Assessment of sewer corrosion in Lebanon

Abstract

A survey on the existing sewer networks in the major coastal cities/urban centers in Lebanon to determine the sites, most susceptible to hydrogen sulfide corrosion was carried out. Thirty-eight sites were selected and inspected in the field and samples from the sewage and the pipe networks .it these sites were obtained and analyzed--Sewage samples from the selected sites were analyzed for corrosion generating indicators. Particularly, dissolved oxygen and chemical oxygen demand - COD. The dissolved ox\ gen results indicated the absence of corrosion conducive conditions excepts for few locations in Beirut and Tripoli. Short pieces (samples) from the live sewage networks were dug out and replaced with new manholes. The samples were visually inspected for corrosion indicators. (ieneralh tiie samples did not exhibit am .id\ anced corrosion. 1 pur diametrical!) opposite pieces were then remov ed from every pipe sample and tested for concrete alkalinity and sulfates. Alkalinity tests indicated the presence of additional neutralization at pipe crowns which demonstrates the presence of a slow corrosion process. Sulfate results did not indicate the presence of a clear trend in this regard.--Field surveys were carried out to determine the sewage network parameters upstream of the selected sites. Using a specialized commercial software, these parameters were utilized to predict the hydrogen sulfide emissions at the selected sites and to estimate the magnitude of corrosion. Except for some few locations ((Cassis and Corniche Al-Manara...) the prediction results indicated negligible sulfide build up w hich does not warrant, the use of additional special internal protection materials/ techniques to protect the pipes against hydrogen sulfide corrosion.