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

is available in Can Tho, therefore N5 was set to value “1”. The city Can Tho had 1,121,141
inhabitants in 2004 and the population density is 807/km 2 (Can Tho government's official
portal , 2004), hence N6 and N7 were estimated with “10”. The research project has the
entitlement of ecological awareness and is a pioneer in this area, thus led to value “10” for
issues S2 and S3.
In total the result of appraisal showed 53.2 % performance in the utility analysis. In this
case, the environmental aspects such as “water scarcity”, “freshwater quality” and “sewer
system available” were not the determining factors to implement a greywater treatment
system. Here, the research issues and economic reasons were in the foreground. Not all
criteria of sustainability were covered, therefore the result scores approximately 50 %.
Hall of residence ("Eastside“) in Mannheim, Germany; (according to Table 24):
Another hall of residence project was selected as an example; it is the “Eastside” building
in Mannheim/Germany with a MBR plant supplied by company Dehoust (see details in
chapter 3.2.).
The legislative requirement for greywater treatment according to the fbr-Information Sheet
H 201 (fbr, 2005) in dependence on the EU bathing water directive, are medium enforced
and rated with “5” in issue H3. In Germany, there are no direct or indirect governmental
subsidies for greywater treatment plants available; hence both criteria were assessed with
“0”. The investment costs for a membrane bioreactor treatment plant are high, hence rating is
“1” for E3 and the operational expenses are medium due to (only) annual maintenance and
therefore E4 is rated with “5”. The charge for energy, drinking and wastewater in Germany is
low, thus E5, E6 and E7 are assessed with “1”. Regarding price of land, the assumption was
made with a rating of “10”, because in the urban area of Mannheim prices are high with
approximately 500 €/m 2 based on an area between 300 m 2 and 600 m 2 (Immowelt AG,
2011). In Germany, no water scarcity exists, hence N1 was rated with “0” and the fresh water
quality according to WQI is high with 79 of 100 scores, therefore N2 was assessed with “1”.
For the issues N3 and N4 values of “10” can be set, due to building size with 70 apartments
and greywater production of 5000 l/d. A sewer system is available in Mannheim, which led to
rating of “1” for N5. In Mannheim the population density and urbanisation is high and was
assessed with “10” for both criteria, the city has 323.794 inhabitants and a population density
of 2160 persons/km 2 (Statistisches Landesamt Baden-Württemberg, 2010). The general
acceptance of greywater reuse is assumed with a medium value of “5”, regarding ecological
awareness a high degree of “10” is presumed. Pioneer in this area is rated with “1”, due to
the fact that in Germany often halls of residence are equipped with greywater treatment
technologies to save water.
With 39.5 % the utility analysis of the hall of residence in Mannheim showed not such a
positive result. In this case there was no primary environmental necessity to implement the
system, here economic reasons were the stimulus. Therefore, the utility analysis did not
show a high utility. Here the limitations of the system are visible; the matrix is designed to
implement all issues of sustainability; to consider the applicability in a holistic approach of
environmental, economic, socio-cultural reasons and so forth. The viability of installation of
the system in this case is based only on one main reason, hence it is not possible to
determine whether it makes sense or not. In this case an economic cost calculation would
show the amortisation and savings.
At each assessment, local conditions must be taken into account, which should be
integrated into the appraisal. For example charges for water or energy prices can be
classified as low according to western standards, but if these rates are judged on the basis of
local income ratios, then this estimation looks quite different. Additionally, the circumstances
can differ widely within the different regions of a country and in urban or rural areas, this
should be taken into consideration as well.
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