Filtration rate above 4 gpm/sf is still considered "high rate" by most regulators in the
United States. The desire to achieve more cost effective filter capacity drives many water
utilities to select a filtration rate of 6 gpm/sf or higher, which is typically implemented
through up-rating existing filters. Regulatory pressures to provide low turbidity water,
and the need to properly handle recycle or discharges of wastewater has placed filter
operations under much more scrutiny than 10 or 20 years ago. The decision of high-rating
existing filters should also take into consideration more than just effluent turbidity
concentrations or particle counts as is commonly done for high rate approvals. The
overall operation of the facility should also be considered.
This paper reviews some of the key results of water plant high rate studies (in Michigan and North Carolina)
for rate increases up to 6 gpm/sf on conventional sand and anthracite dual media filters,
with media depths ranging from 24 to 48 inches. The studies showed that during normal
operations, the plants were obvious candidates for higher rate filtration, however, from an
operations standpoint; the plant(s) performed much differently under high production
periods or problematic source (high algae or manganese) water periods. Filter runs, filter
to waste periods, washwater handling volumes and facilities, unit filter run volumes
(UFRV), and overall plant reliability was discussed in light of both regulatory limits and
Partnership for Safe Water goals of 0.10 ntu. Recommendations for review of operational
factors outside of simple filter effluent water quality were presented to allow for better
assessment of higher filtration rates, and related facility improvements as part of future
plant upgrades. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 700 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 06/01/2006 |
