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Coating and lining materials for corrosion control
While concrete is the most widely used construction material in large wastewater treatment plants, clay bricks have been used in manholes and old sewers. Concrete is used for below-grade wet wells or holding tanks, sewer pipelines and open-top channels. Many municipalities are discovering that certain concrete structures in wastewater treatment facilities are degrading rapidly due to acidic environment generated by bacterial activities [EPA, 1974, 1985]. There are several methods in practice to control the degradation of the concrete and clay brick wastewater facilities [Kienow et al. 1993]. The primary goal of rehabilitating these facilities is to return the structure to its original working condition using in situ methods. The addition of base materials at regular intervals is expensive especially when there is regular sewer flooding. Regularly cleaning the pipes by increasing the velocities of flow has not proved to be effective. Coating is one method currently being adopted but the effectiveness of this method for rehabilitating lift stations and sewer treatment facilities is still in question.
Sewer facilities are wet and experience hydrostatic pressure under normal service conditions. Application of coating materials to such surfaces is considered a challenge and must be evaluated [Steele, 1999]. Bonding between the concrete surface and the coating material is another key factor that must be evaluated to determine the performance of the coating. Chemical resistance of coated materials to acidic environment is also essential.