020-11 Wyo. Code R. §§ 11-11 - General Treatment Plant Considerations
(a) Surface water
protection. Discharges to surface waters shall meet or exceed quality
limitations in the National Pollution Discharge Elimination System permit.
Plant configurations and piping shall be arranged to avoid the bypassing of
process units that could result in inadequately treated sewage reaching the
receiving surface water.
(b)
Groundwater protection. Seepage and/or discharge to groundwater shall comply
with Chapter 8 of the Water Quality Regulations. Plan configurations and piping
shall be arranged to avoid the bypassing of process units that could result in
inadequately treated sewage reaching the groundwater.
(c) Siting requirements.
(i) Isolation. Treatment facilities shall be
located to minimize public and private nuisances and health hazards on
inhabited areas or residential areas. Where treatment plant siting does
potentially affect inhabited areas, appropriate measures to minimize nuisances
or hazards shall be incorporated in the design.
(ii) Flood protection. All treatment process
structures, mechanical equipment, and electrical equipment shall be protected
from the 100-year flood. The treatment facilities shall remain fully
operational and accessible during the 25-year flood.
(d) Hydraulic and treatment reliability.
(i) Alternative power source. All treatment
plants shall have an alternative source of power to provide reliable pumping
and disinfection of sewage if required. The alternative source of power shall
be sized to provide the capability to pump design maximum day flow rates
through the treatment process and to disinfect the sewage if necessary.
Acceptable alternative power sources include:
(A) A diesel, natural gas, or propane fueled
engine generator.
(B) A second
independent electrical supply.
(C)
Storage of sewage and subsequent treatment
(ii) Bypass treatment units. Complete
by-passing of treatment units is prohibited. Provide means to bypass any
duplicate process unit or single unit where adequate downstream process
capability is provided. Sewage shall be treated in parallel singular units
and/or subsequent processes.
(iii)
Multiple units. For average design flows greater than 100,000 gpd (378
m3/d), more than one unit of each unit process shall
be provided. For average design flows of less than 100,000 gpd (378
m3/d), one unit of each unit process may be provided
if electrical or mechanical equipment or diffusers can be removed while the
unit is in operation, or if the unit can be compartmentalized to permit access.
There shall be no provision to bypass the entire plant nor shall bypass
provisions be made that will allow inadequately treated sewage to reach the
ground or surface waters.
Where more than one parallel unit is provided, positive means of dividing the flow proportionally between units shall be included (such as splitter weirs or valves and meters).
(iv) Multiple equipment. Mechanical process
equipment shall be provided in multiple units. All pumping functions shall
include sufficient pumping capacity that the peak flow can be pumped with the
largest single unit not in service. Blowers and mechanical aerators for process
aeration shall include sufficient capacity that the maximum day design capacity
can be delivered with the largest single unit not in service. Other equipment
shall have standby units where their function is critical to the treatment
process.
(e) Electrical.
(i) Equipment location. Service transformers
and other critical electrical equipment shall be located above the 100-year
flood and above grade. Transformers shall be located in a manner that they are
remote from or protected by substantial barriers from traffic. Motor controls
shall be located in superstructures and in rooms that do not contain sewage,
chemical processes, or corrosive atmospheres.
(ii) Code requirements. All electrical work
shall comply with the National Electrical Code as enacted and amended by the
Wyoming Department of Fire Prevention and Electrical Safety. Areas in which the
occurrence of explosive concentrations of hazardous gases or flammable fluids
can occur Class 1, groups C and D, Division 1 locations shall be designed for
hazardous locations in accordance with the National Electrical Code.
(f) Structural.
(i) Construction materials. Construction
materials shall be selected, apportioned, and/or protected to provide water
tightness, corrosion protection, and resistance to weather
variations.
(ii) Coatings. Coatings
used to protect structures, equipment and piping shall be suitable for
atmospheres containing hydrogen sulfide and volatile organics. Surfaces exposed
in chemical areas shall be protected from chemical attack. Concrete surfaces in
confined spaces containing sewage shall be protected. Paints containing lead or
mercury shall not be used.
(iii)
Geological conditions. Structural design shall consider the seismic zone,
groundwater and soil support. Soils investigations shall be made, or adequate
previous soils investigations shall be available to develop structural
design.
(g) Safety. The
Wyoming Occupational Health and Safety Rules and Regulations shall be complied
with. The following items shall also be provided:
(i) Instruction manuals. Instruction manuals
shall be provided for all mechanical and electrical equipment describing
operation, maintenance, and safety.
