Corrosion Below: Sewer Structures

Kienow, Kenneth K.; Kienow, Karl E.; ,

Corrosion Below: Sewer Structures

by Kenneth K. Kienow, (M.ASCE), CEO; Kienow Assoc., Inc., Redlands, CA,
Karl E. Kienow, Principal; Kienow Associate, Inc., Tucson, AZ,

Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 9, Pg. 57-59

Document Type: Feature article

Abstract:

When a sewer system fails, the cause is often not the pipe but a manhole, junction or other special-purpose structure. Most of these structures are concrete, either cast in place or precast. There are two major causes of internal corrosion in a sanitary sewer. One is conventional acid attack caused by low pH industrial waste discharged directly into the sewer system; the other goes by several terms: sulfide corrosion, hydrogen sulfide corrosion or sulfide attack. In general, any sewer structure configuration that results in significant hydraulic energy loss will accelerate corrosion and may also induce serious corrosion of the downstream pipe. Many factors increase the amount of sulfide produced in sewage and the amount of H₂S escaping from the wastewater. Coatings, liners and proper hydraulic design all help to protect the structures. Modifying the concrete mix usually involves increasing the alkalinity, since the corrosion rate is inversely related to concrete alkalinity. Coating performance is sensitive to proper application and weather conditions.

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