Newsletter and Technical Publications
Freshwater Management Series No. 10
Managing Urban Sewage
An Introductory Guide for Decision-makers
V. Operation and Maintenance
Sewage facilities must operate under severe conditions created by the constant flow of highly
corrosive wastewater and have to continuously pump and treat wastewater on a 24-hour
basis. To ensure the provision of safe and reliable services, it is necessary to operate and
maintain these facilities in an efficient manner.
Since most sewer mains and pipelines are located under roads, they are affected by external
factors such as loads and vibrations caused by traffic as well as the settling or sinking of
ground, often resulting in breakage or cracking of pipes. For this reason, regular inspections,
cleaning and repair work are essential for maintenance. In addition to constant surveillance,
systematic inspections are carried out to ensure that damage is detected at an early stage and
that repairs are made. To maintain the flow and capacity of the system, cleaning is performed
on a regular basis. Care must also be taken to ensure that damage identified during monitoring
or cleaning does not lead to a future accident or system failure.
To ensure that sewer mains and pipelines are properly operated and that their status is clearly
understood, data relating to sewer mains, pipes and soil chambers should be collected and
recorded using a sewage ledger system. This can help facilitate improved preventative
operation and maintenance, allowing damage to be identified sufficiently in advance to prevent
the occurrence of accidents. Furthermore, by adopting new techniques, such as nondestructive
inspection, operational costs can be reduced.
B. Pumping Stations
When heavy rain occurs, pumping stations must quickly drain away rainwater runoff that
rushes into the sewers and discharge it into the sea, adjacent rivers, or underground. Pumping
stations are often unmanned and remotely controlled or monitored by master pumping stations,
however they must be operated continuously and maintained, since swift operation is essential.
C. Wastewater Treatment Plants
The operation and maintenance of a wastewater treatment plant is complex and requires
trained operators and sufficient financial resources to ensure that these facilities continue to
operate in an acceptable manner. The volume of wastewater requiring treatment in a large
city can be substantial. For example, in Tokyo, the amount of wastewater treated in 1999
was on average 4,740,000 cubic meters a day, and the amount of sludge treated was on
average 154,330 cubic meters a day.