Current through Register Vol. 48, No. 38, September 20, 2024
a)
Pressure filters must not be used in the filtration of surface water,
groundwater under the direct influence of surface water, or water treated by
lime soda softening.
b) The rate of
filtration must not exceed 4 gal/min/ft2 of filter
area unless otherwise approved by the Agency under Section
604.145(b).
c) Minimum criteria at
Section 604.605(e) and (g) relative to structural details, hydraulics, and
filter media provided for rapid rate gravity filters also apply to pressure
filters when appropriate.
d) Number
1) A minimum of two units must be provided.
Each unit must be capable of meeting the plant design capacity or the projected
maximum daily demand at the approved filtration rate.
2) When more than two filter units are
provided, the filters must be capable of meeting the plant design capacity at
the approved filtration rate with one filter removed from service.
e) Rapid rate pressure filters
must be designed to provide for the following:
1) loss of head gauges on the inlet and
outlet pipes of each battery of filters;
2) an easily readable meter or flow indicator
on each battery of filters;
3)
filtration and backwashing of each filter individually;
4) minimum sidewall shell height of 5 feet,
unless otherwise approved by the Agency under Section 604.145(b);
5) the top of the washwater collectors at
least 18 inches above the surface of the media;
6) an underdrain system to collect the
filtered water and to uniformly distribute the backwash water at a rate not
less than 15 gal/min/ft2 of filter area;
7) backwash flow indicators and controls that
are readable while operating the control valves;
8) an air release valve on the highest point
of each filter;
9) when the filter
exceeds 36 inches in diameter, a manhole at least 24 inches in
diameter;
10) means of observing
backwash discharge water; and
11) a
six inch or larger air gap, or other Agency approved cross connection control
measure.
f) Rapid rate
pressure filters should have a flow indicator on each filtering unit.
