Content deleted Content added
Thewellman (talk | contribs) m →Significance: format correction |
Moved the image to the more relevant part of the article. It is not a photo of an inflow, but an effect (overflow) that could be a result if an excessive inflow. |
||
Line 1:
[[File:Sewer overflow RI EPA.jpg|thumb|right|Excessive infiltration/inflow may cause sanitary sewer overflows during wet weather.]]▼
'''Infiltration/Inflow''' ('''I/I''' or '''I&I''') causes dilution in [[sanitary sewer]]s. Dilution of sewage decreases the efficiency of treatment, and may cause sewage volumes to exceed design capacity. Although inflow is technically different from infiltration, it may be difficult to determine which is causing dilution problems in inaccessible sewers. The [[United States Environmental Protection Agency]] defines the term infiltration/inflow as combined contributions from both.<ref name="EPA definition">U.S. Environmental Protection Agency (EPA), Washington, D.C. ''Code of Federal Regulations.'' "Part 35—State and Local Assistance."
* "Definitions; Excessive inflitation/inflow." 40 CFR 35.2005 (b)(16). {{USCFR|40|35|2005}}
Line 18 ⟶ 17:
Dilution of sewage directly increases costs of pumping and [[Water chlorination|chlorination]], ozonation, or [[ultraviolet disinfection]]. Physical treatment structures including screens and pumps must be enlarged to handle the peak flow. Primary clarifiers must also be enlarged to treat average flows, although [[primary treatment]] of peak flows may be accomplished in [[detention basin]]s. Biological [[secondary treatment]] is effective only while the concentration of soluble and colloidal pollutants (typically measured as [[biochemical oxygen demand]] or BOD) remains high enough to sustain a population of microorganisms digesting those pollutants. Secondary treatment is expected to remove 85 percent of soluble and colloidal organic pollutants from sewage containing 200 mg/L BOD;<ref>EPA "Part 133—Secondary Treatment Regulation." {{uscfr|40|133}}</ref> but BOD removal by conventional biological secondary treatment becomes less effective with dilution and practically ceases as BOD concentrations entering the treatment facility are diluted below about 20 mg/L. Unremoved organics are potentially converted to [[disinfection by-products]] by chemical disinfection prior to discharge.
▲[[File:Sewer overflow RI EPA.jpg|thumb|right|Excessive infiltration/inflow may cause sanitary sewer overflows during wet weather.]]
High rates of infiltration/inflow may make the sanitary sewer incapable of carrying sewage from the design service area. Sewage may back up into the lowest homes during wet weather, or street manholes may overflow.<ref name="hammer"/>
| |||