11/01/2007 |
