An innovative greywater treatment system for urban areas ... - SuSanA

2.4 GREYWATER TREATMENT VIA MBR TECHNOLOGY - ANALYSIS AND
EVALUATION OF INTERNATIONAL TRANSFERABILITY VIA MULTI CRITERIA
DECISION ANALYSIS
Prior to the assessment of the transferability of membrane bioreactor treatment
technology, it is necessary to find a decision making tool which can support the process. It is
difficult to come up with a decision that determines in which regions of the world greywater
treatment using MBR is reasonable. The technology of membrane bioreactor provides a
capable method to recycle greywater with an effective cleaning process. It requires minor
space and provides a high quality. However, the investment costs and energy consumption
of the plant is relatively high. In this respect, international applications need to be identified,
where the requirements and circumstances harmonise ideally with MBR technology, such as
water scarcity combined with lack of space and high reuse requirements for permeate. Due
to many influencing factors, this challenge has to be mastered by a decision making tool.
Certainly it can be answered only by taking into account the immediate context of a specific
application. However, it is important that it is based on transparent criteria. Not every factor
has the same importance; therefore it is necessary to find a capable instrument for decision
making.
2.4.1 DECISION MAKING TOOL
Figure 16 illustrates different methods of multi criteria decision analysis (MCDA) in a tree
structure. At first, there is a main distinction between multi objective decision making
(MODM) and multi attributive decision making (MADM). Based on the number of alternatives
under evaluation, MADM methods are designed to select discrete alternatives, while MODM
are more adequate when dealing with multi-objective planning problems with a theoretically
infinite number of continuous alternatives (Mendoza & Martins, 2006).
To identify the international transferability of MBR technology, the multi attributive decision
making (MADM) is an appropriate method based on a particular number of alternatives.
Within the MADM there is the group of multi criteria methods, here the preference structure
of decision-maker is incorporated in the model. The analysis performs a complete mapping
and evaluation of pre-selected crucial characteristics.
A reasonable model within the group of multi criteria methods is the multi attribute utility
theory (MAUT), it is based on strict adherence to use theoretical rationality axioms. In
contrast, the utility analysis is a more heuristic method. The cost benefit analysis (CBA) is
regarded as a preliminary investigation on these two methods mentioned before and will not
be described here. Finally the analytic hierarchy process (AHP) represents a standardized
and process-oriented method (Rohr, 2004).
goal
programming
methods of
mathematical
programming
Multi criteria decision analysis (MCDA)
multi objective
decision methods
(MODM)
...
outranking
multi attributive
decision methods
(MADM)
multi attribute
utility theory
(MAUT)
cost benefit
analysis (CBA)
multi crteria
methods
analytical
hierarchy
process (AHP)
utility analysis
Figure 16: Overview of multi criteria decision making methods; (Oesterdiekhoff, 1993; modified)
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