Wastewater contains a variety of suspended solids and organic matter. When hydraulic conditions do not assure their transportation, sediments can accumulate in the network and diminish the hydraulic capacity of sewer pipes. Accumulated sediments are washed off during intense rainfalls and discharged to surface waters via combined sewer overflows (CSO) and separate stormwater outlets. Besides the pollution of rivers and lakes, sediments also contribute to urban flooding. In England about 75% of sewerage derived flooding per year are due to blockages occurring in the sewer network (Arthur et al., 2009). Further, sediments in the sewer network are also responsible for H2S gas formation and hence a source of odour and corrosion.
The issue of sediments is generally addressed by utilities with reactive maintenance (sewers are cleaned after blockages occur) or regular sewer cleaning programs. This activity represent a major expense for sewer operation and maintenance and utilities are lacking solutions to support them in the planning of cost-effective programs.
Arthur, S., Crow, H., Pedezert, L., & Karikas, N. (2009). The holistic prioritisation of proactive sewer maintenance. Water Science and Technology, 59(7), 1385–1396. doi:10.2166/wst.2009.134
Limitations of current practices
Sewer cleaning is a standard and necessary procedure performed by sewer operators to ensure network performance, avoid sewer blockages and flooding. The sewer cleaning is generally separated from the inspection procedure using separated trucks and operation teams. The blind cleaning of sewers lead to unknown cleaning efficiency. The control of sewer cleaning performance is costly since it requires a dedicated team, truck and equipment to monitor the results of the cleaning procedure. The lack of coordination of cleaning and inspections hampers the performance of the operations.
XPECTION increases the performance of the sewer cleaning process by time, fuel and water. The operator can see the condition of the pipe during the cleaning procedure, identify cleaning needs, analyze immediately the efficiency of the cleaning procedure and communicate repair needs to the team in charge. The combination of proactive cleaning and CCTV survey will allow a better allocation of resources engaged in sewer operation. Operators engaged in the control of sewer cleaning efficiency with quick view camera would not be useful anymore and could be allocated to other priority tasks.
Xpection is being tested in Sofia and Berlin to optimize the cleaning practices in large catchment with known issues of blockages and sediments. The tool will be implemented by the local teams to perform cleaning activities and its benefits will be evaluated compared to standard cleaning practices.
IPEK – Victor Ferre