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

and the resultant wastewater characteristics. Further, many intangible
influences such as location, popularity, and price may produce substan-
tial wastewater variations between otherwise similar establishments.
Finally, there is considerable difficulty in presenting characterization
data in units of measurement that are easy to apply, yet predictively
accurate. (For example, at a restaurant, wastewater flow in gal/seat is
easy to apply to estimate total flow, but is less accurate than if
gal/meal served were used.)
In this section, limited characterization data for nonresidential estab-
lishments, including commercial establishments, institutional facili-
ties, and recreational areas, are presented. These data are meant to
serve only as a guide, and as such should be applied cautiously. Wher-
ever possible, characterization data for the particular establishment in
question, or a similar one, in the vicinity, should be obtained.
4.3.1 Wastewater Flow
4.3.1.1 Average Daily Flow
Typical daily flows from a variety of commercial, institutional, and
recreational establishments are presented in Tables 4-6 to 4-8.
4.3.1.2 Wastewater Flow Variation
The wastewater flows from nonresidential establishments are subject to
wide fluctuations with time. While difficult to quantify accurately, an
estimate of the magnitude of the fluctuations, including minimum and
maximum flows on an hourly and daily basis, can be made if consideration
is given to the characteristics of the water-using fixtures and appli-
ances, and to the operational characteristics of the establishment
(hours of operation, patronage fluctuations, etc.).
Peak wastewater flows can be estimated utilizing the fixture-unit method
(19) (20). As originally developed, this method was based on the premise
that under normal usage, a given type of fixture had an average flow
rate and duration of use (21)(22). One fixture unit was arbitrarily set
equal to a flow rate of 7.5 gpm (0.5 l/set), and various fixtures were
assigned a certain number of fixture units based upon their particular
characteristics (Table 4-9). Based on probability studies, relation-
ships were developed between peak water use and the total number of fix-
ture units present (Figure 4-2).
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