excess of their self-purification capabilities. Purification by dilution requires about 20 to
40 times as much water as wastewater. With ever-increasing metropolitan populations,
such vast quantities of our unpolluted water are no longer available. Accordingly,
navigable or interstate waters.
CHARACTERISTICS OF WASTEWATER
a. Physical Characteristics. These characteristics are concerned with
detection of wastewater by using the physical senses: temperature, odor, color, and
feel of solid material. Fresh wastewater is turbid, grayish-white in color, and has a
musty odor. Small particles of feces and paper are visible in the waste stream, but
these will rapidly settle if the wastewater is quiescent. Fresh wastewater becomes stale
in 2 to 6 hours, depending upon temperature, nature of materials present, and the
addition of oxygen through turbulent flow. Warm wastewater becomes stale more
rapidly than cold wastewater. The addition of oxygen helps extend the time that
wastewater will remain fresh. Stale wastewater is dark brown to black and has a
pronounced hydrogen sulfide (rotten egg) odor. See Table 1-1 for significant colors of
wastewater. Frequently, gas bubbles will evolve from the surface. Carbon dioxide (a
product of aerobic decomposition and necessary for the support of algae growth) and
sometimes methane (a product of anaerobic decomposition which occurs during
wastewater digestion) are found in wastewater.
Industrial wastes not
pretreated (paints, etc.)
Blood, other industrial
wastes, or TNT complex
Red or other
Surface runoff into influent,
also industrial flows
Dark brown to black
Septic conditions or industrial flows
Table 1-1. Significant colors in wastewater.
b. Chemical Characteristics. The chemical characteristics of wastewater
include: dissolved oxygen, pH, oxygen demand, toxic material, and nutrients.