An acoustic based approach for mitigating sewer system overflows

Abstract

Sewer piping networks are prone to damage due to aging, natural disasters, excessive traffic and chemical reactions with the contaminants and the soil. The released effluents from sewer system overflows (SSOs) can contaminate the water reservoirs, cause property damage and pose public health hazard. The SSOs are caused by blockages, breaks due to structural weaknesses and other pipe defects. To mitigate SSOs by effectively deploying cleaning resources, periodic condition assessment is important. Traditionally, a remotely controlled robot with a closed-circuit television (CCTV) camera is used to assess the condition of sewer pipes. This method, however, is expensive, man-hour intensive and the robot mobility depends on extent of blockage. Acoustics based pipeline monitoring systems are, therefore, augmenting traditional robot based methods. Acoustic pressure signals in pipes suffer attenuation due to blockages. The signal attenuation can be used as a good indicator of the extent of blockage in a pipe. This paper proposes an approach that models the pipe section between two manholes as lossy acoustic waveguide. The analytical results from the proposed model are compared with those from field measurements and laboratory tests. The findings can be used in the development of acoustic based pipeline condition monitoring applications.