6 Sewage may be collected into storage tanks,
either for holding prior to transfer to a treatment unit, or for later
discharge. Any tank used for holding sewage is a potential source
of anaerobic activity, and the resultant production of toxic and flammable
gas. The design of a tank may include features to maintain an adequate
oxygen level in the liquid, thereby eliminating anaerobic conditions.
This may be achieved by direct air injection, or by air entrainment
into the liquid whilst pumping through an ejector nozzle, etc.
7 When not equipped with an active aeration feature,
the conditions within the storage tanks should be especially monitored.
These tanks should be completely emptied and flushed through at intervals
which will ensure that satisfactory conditions are maintained. The
design and configuration of such tanks should be such as to facilitate
the effective drainage and flushing of the tanks.
8 Treatment systems may use the aerobic digestion
process, or may use other means to purify the effluent. The manufacturer's
recommendations for the operation and maintenance should be followed
to ensure satisfactory operation at all times. All tanks and associated
systems should be subjected to a thorough inspection at least every
year or whenever unsatisfactory conditions are detected. Such inspections
should include the following:
-
.1 Removal of tank inspection covers, and the
cleaning out of any deposits, paying particular attention to areas
behind internal tank divisions.
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.2 Inspections of the tank structure, internal
divisions, pipework, etc.
-
.3 Checking of sensing instruments, level measuring
devices and valves.
-
.4 Confirmation that air distribution systems
are free from leaks and any nozzles or diffuser elements used to introduce
air are in satisfactory condition.
-
.5 Checking that any internal systems used to
transfer tank contents are in a satisfactory condition.
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.6 Inspecting air blowers to check discharge pressure
is within allowable limits.
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.7 It is recommended that any alarms fitted to
air blower systems operate on sensing of unsatisfactory air pressure
rather than only monitoring the fans and their prime movers.