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

Chapter 2 New Conception
Chapter 2 · New Conception 9
Based on the concept of water cycle, the urban water system is mapped by the hierarchy
of four levels. The urban water end-users are defined as different types of the grouped users.
Certain types of water end uses are categorised so that their required water quality can be
identified. The desired water quality is therefore redefined. The treatment processes for both
raw water and used water are classified into certain steps. Five subsystems are built up, i.e.
water usage, water sources, desired water, used water and rainwater systems, which have
individual structures, system otpions and planning processes. Eventually, all subsystems are
constructed together as one IUWS.
2.1 Fundamentals of modern urban water systems
2.1.1 Water cycle in cities
Historically, the development of our urban water systems started from water transmission
and distribution, followed by drinking water treatment, and then wastewater collection and
discharge, followed by wastewater treatment, till wastewater reuse. It reveals that the faults
and problems are recognised only when they already seriously impact on our daily life. More
over, the problems are tried to resolve isolated. In a sustainable way, the urban water
systems need to be looked at in a holistic view, whereby the water cycle needs to be properly
completed relying on natural and artificial processes. Thereby, the water cycle is one of the
headstones of this research.
Figure 4 shows the basic and possible components as well as the water pathways in
modern urban water systems. Besides the traditional water systems, i.e. drinking water
supply (left side in Figure 4), wastewater disposal (right side), and rainwater elimination
(bottom area), more elements can be involved, such as on-site water advanced treatment,
independent water sources, rainwater utilisation and wastewater reuse, etc. Obviously, the
water cycle can occur in different locations with different system scales.
Considering this water cycle in modern cities, two sides can be formed, i.e. water usage
side and water infrastructure side. The water usage side considers and organises the
information of possible water demands, generated wastewater, available water sources, and
the water qualities. The water demands and water sources are matched, whereby the water
use is optimised. On the water infrastructure side, the urban infrastructure, including water
intake, treatment facilities, transmission, distribution and collection, is planned and manage,