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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.

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