(ii) Handrails. In addition to all Wyoming
OSHA requirements, barriers around treatment basins shall be
provided.
(iii) Warning Signs.
Provide warning signs for nonpotable water, electrical hazards, chemical
hazards, or other unsafe features. Warning signs shall be permanently attached
to the structure or appropriate equipment.
(iv) Equipment guards. Provide shields to
protect from rotating or moving machinery.
(v) Lighting. Provisions shall be made to
light walkways, paths, and other accessways around basins, in buildings and on
the site. All areas shall be lit in a manner that the failure of one lighting
fixture will not cause an area to be dark, or the loss of power will not cause
a room or enclosed area to be dark.
(vi) Climate conditions. Design of facilities
such as exposed stairs, walkways, and sidewalks shall include nonskid
surfaces.
(h)
Instrumentation.
(i) Location. A flow
measuring device shall be provided for the plant effluent unless it is a
mechanical plant where an influent flow measuring device will be
acceptable.
(ii) Type. For plants
having an average design flow of 50,000 gpd (189
m3/d) or more, the flow
measuring device shall provide recording of instantaneous flow rate, enable
calculation of average daily flow rate and have provisions for calibration and
correction.
(iii) Controls.
Automatic controls shall be designed to permit manual override.
(iv) Alarms. Conditions that may affect
discharge quality or personnel or public safety shall be alarmed at an attended
location.
(i) Sampling.
Access shall be provided to sample untreated wastewater ahead of the treatment
facilities prior to adding any process return flows, and sampling of the
effluent after all treatment process units, but before discharge to the
receiving stream. An automatic sampler that composites samples in proportion to
the flow rate on the effluent shall be provided if required by the NPDES
permit.
(j) Ventilation. All
enclosed spaces shall be provided with forced ventilation, excepting pumping
station wetwells, scum pits, anaerobic process units, and man-holes. In areas
where there are open sewage channels, wet pits exposed to the room or process
units without gas tight enclosures, ventilation shall be provided to maintain a
higher pressure in the room than atmospheric and shall provide twelve (12) air
changes per hour. In equipment rooms, ventilation shall be provided to limit
the temperature rise in the room to less than 15° F (8° C) above
ambient, but not less than six air changes per hour. Rooms housing chlorine
storage and/or feeders shall have provisions for exhausting the room contents
in two (2) minutes and continuous ventilation to provide twelve (12) air
changes per hour.
(k) Dewatering of
treatment units. All treatment units, channels, housing screens, or other
embedded equipment, and wetwells shall be provided with drains or sumps that
facilitate draining the unit for access and maintenance. Drainage shall be to
upstream process units. Basin slabs shall be designed to successfully resist
the hydrostatic uplift pressure or relief valves shall be provided.
(l) Cold weather protection. All equipment
including pumps, bar screens, grit washers, electrical equipment and other
equipment not required to be in or on open basins (such as clarifier drives and
surface aerators) shall be housed in heated, lighted, and ventilated
structures. Structure entrances shall be above grade. Piping shall be buried
below frost level, placed in heated structures, or provided with heat and
insulated. Walkways shall be located away from areas of spray and/or ice
buildup.
(m) Chemical storage. All
chemical storage shall be housed or buried. Areas designated for storage of
specific chemicals shall be separated from areas designated for other reactive
chemicals. Liquid storage containers shall be isolated from other portions of
the structure by a curb that will contain and/or drain ruptured tank contents.
Concrete floors, walls and curbs in chemical storage and feed areas shall be
coated to protect the concrete from aggressive chemicals. Floors in polymer
feed and storage areas shall be provided with nonslip surfaces. Rooms for
chlorine storage and feed equipment shall be gas tight and be provided with
entry from outdoors. All toxic chemical storage areas shall be provided with
lighting and ventilation that are switched from outside the room, and windows
to permit viewing the room from outside.
(n) Design capacities.
(i) Flow. In the absence of flow measurement
information, the design average daily flow shall be based on a per capita daily
flow rate of 100 gallons (378 liters). Allowances shall be made for return
flows from digesters, sludge thickeners and the like, and the infiltration and
wet weather inflow into older sewer systems. Significant industrial waste flows
shall be added to the per capita flow rate.
(ii) Organic loads. In the absence of
wastewater strength data, domestic waste treatment design shall be based on a
per capita daily BOD and suspended solids contribution of 0.22 lb (0.10 kg) and
0.25 lb (0.11 kg), respectively. The influence of sidestream return flows and
significantly strong industrial wastes shall be considered and included in the
design where applicable.
Notes
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No prior version found.