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

Only the legislative requirements for wastewater treatment technologies (H3) were
counted within this main group. This criterion refers to regulations and directives for treated
greywater and for reuse applications in evaluated countries. In this regard, the ratings “highly
enforced” = 10, “medium enforced” = 5, “low enforced” = 1, and “no requirements” = 0 were
given. If there are highly enforced requirements on the quality of purified greywater, then it is
a strong motivation to use high-tech treatment via MBR. In the weighting of utility analysis,
legislative requirements are included with 6 %.
Economic issues (E) are given a high weighting of 39 % within the utility analysis. This is
because there are holistic cost approaches that always provide strong reasons for the
decision of greywater treatment plant implementation.
Direct governmental funding for treatment plants (E1) by e.g. subsidies, allowances,
loans for plant investment, or financial support is the first sub issue. It was weighted with 4 %
within this group. The indirect incentives on greywater treatment systems (E2) add
another 4 % to the weighting. It includes e.g. tax reductions, discounts, minimised fresh
and/or wastewater charges, reimbursements of taxes, or charges. For both criteria, the
appraisal is: “high support” = 10, “medium support” = 5, “low support” = 1 and “no support” =
0.
Investment costs of the system (E3), which include the treatment plant, a separate
piping system, and all installations necessary for the greywater treatment system, were
weighted with 4 % in the utility analysis. Membrane bioreactor treatment plants are relatively
expensive. It is expected that the investment expenses are to be amortised at least within 7 -
8 years of operation, then it is possible to save enough money within the next 7 - 8 years to
substitute the plant; (lifecycle 15 years). Otherwise there is no stimulus to install such a
technology in a building. Therefore, this sub criterion was only weighted with 4 %, as an
economic feasibility of the system was presumed. The estimation is: “high price” = 1,
“medium price” = 5 and “low price” = 10.
Operating expenses (E4), including maintenance, spare parts, and working time, were
weighted with an influence of 5 %. For the appraisal, the regular payments were weighted
with a bit more influence than investment cost: This is due to the fact that regular payments
are an important factor which stands for a big amount of money which must be spent on a
regular basis. The classification is as follows: “high expenses” = 1, “medium expenses” = 5
and “low expenses” = 10.
If the energy price (E5) is very high, there is no incentive to implement a MBR treatment
system, because of relatively high energy consumption of the plant (see energy calculation in
section 3.53.5.1). Therefore, the appraisal of criterion is: “high expenses” = 1, “medium
expenses” = 5 and “low expenses” = 10. To assess those issues, the energy price can
generally be considered in the country or region. Together with operating expenses, it is a
regular payment that can be a high cost factor; hence it was assessed with 5 %.
In contrary, there are charges for drinking and wastewater (E6 & E7) which can be
saved by greywater treatment. Both criteria are classified with “high charges” = 10, “medium
charges” = 5 and “low charges” = 1. If high expenses can be avoided, it is an appeal to
implement a recycling system. Each criterion (charge for drinking and wastewater) was
weighted with 7 %. The idea behind it was to have a balanced situation of costs, which need
to be spent, and expenses that can be saved. The assessment counts 14 % in total for
investment, maintenance and energy costs. In contrary, 14 % for drinking and wastewater
that can be saved.
Often the charge for drinking water (E6) is very high because of water scarcity or
missing water pipes. Therefore, supply by tank vehicles is necessary. In this case, it is very
useful to recycle greywater in order to use water several times within a building. However, in
some countries the price of water is low due to governmental subsidies, despite critical water
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