Current through Register Vol. 41, No. 3, September 23, 2024
A.
Equipment. The specifications should be so written that the installation and
essential items of mechanical equipment will be certified by a representative
of the manufacturer. The specifications shall require that the equipment
manufacturers provide to the owner one complete set of operational
instructions, equipment and maintenance manuals, and emergency procedures for
each essential mechanical and electrical equipment item. The manuals shall
contain drawings of equipment and a numbered parts list keyed to a list of
components.
B. Instrumentation.
Insofar as possible, all indicating, recording, and totalizing flow meters
shall be identical so that repair components and charts are interchangeable.
Recording equipment for dissolved oxygen, temperature, pH, and other operating
data, along with flow metering equipment, shall be located in areas free from
high humidity, extreme temperatures, and corrosive gases. Instrumentation
requirements for each treatment works shall be decided on a case-by-case basis.
Facilities for measuring the volume of sewage flows shall
be provided at all treatment works. Treatment works having a capacity of equal
to or less than 40,000 gallons per day shall be equipped with a primary
metering device such as a Parshall flume with separate float well and staff
gauge, weir box with plate and staff gauge, or other approved devices, as a
minimum unless nonfluid contact measuring devices are provided. All treatment
works having a capacity of greater than 40,000 gallons per day shall be
equipped with indication, recording, and totalizing equipment. The recording
scale shall be sufficient to accurately record and depict the flow measured.
Flows passed through the treatment works and flows passed through controlled
diversions shall be measured in a manner that will allow them to be
distinguished and separately reported.
C. Component isolation. Properly located and
arranged diversion piping or structures shall be provided so that any component
of the treatment works process can be independently operated in accordance with
the reliability classification, or removed from service independently for
inspection, maintenance, and repairs. Adequate access and removal space shall
be provided around all components to provide for proper maintenance or removal
and replacement without interfering with the operation of other equipment. Due
consideration shall be given to the need for lifting and handling equipment
available to aid in the maintenance and replacement of all components. In
addition, the placement of structures and other devices, such as pad-eyes and
hooks to aid handling of heavy or large components, should be considered in the
preliminary design. These criteria for adequate access and handling equipment
do not apply to the removal or replacement of large tanks, basins, channels, or
wells. Lines feeding chemicals or process air to basins, wet wells, and tanks
shall be designed to enable repair or replacement without drainage of the
basins, wet wells, or tanks.
D.
Maintenance provisions. The design of a treatment works should facilitate
access for both routine maintenance and equipment failure response.
1. Provisions should be made for flushing,
with water or air, all scum lines, sludge lines, lime feed and lime sludge
lines, and all other lines that are subject to clogging. All piping subject to
accumulation of solids over a long period of time should be arranged in a
manner to facilitate mechanical cleaning if possible. The design shall be such
that flushing and mechanical cleaning can be accomplished without causing
violation of effluent limitations or without cross-connections to the potable
water system.
2. Provisions should
be made for dewatering each unit. Drain lines should discharge to points within
the system such that maximum treatment of the contents of the drained unit is
provided. Due consideration shall be given to the possible need for hydrostatic
pressure relief devices. Where practicable, all piping shall be sloped or have
drains (drain plug or valve) at the low points to permit complete draining.
Piping shall not be installed with isolated pockets that cannot be
drained.
3. Concrete, metals,
control and operating equipment, and safety devices shall, insofar as
practical, be designed to protect against corrosion, moisture and heat induced
damage.
4. Positive identification
of the content of a piping system shall be by lettered legend giving the name
of the contents. Arrows should be used to indicate direction of flow. Legends
shall be applied close to valves and adjacent to changes in direction, branches
and where pipes pass through walls or floors, and at frequent intervals on
straight pipe runs. The lettering shall be of such color, size, and location to
be clearly visible and readable.
5.
A complete outfit of tools and accessories for the treatment works operator's
use, such as wrenches, valve keys, rakes, shovels, etc., and such spare parts
as may be needed, shall be specified as either contractor or owner furnished. A
portable pump is desirable. Readily accessible storage space and work bench
facilities shall be specified. Consideration shall be given to provision of a
garage area that would also provide space for large equipment maintenance and
repair.
6. Concrete, paved, or
gravel walkways shall be provided for access to all units. Where possible,
steep slopes and narrow stairways shall be avoided to increase access for
maintenance. Surface water shall not be permitted to drain into any units.
Provision should be made for erosion protection and landscaping, particularly
when a treatment works must be located near residential areas.
E. Essential facilities. The
design of treatment works shall include both proper physical support for
operation personnel and specific safety features to protect operators and
visitors from exposure to hazards.
