Utah Administrative Code
Topic - Environmental Quality
Title R317 - Water Quality
Rule R317-3 - Design Requirements for Wastewater Collection, Treatment and Disposal Systems
Section R317-3-8 - Disinfection
Universal Citation: UT Admin Code R 317-3-8
Current through Bulletin 2024-06, March 15, 2024
8.1. General
A. All wastewaters containing pathogens or
coliform bacteria must be disinfected before discharge to a water course. The
disinfection procedures must consider any effect on the natural aquatic habitat
and biota of the receiving water course. Effectiveness of disinfection also
varies with BOD5 and suspended solids in the effluent.
If chlorination is utilized, it may be necessary to dechlorinate if the
residual chlorine level would otherwise impair the receiving water course. The
applicant must submit justification to the Director for the determination of
the acceptability of any disinfection system other than chlorination or
ultraviolet irradiation.
B. If
effluent to be discharged meets applicable bacteriologic standards before
disinfection, the Director may waive the disinfection process. However, all
plants must have an ability to introduce a disinfectant in the effluent with
proper reaction time before discharge. An example could be multi-celled (more
than three cells) lagoon discharge following extended storage in excess of 150
days.
C. The disinfection method
should be selected after due consideration of wastewater flow rates,
application rates, demand rates and effects, pH of the wastewater, cost of
equipment, availability, maintenance, reliability and safety
problems.
D. Chlorine is the most
commonly used chemical for wastewater disinfection. The forms most often used
are liquid-gaseous chlorine and sodium and calcium hypochlorite. The Director
may review and accept other disinfection methods based on the information
submitted.
8.2. Design
A. Capacity of System
1. Required disinfection capacity will vary,
depending on the uses and points of application of the disinfectant, e.g.,
prechlorination, post chlorination, odor and process control uses,
etc.
2. For disinfection of the
wastewater before its discharge to a water course, the disinfection system
capacity shall be sufficient to produce an effluent that will meet the coliform
bacteria limits specified for that installation at all times. This condition
must be attainable when maximum flow rates occur and during emergency
conditions. For non-chemical disinfecting systems, an equivalent installed
capacity shall be provided. Normal dosage requirements for disinfection will
vary with the quality of effluent to be treated.
3. Duplicate disinfection systems shall be
provided. Where only two units are installed, each shall be capable of feeding
the expected maximum dosage rate.
4. Disinfection system equipment should be
provided with necessary changeable parts to permit operation of system at
initial anticipated flows at mid-scale on flow meters and other devices. Spare
parts shall be provided for all disinfection equipment to replace parts which
are subject to wear and breakage. Operation and maintenance data for all
equipment shall be furnished.
5.
Dosage control based on effluent flow rate should be provided because of the
diurnal variations in the disinfectant demand of the wastewater. A residual
disinfectant concentration must be maintained to insure the pathogen
destruction, and subsequent reactivation, if any.
B. Contact Period
1. For a chlorination system, a minimum
contact period is required after a thorough mixing of disinfectant with the
effluent. The minimum contact period shall be greater of:
a. 30 minutes at the maximum design rate of
flow (peak daily rate of flow) or the maximum pumping rate, or
b. 60 minutes at the average design rate of
flow.
2. This contact
period shall normally be provided in the contact tank. Contact period in
pipeline or outfalls before discharge into a water course, may be credited
towards the contact time if the effluent discharge point can be
sampled.
C. Contact
Chambers
1. The contact chambers must be
designed such that:
a. effectiveness of
disinfection is maximized;
b.
accumulation of solids is minimized;
c. maintenance and cleaning is facilitated;
and
d. short circuiting of flow is
reduced to a practical minimum by installation of baffles.
2. Two tanks are required for all plants
treating more than 1 million gallons per day (3,785 cubic meters per day).
Means of removal of solids from the tank bottom shall be provided. Solids and
drainage water must be returned to the head end of the plant. Skimming devices
should be provided in all contact tanks. Covered tanks must have means of
access for maintenance and cleaning.
3. Pipelines and outfall sewers may be
acceptable as effective plug-flow contact chambers.
4. The applicant must incorporate all of the
above process and design features in devices using other disinfecting
methods.
