Current through Register Vol. 48, No. 38, September 20, 2024
a) Adequate
piping with sampling taps must be provided to allow for the collection of
samples from various depths of the units.
b) Chemical Feed. Chemicals must be
satisfactorily mixed in accordance with Section 604.1100(b).
c) The Agency may require a rapid mix device
or chamber ahead of solids contact units to assure proper mixing of the
chemicals applied. If required by the Agency, the mixing devices must be
constructed to:
1) provide good mixing of the
raw water with previously formed sludge particles; and
2) prevent deposition of solids in the mixing
zone.
d) Flocculation
equipment:
1) must be adjustable (speed
and/or pitch);
2) must provide for
coagulation in a separate chamber or baffled zone within the unit;
and
3) should provide that the
flocculation and mixing period will not be less than 30 minutes.
e) Sludge removal design must:
1) require sludge pipes be not less than 3
inches in diameter and arranged to facilitate cleaning;
2) prevent clogging at the entrance to sludge
withdrawal piping;
3) locate valves
outside the tank for accessibility; and
4) allow the operator to observe and sample
sludge being withdrawn from the unit.
f) Cross Connections
1) Blow-off outlets and drains must terminate
in a location with an air gap of 6 inches for backflow protection.
2) Cross connection control must be included
for the potable water lines used to back flush sludge lines.
g) Detention Period. Detention
period must be established on the basis of the raw water characteristics and
other local conditions that affect the operation of the unit.
1) When treating surface water with upflow
clarifiers using mechanical mixing, detention times must be based on design
flow rates and should be two to four hours;
2) When softening groundwater with upflow
clarifiers using mechanical mixing, detention times must be based on design
flow rates and should be one to two hours;
3) When treating surface water using cone
shaped, helical upflow, solids contact clarifiers or softeners, the detention
time must be a minimum of 60 minutes; and
4) When treating groundwater using cone
shaped, helical upflow, solids contact softeners, the detention time must be a
minimum of 45 minutes.
h) Water Losses
1) Solids contact units must be provided with
controls to allow adjusting the rate or frequency of sludge
withdrawal.
2) Total water losses
must not exceed:
A) five percent for
clarifiers; and
B) three percent
for softening units.
3)
Solids concentration of wasted sludge to waste must be:
A) three percent by weight for clarifiers;
and
B) five percent by weight for
softeners.
i)
Weirs or Orifices
1) Upflow Clarifiers Using
Mechanical Mixing
A) The units must be
equipped with either overflow weirs or orifices constructed so that water at
the surface of the unit does not travel over 10 feet horizontally to the
collection trough.
B) Weirs must be
adjustable, at least equivalent in length to the perimeter of the
tank.
C) Weir loading must not
exceed:
i) 10 gpm per foot of weir length for
units used as clarifiers; and
ii)
20 gpm per foot of weir length for units used as softeners.
D) Where orifices are used, the
loading rates per foot of launder rates should be equivalent to weir loadings.
Either must produce uniform rising rates over the entire area of the
tank.
2) Cone Shaped,
Helical Upflow, Solids Contact Clarifiers or Softeners
A) Weir loadings on cone shaped, helical
upflow, solids contact units that utilize reversing flow weirs must not exceed:
i) 100 gpm per lineal foot of weir length for
cone shaped, helical upflow, solids contact units; or
ii) 200 gpm per foot of weir length for units
used as softeners.
B)
Where orifices are used, the loading rates per foot of launder rates should be
equivalent to weir loadings. Either must produce uniform rising rates over the
entire area of the tank.
j) Upflow Rates. Unless otherwise approved by
the Agency under Section 604.145(b), the upflow rates must not exceed:
1)1.0 gpm per square foot of area at the
sludge separation line for units used as clarifiers; and
2)
1.75
gpm per square foot of area at the slurry separation line, for units used as
softeners.
k) Cone
shaped, helical upflow, solids contact units must be equipped with one or more
tangentially oriented inlets that introduce flow into the bottom cylindrical
section of the unit. The inlets must be equipped with a means for controlling
the velocity of the water flowing into the unit.
