To produce water which is friendly to the environment and tasty with bringing operators and the like at each plant into operation controls, provision of maintenance information for plants from the side of a service center and high level operations without introductions of an expensive knowledge support system and the like to each plant.

In an operation control system of water and sewerage, the know-how relating to operations and maintenance of the plants provided in each plant 2a-2n is registered as knowledge data into a knowledge base part 8 of service server equipment 6, when a searching demand is requested from, for example, a plant side terminal device 3 at the plant 2a, the base part 8 is brought into access and extraction the knowledge data specified by the demand to supply it to the terminal device 3.