Methods of protecting tunnel sewers and in-line structures from corrosion

Summary

Hundreds kilometers of tunnel sewers and in-line structures mostly made of reinforced concrete have been in operation in Russia. A pressing problem of their damage exists caused by microbiologic (gas) corrosion. Common and theoretical possible methods of protecting sewers and in-line structures from microbiologic corrosion are considered. The classification of methods with the use of foreign and domestic literary sources and from own operation experience was carried out. The classification is based on the principle of the method group capability compliance to counteract any mechanism occurring in the process of reinforced concrete structure corrosion. The methods have been summarized in four tables according to the processes occurring in sewers. The analysis of corrosion protection methods has been carried out; the main drawbacks of each method have been determined together with the conditions of using the methods at the stages of design and construction, operation and upgrade. Special attention is paid to the methods of passive protection most often used by water companies to solve the given problem. As a main method of passive protection the use of different protection coatings is considered. The results of studying the rigidity of the protection coatings made by various manufacturers under corrosive medium impact caused by the operation of a pressure suppression chamber in Novosibirsk are presented. The principle of the studies was long-term exposure of concrete samples with surface protection coatings. The possible use of two common trademarks for protecting underground reinforced concrete sewers from destruction was approved.

Key words

composite material , microbiologic corrosion , sewer shaft , tunnel sewer , corrosion control method , corrosion protection , passive protection

Problems in sewer network operation and ways of their elimination

Summary

The main problems arising during the operation of sewer networks – blockages, network deterioration and odors are highlighted. The causes of their occurrence are considered and methods of their elimination are proposed. Under the conditions of Russia blockages are most likely to occur as a result of errors in design and erection. These are violation of the pipe turnout grade, pipe diameter mismatch, turnout grade fault because of soil movement, unsatisfactory state of sewer and pipeline failure. Design and erection errors and low cultural level of the users of the sewer system can lead to the emission of high concentrations of hydrogen sulfide. Any blockage in the sewerage system is accompanied by foul odor above ground that is explained by the emission of hydrogen sulfide. By using advanced computer aids it is possible to keep account of all the factors that affect the useful life of sewers. Systematization of the obtained data and its further use provide for extending the pipe life and reduce the expenditures for renovation and maintenance of sewers. The paper is written on the basis of designing and operating the sewer networks in Saint-Petersburg.

Key words

pipeline , odor , sewer , sewerage system , clogging , microbiologic corrosion , sewer network deterioration , soil failure

Deterioration of sewage tunnels and in-line structures as a result of microbiologic corrosion

Summary

The process of microbiology corrosion of sewers and structures was considered; corrosion protection is a most expensive issue in operating wastewater facilities. General cost of rehabilitating corroded structures amounts to billions euro annually. The present-day concept of a complicated microbiologic corrosion process affected by a great number of different factors such as higher turbulence, and as a result high degree of wastewater flow degassing, is presented. The main indicator of the problem, i. e. concentration of hydrogen sulfide in the ambient air of the structure, is determined. The results of sewer wells inspection in St. Petersburg and their analysis are presented. The high rate of corrosion and extreme operating conditions of No. 10 sewer well are recorded.

Key words

wastewater , sewer , microbiologic corrosion , reinforced concrete