Newsletter and Technical Publications
Freshwater Management Series No. 10
Managing Urban Sewage
An Introductory Guide for Decision-makers
II. The Importance of Managing Sewage
The scope of sewage management has evolved throughout history with changes in socioeconomic
conditions, city structures, and the environment. Today, sewage infrastructure that
is well planned and operated supports urban sanitation and related activities. Effective sewage
management is essential for nutrient recycling and for maintaining ecosystem integrity. It is
also important for:
- Improving the environment through proper drainage and disposal of wastewater;
- Preventing floods through removal of rainwater;
- Preserving receiving water quality.
The sewage treatment process facilitates the achievement of water quality objectives. In addition
to nutrient recycling, advanced treatment of wastewater often includes associated unit processes
which support the optimization of resource use. Some of these unit processes include the
conversion of sludge into various beneficial by-products, and the process of extracting thermal
energy from sewage and wastewater. In addition, the sewage collection system can be used as
a conduit for optical fibre cables and other communications infrastructure.
A. Sewage Works Planning and Administration
Sewage works should be planned and executed by municipalities in collaboration with other
levels of government. The authority for the construction and management of treatment plants,
trunk sewers and branch collectors varies depending upon the jurisdictional arrangements in
a given country. In the City of Tokyo for example, sewage treatment and the provision of
trunk sewers for the City's 23 ward areas is carried out by the Metropolitan Government.
The Metropolitan Government carries out the construction and management of these facilities
within the regional sewage system, while the municipalities themselves are responsible for
connecting the branch sewers with the trunk sewers.
B. Water Recycling Master Plans
Some cities have established a water recycling master plan to ensure the efficient use of
precious water resources. Under such a plan, water-related measures are examined from the
viewpoint of water recycling and all activities within the city are carried out in a manner
consistent with the master plan. The objectives of a water recycling master plan should
include the creation and nurturing of a water cycle that has a minimal impact on the
environment while fostering a beneficial relationship between humans and nature. This
involves the establishment of an efficient water and wastewater systems within the city and
ensuring sufficient flexibility to cope with the possibility of environmental emergencies and
possible disasters such as earthquakes and drought.