Current through Bulletin 2024-06, March 15, 2024
4.1. Plant Location
A. The treatment plant structures and all
related equipment shall be protected from physical damage by the 100-year
flood. Treatment works must remain fully operational and accessible during the
25-year flood.
B. These conditions
shall apply to all new facilities under construction as well as the existing
facilities being expanded, upgraded or modified.
4.2. Quality of Effluent. The effluent
requirements and water quality standards established in the discharge permit,
R317-1 (Definitions and General Requirements), R317-2 (Standards of Quality for
Waters of the State) shall be used to determine the required degree of
wastewater treatment, and unit processes and operations.
4.3. Design
A. Basis of Design. The plant design shall be
based on the higher value of:
1. a moving
average of daily rates of flow and wastewater strength as measured by five-day
biochemical oxygen demand (BOD5) and suspended solids
determination tests over a period of 30 consecutive days; or
2. an average of values rate of flow and
wastewater strength as measured by five-day biochemical oxygen demand
(BOD5) and suspended solids determination tests, over a
period of month; or
3. the rate of
flow and wastewater strength as measured by five-day biochemical oxygen demand
(BOD5) and suspended solids determination tests, equal
to or greater than 92 percent of the daily flow rate and wastewater strength
data.
B. Hydraulic
Design. The hydraulic capacities of all units and conveyance structures shall
be computed and checked for the maximum and average design rates of flow with
one largest unit out of service. No overtopping of any structure under any
condition shall be permitted.
1. New Systems.
The design for sewage treatment plants shall be based upon an average daily per
capita flow of 100 gallons (0.38 cubic meter) unless the applicant provides and
justifies a better estimate of flow based on water use data. An allowance shall
be made in the design for industrial wastewaters and rates of
infiltration/inflow.
2. Existing
Systems. For an existing system, the applicant may use the data based on both
dry- weather and wet-weather conditions. The data over a minimum period of one
year shall be taken as the basis for the design.
C. Organic Design
1. New System Design
a. Domestic waste treatment design shall be
on the basis of at least 0.17 pounds (0.08 kilogram) or 200 milligrams per
liter of BOD5 per capita per day and 0.20 pounds (0.09
kilogram) or 250 milligrams per liter of suspended solids per capita per day,
unless information is submitted to justify alternate designs.
b. When garbage grinders are used in areas
tributary to a domestic treatment plant, the design basis may be increased to
0.22 pounds (0.10 kilogram) or 260 milligram per liter of
BOD5 per capita per day and 0.25 pounds (0.11 kilogram)
or 300 milligram per liter of suspended solids per capita per day.
c. An allowance shall be made in the design
for industrial wastewaters and rates of infiltration/inflow.
d. Other approved methods for measurement of
organic strength of wastewater published in Standard Methods for Examination of
Water and Wastewater, jointly prepared by American Public Health Association
(APHA), American Society of Civil Engineers (ASCE), American Water Works
Association (AWWA), and Water Pollution Control Federation (WPCF), will be
accepted in lieu of the five-day biochemical oxygen demand
(BOD5) test.
2. Existing Systems
a. For an existing system, the applicant may
use the data based on the actual strength of the wastewater as determined by
analysis of composite samples for five-day biochemical oxygen demand
(BOD5) and suspended solids. An appropriate increment
for growth shall be included in the basis of design.
b. The data over a minimum period of one year
shall be taken as the basis for the design.
D. Shock Loadings. The applicant shall
consider the shock loadings of high concentrations and diurnal peaks for short
periods of time on the treatment process, particularly for small treatment
plants.
E. Design by Analogy. The
applicant may utilize the data from similar municipalities in the case of new
systems, provided that the reliability and applicability of such data is
established through thorough investigations and documentation.