D. Point of
Application
1. The design shall provide for
application of chlorine or other disinfectants to all fully treated, partially
treated, or untreated wastewater discharged from the treatment plant. Other
points of application shall be incorporated in the design for process
considerations such as prechlorination, odor control, control of sludge
bulking, etc. All application points shall be submerged below the wastewater
surface.
2. Chlorine shall be
positively mixed as rapidly as possible, with a complete mix being effected in
three seconds. This may be accomplished by either the use of turbulent flow
regime or a mechanical flash mixer.
8.3. Disinfection Methods
A. Chlorination (Liquid or Gaseous Chlorine)
1. Equipment
a. The installed capacity of a chlorine feed
system shall be sufficient to provide a dosage of 25 milligrams per liter at
the maximum design rate of flow. Procedures recommended by the Chlorine
Institute and the Occupational Safety and Health Administration, the US
Department of Labor, and succeeding organizations should be carefully followed
in handling, installation, operation and maintenance of chlorination equipment.
The requirements, procedures and recommendations from these organizations take
precedence over the requirements stated herein, if more stringent.
b. Liquid chlorine lines from tank cars to
evaporators shall be buried and installed in a conduit and shall not be exposed
in below grade spaces. Systems shall be designed for the shortest possible pipe
transportation of liquid chlorine. When chlorine cylinders are used, two
scales, indicating and recording type, should be used for weighing the
cylinders in use. Each scale should be sized to accommodate the maximum number
of cylinders required to deliver chlorine at the maximum chlorine feeding rate.
Adequate means for supporting cylinders on the scales should be provided.
Scales shall be of corrosion-resistant material.
c. Separate manifolds shall be provided for
the bank of cylinders on each scale. The manifolds shall be properly valved so
that one bank of cylinders may be replaced while chlorine is being withdrawn
from the other bank of cylinders. Provision should be made for automatically
changing the withdrawal of chlorine from one bank of cylinders to the second
when the chlorine in the first bank of cylinders has been exhausted.
d. Gas chlorinators shall be of the solution
feed type. The design capacity of evaporators must correspond to gaseous
chlorine demand, where several cylinders or ton containers are manifolded to
evaporate sufficient chlorine. Chlorine gas systems and piping should be of
vacuum type.
2. Housing
and Storage
a. Local, state and federal
safety requirements, including fire code, shall be carefully followed in
storing and handling of chlorine containers, cylinders or tank cars.
b. Gaseous chlorine and chlorination
equipment rooms shall be isolated from other sections of the building by
gas-tight partitions. Separation of the chlorine storage room and the
chlorination equipment room is required for safety. All doors and rooms
containing gas chlorination equipment and rooms used for chlorine gas storage
should open only to the outside of the building, and all doors should be
equipped with panic hardware and a viewing window. Multiple exits to the
outside should be provided for each room in which chlorine gas is stored or
used. Rooms housing chlorination equipment should be heated to 70 degrees
Fahrenheit (21 degrees Centigrade), but never in excess of normal summer
temperatures. Rooms containing chlorine cylinders from which chlorine is being
withdrawn should be heated to above 60 degrees Fahrenheit (16 degrees
Centigrade), but never above the temperature of the equipment room. Where
chlorine containers are stored out of doors, the storage area shall be provided
with a canopy. Similar precautions should be taken for tank cars. Also, if
containers are stored out of doors, cylinders and containers must be allowed to
reach room temperature before being placed in use. Floor drains from chlorine
rooms must not be connected to floor drains from other rooms.
c. Chlorine rooms shall be at ground level,
and should permit easy access to all equipment. The storage area should be
separated from the feed area. Chlorination equipment should be situated as
close to the application point as reasonably possible.
3. Ventilation and Heating
a. With chlorination systems, forced,
mechanical ventilation shall be installed which will provide one complete air
change per minute when the room is occupied.
b. When unoccupied, facilities in the
ventilation system may be provided with means to reduce the number of air
changes to twenty per hour to conserve energy. Whenever such a two-speed
ventilation system is used, adequate provisions shall be made to insure that
one complete air change per minute is provided when the room is
occupied.
c. The entrance to the
air exhaust duct from the room shall be near the floor and the point of
discharge shall be so located as not to contaminate the air inlet to any
buildings or inhabited areas.
d.
