Sewer system
Sewerage is the infrastructure that conveys sewage or surface runoff (stormwater, meltwater, rainwater). It encompasses components such as receiving drains, manholes, pumping stations, storm overflows, and screening chambers of the combined sewer or sanitary sewer. Sewerage ends at the entry to a sewage treatment plant or at the point of discharge into the environment. It is the system of pipes, chambers, manholes, etc. that conveys the sewage or storm water.
According to this definition, sewerage and sewage are two different terms. However, at least in American English colloquial usage, both terms are sometimes used interchangeably.
The main part of a sewerage system is made up of large pipes (i.e. the sewers, or "sanitary sewers") that convey the sewage from the point of production to the point of treatment.
Types of sanitary sewer systems which are all usually gravity sewers include:
Sanitary sewers not relying solely on gravity include:
Severe constraints are applied to sewerage, which may result in premature deterioration. These include root intrusion, joint displacement, cracks and holes formation leading to a significant volume of leakage with an overall risk for the environment and public health. For example, it is estimated that 500 million m3 of contaminated water per year can leak into soil and ground-water in Germany. The rehabilitation and replacement of damaged sewers is very costly. Annual rehabilitation costs for Los Angeles County are about €400 million, and in Germany, these costs are estimated to be €100 million.
Hydrogen sulfide (H2S) is indirectly responsible for biogenic sulfide corrosion and consequently, sewerage need rehabilitation works. Various repairs options are available to Owners over a large range of costs and potential durability. One option is the application of a cementitious material based on calcium aluminate cement, after a cleaning of the corroded structure to remove loose material and contaminants in order to expose a sound, rough and clean substrate. Depending of the concrete condition and contamination, the cleaning can range from simple high pressure jet water cleaning (200 bar) up to real hydro-demolition (2000 bars).
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