| (1) Pretreatment. Wastewater stabilization ponds shall
be preceded by facilities for primary sedimentation of the raw sewage.
Aerated lagoons or facultative lagoons may be utilized in place of
conventional primary treatment facilities.
(2) Imperviousness. All earthen structures proposed
for use in domestic wastewater treatment or storage shall be constructed
to protect groundwater resources. Where linings are necessary, the
following methods are acceptable:
(A) in-situ or placed clay soils having the following
qualities may be utilized for pond lining:
(i) more than 30% passing a 200-mesh sieve;
(ii) liquid limit greater than 30%;
(iii) plasticity index greater than 15; and
(iv) a minimum thickness of two feet;
(B) membrane lining with a minimum thickness of 20
mils, and an underdrain leak detection system;
(C) other methods with commission approval.
(3) Distribution of flow. Stabilization ponds shall
be of such shape and size to insure even distribution of the wastewater
flow throughout the entire pond. While the shapes of ponds may be
dictated to some extent by the topography of the location, long narrow
ponds are preferable and they should be oriented in the direction
of the prevailing wind such that debris is blown toward the inlet.
Ponds with narrow inlets or sloughs should be avoided.
(4) Access area. Storm water drainage shall be excluded
from all ponds. All vegetation shall be removed from within the pond
area during construction. Access areas shall be cleared and maintained
for a distance of at least 20 feet from the outside toes of the pond
embankment walls.
(5) Multiple ponds. The use of multiple ponds in pond
systems is required. The operation of the ponds shall be flexible,
enabling one or more ponds to be taken out of service without affecting
the operation of the remaining ponds. The ponds shall be operated
in series during routine operation periods.
(6) Organic loading. The organic loading on the stabilization
ponds, based on the total surface area of the ponds, shall not exceed
35 pounds of BOD5 per acre per day. The
loading on the initial stabilization pond shall not exceed 75 pounds
of BOD5 per acre per day.
(7) Depth. The stabilization ponds or cells shall have
a normal water depth of three to five feet.
(8) Inlets and outlets. Multiple inlets and multiple
outlets are required. The inlets and outlets shall be arranged to
prevent short circuiting within the pond so that the flow of wastewater
is distributed evenly throughout the pond. Multiple inlets and outlets
shall be spaced evenly. All outlets shall be baffled with removable
baffles to prevent floating material from being discharged, and shall
be constructed so that the level of the pond surface may be varied
under normal operating conditions. Submerged outlets shall be used
to prevent the discharge of algae.
(9) Embankment walls. The embankment walls should be
compacted thoroughly and compaction details shall be covered in the
specifications. Soil used in the embankment shall be free of foreign
material such as paper, brush, and fallen trees. The embankment walls
shall have a top width of at least 10 feet. Interior and exterior
slope of the embankment wall should be one foot vertical to three
feet horizontal. There shall be a freeboard of not less than two feet
nor more than three feet based on the normal operating depth. All
embankment walls shall be protected by planting grass or riprapping.
Where embankment walls are subject to wave action, riprapping should
be installed. Erosion stops and water seals shall be installed on
all piping penetrating the embankments. Provisions should be made
to change the operating level of the pond so the pond surface can
be raised or lowered at least six inches.
(10) Partially mixed aerated lagoons.
(A) Horsepower. With partially mixed aerated lagoons,
no attempt is made to keep all pond solids in suspension. Mechanical
or diffused aeration equipment should be sized to provide a minimum
of 1.6 pounds of oxygen per pound of BOD5 applied
with the largest unit out of service. Where multiple ponds are used
in series, the power input may be reduced as the influent BOD5 to each pond decreases. proposed oxygen transfer
rates in excess of two pounds per horsepower-hour must be justified
by actual performance data.
(B) Pond sizing. Partially mixed aerated lagoons should
be sized in accordance with the formula in subsection (i)(3) of this
section using K-0.28. Pond length to width ratios should be three
to one or four to one.
(C) Imperviousness. Requirements for imperviousness,
multiple cells, embankment walls, and inlets and outlets shall be
the same as for other secondary treatment ponds.
(k) Facultative lagoon (raw wastewater stabilization
pond).
(1) Configuration. The length to width ratio of the
lagoon should be three to one, with flow along the length from inlets
near one end to outlets at the opposite end (other configurations
may be approved if adequate means of prevention of short circuiting
are provided). The length should be oriented in the direction of the
prevailing winds with the inlet side located such that debris will
be blown toward the inlet (generally, the north-northwest side). Inlet
baffles shall be provided to collect flotable material. The outlets
shall be constructed so that the water level of the lagoon may be
varied under normal operating conditions. Storm water drainage shall
be prevented from entering the lagoon. The design engineer may wish
to locate the facultative lagoon in a central location with regard
to the surrounding secondary ponds to facilitate compliance with the
buffer zone requirement specified in Chapter 309 of this title (relating
to Domestic Wastewater Effluent Limitations and Plant Siting).
(2) Imperviousness. Requirements for imperviousness
shall be the same as those for secondary treatment ponds.
(3) Depth. The portion of the lagoon near the inlets
shall have a 10 to 12 foot depth to provide sludge storage and anaerobic
treatment. This deeper portion should be approximately 25% of the
area of the lagoon bottom. The remainder of the pond should have a
depth of five to eight feet.
(4) Organic loading. The organic loading, based on
the surface area of the facultative lagoon, shall not exceed 150 pounds
of BOD5 per acre per day.
(5) Odor control. The facultative lagoon shall have
multiple inlets and the inlets should be submerged approximately 24
inches below the water surface to minimize odor but not disturb the
anaerobic zone. Capabilities for recirculation at 50% to 100% of the
design flow should be provided. Care should be taken to avoid situations
where siphoning of lagoon contents through submerged inlets can occur.
(6) Embankment walls. Refer to subsection (j)(9) of
this section.
(7) Subsequent treatment. The facultative lagoon effluent
will normally be routed to a wastewater stabilization pond system
for secondary treatment. In designing the stabilization pond system,
it may be assumed that BOD removal in the facultative lagoon is 50%.
The stabilization pond system shall contain two or more ponds.
(l) Filtration. Filtration must be employed as a unit
operation to supplement suspended solids removal for those treatment
facilities with tertiary effluent limitations (suspended solids effluent
quality equal to or less than 10 mg/liter). Filtration may be employed
as a unit operation for those treatment facilities with secondary
or advanced secondary effluent limitations. The utilization of filtration
in the design of the treatment facility normally provides effective
removal of suspended biological floc and neutral density trash material
which may remain in secondary clarifier effluent. Intermittent filter
operation is acceptable where on line controls monitor plant performance
or filters are not necessary to meet a specific discharge limitation.
(1) General requirements.
(A) Filter units shall be preceded by final clarifiers
designed in accordance with subsection (d) of this section for secondary
treatment criteria.
(B) Filtered effluent, and not potable water, shall
be utilized as the source of backwash water.
(2) Deep bed, intermittently backwashed granular media
filters.
(A) Single media (sand filters), dual media (anthracite-sand
filters), or mixed media filter types (nonstratified anthracite, sand,
garnet, or other media) are acceptable for application; however, single
media filters shall be designed for maximum filtration runs of six
hours between backwash periods.
Cont'd... |
