Current through August 26, 2024
Aeration treatment devices described in this section may
be used for oxidation, separation of gases, or for taste and odor control. Air
stripping towers shall meet the requirements of s.
NR 811.53 (2), which can be used for the removal or
reduction of some volatile organic compounds. The following requirements shall
be met:
(1) NATURAL DRAFT AERATION.
The design for natural draft aeration shall provide that:
(a) Water is distributed uniformly over the
top tray.
(b) Water is discharged
through a series of 3 or more trays with separation of trays not less than 6
inches.
(c) Trays are loaded at a
rate of one to 5 gallons per minute for each square foot of total tray
area.
(d) Trays have slotted, heavy
woven wire mesh with 0.5-inch openings or perforated bottoms.
(e) Perforations are 3/16 to 1/2 inches in
diameter, spaced one to 3 inches on center, when perforations are
used.
(f) Construction is of
durable material resistant to the aggressiveness of the water and dissolved
gasses.
(g) Contamination from
sources such as those listed is sub. (7) is minimized by providing down-turned,
louvered or hooded, screened air inlet or outlet openings. Screens shall be
constructed of 24-mesh corrosion resistant material.
(h) Exhaust air is discharged directly to the
outside atmosphere and in a location that will be protective of public
health.
(2) FORCED OR
INDUCED DRAFT AERATION. The design for forced or induced draft aeration shall
provide that:
(a) Water is distributed
uniformly over the top tray.
(b)
The blower and blower motor are weatherproof and are installed in a
weather-tight, screened enclosure.
(c) There is an adequate countercurrent flow
of air through the enclosed aeration column.
(d) Aerator trays are loaded at a rate of one
to 5 gallons per minute for each square foot of total tray area.
(e) Water will discharge through a series of
5 or more trays with separation of trays not less than 6 inches or as approved
by the department.
(f) Construction
is of durable material resistant to the aggressiveness of the water and
dissolved gasses.
(g) The aerator
is insect-proof, watertight, and light-proof.
(h) The air intake is located above grade and
the air introduced into the column is as free as possible from contamination
sources such as those listed in sub. (7).
(i) The water outlet is adequately sealed to
prevent unwanted loss of air.
(j)
Interior and exterior sections of the aerator can be easily reached or removed
for maintenance.
(k) The air inlet
to the blower and the tower discharge vent shall meet all of the following
requirements:
1. Be screened.
2. Be provided with a downturned, hooded, or
mushroom cap that protects the screen from the entrance of extraneous matter
including insects and birds, obnoxious fumes, all types of precipitation and
condensation, and windborne debris or dust.
3. Be constructed of 24-mesh corrosion
resistant material and installed at a location least susceptible to vandalism
or damage.
4. Contain an air inlet
that is provided with a dust filter.
(l) Exhaust air is discharged directly to the
outside atmosphere and in a location that will be protective of public
health.
(3) PRESSURE
AERATION. Pressure aeration installations shall meet the following
requirements:
(a) Pressure aeration may be
used for oxidation purposes. Pressure aeration will not be approved for removal
of dissolved gases.
(b) Filters
following pressure aeration shall be provided with adequate exhaust devices for
release of air.
(c) Pressure
aeration devices shall be designed to cause a thorough mixing of compressed air
with the water being treated.
(d)
Pressure aeration devices shall provide screened and filtered air that is free
of obnoxious fumes, dust, dirt, and other contaminants.
(e) Air compressors supplying pressure
aerators shall be oil-less.
(3m) PACKED TOWER AERATION. Packed tower
aeration systems shall meet all of the following requirements:
(a) Materials of construction shall meet all
of the following requirements:
1. The packing
material shall be certified by ANSI/NSF standard 61 dated March 15, 2022, which
is incorporated by reference.
Note: A copy of ANSI/NSF standard 61 dated
March 15, 2022 is available for inspection at the Legislative Reference Bureau
and may be obtained for personal use from NSF International,
https://www.nsf.org.
2. The tower shall be constructed of
stainless steel, concrete, or aluminum.
(b) Process design shall meet all of the
following requirements:
1. Water loading rates
shall be in the range from 15 to 30 gallons per minute per square foot. Water
loading rates outside of this range may be used if justified to the department
by pilot testing under s.
NR 811.44.
2.
The ratio of the packing height to column diameter shall be at least 7:1 for
the pilot unit and at least 10:1 for the full-scale tower. The type and size of
the packing used in the full-scale unit shall be the same as that used in the
pilot study.
3. The minimum
volumetric air to water ratio at peak water flow shall be 25:1 and the maximum
shall be 80:1. Air to water ratios outside of these ranges may be justified to
the department by pilot testing under s.
NR 811.44.
