Wireless Sewer Monitoring Research

Abstract

The Wireless Camera Network for Sewer Inspection monitoring project is developing a distributed floating network of wirelessly connected camera nodes working together to gather video imagery of the inside of pipelines to continuously monitor the sewer pipeline network. The sewerage network in Japan is old and in need of regular repair. With an estimated 4,000 incidents of road collapse due to pipeline failure each year, it is imperative that authorities can detect damage and carry out preventative repair before pipeline collapse can occur. Professor Susumu Ishihara, from Shizuoka University in Japan explains: ‘In Japan, we have about 460,000 kilometres of sewer and stormwater pipelines, around 20 percent of which are over 30 years old. Much of this infrastructure is concrete, and subject to corrosion over time.’ Ishihara and Associate Professor Hiroaki Sawano from the Aichi Institute of Technology in Japan are collaborating to propose a solution involving floating capsules equipped with cameras that regularly transmit data to temporary wireless antennae placed in manholes. The basic premise behind the project is that small capsules will float on the liquid in the pipelines, taking video footage of the inside of the pipe as they drift with the flow. This approach has many advantages, ‘The capsules do not need any motive power and are fully autonomous once they have been placed in a pipeline. They dispense with the need for cables, pipelines do not have to be taken out of commission and there is little labour involved.’ explains Sawano. Video is still considered the best means of monitoring pipeline condition, despite the time needed to review images and identify areas of damage. Other methods, such as ultrasound and gas detection, were rejected as technically impractical or insufficiently sensitive to pipeline damage. The capsules are small, lightweight and round, with an outer shell of a clear, tough plastic. Within this outer casing is an active capsule that floats on a small amount of water in the annulus. This configuration keeps the omni-directional camera, mounted on the inner capsule, on a relatively even keel. The inner capsule is equipped with powerful, diffused lights that minimise reflection from the outer shell. Also packaged into the capsule is wireless communication functionality, various sensors, data storage and batteries for powering the system. The capsules are small, cheap and designed to be used in distributed groups. In full scale experimental conditions, they have been shown to negotiate changes in direction and differences in the internal surfaces and bore diameters with ease.