Environmental Engineering Reference
In-Depth Information
Primary clarifiers
(settling)
Biological treatment
(aeration)
Secondary clarifiers
(settling)
Surface water
Inflow
Disinfection
Pretreatment Lab/admin
Solids
processing
Solids
processing
storage
Maintenance Outflow pipe to
surface water
FIGURE 11.25
Wastewater treatment plant. (From Portage Lake Water and Sewer Authority, Houghton, Michigan, http://
www.plwsa.org/index/php (accessed June 25, 2010), 2010.)
A significant component of the flows within many surface streams is the discharge from
wastewater treatment plants (WWTP). An aerial view of a municipal WWTP is shown in
Figure 11.25.
The level of treatment applied before wastewater is discharged to surface water depends
on the concentration and types of contaminants present. The spectrum of wastewater
treatment spans simple methods, such as constructing a settling pond to remove solids
and suspended particles before treatment, to a very complex multistep process removing
several contaminants before discharge. Figure 11.26 shows the multistep process used by
municipal wastewater treatment systems involving the removal of solids and biological
treatment before the water is discharged.
Bio-solids storage
Bio-solids
processing
Thickened biosolids
hauled to swtp
for digestion
Bio-solids
pumps
Clarifiers
UV disinfection
Gravity
thickener
Plant drain
UV
Screenings
and grit
removal
Aeration process
Post
Air
MLRPS
Blower
building
Influent
Phosphorus and nitrogen
removal process
Little Sac River
FIGURE 11.26
Schematic of a municipal wastewater treatment system. (From City of Springfield Missouri, Northwest Wastewater
Treatment Plant, http://www.springfieldmo.gov/sanitary/nw_treatment.html (accessed November 27, 2010), 2010.)
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