F. Flow Conduits. All piping and channels
shall be designed to carry the maximum rates of flows. The incoming sewer shall
be designed for unrestricted flow. Bottom corners of the channels must be
filleted. Conduits shall be designed to avoid creation of pockets and corners
where solids can accumulate. Suitable gates shall be placed in channels to seal
off unused sections which might accumulate solids. The use of shear gates or
stop planks is permitted where they can be used in place of gate valves or
sluice gates. Corrosion resistant materials shall be used for these control
gates.
G. Arrangement of Process
Units. The design should provide for an arrangement of component parts of the
plant, for greatest operating and maintenance convenience, reliability
flexibility, economy, continuity of maximum effluent quality, and ease of
installation of future units.
H.
Flow Division Control. The design shall provide for flow division control
facilities to insure organic and hydraulic loading control to various process
units. Convenient, easy and safe access, change, observation, and maintenance
shall be considered in the design of such facilities. Flow division shall be
measured using flow measurement devices to assure uniform loading of all unit
processes and operations.
4.4. Plant Design Details
A. Mechanical Equipment. The specifications
should provide for:
1. services of a
representative of the manufacturer to supervise the installation and initial
operation of major items of mechanical equipment; and
2. performance tests of the installed
equipment before acceptance by the applicant.
B. Unit Bypasses
1. A minimum of two units in the liquid
treatment process train shall be provided for all unit processes and operations
in all plants rated at over 1 million gallons per day (3,785 cubic meters per
day).
2. The Director will approve
any exceptions based on reliability and operability of the
components.
3. The design shall
provide for properly located and arranged bypass structures and piping so that
each unit of the plant can be removed from service independently. The bypass
design shall facilitate plant operation during unit maintenance and emergency
repair so as to minimize deterioration of effluent quality and insure rapid
process recovery upon return to normal operational mode.
C. Unit Bypass During Construction. Any
bypass during construction or operation must be approved by the Director before
such bypass occurs, as provided in this rule.
D. Drains. The design shall incorporate means
to completely drain each unit with a discharge to a point within the process or
the plant.
E. Protection of
Structures. The design shall incorporate hydrostatic pressure relief devices to
prevent flotation of structures.
F.
Pipe Cleaning and Maintenance. Fittings, valves, and other appurtenances shall
be provided for pipes subject to clogging, to facilitate proper cleaning
through mechanical cleaning or flushing. Pipes subject to clogging, such as
pipes carrying sludge, shall be lined with a material which creates a smooth
and nonadhering surface, thereby reducing clogging and resistance to
flow.
G. Construction Materials.
The materials of construction and equipment shall be resistant to hydrogen
sulfide and other corrosive gases, greases, oils, chemicals, and similar
constituents frequently present in sewage. This is particularly important in
the selection of metals and paints. Contact between dissimilar metals should be
avoided to minimize galvanic action, and consequent corrosion.
H. Painting
1. Piping within the plant shall be color
coded to facilitate identification of piping, particularly in the plants rated
over 5 million gallons per day (18,925 cubic meters per day). Table
R317-3-4.4(H)(1) shows color and identification scheme recommended by the
American National Standards Institute (ANSI 253.1 and 13.1) shall be used for
the purposes of standardization.
2.
The labels shall be stenciled in conformance with the ANSI standard
A13.1.
3. The Director may approve
painting of piping with one color with a labelling scheme in conformance with
the ANSI standard A13.1 provided that:
a.
labels are color coded as directed above;
b. piping contents and direction of flow are
legibly stenciled on the label; and
c. labels are securely on the piping at
interval and all locations required in the above referenced standard.
I. Operating Equipment.
A complete outfit of tools, accessories, and spare parts necessary for the
plant operator's use should be provided. Readily-accessible storage space and
workbench facilities should be provided, and consideration be given to
provision of a garage for large equipment storage, maintenance, and
repair.
J. Erosion Control During
Construction. Effective site erosion control shall be provided during
construction.
K. Grading and
Landscaping. The site should be graded and landscaped upon completion of the
plant. Concrete or gravel walkways should be provided for access to all units.
