On-Site Wastewater Treatment and Disposal Systems - Forced ...

oils, and greases, can cause failure. This is. particularly true of sys-
tems serving restaurants and laundromats. These failures can be correc-
ted by segregating the wastewaters to eliminate the troublesome waste-
waters (see Chapter 51, or by improving pretreatment (see Chapter 6).
Lack of proper maintenance of the treatment unit may have resulted in
excessive clogging due to poor solids removal by the unit. This can be
determined by checking the maintenance record and the condition of the
unit. If this appears to be the problem, the unit should be pumped and
repaired, or replaced if necessary. The infiltrative surface of the ab-
sorption field should also be checked. If siting, design, or mainten-
ance do not appear to be the cause of failure, excessive clogging is
probably the problem. In such cases, the infiltrative surface can some-
times be rejuvenated by oxidizing the clogging mat (4)(9)(13)(16). This
can be done by allowing the system to drain and rest for several months
(4). To permit resting, a new system must be constructed with means
provided for switching back and forth. Alternatively, the septic tank
could be operated as a holding tank until the clogging mat has been
oxidized. However, this involves frequent pumping, which may be costly.
Another method, still in the experimental stage, is the use of the
chemical oxidant, hydrogen peroxide (16). Because it is new, it is not
known if it will work well in all soils. Extreme care should be used in
its application because it is a strong oxidizing agent. Only individu-
als trained in its use should perform the treatment.
7.2.2.6 Considerations for Multi-Home and Commercial
Wastewaters
Design of trench and bed soil absorption systems for small institutions,
commercial establishments, and clusters of dwellings generally follows
the same design principles as for single dwellings. In cluster systems
serving more than about five homes, however, peak flow estimates can be
reduced because of flow attenuation, but contributions from infiltration
through the collection system must be included. Peak flow estimates
should be based on the total number of people to be served (see Chapter
4). Rates of infiltration will vary with the type of collection sewer
used (191(20).
With commercial flows, the character of the wastewater is an important
consideration. Proper pretreatment is necessary if the character is
significantly different than domestic wastewater.
Flexibility in operation should also be incorporated into systems serv-
ing larger flows since a failure can create a significant problem. Al-
ternating bed systems should be considered. A three-field system can be
constructed in which each field contains 50% of the required absorption
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