California, no stranger to extended dry spells, is struggling with the most extreme drought the state has endured in more than 500 years. As climate change—projected to worsen the country’s water woes with more frequent and severe droughts—becomes the “new normal,” many are finally waking up to the water scarcity realities facing the nation’s arid western and southern states. Given the severity and far-reaching impacts of dwindling water supplies on cities, farms, native fisheries and the environment, one has to wonder: Why do we still water lawns and flush toilets with increasingly scarce and expensive potable water?
Reduce, reuse, recycle—a phrase many of us are familiar with from elementary school and usually associate with trash—is a concept that also is applicable to water. For communities to be resilient and prepare for the worst effects of climate change, people need to rethink how they use, and reuse, water and wastewater so they can sustainably manage the full water cycle and make the most of limited resources. While recycling—which in this case refers to municipally recycled water—depends on several factors outside of the typical consumer’s control, the first two represent excellent opportunities to make a positive impact on a community’s sustainability.
The first step to reducing water consumption on an individual level is by making small changes to daily activities, such as watering lawns less often and taking shorter showers. The next step, at a building level, is replacing inefficient products like washing machines, toilets, faucets and showerheads. The final step is reusing water in homes and businesses to the greatest extent possible. One of the easiest and safest applications of this concept is the onsite use of lightly used water, or greywater, that otherwise would be discarded as waste.
What Is Greywater?
Greywater typically is defined as untreated wastewater that has not come in contact with toilet waste and includes wastewater from bathtubs, showers, washbasins, washing machines and laundry tubs. It does not include wastewater from kitchen sinks or dishwashers. Generally, greywater can only be used for nonpotable applications such as outdoor landscape irrigation, toilet flushing and clothes washing.
Depending on the type of greywater system employed, greywater sources can account for almost 50% of indoor residential water use, while end uses that can utilize greywater consume almost 75% of total indoor and outdoor residential water demand. Greywater technologies vary in complexity; the three general categories of systems include:
- 1. Manual bucketing, the act of collecting water from a shower in a bucket while waiting for the water to heat up sufficiently. It can be used to water plants and supplement outdoor irrigation;
- 2. Diversion and filtration systems, such as laundry-to-landscape that, as the name implies, divert discharge water from a clothes washer to the outdoors to irrigate the landscape; and
- 3. Treatment and reuse systems that treat water to a standard fit for nonpotable use and can be used for flushing toilets, washing clothes and aboveground irrigation.
In addition to saving water, the use of greywater reduces the volume of water discharged to the sewer. Potential benefits of such reduced flows for wastewater collection and treatment systems include increased capacity that can avoid, downsize or defer the need for new capital projects; improved efficiencies in primary treatment due to increased concentration of biological oxygen demand; and reduced energy demand and costs for treatment. Additional research would be valuable to further characterize and quantify these and other impacts of reduced wastewater flows.
Despite the well-documented widespread adoption of greywater use in other developed countries with similar climates and water scarcity issues, such as Australia and New Zealand, urban areas in water-stressed states in the U.S. have been slow to encourage it as a standard measure for conserving water. But at least one state, Arizona, already has started to follow the lead of Australia, implementing water-smart strategies to overcome the barriers in the way of more widespread and efficient use of this resource.
Educating the Public
Generally, people in the U.S. may not be as well informed about water resource limitations and the use of alternative water sources as Australians, who have spent the better part of this century coping with severe drought. Education of both the public and the regulatory community is an essential first step to expanding the use of greywater in this country. If people do not know what greywater is, they will not request incentives and guidance from their water suppliers, encourage local market demand or advocate for sensible regulations. If the public health concerns of regulators are not addressed and the mitigation of risk with proper management strategies is not fully understood, there will be reluctance to allow the use of greywater—even though there have been no documented cases of illness from greywater in the U.S. reported to the U.S. Centers for Disease Control and Prevention.
Inadequate understanding of the risks of greywater use is one factor that has led to regulatory structures and permit requirements that can be confusing, cost-prohibitive and time consuming, even for simple laundry-to-landscape applications.
Another barrier can be the expense of modifying the plumbing in an existing building. For most existing buildings, collecting water from lavatory faucets, showers and bathtubs is a difficult and expensive task. In these cases, diversion or simple self-contained treatment systems (like faucet to toilet) are the only affordable options.
Climate change means more water uncertainty for everyone. But greywater can address some of our water scarcity challenges today. We need public education that provides water-smart guidance and introduces both new and time-tested ways to save every last drop. That public awareness will create a thriving greywater market. Equally important, local authorities, including city planners and public health officials, can do more to facilitate greywater permitting and safe use by developing sensible regulations that encourage the use of alternative water sources like greywater while remaining protective of public health—and adequate rebates and incentives to jump start the market. Now is the time to take action.
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