Failure Analysis of a Sewer Pipeline Confirms Link Between Regulatory Changes and Resultant Biochemical Impact on Pipe Materials

The authors investigated two failures on a 12-year-old, 76.2-cm (30-in.) diameter ductile iron wastewater interceptor pipeline, termed an outfall line, that traveled across hilly terrain towards a wastewater treatment plant. In both cases, the catastrophic failure resulted in significant property damage due to the large volume of sewage that escaped from the failure location. The interior of the pipe was lined with coal tar epoxy and the claim was that the protective coating failed; purportedly the fault of the manufacturer. The pipeline contained a large siphon and the designers anticipated elevated concentrations of hydrogen sulfide gas generation at the outlet of the siphon; and thus, incorporated a sulfide control station at this location. The method of sulfide control was to inject liquid hydrogen peroxide into the siphon upstream of the outlet to neutralize the liquid-phase hydrogen sulfide. In an effort to reduce operating costs, far too little hydrogen peroxide was added to the pipeline resulting in catastrophic failure due to sulfuric acid attack of the coating and pipe. The crown of the pipe was essentially missing in the downstream section of the pipeline following the siphon. This type of failure and the age of the pipe coincide with changes in the regulatory framework governing wastewaters, notably, the Clean Water Act of 1980. This act resulted in a reduction in the allowable metals concentration in sewage. The net result was increased sulfate reduction and corresponding sulfuric acid production, which increases the corrosive environment within sewage pipelines. For this reason, operators need to be more diligent in protecting their pipelines from the catastrophic effects of internal corrosion.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Photos; References;
  • Pagination: 9p
  • Monograph Title: Pipeline Engineering and Construction: What's on the Horizon? Proceedings of the Pipelines 2004 International Conference, August 1-4, 2004, San Diego, California

Subject/Index Terms

Filing Info

  • Accession Number: 01003214
  • Record Type: Publication
  • ISBN: 0784407452
  • Files: TRIS
  • Created Date: Aug 18 2005 9:38AM