Abstract
Combined sewer overflow structures (CSO) play an important role in sewer networks. When the local capacity of a sewer system is exceeded during intense rainfall events, they act as a “safety valve” and discharge excess rainfall run-off and wastewater directly to a natural receiving water body, thus preventing widespread urban flooding. There is a regulatory requirement that solids in CSO spills must be small and their amount strictly controlled. Therefore, a vast majority of CSOs in the UK contain screens. This paper presents the results of a feasibility study of using low-cost, low-energy acoustic sensors to remotely assess the condition of CSO screens to move to cost-effective reactive maintenance visits. In situ trials were carried out in several CSOs to evaluate the performance of the acoustic sensor under realistic screen and flow conditions. The results demonstrate that the system is robust within ±2.5% to work successfully in a live CSO environment. The observed changes in the screen condition resulted in 8–39% changes in the values of the coefficient in the proposed acoustic model. These changes are detectable and consistent with observed screen and hydraulic data. This study suggested that acoustic-based sensing can effectively monitor the CSO screen blockage conditions and hence reduce the risk of non-compliant CSO spills.
Highlights
In the UK, there is over 600,000 km of sewer pipes and over 70% of these are combined, in that they carry both wastewater and rainfall run-off from urban surfaces [1]
Under dry weather flow conditions, wastewater flows in the direction of the green arrow direction underneath the screen and downstream of the Combined sewer overflow structures (CSO)
The results obtained from two field trials deployed in urban residential areas provide an informed decision when the screen needs to be cleaned
Summary
In the UK, there is over 600,000 km of sewer pipes and over 70% of these are combined, in that they carry both wastewater and rainfall run-off from urban surfaces [1]. Water companies are regulated by the Office of Water Services (OFWAT), which is a non-ministerial government department that is responsible for ensuring that water companies offer adequate service to the customers at a fair price [2]. With these stringent regulations, water companies have invested more than £8 billion in 2019–20 to improve their level of services. Water companies have invested more than £8 billion in 2019–20 to improve their level of services These include customers’ sewer repair, replacement and rehabilitation, one of the major areas of spend [3]. This has opened an unprecedented opportunity for instrument makers and researchers to develop partnerships to offer novel approaches to proactively reduce the risk of failure and allow better understanding of the behaviour of the sewer network under both normal and extreme operating conditions [4,5,6,7,8,9,10,11,12]
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