residential home is 3 to 5 years. Any known, significant
industrial, institutional, or commercial contributions would need
to be added to this estimated volume.
The pumping of septic tanks is typically seasonal,
depending on the geographic location. Most of the pumping occurs
during periods of high groundwater or significant rainfall or
snowmelt. During the winter months in cold climates, less
septage is pumped because of the problems associated with
locating and uncovering septic tanks under snow or in frozen
Characteristics of Septage. Septage can be
generally described as having large quantities of grease, oil,
suspended solids, organic matter and grit; foaming upon
agitation; being anaerobic and odorous; being difficult to
dewater; and having poor settleability. Septage has a high waste
strength because of the accumulation of scum and sludge in the
The specific constituents of septage vary significantly
depending on the source. Table 4 summarizes septage
constituents, the range of concentrations of these constituents,
and typical design values used for septage treatment facilities
(EPA Septage Treatment and Disposal Handbook, October 1984).
Comparison of Septage and Domestic Wastewater
Characteristics. Many of the constituents of septage are similar
to those of domestic wastewater. Table 5 compares septage and
domestic wastewater characteristics (EPA Septage Treatment and
Disposal Handbook, October 1984). The primary difference is that
the constituents in septage are more concentrated, including
greater amounts of organics, plastics, hair, and grit.
Therefore, depending on the volume of septage discharged, septage
could impart a significant demand on the wastewater treatment
processes and increase the maintenance of pipes and equipment.
The organic loading from the daily discharge of septage from one
1,000-gallon (4 cubic meters) tank truck is equivalent to a
domestic wastewater flow of about 30,000 gallons (120 cubic
meters) per day.
Monitoring the Quantity and Quality of Incoming
Septage. Because of the variability of the constituents and
strength of septage, monitoring incoming septage is necessary to
ensure its compatibility with the downstream treatment processes
and effluent and biosolids disposal requirements. Comprehensive
and organized procedures for monitoring, sampling, and