(5) Electrical controls. A common control for the fans and lights keyed to
an exterior lock on the entrance door is to be installed so that the fans and lights will
automatically come on when the door is opened, will only be deactivated by relocking
the door externally, and can also be manually operated from the outside without
opening the door.
(6) Cylinder storage. A storage area is to be provided that allows for a
minimum 15-day inventory of reserve and empty containers. Cylinders may be stored
outdoors on suitable platforms at or above grade and under cover of a well-ventilated,
(7) Use of chlorine actions. The presence of chlorine gas in the
atmosphere can pose immediate and serious hazards to the health of any person
breathing the air. Therefore, precautions are required. Gas masks approved by the
National Institute for Occupational Safety and Health (NIOSH) are to be provided
outside any area where an individual would be exposed in the event of chlorine leaks or
spills. All rooms in which chlorine is to be stored or handled should be adequately
ventilated to the outside. A fan, automatically turned on prior to entry into the
chlorination or storage facility, must be provided. Chlorine detectors (the liquid-reagent,
electrode-cell, meter type, sensitive to one ppm of chlorine by volume in air) that
continuously monitor the air are to be installed to provide a visual/audible alarm in the
event of a chlorine leak. The enclosed space is to be entered only if the worker is under
observation by a co-worker and only if the worker has in his possession a respirator
suitable for escape. When hydrochlorite compounds and generators are used, the
above requirements do not apply. For safe handling of chlorine, follow local directives.
Chlorine gas has a suffocating odor and can kill. Be observant to all
audible and visual alarms. Follow all procedures as noted above and
those in the local SOP.
2-4. FLOW MEASUREMENT
Every wastewater treatment plant must have some means of measuring and
recording the flow of incoming wastewater and wastewater flow throughout the plant.
Such information is necessary for proper plant sampling and control as well as for
planning additions to the plant. Metering of wastewater normally takes place in the
influent line preceding primary settling. Two types of metering devices in common use
are weirs and Parshall flumes.
a. Weirs. Weirs are regularly formed notches or openings placed perpendicular
to a channel through which water flows (see Figure 2-5). As the flow increases, the
resistance created by the weir causes the water to rise in the channel ahead of the weir.
The height of the water is measured as it passes over the weir and, by means of tables,
this height is converted to flow in gallons per minute or similar units.