Chapter 3 Decision Support Model (IUWS-DSM) - Tubdok

2 New Conception and Decision Support Model for IUWS
Standing at the crossroads of the new millennium, we have to find out the appropriate
and sustainable solutions to resolve our overall water crisis.
1.1.1 Conventional concepts
Aiming to satisfy the demands of water consumers and maintain a proper water environment
in the meantime, urban water systems generally involve three systems, water supply,
wastewater disposal and rainwater elimination. Conventionally, three systems are planned,
constructed and administrated individually. The water supply system consists of water intake,
waterworks, and distribution networks. The wastewater system consists of sewage sewer
and treatment plants. The rainwater system is mainly composed of storm drain, where
certain processing facilities can be involved, if rainwater is heavily polluted. Besides, there
are ancillary works, such as pumping stations in both distribution and collection systems.
Today’s urban water supply and wastewater disposal systems in most countries are
based on the experience of the 19 th century in Europe (Eiswirth 2000), which have the main
goals of safely supplying clean water, disposing wastewater, and simultaneously preventing
waterborne diseases. Urban water systems enlarged step by step along with the expansion
of cities. The centralised systems of both water supply and wastewater disposal are therefore
formed, which means the water is treated centralised to the highest required water quality
and distributed to users by one set of networks, and the wastewater is collected together and
transported to the centralised wastewater treatment plants (WWTP). Centralised systems
have many advantages, such as simple system structure, easy construction and operation,
etc. As they were born in Europe, i.e. the advanced developed area, and have century-long
successful operation experience, the centralised water systems are adapted worldwide, and
still act as the standard patterns of urban water system in many countries and regions.
Tracing back the history, engineers have different philosophies in different periods to deal
with the wastewater, from direct discharge to end-pipe treatment till today’s source separated
collection systems (Hahn and Song 2006). Due to its flooding risks, rainwater is conventionally
eliminated from urban area as soon as possible, which effects the large storm water
drains. Meanwhile, both seen as unwanted water, the collection systems of rainwater and
wastewater can be merged, whereby several forms of urban drainage are have several
prevailing forms, i.e. combined, separate, and hybrid systems, etc. (Butler and Davies 2000).
Combined and hybrid collection systems often occurs in old cities.
Nonetheless, such conventional urban water systems have many intrinsic deficiencies,
such as high water consumption rate, low water use efficiency, and high environmental loads,
etc. Currently, the water scarcity is becoming the problem in many regions of the world,
where many man-made reasons exacerbate it, such as population explosion, industrialisation
and urbanisation, as well as the climatic changes, etc. The conventional water systems are
most often neither sustainable nor optimal systems. Therefore, the better solutions for our
urban water systems are needed urgently.