Current through Register Vol. 48, No. 38, September 20, 2024
a)
Safety
Safety Features Relative to Location
1) Railings and Gratings
A) Manually cleaned channels shall be
protected by guard railings and deck gratings, with adequate provisions for
removal or opening to facilitate raking.
B) Mechanically cleaned channels shall be
protected by guard railings and deck gratings. Consideration should also be
given to temporary access arrangements to facilitate maintenance and
repair.
2) Mechanical
Devices
A) Mechanical screening equipment
shall have adequate removable enclosures to protect personnel against
accidental contact with moving parts and to prevent dripping in multi-level
installations.
B) A positive means
of locking out each mechanical device shall be provided.
3) Units and Equipment in Deep Pits
Manually cleaned screens located in pits deeper than 4 feet
shall be provided with stairway access, adequate lighting and ventiliation, and
convenient and adequate means for removing screenings. Access ladders may be
used instead of steps in pits less than 4 feet deep. Hoisting or lifting
equipment shall be used where necessitated by the depth of the pit or the
amount of material to be removed.
4) In Buildings
Units and equipment installed in buildings where other
equipment or offices are located shall be isolated from the rest of the
building, and shall be provided with separate outside entrances and separate
and independent means of ventilation.
5) Ventilation
A) Adequate ventilation shall be provided for
installations described in subsections (a)(3) and (4). Ventilation may either
be continuous or intermittent. If continuous, ventilation shall provide at
least 12 complete air changes per hour; if intermittent, ventilation shall
provide at least 30 complete air changes per hour.
B) Where the pit is deeper than 4 feet
mechanical ventilation is required, and the air shall be forced into the screen
pit area rather than exhausted from the screen pit. The maximum distance from
the fresh air discharge and the working deck floor shall be 24 inches. Dampers
should not be used on fresh air ducts. Obstructions in air ducts should be
avoided to prevent clogging. Air intake screens (bird and insect) shall be
located so as to be easily accessible for cleaning.
C) Switches for operation of ventilation
equipment should be marked and located at the entrance to the screen pit area.
All intermittently operated ventilating equipment shall be interconnected with
the respective lighting system. Consideration should be given to automatic
controls where intermittent operation is used. The manual lighting-ventilation
switch shall override the automatic controls.
D) The fan wheel shall be fabricated from
non-sparking material. Refer to Section
370.610(a)(3)(C)
for motor and electrical
requirements.
6)
Electrical Fixtures
Electrical fixtures and controls in enclosed places where gas
may accumulate shall comply with Section
370.610(a)(3)(C).
b) Communition
Communition or other in-stream shredding of sewage solids
shall be followed by primary settling or fine screening devices to remove the
shredded stringy materials prior to the activated sludge process to minimize
operational problems associated with reaglomeration of stringy
materials.
c) Channels
Channels shall be equipped with the necessary gates to divert
flow from any one unit. Provisions must also be made for dewatering each unit.
Channels preceding and following screens shall be shaped and filleted as
necessary to eliminate settling of solids.
