Page 306 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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266 Chapter 8 Pumping, Storage, and Dual Water Systems

Figure 8.2 General View of the Pumping Station Van Sasse in Grave,
the Netherlands
Source: Wikipedia, http://en.wikipedia.org/wiki/Image:Gemaal_van_
sasse.jpg

Pumps and pumping stations also serve the following purposes in wastewater systems:
1. Lifting wastewater from low-lying basements or low-lying secondary drainage
areas into the main drainage system, and from uneconomically deep runs in
collecting or intercepting systems into high-lying continuations of the runs or into
outfalls
2. Pumping out stormwater detention tanks in combined systems
3. Lifting wastewater to and through treatment works, draining component settling
tanks and other treatment units, withdrawing wastewater sludges and transporting
them within the works to treatment units, supplying water to treatment units,
discharging wastewater and wastewater sludge through outfalls, and pumping
chemicals to treatment units.
In addition to centrifugal and propeller pumps, water and wastewater systems may in-
clude (a) displacement pumps, ranging in size from hand-operated pitcher pumps to the
huge pumping engines of the last century built as steam-driven units; (b) rotary pumps
equipped with two or more rotors (varying in shape from meshing lobes to gears and often
used as small fire pumps); (c) hydraulic rams utilizing the impulse of large masses of low-
pressure water to drive much smaller masses of water (one-half to one-sixth of the driving
water) through the delivery pipe to higher elevations, in synchronization with the pressure
waves and sequences induced by water hammer; (d) jet pumps or jet ejectors, used in wells
and dewatering operations, introducing a high-speed jet of air through a nozzle into a con-
stricted section of pipe; (e) air lifts in which air bubbles, released from an upward-directed
air pipe, lift water from a well or sump through an eductor pipe; and (f) displacement ejec-
tors housed in a pressure vessel in which water (especially wastewater) accumulates and
from which it is displaced through an eductor pipe when a float-operated valve is tripped
by the rising water and admits compressed air to the vessel.