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

4 CONCLUSIONS
The membrane bioreactor treatment technology to purify greywater shows excellent
cleaning performance with minimal space requirements, but a relatively high energy demand.
Therefore, it makes sense to implement such a system only where a high quality of recycled
water is required, space is limited and the energy supply is uninterrupted. This is mainly the
case in urban areas, where reuse applications are within buildings, where recycled water
supplies reuse applications such as toilet flushing.
The functionality of MBR treatment technology has been proven to work in an international
context by exemplary projects worldwide. The positive aspects of this technology have been
shown based on economic and environmental advantages, demonstrated with many
examples collected in this work.
The outcome after a short period of greywater treatment in the existing membrane
bioreactor plant in Eschborn showed good results regarding functionality of the system and
quality of the permeate. The specifications of EU bathing water directive RL 2006/7/EG
(2006) and fbr requirements H 201 (2005) are fulfilled.
Due to the research character of the SANIRESCH plant with all its special features, it is not
feasible to transfer it on a one to one basis, when considering economic aspects. Hence, a
fictitious cost calculation based on a simplified system design for the whole GIZ headquarters
building was conducted to make the system comparable to standard applications. With
respect to economic aspects, an amortisation of the complete treatment system, in the
context of the GIZ headquarters was not achievable. Only 45 % of daily process water
demand in the building can be covered by greywater production. The amount of greywater
production and process water demand is not balanced. Only with big efforts, such as super
saving toilets, equilibrium can be reached, however accompanied by immense acquisition
costs. With the average cost for energy and maintenance in comparison to water charges,
the calculation showed that savings of € 1,412 on operating costs in the first year are
possible. But in an amortisation calculation, the investment costs account to € 38,383 for
treatment plant and additional piping system in the building, therefore a benefit is not
obtainable. In an office building, the mismatch with respect to the water balance is too high,
thus there is no stimulus to use a greywater treatment plant for this specific application.
However, economic incentives do exist for the application of greywater treatment plants in
different circumstances, such as in buildings where people stay overnight, where an
advantageous water balance is much easier to achieve. Examples of such buildings are
apartment buildings, halls of residence, hospitals, hotels, etc., here an amortisation of the
system can be achieved after only a few years. Based on an exemplary cost calculation for a
4-star hotel in Berlin, an application with a high amount of water consumption, the calculation
shows much better results and the break even can be achieved after approximately 6 years
of operation.
Especially in Germany, where no water scarcity exists, economic aspects are in the
foreground when greywater recycling technologies are implemented, whereas in regions of
the world, where low availability of water causes significant problems, the reuse technology
meets many more targets, such as protection of the environment and water resources,
reduction of the volume of produced wastewater and consequently, the water pollution risk
as well.
In this respect, the international transferability of greywater treatment via membrane
bioreactor technology was assessed, based on the sustainability criteria for sanitary
concepts by means of a utility analysis. According to the main groups health and hygiene,
economic, functional and technical, environmental, and socio-cultural criteria; 19 appropriate
criteria for the subgroups were identified. To every sub criterion, a certain weighting value
was given, in order to result 100 % in total in the utility analysis.
The evaluation to locate global hotspots for greywater recycling applications was based
on water scarcity, defined as the indicator criterion to identify the most meaningful countries
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