Population equivalents

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TM 5-814-3/AFM 88-11, Volume III
plus the number of shift employees having one meal there. This total is the number of resident personnel to be
used in the design calculations. Individuals will be counted only once, either at home or at work. The capacity
factor still applies in calculating design populations.
d. Industrial flow. Industrial wastewater flows will be minimal at most military installations. When industrial
flows are present, however, actual measurement is the best way to ascertain flow rates. Modes of occurrence
(continuous or intermittent) and period of discharge must also be known.
Typical industrial discharges include wastewaters from the following:
wastewater treatment plant itself;
maintenance facilities;
vehicle wash areas;
weapons cleaning buildings;
boiler blowdowns;
swimming pool backwash water;
water treatment plant backwash;
cooling tower blowdown;
fire fighting facility;
photographic laboratory;
medical or dental laboratories.
e. Stormwater flow. Including stormwater flows is important in treatment plant design either when combined
sewer systems are served or when significant inflow enters the sewer system. Combined sewer systems will not
be permitted in new military installations. Separate sewers are required and only sanitary flows are to be routed
through treatment plants. For existing plants that are served by combined sewer systems, capacities will be
determined by peak wet-weather flow determined from plant flow records. In the absence of adequate records,
hydraulic capacities of four times the dry-weather flow will be used in the design. (Reference to existing systems
is applicable to Army facilities only.)
4-5. Population equivalents.
Suspended solids and organic loading can be interpreted as population equivalents when population data
constitute the main basis of design. Typical population equivalents applicable to military facilities were given in
table 4-3. These equivalent values can also be used to convert non-domestic waste loads into population design
values. The effects of garbage grinding will be incorporated into population-equivalent values when applicable.
The waste stream to be treated at existing military installations should, when feasible, be characterized; this
actual data should be used in the design.
4-6. Capacity factor.
A capacity factor (CF) taken from table 4-1 is used to make allowances for population variation, changes in
sewage characteristics, and unusual peak flows. The design population is derived by multiplying the actual
authorized military and civilian personnel population (called the effective population) by the appropriate capacity
factor. Where additions are proposed, the adequacy of each element of the plant will be checked without
applying the capacity factor. When treatment units are determined to be deficient, then capacity factors should
be used to calculate the plant capacity required after expansion. However, the use of an unnecessarily high CF
may so dilute waste as to adversely effect some biological processes. If the area served by a plant will not,
according to the best current information, be expanded in the future, the capacity factor will not be used in
designing treatment components in facilities serving that area. The following equation (eq 4-1) may be used to
estimate total flow to the sewage plant where domestic, industrial and stormwater flows are anticipated.

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