Steep slopes should be avoided to prevent erosion. Surface water shall not be
permitted to drain into any unit. Particular care shall be taken to protect all
treatment plant components from storm water runoff.
4.5. Plant Outfall Lines
A. Discharge Impact Control. The outfall
sewer shall be designed to discharge to the receiving stream in a manner not to
impair the beneficial uses of the receiving stream and acceptable to the
Director. The outfall design should provide for:
1. Free fall or submerged discharge at the
site selected;
2. Cascading of
effluent to increase dissolved oxygen concentration in the effluent;
and
3. Limited or complete
dispersion of discharge across stream to minimize impact on aquatic life
movement, and growth in the immediate reaches of the receiving stream;
and
B. Protection and
Maintenance. The outfall sewer shall be so constructed and protected against
the effects of floodwater, ice, or other hazards as to reasonably insure its
structural stability and freedom from stoppage.
C. Sampling Provisions. All outfall lines
shall be designed with a safe and convenient access, preferably using a
manhole, so that a sample of the effluent can be obtained at a point after the
final treatment process, and before discharge to or mixing with the receiving
waters.
4.6. Essential
Facilities
A. Emergency Power Facilities
1. General. All plants shall have an
alternate source of electric or mechanical power to allow continuity of
operation during power failures. Methods of providing alternate sources
include:
a. provision of at least two
independent sources of power, such as feeders, grid, etc., to the
plant;
b. portable or in-place
internal combustion engine equipment which will generate electrical or
mechanical energy; or
c. portable
pumping equipment when only emergency pumping is required.
2. Power for Aeration. Standby power
generating capacity normally is not required for aeration equipment used in the
activated sludge type processes or aerated lagoons. In cases where a history of
long-term (4 hours or more) power outages have occurred, auxiliary power for
minimum aeration of the activated sludge type processes or aerated lagoon will
be required. Full power generating capacity may be required when discharge is
to critical stream segments to protect downstream uses identified in R317-2
(Standards for Quality for Waters of the State).
3. Power for Disinfection. Standby power
generating capacity shall include the capacity needed for continuous
disinfection of wastewater during power outages.
B. Plant Water Supply
1. General. An adequate supply of potable
water under pressure should be provided for use in the laboratory and for
general cleanliness around the plant. No piping or other connections shall
exist in any part of the treatment works which, under any conditions, might
cause the contamination of a potable water supply. The chemical quality of the
water should be checked for suitability for its intended uses such as in heat
exchangers, chlorinators, etc.
2.
Direct Connections
a. Potable water from a
municipal or separate supply may be used directly at points above grade for hot
and cold supplies in lavatory, water closet, laboratory sink (with vacuum
breaker), shower, drinking fountain, eye wash fountain, and safety shower;
unless local authorities require a positive break at the property
line.
b. The applicant must review
the requirements stated in R309-112.2 - Distribution System Rules, Drinking
Water and Sanitation Rules, to assure compliance with the said rule.
c. Hot water for any of the above units shall
not be taken directly from a boiler or piping used for supplying hot water to a
sludge heat exchanger or digester heating unit.
3. Indirect Connections
a. Where a potable water supply is used for
any purpose in a plant, a break tank, pressure pump, and pressure tank shall be
provided. Water shall be discharged to the break tank through an air gap at
least 6 inches (15.2 centimeters) above the maximum flood line or the spill
line of the tank, whichever is higher.
b. A sign shall be permanently posted at
every hose bib, faucet, hydrant, or sill cock located on the water system
beyond the break tank to indicate that the water is not safe for
drinking.
4. Separate
Potable Water Supply. Where it is not possible to provide potable water from a
public water supply, a separate well may be provided. Location and construction
of the well shall be in accordance with the requirements of R309, Drinking
Water and Sanitation Rules.
5.
Separate Non-Potable Water Supply. Where a separate non-potable water supply or
plant effluent is to be provided, a break tank will not be necessary, but all
system outlets shall be posted with a permanent sign indicating the water is
not safe for drinking.
