Introducing Greywater Systems into the Built Environment: An Introduction and Overview

As the urban population grows, increasing quantities of water are diverted to cities. Such diversions require massive infrastructure, and have substantial implications for aquatic ecosystems from which the water is taken. In many cases such abstractions can lead to basin closures, whereby all the water in the basin is utilized, with none reaching the sea for at least part of the year (Falkenmark and Molden, 2008). Moreover, water conveyance requires substantial energy inputs (Glieck, 1994). Supplying the increasing urban demand, thus, has major implications for energy use, and consequently for greenhouse gas emissions. Therefore, any policy that can reduce the need to convey water to the cities has potentially widespread environmental and financial benefits.

There are two possible approaches to addressing the rising water demand of cities without further stressing freshwater resources. The first is supply augmentation from extra large seawater desalination plants (Feitelson and Jones, 2014). However, seawater desalination has a substantial energy cost (Stokes and Horvath, 2009), and is primarily useful for seaside cities. The second is the so-called ‘soft water path’ (Brooks et al., 2009) that emphasizes conservation, recycling and re-use. The purpose of the soft water path is to reduce the demand for water in urban settings, and thus dampen the pressure on resources.

One option for reducing the demand for water in the urban sphere is greywater recycling within the built environment. Essentially, water that is used for bathing and laundry can be recycled for toilet flushing and the irrigation of gardens. The water that can be recycled, termed greywater, amounts to 20–80 per cent of the freshwater that enters the house (Al-Jayousi, 2003). The technical options for utilizing this water are well known (Christova-Boal et al., 1996; Gross et al., 2015). Previous studies have shown they may have potential for significantly reducing freshwater demand (Dixon et al., 1999; Friedler and Hadari, 2006), although their utilization can raise health concerns (Maimon et al., 2010). However, the extent to which greywater systems have been implemented is limited.

The purpose of this issue is to examine the potential, means and limitations for introducing greywater systems into the built environment. The introduction of greywater into the urban fabric is complex. It involves many players with different concerns. Essentially, it needs to be approved not only by local government and health authorities, but ultimately by homeowners and residents as well. The formal authorities who have to approve the introduction of greywater systems reside in different institutions, the nature of which varies from country to country, and sometimes within countries. In some countries, such as Israel, greywater systems are currently illegal (Gross et al., 2105). But even if they are approved by the various authorities, they will not be implemented unless homeowners are willing to have them introduced and developers are ready to incorporate them in developments. All these parties have concerns beyond the economic feasibility of such systems, such as health, image, effects on soil and environment. The question this issue addresses is the extent to which these concerns affect the diffusion of water saving systems.

The main impediments to the introduction of greywater systems are the health and environmental concerns many have about them. We begin, therefore, with a review by Maya Benami, Osnat Gillor and Amit Gross of the potential health and environmental risks associated with onsite greywater reuse. This review shows that while there is place for concern, these concerns can readily be mitigated at reasonable cost, and thus should not preclude the introduction of such systems. Yet the introduction of such systems has to be regulated. Christina Cook then analyzes how greywater reuse is being regulated in two contexts: England and California. This comparison indicates that the way greywater recycling is regulated is a function of the importance that is accorded to greywater in water management, and the

regulatory approach can affect the transaction cost associated with the introduction of greywater systems.

As noted above, the introduction of greywater has to be accepted by a wide variety of actors, the attitude of which may vary from place to place. Hence, the rest of the papers in this issue examine various facets of the factors that affect the acceptability and implementation of greywater systems in different contexts.

Maria Vallès, Hug March and David Saurí examine the diffusion of rainwater harvesting and greywater recycling systems as alternative water sources in a high-income municipality of Barcelona (Spain), assessing the influence of political will and the users’ acceptance. In so doing, they depict the main success and hindering factors, with special attention paid to the co-evolution of policy measures, technological developments, environmental framework conditions and societal needs and perceptions.

Then, the potential to adopt greywater recycling systems in Israel is analyzed in two of the papers. The case of this Mediterranean country is very interesting due to the water scarcity that affects its territory and to the specific institutional framework, which has recently focused on promoting water desalination (Feitelson and Rosenthal, 2012) to address that problem, while the implementation of water saving systems has been mostly undervalued. Dan Kaufmann, Lior Hayoon-Davidov and Anat Tchetchik argue that a proper regulatory framework for the installation of water saving systems that guarantees the quality of the water and minimizes health risks constitutes an essential pre-requisite to favour the willingness to adopt them. Their paper reveals that, for a representative sample of the Israeli population, those people who have a strong environmental attitude and a great concern for the environment are more willing to hire the service of a company to install and maintain greywater recycling systems. Their research suggests that although grey water has limited uses in typical Israeli multi-family dwellings, it would be possible to promote its extensive adoption and achieve important societal benefits.

