The world is on the brink of a water crisis. United Nations in World Water Day 2002
has warned that more than 2.7 billion people will face severe water shortages by
2025 [1]. Shortage of quality raw water, rising costs of water management and
drive towards environmental sustainability have encouraged widespread water
conservation efforts and stimulated the development of systematic techniques for
water minimisation. Over the past decade, the advent of water pinch analysis
(WPA) as a tool for the design of a maximum water recovery (MWR) network
has been one of the most significant advances in the area of water
minimisation. Water pinch analysis is a systematic technique for implementing
strategies to maximise water reuse and recycling through integration of waterusing
activities or processes. Since its introduction by Wang and Smith [2],
various noteworthy WPA developments on targeting, design and improvement of
an MWR network have emerged. Most authors claimed that their methods lead to
the minimum fresh water and wastewater targets. It is important to note that the
concept of MWR based on WPA which relates to maximum reuse, recycling and
regeneration (partial treatment before reuse) has two limitations. Firstly, MWR
only partly addresses the issue of water minimisation which should holistically
consider all conceivable methods to reduce water usage through elimination, reduction,
recycling, outsourcing and regeneration [3]. Secondly, since MWR focuses on
water reuse and regeneration, strictly speaking, MWR only leads to MWR
targets as opposed to the minimum water targets as widely claimed by researchers
over the years. Note that, the minimum water targets can only be achieved when
all options for water minimisation including elimation, reduction and
outsourcing have been holistically applied. Even though WPA has been wellestablished
for synthesis of MWR networks, research towards water
conservation from the holistic water minimisation viewpoint has significantly
lagged behind. There is a clear need to develop a holistic framework to effectively
and systematically generate a minimum water utilisation network to maximise water
savings for the industry and urban sectors.
A HOLISTIC FRAMEWORK FOR DESIGN OF A MINIMUM WATER
NETWORK
Application of an MWR network for grassroots and existing water distribution
systems have solely focused on industrial sectors and have only recently been
introduced into the urban system [4]. Manan et al. [5] had applied reuse,
outsourcing of rainwater and regeneration to Sultan Ismail Mosque (SIM) using the
water pinch technique to yield what was thought to be colossal savings of up to
85.5% freshwater and 67.7% wastewater. However, the potential savings could be
further stretched by implementing the holistic framework described as follows:
The new holistic framework to generate a minimum water network involves
four key steps (see Figure 1). The first step is water data specifications which
involves identifying the appropriate water demands (inputs) and water sources
(outputs) in a water distribution system having potential for integration. The
limiting data for the water demands and sources is as summarised in Table 1 in
terms of flow rate and maximum contaminant concentration. The MWR targets
were established using the WCA technique [6] in step 2.
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