Air inlets shall be so located as to provide cross ventilation with air and at
such temperature that will not adversely affect the chlorination equipment. The
vent hose from the chlorinator shall discharge to the outside atmosphere above
grade or to the scrubbing system.
e. Switches for exhaust fans and cylinders
shall be kept at essentially room temperature.
f. Chlorine scrubbing systems should be
incorporated in the design of handling and storage areas where required by the
state or local codes.
4.
Ancillary Services
a. Water Supply. An ample
supply of water meeting a minimum of secondary effluent quality, R317-1,
Definitions and General Requirements, shall be available for operating the
chlorinator. All in-plant use of effluent shall be taken from downstream of the
sampling point for effluent quality monitoring and permit compliance. Where a
booster pump is required, a standby booster pump shall be provided, and standby
power shall be available.
b. Other
Equipment. All electrical fixtures and drainage conduits in chlorination
equipment rooms and chlorine storage rooms shall be gas-tight to prevent the
spread of chlorine gas in the event of a leak.
5. Piping and Material. Piping systems should
be as simple as possible, specifically selected and manufactured to be suitable
for chlorine service, with a minimum number of joints. Piping should be well
supported and protected against temperature extremes. Low pressure lines made
of hard rubber, saran-lined, rubber-lined, polyethylene, polyvinyl chloride
(PVC), or Uscolite materials are satisfactory for wet chlorine or aqueous
solutions of chlorine.
6.
Reliability. The design of the system must include the necessary provisions
that will either prevent failures or allow immediate corrective action to be
taken. Standby power, duplicate equipment and water storage shall be
incorporated in the design to prevent interruption of feed, water supply and
backup to power and equipment failures.
7. Residual Monitoring
a. An indicating and recording type residual
chlorine analyzer using accepted test procedures shall be installed to monitor
residual chlorine as required in the discharge permit.
b. Where dechlorination is used, residual
chlorine analyzers shall be equipped with audible and visual alarms to indicate
discharge of chlorine in the effluent.
8. Safety
a. At least two complete sets of respiratory
air-pac protection equipment, meeting the requirements of the Occupational
Safety and Health Administration (OSHA), shall be available where chlorine gas
is handled, and shall be stored at a convenient location, but not inside any
room where chlorine is used or stored. Instructions for using the equipment
shall be posted near the equipment. The equipment shall, using compressed air,
have at least 30-minute capacity, and be compatible with the equipment used by
the fire department responsible for the plant.
b. Where ton containers or tank cars are
used, a leak repair kit approved by the Chlorine Institute shall be provided.
Caustic soda solution reaction tanks for absorbing the contents of leaking ton
containers must be provided where such containers are in use. The installation
of automatic gas detection and related alarm equipment must be
provided.
B.
Ultraviolet Irradiation
1. The Director will
consider and approve the use of ultraviolet irradiation for disinfection of
wastewater treatment plant effluent based on the information submitted.
Effectiveness of this system depends upon shallowness of depth or contact
volume at the point of application and relative absence of suspended solids.
a. The applicant must submit supporting data
describing the proposed system and including such items as contact geometry
between the ultraviolet light source and water, reliability, and suitability of
the effluent for this process. Designs should be investigated for sound
application of the fundamentals of UV disinfection theory.
b. The design shall be based on factors such
as, plug-flow hydraulics, intimate contact with the UV light for a sufficient
period, short-circuiting, illumination. Tracer test results are helpful in
assessment of hydraulic characteristics.
c. Materials of construction should be
consistent with the wastewater and environment.
2. The design of ultraviolet disinfection
systems shall be based on on-site testing and the following considerations:
a. Wastewater characteristics. Concentration
of total suspended solids (TSS), calcium, magnesium, iron, etc., should be such
that UV disinfection is effective. The wastewater should contain low levels of
total suspended solids, preferably 20 milligrams per liter or below, and must
transmit at least 50 percent of UV light through a wastewater depth of one (1)
centimeter.
b. Layout
(1) Adequate space around the UV units to
accommodate maintenance activities is required.