(c) The water flow system shall meet all of
the following requirements:
1. Water shall be
distributed uniformly at the top of the tower using spray nozzles or
orifice-type distributer trays that prevent short circuiting.
2. A mist eliminator shall be provided above
the water distributor system.
3. A
side wiper redistribution ring shall be provided at least every 10 feet in
order to prevent water channeling along the tower wall and short
circuiting.
4. Smooth-end sample
faucets shall be provided on the influent and effluent piping.
5. The effluent sump shall have easy access
for inspection and cleaning.
6. A
pump to waste line shall be provided in the effluent piping to allow for
discharge of water and chemicals used to clean the tower.
7. The design shall prevent freezing of the
influent riser and effluent piping when the unit is not operating. If piping is
buried, it shall be maintained under positive pressure higher than the ground
surface.
8. The water flow to each
tower shall be metered.
9. Include
an overflow line that discharges 12 to 24 inches above a splash pad or drainage
inlet. Proper drainage shall be provided to prevent flooding of the
area.
10. Butterfly valves may be
used in the water effluent line for better flow control and to minimize air
entrainment.
11. Include means to
prevent flooding of the air blower.
12. The water influent pipe shall be
supported separately from the tower's main structural support.
(d) The air flow system shall meet
all of the following requirements:
1. The air
intake and outlet vent shall be protected with a 24-mesh corrosion resistant
screen and cover and be accessible for maintenance and inspection.
2. The air inlet shall be in a location
protected from airborne contaminants.
3. An air flow meter or an alternative method
to determine air flow shall be provided on the influent air line.
4. A positive air flow sensing device and a
pressure gauge shall be installed on the air influent line. The positive air
flow sensing device shall be a part of an automatic control system that will
turn off the influent water if positive air flow is not detected. The pressure
gauge shall serve as an indicator of the fouling buildup. The backup motor for
the air blower shall be readily available.
(e) Other design features shall meet all of
the following requirements:
1. Include a
sufficient number of access ports with a minimum diameter of 24 inches to
facilitate inspection, media replacement, media cleaning, and maintenance of
the interior.
2. Include a method
of cleaning the packing material when fouling may occur.
3. Tower effluent collection and pumping
wells shall be constructed to potable reservoir construction standards as
required under subch. IX.
4.
Include provisions for extending the tower height without major
reconstruction.
5. Include
disinfection application points both ahead of and after the tower to control
biological growth.
6. Include
disinfection and adequate contact time after the water has passed through the
tower, prior to the distribution system.
7. Include adequate packing support to allow
free flow of water and prevent deformation with deep packing heights.
8. Include adequate foundation to support the
tower and lateral support to prevent overturning to wind loading.
9. Include protections to prevent vandalism
to the tower.
10. Provide access of
all components of the tower, including the exhaust port and demister.
11. The operation of the blower and chemical
feed pump shall be interlocked with the operation of the appropriate well or
service pump.
(4) OTHER METHODS OF AERATION. Other methods
of aeration may be approved by the department only if a pilot plant study
conducted in accordance with s.
NR 811.44 demonstrates the method's effectiveness.
Methods include spraying, diffused air, and mechanical aeration. The treatment
processes shall be designed to meet the particular needs of the water to be
treated.
(5) DISINFECTION. Aerated
water other than from pressure aeration shall receive continuous disinfection
treatment. A corporation stop shall be provided on the inlet piping to all
non-pressure aerators to allow disinfection for emergency or maintenance
purposes.
(6) PROTECTION FROM WIND.
Aerators that discharge through the atmosphere shall be protected by being
placed in a louvered enclosure designed to provide easy access to the
interior.
(7) PROTECTION FROM
CONTAMINATION. Aerators that are used for oxidation or removal of dissolved
gases from waters that will be given no further treatment other than
chlorination shall be protected from contamination from insects and birds,
obnoxious fumes, all types of precipitation and condensation, and windborne
debris or dust.
(8) BYPASS PIPING.
Bypass piping and any associated valves or other appurtenances shall be
installed to allow water to be bypassed around a non-pressure aerator unless
the aerator is necessary to comply with primary maximum contaminant levels or
the requirement is waived by the department because the water system has access
to other water sources that can provide at least an average day supply of
water.
(9) REDUNDANCY. Redundant
aeration systems shall be provided for units installed to comply with primary
maximum contaminant levels unless the requirement is waived by the department
because the water system has access to other water sources that can provide at
least an average day supply of water.
(10) WATER QUALITY. A metal smooth-end
sampling faucet installed on the aerator outlet piping and test equipment shall
be provided to test for appropriate water quality parameters following aeration
such as dissolved oxygen, pH, iron, manganese, radon gas, and carbon dioxide
when required by the department to insure proper operation of the aeration
equipment.
