INFLUENT TO PLANT
Figure 6-1. The effect of equalization on a wastewater with variable pH.
operations. Domestic waste may also contain
U.S. EPA requires this flexibility for municipal
large quantities of grease from food preparation.
facilities. Guidelines for pumping facilities are
Use of air to float materials may relieve scum
available in TM 5814-3.
handling in a sedimentation tank and lower the
(b) Flow Measurement. Metering and in-
grease load to subsequent treatment units. Grit
strumentation devices in numerous sections of a
removal is often incorporated with a flotation unit
wastewater treatment facility are necessary for
providing sludge-removal equipment. Flotation de-
adequate plant control and operating flexibility.
Proper monitoring of effluent characteristics is
sign guidelines are available, but bench testing is
required to comply with NPDES permits. Use of
desirable to finalize the criteria and expected
devices such as Venturi meters, weirs, and
Parshall flumes predominate. Parshall flumes are
(7) Other methods. Other preliminary treat-
ment steps include coagulation and chlorination.
the preferred flow measuring method for military
Coagulation is a part of sedimentation as pre-
installations. TM 5-814-3 provides a description
of sizing and design considerations. The need for
sented later in this chapter. Chlorine additions
are often made to the plant influent for odor
control (120). Two other operations which usually
treatment facility will be dictated by the size of
precede any treatment process include pumping
the facility, complexity, and need for record-
keeping and operator control of the process. In
and flow measurement. Wastewater bypasses
must also be provided.
small installations, where maintenance and avail-
(a) Pumping. Pumping facilities may be
ability of spare parts may be difficult, metering
e m p l o y e d t o g a i n s u f f i c i e n t head for the
can be a problem. Reference should be made to
wastewater to flow through the treatment works
publications (120) for guidelines on types of
to the point of final disposal. Pumping is also
measurement systems available, limitations, and
preliminary design criteria. Also standard text-
generally required for recirculation of all or part
of the flow around certain units within the plant.
books and literature from equipment manufactur-
Pumping facilities are classified as influent, efflu-
ers should be investigated thoroughly prior to
selection of type and degree of plant measure-
ent, or recirculation stations and perform a criti-
cal function. Provisions shall be made for reliabil-
ity to ensure the facility is operable at all times.
(c) Wastewater bypasses. Piping arrange-
This means the largest pump has a standby
ments and duplicate treatment units may be
duplicate so that pumping capacity is available to
provided to the maximum practical extent so that
meet peak flows. It also means duplicate sources
an inoperative unit, such as a clarifier, may be
of power and/or standby power must be provided.
bypassed without reducing the overall treatment