C. Sanitary Facilities. Toilet, shower,
lavatory, and locker facilities shall be provided in convenient locations to
serve the expected staffing level at the plant.
D. Floor Slope. All floor surfaces shall be
sloped adequately to a collection floor drain system.
E. Stairways
1. Stairways shall be installed wherever
possible in lieu of ladders. Spiral or winding stairs are permitted only for
secondary access where dual means of egress are provided. Stairways shall have
slopes between 50 degrees and 30 degrees (preferably nearer the latter) from
the horizontal to facilitate carrying samples, tools, etc. Each tread and riser
shall be of uniform dimension in each flight. Minimum tread run shall not be
less than 8 inches (20.3 centimeters). The sum of the tread run and riser shall
not be less than 17 inches (43 centimeters) nor more than 18 inches (46
centimeters). A flight of stairs shall consist of not more than a 12-foot (3.7
meters) continuous rise without a platform.
2. Local, state and federal safety
requirements, including those in applicable fire code, the Uniform Building
Code, etc., must be reviewed and complied with. Those requirements take
precedence over the foregoing requirements, if more stringent, and should be
incorporated in the design.
4.7. Flow Measurement. Flow measurement
devices, preferably of the primary type (devices which create a hydrodynamic
condition that is sensed by the secondary element), shall be provided at the
plant to continuously indicate, totalize and record volume of wastewater
entering the plant in a unit time.
A. Flumes.
Installation of flumes shall be as follows:
1. Flumes with throat widths of less than 6
inches (15 centimeters) shall not be installed. Throat width shall be selected
to measure the entire range of anticipated flow rates at all measurement
locations.
2. Locations close to
turbulent, surging or unbalanced flow, or a poorly distributed velocity pattern
shall be avoided. For super-critical upstream flow, a hydraulic jump should be
forced to occur in a section upstream of the flume at a distance of at least 30
times maximum upstream operating depth of flume followed by a straight approach
section of a length specified in this rule.
3. For flumes with throat width less than
half the width of the approach channel, the length of approach channel -
straight upstream section - shall be the greater of 20 times the throat width
or ten times maximum upstream operating depth in flume.
4. For flumes with throat width greater than
half the width of the approach channel, the length of approach channel -
straight upstream section - shall be not less than ten times the maximum
upstream operating depth in flume.
5. Parshall flumes shall be permitted only in
locations where free discharge conditions exists on the downstream side at the
average design flow. Submergence must not exceed 60 percent at the maximum
design flow.
6. The stilling well,
if used, and secondary measuring elements, such as floats, sensors, or gages,
shall be protected against extreme weather conditions.
B. Other Flow Measurement Devices. Effluent
discharged to receiving waters should be measured using flow measurement
devices, such as weirs, sonic or capacitance type, etc.
C. Flow Recorders
1. Clock-wound mechanisms for recording of
flow are not permitted.
2. Battery
powered flow measurement devices may be permitted at locations where electrical
power is not available, and continuous operability of flow measurement devices
is demonstrated.
4.8. Safety and Hazardous Chemical Handling.
Adequate provision shall be made to effectively protect the operator and
visitors from hazards. Local, state and federal safety requirements must be
reviewed and complied with. Typical items for consideration are fence, splash
guards, hand and guard rails, labeling of containers and process piping,
warning signs, protective clothing, first aid equipment, containments, eye-wash
fountains and safety showers, dust collection, portable emergency lighting,
etc.
4.9. Laboratory.
A. Treatment plants rated in excess of 1
million gallons per day (3,785 cubic meters per day) shall include a laboratory
for making the necessary analytical determinations and operating control tests.
Otherwise, the applicant shall show availability of services of state-certified
laboratories on a continuous contract basis.
B. The laboratory size, bench space,
equipment and supplies shall be such that it can perform analytical work for:
1. All self-monitoring parameters required by
discharge permits;
2. The process
control necessary for good management of each treatment process included in the
design; and
3. Industrial waste
control or pretreatment programs.