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

supply (such as in Jordan (Rothenberger et al., 2011)). That aspect should be kept in mind
whenever the water price in arid areas is low.
Regarding wastewater (E7), often no sewer system is available in a country or region.
Thus, the sewage needs to be removed frequently from own collection systems (tanks), and
tank vehicles must then pick it up. Ideally the wastewater is transported to central sewage
treatment plants, but often it is only dumped into rivers or the sea. The reduction of
wastewater by dual use for showering and toilet flushing is interesting from an economic
point of view and secondly also due to less effort of sewage removal.
The price of land (E8) is an indirect indicator that determines the decision in urban areas
wether to implement greywater treatment via biomembrane reactor, or instead using other
systems like constructed wetlands. The MBR technology is extremely compact and can be
installed ideally in buildings where space is limited. It was weighted by a low percentage of
only 3 %, since it is only a supporting factor. The rating is as follows: “high price” = 10,
“medium price” = 5 and “low price” = 1.
The functional and technical criteria (T) are considered as obsolete in respect of
importance for this evaluation. A comparison with other technologies, which might be better
or worse, is not destined. The appraisal of international transferability based on MBR
treatment is not influenced by functional or technical criteria. There is no variation in yearly
maintenance (T1), stability of operation and quality (T2) and break downs (T3).
According to experiences drawn by company HUBER SE, e.g. yearly maintenance is
necessary, independent of region of application (cf. Table 13 data of maintenance). The
stability of operation does not vary if there are big or small greywater volumes. It results
always in good permeate quality. Furthermore, an accumulation of breakdowns, caused by
environmental conditions such as climate, is not expected. Therefore, this main group can be
disregarded.
Environmental criteria (N) are considered as the second strong influencing factor in
order to make a decision for implementing a greywater treatment plant. That main criterion
was weighted in total with 41 %.
The most important factor within the assessment is water scarcity (N1). It is of urgency to
implement water saving technologies in buildings. Hence, the criterion was weighted with 12
% in the utility analysis. In this sub group, water scarcity stands for both, physical and
economical water scarcity. Physical water scarcity applies to the dry parts of the world or arid
regions. However, in an increasing number of regions in the world, physical water scarcity is
considered asan anthropogenic problem. Often, overuse and over management of river
basins can lead to very serious physical water scarcity. The expression “economic water
scarcity” refers to a situation, when a state does not have the necessary monetary means to
utilise an adequate source of water (The water project, 2011). For both types, the estimation
is: “high” = 10, “medium” = 5, “low” = 1 and “no scarcity” = 0.
If fresh water quality (N2) in a country or region is very poor due to chemical or hygienic
pollution, it is necessary to provide drinking water from water supply trucks. It is often also an
indicator for water scarcity or bad infrastructure. The sub criterion is an indirect factor which
supports the implementation of greywater treatment plants, because it can diminish the
consumption of drinking water. It was weighted with 5%. In this respect, the following
classification was chosen: “high quality” = 1, “medium quality” = 5 and “low quality” = 10.
A further important issue is the number of persons (N3) living in the building where the
greywater treatment plant shall be installed. Together with the accumulation of greywater
(N4), it is an indirect factor to estimate the volume of greywater which is accumulated in the
project. This type of evaluation was chosen, because it is easier to answer these both
questions, instead of responding to the question of exact greywater volume accumulation.
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