1. A supply
of potable water with adequate pressure shall be provided for use in the
laboratory and bathroom facilities. All potable water supplies within the
treatment works shall be protected with reduced pressure zone backflow
prevention devices. To facilitate cleaning wet wells, tanks, basins, and beds,
water supplied from a nonpotable water system or the treatment works effluent
may be supplied at these points by means of an adequately pressurized water
system with hydrants or hose bibs having minimum outlets of one inch in
diameter.
The potable water supply line to each treatment works
shall be equipped, as a minimum, with an approved reduced-pressure zone
backflow preventer. These devices shall be installed in an above-ground
location, no more than 36 inches above the ground floor elevation and with
adequate clearance for access on all sides, to prevent corrosion and to allow
for adequate, quick service and periodic inspections. Designers shall consult
with the appropriate field office of the department for such requirements at
individual treatment works in accordance with the Waterworks Regulations
(12VAC5-590).
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 comply with requirements of the department.
2. All sewage treatment works shall be
provided with or have ready access to a toilet and lavatory. For a treatment
works at which the operator is required to be on duty for eight or more hours
per day, a shower shall also be provided.
3. Minimum laboratory space for treatment
works not performing BOD and suspended solids testing on-site shall be 50
square feet of floor space with 20 square feet of bench area. Treatment works
providing on-site BOD, suspended solids, or fecal coliform analysis shall
provide a minimum of 400 square feet of floor space and 150 square feet of
bench space. If more than two persons will be working in the laboratory at any
given time, 100 square feet of additional space should be provided for each
additional person. Advanced sewage treatment works shall provide a minimum of
100 additional square feet of floor space, with a proportionate increase in
bench space. On-site laboratories shall be isolated from treatment works
equipment, vehicular traffic, etc., so as to render the laboratory reasonably
free from the adverse effects of noise, heat, vibration, and dust in accordance
with VOSH requirements.
4. Safety
provisions should protect operators and visitors at treatment works from
exposure to hazards in accordance with VOSH requirements. The designer should
refer to the applicable occupational safety and health standards of the
Virginia Department of Labor and Industry for the appropriate requirements. The
following shall be required as a minimum, as applicable:
a. Enclosing the treatment works site with a
fence designed to discourage the entrance of unauthorized persons and
animals.
b. Providing adequate
lighting, installing handrails, and establishing access guards, where
necessary, and posting "No Smoking" signs in hazardous locations.
c. Providing first aid supplies and safety
equipment, including protective clothing and equipment such as gas masks,
goggles and gloves.
d. Providing
explosion-proof electrical equipment, nonsparking tools, etc. in work areas
where hazardous conditions may exist, such as digester vaults and other
locations where potentially explosive atmospheres of flammable gas or vapor
with air may accumulate.
e.
Providing properly grounded and insulated electrical wiring, with no part of
the treatment works piping being used for grounding.
f. Providing railroad type manhole steps with
slip-proof rungs, unless access is to be provided by lifting devices. The
railroad type step is designed to help prevent foot slippage off the ends of
the rungs. Also, providing intermediate landings or other suitable protection
between height intervals of 10 feet or less, unless adequate lifting devices
are to be provided.
g. Providing
adequate protective storage for flammable and hazardous materials and safety
devices for gas collection piping.
h. Providing adequate ventilation for all
areas subject to accumulation of hazardous or toxic gases and providing
equipment (accuracy of + or-5%) for measuring the concentration of gases in the
atmosphere of confined spaces, enclosed areas, underground areas, or other
areas where hazardous gases may accumulate or oxygen deficiencies may occur.
Providing a portable blower and hose sufficient to ventilate accessed confined
spaces.
i. Locating heating devices
with open flames in separate rooms with outside entrances located at grade
level or above.
j. Locating
laboratory and office space at sewage treatment works to minimize interference
from motors, generators, compressors, etc. and providing adequate floor slope
to a point of drainage.
k.
Providing stairways with a slope of 30° to 50° from the horizontal,
with risers all of equal height, and with handrails on the open sides of all
exposed stairways and stair platforms.
F. Odor control. The potential for odor
problems at new treatment works shall be evaluated. The evaluation shall
include possible sources of odors, types of odors, and various methods (i.e.,
covered units, physical treatment, chemical treatment, or biological treatment)
of controlling odors. Provisions for odor control shall be included in the
design if the sewerage system is primarily composed of force mains or otherwise
provides lengthy retention times (i.e., on the order of two or three days), or
if the treatment works will provide raw sludge holding, raw sludge dewatering,
or thermal treatment. Odor control provisions should be considered for sludge
digestion processes, sludge dewatering processes, preliminary and primary
sewage treatment processes, and other processes that provide the opportunity
for gas transfer or gas stripping activities to occur.
Statutory Authority
§ 62.1-44.19 of the Code of Virginia.