(2) Easy removal and replacement of lamps
without the use of special tools by one man should be a feature of the
equipment design.
(3) The ballasts
should be arranged for ready and unhindered access for removal or replacement
of any ballast without having a need to remove others.
(4) The layout design must provide adequate
floor space for any separate components of the UV system in addition to the UV
reactor itself, including requirements for power supply cabinets or cleaning
equipment.
(5) Modular design with
multiple units to allow uninterrupted service when performing maintenance must
be specified.
3. Electrical Requirements
a. power consumption of this process alone
should be separately metered.
b. UV
lamps and ballasts must be properly matched. The proper matching of lamp and
ballast will improve the lamps output and extend its useful life.
c. arrangements for shutting off banks of
lamps within a single unit must be provided for lamp replacement or
maintenance.
d. power controls
should be provided for matching output of lamps with the rate of flow, and
system maintenance by the plant staff.
e. minimum electrical standards of
construction shall conform to the National Electrical Code, and other
applicable codes and standards, consistent with the location or environment
surrounding the UV unit and associated equipment.
4. Ventilation. Adequate ventilation to the
structure housing the electrical components of the system must be provided to
prevent failures from overheating.
5. Cleaning
a. The various means of chemical cleaning
available must be evaluated. The evaluation must cover methods required for the
unit to be drained; volume of cleansing agent required per cleaning;
disposition of spent cleaning solution; manpower requirements to accomplish a
cleaning cycle; capital costs of the cleaning and equipment; cleaner cost
availability; and special storage and handling needs.
b. The system design must provide for
complete draining and easy cleaning.
c. Ultrasonic cleaning must be considered for
prevention of biofilm growth on non-illuminated quartz sleeves.
6. Monitoring and Instrumentation
i. Adequate staffing and resources to conduct
the data collection and monitoring required for assessing performance must be
provided.
ii. Each individual lamp
output shall be measured and recorded.
8.4. Dechlorination
A. Sulfur Dioxide
(SO2)
1. Sulfur
dioxide is most readily available in liquid (gaseous) form in ton containers
similar to chlorine. Approximately, 1 milligram per liter of sulfur dioxide is
required to dechlorinate 1 milligram per liter of chlorine residual (free or
combined).
2. The dechlorination
reaction between sulfur dioxide and both free and combined chlorine is a rapid
reaction and requires only a few seconds of contact. The design of sulfur
dioxide system must be based on the following considerations:
a. Equipment. Generally sulfur dioxide shall
be fed as a gas similar to chlorine gas, as described in R317-3-8. The sulfur
dioxide header should be heated to prevent re-liquefaction.
b. Housing and Storage. These requirements
are same as to those for chlorine, as described in R317-3-8.
c. Ventilation. These requirements are same
as to those for chlorine, as described in R317-3-8.
d. Ancillary Services. These requirements are
same as to those for chlorine, as described in R317-3-8.
e. Piping and Material. Pipe material
(plastics) inside the sulfonator must be compatible with continuous exposure to
sulfur dioxide gas.
f. Reliability.
These requirements are same as to those for chlorine, as described in
R317-3-8.
g. Residual Monitoring.
Control is critical when sulfur dioxide is used as the dechlorinating agent
because excess sulfur dioxide consumes excess dissolved oxygen in the
wastewater or receiving waters. The dechlorination reaction between sulfur
dioxide and both free and combined chlorine is rapid, a few seconds at the
most, so sampling can be performed immediately downstream of good mixing. The
system should be monitored with a residual chlorine analyzer.
h. The design shall incorporate reaeration of
the effluent to be in compliance with the dissolved oxygen requirement, if any,
of the discharge permit.
i. Safety
(1) Adequate precautions must be taken for
storing sulfur dioxide as it is a potentially hazardous chemical to
store.
(2) Provide the same amount
of air changes per hour as would be required for chlorine, together with a
sulfur dioxide sensing and alarm detector.
B. Other Dechlorinating Agents.
The Director may review and approve other methods and chemicals for
dechlorination based on the information submitted.
Disclaimer: These regulations may not be the most recent version. Utah may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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