A whole set of factors needs to be taken into account when analysing the likelihood of successfully diffusing water saving systems which are not yet very well known by the receiving population. The paper co-authored by Anat Tchetchik, Dan Kaufmann and Vered Blass reveals interesting insights into

the Israeli population and their awareness of water scarcity, environmental attitudes and behaviour, as well as knowledge about greywater recycling systems. Their analysis shows the importance of taking into account a whole set of factors that feature the consumers, including water demand elasticity, beliefs regarding water scarcity, effects of water desalination on the environment, environmental awareness and pro-environmental behaviour, water saving attitudes and translation of this into action, when studying the possible diffusion of greywater systems. Apart from those people who generally think that the Earth belongs to human beings and that resources are not limited, the paper identifies a paradoxical relation between those people that perform water saving practices in order to save costs and their willingness to adopt greywater systems.

In countries where a relatively low level of water is already consumed, serviced water saving systems could drive further reduction in water consumption. Jonathan Chenoweth, Alma López-Avilés, Angela Druckman and Steve Morse estimate the potential of widely adopted greywater recycling systems to reduce the consumption of water in a typical English city. From a theoretical point of view, the chance to achieve the absolute decoupling of population growth from water consumption is possible through this second level servicing.

Introducing widespread greywater recycling in urban environments is clearly challenging legally, socially, economically and practically. Coordinated policy development is required to manage the health risks, advance technology development and implementation, address the economics of recycling, and foster social acceptance of the technology. If appropriate policy is implemented and the widespread adoption of greywater recycling is achieved, then decoupling of urban population and domestic water consumption is possible. Such a decoupling will benefit the environment as a result of reduced water withdrawals from river and groundwater bodies and reduced energy consumption from avoided desalination. The papers in this special issue suggest that policy-makers need to grasp the nettle and make a greywater recycling revolution occur via coordinated policy development if these benefits are to be achieved.

References

Al Jayousi, O.R. (2003) Greywater reuse: toward sustainable water management. Desalination, 156, pp. 181–192.

Brooks, D., Brandes, O. and Gurman, S. (eds.) (2009) Making the Most of the Water We Have: The Soft Path Approach to Water Management. London: Earthscan.

Christova-Boal, D., Eden, R.E. and McFarlane, S. (1996) An investigation into greywater reuse for urban residential properties. Desalination, 106, pp. 391–397.

Dixon, A., Butler, D. and Fewkes, A. (1999) Water saving potential of domestic reuse systems using greywater and rainwater in combination. Water Science and Technology, 39, pp. 25–32.

Falkenmark, M. and Molden, D. (2008) Wake up to the realities of basin closure. Water Resources Development, 24, pp. 201–215.

Feitelson, E. and Jones, A. (2014) Global diffusion of XL-capacity seawater desalination. Water Policy, 16, pp. 1031–1053.

Feitelson, E. and Rosenthal, G. (2012) Desalination space and power: the ramifi cations of Israel’s changing water geography. Geoforum, 43, pp. 272–284.

Friedler, E. and Hadari, M. (2006) Economic feasibility of on-site greywater reuse in multi-story buildings. Desalination, 190, pp. 221–234.

Glieck, P. (1994) Energy and water. Annual Review of Energy and the Environment, 19, pp. 267–299.

Gross, A., Maimon, A., Alfi ya, Y. and Friedler, E. (2015) Greywater Reuse. Boca Raton, FL: CRC Press.

Maimon, A., Tal, A., Friedler, E. and Gross, A. (2010) Safe on-site reuse of greywater for irrigation – a critical review of current guidelines. Environmental Science and Technology, 44, pp. 3213–3220.

Stokes, J.R. and Horvath, A. (2009) Energy and air emission effects of water supply. Environmental Science and Technology, 43, pp. 2680–2687.

Acknowledgements

This special issue originated from the SPREE (Servicing Policies for Resource Effi cient Environment) project, funded by the FP 7 framework (Grant Agreement No. 308376). We thank the members of the teams who comprised this project for many helpful insights along the way, and particularly Yael Marom who coordinated it. Three of the papers in this issue are based on this project. The editors also wish to thank the external reviewers of the papers included: Eran Friedler, Paul Kay and David Brooks.