Safe on-Site Reuse of Greywater for Irrigation - A Critical Review of Current Guidelines

Abstract

Reuse of greywater for landscape irrigation can significantly reduce domestic water consumption. Alongside its benefits, there are potential drawbacks to greywater reuse, raising legitimate concerns about the impact on human and environmental health. In this review, a risk assessment framework is used to assess the adequacy of different regulations to ensure safe and long-lasting, onsite greywater reuse for irrigation. Existing regulations from around the world are assessed along with a standardized evaluation of measures taken to protect public and environmental health. In most cases, human health considerations currently dominate regulatory strategies, while environmental risks are either ignored or underrepresented. A distinction between single and multiple households was found to be a fundamental component of the regulations which often lead to approved utilization of untreated greywater among single households. We concluded that the use of untreated greywater is not recommended, especially in multihousehold systems as it may compromise public health, with single household systems posing more likely risks to the environment. Existing rules to control greywater use should be further revised toward the establishment of a more advanced regulatory system which can avert the salient potential risks associated with greywater reuse, while exploiting the enormous potential of this alternative water resource.

Supplementary household water sources to augment potable municipal supply in South Africa

“…Another concern with HWS application is the non-potable water quality, associated risks and personal liability to manage the decentralised 'private' system, especially when it comes to greywater reuse . Maimon et al (2010) note that '...the use of untreated greywater is not recommended due to associated risks, even for single households'. Despite a HWS being considered 'legal', consumers with HWS are not excluded from personal liability, which may arise for individual homeowners who make non-potable supplementary water available on the property.…”

Is Gray Water the Key to Unlocking Water for Resource-Poor Areas of the Middle East, North Africa, and Other Arid Regions of the World?

“…• Households with individuals who are carriers of infectious disease or who perform practices such as bathing babies and laundering diapers may be at greater risk for spreading the disease as a result of GW reuse (Rose et al 1991;Eriksson et al 2002;Ottoson and Stenstrom 2003;Friedler 2004;Gross et al 2005;Maimon et al 2010). …”

“…• Because enteric pathogens most commonly occur in GW when an individual contributing to a system is a carrier, using GW in multiple household systems might be more dangerous than in an individual household (Maimon et al 2010). Multiple household systems provide a larger pool of susceptible individuals to overlap with a contributing infectious disease carrier and subsequently increase the likelihood that infections are proliferated into new hosts.…”

“…These guidelines recommend practices such as using GW only on trees or forage crops or if used on vegetables requiring a minimum number of days between last irrigation, harvest, and consumption of these products. Some have argued that current guidelines do not accurately characterize the health risks associated with wastewater reuse and have disparaged the fact that current standards fail to account for environmental risks (Shuval et al 1997;Maimon et al 2010). For this reason guidelines are periodically updated.…”

“…The limiting factors that continue to undermine attempts to conduct observational epidemiologic investigations of GW are the sample sizes and the laboratory and diagnostic procedures required to achieve sufficient power and sensitivity to make inferences at the population level (O'Toole et al 2012). To circumvent these logistical constraints, many have turned to probabilistic models, such as quantitative microbial risk assessment (QMRA), to determine the excess risk of infectious disease as a result of using GW (Shuval et al 1997;Ottoson and Stenstrom 2003;Mara et al 2007;Maimon et al 2010;Barker et al 2013). The accuracy of these models depends upon reliability of prior information taken from epidemiological investigations.…”