What’s an “Onsite Non-potable Water System” (ONWS)?
- Onsite: Treatment occurs where water will be re-used
- Non-potable: We can’t drink it, but it’s great for many other uses!
- Water: That substance that we’re all mostly made of and we can’t live without for more than a few days.
- System: The pipes, tanks, pumps, and equipment that stores, treats and moves water.
Combine these words and onsite non-potable water systems include:
- Rainwater harvesting (rain that falls on roofs)
- Condensate harvesting (water from the air is collected)
- Stormwater harvesting (rain that falls on non-roof surfaces)
- Re-use of water from plumbing fixtures without poop (e.g. sink, tub/shower)
- Re-use of water from plumbing fixtures with poop (e.g. toilet)
The scale of these systems varies in size and land use:
- Single Family Residential (e.g. Re-use of water from fixtures without poop,various places)
- Government (e.g. San Francisco’s Public Utilities Commission, San Francisco, CA, see page 4)
- Institutions (e.g. Brock Environmental Center, Virginia Beach, VA)
- Commercial (e.g. Montgomery Park Office Building, Baltimore, MD)
- Neighborhood or district (e.g. Hassalo on 8th, Portland, OR).
- Large regional treatment facility when water is re-used very close to the facility (e.g. John Day, Oregon facility that uses treated “waste”water to grow plants in greenhouses).
Why is this important?
We shouldn’t be treating water to a standard higher than needed for the end use. For instance, we shouldn’t be using drinking water to flush our toilets! This is called “fit-for-purpose” water. Saving a lot of water and energy this way protects environmental quality and makes us more resilient in the face of climate change. With the right standards in codes, we protect public health, too.
- Proper sanitation prevents disease. Water systems were first created to prevent water-borne disease. They provide clean drinking water and remove poop, but use too much water to do this. Population growth and climate change now impacts our access to water supplies. Demands on our drinking water systems can be relieved by re-using onsite water for uses that don’t require drinking water. This can reduce water use in homes by up to 60% when applied to uses like watering gardens and toilet flushing. Source: US Department of Energy
- Reduce urban heat islands. Urban heat islands are caused by too many hard surfaces in one place. This increases: 1) heat-related illness and deaths, 2) air pollution and climate change, 3) summer peak energy demand, 4) air conditioning costs, and 5) water quality. Many plants, from flowers to trees should be irrigated with non-potable onsite water to reduce air and surface temperatures. Sources: Purdue University, EPA: Heat Island Effect
- Free model codes are ready for use by under-resourced public bureaus. Language to launch onsite non-potable programs was created by public health and environmental agency staff. The approach protects public health better than current federal standards for water coming out of your tap. Source: National Blue Ribbon Commission for Onsite Nonpotable Water Systems, Source: Water Environment & Reuse Foundation (WE&RF)
- Give communities control over their water supply. Most onsite water systems are much smaller than municipal systems and cost less to build. This could mean loans are easier to get, making communal ownership a feasible option. The water supply produced can be sold to pay off the systems and even make a profit.
- Create good-paying green jobs. Jobs in water pay well. Ideally, many small onsite non-potable water systems would be located throughout a region. This creates more chances to plan, design, construct and operate and maintain (O&M) these systems. Splitting O&M needs into distinct skill levels can create more entry-level jobs. On-the-job training and professional development (creating more jobs) should be offered to help people access even higher paying jobs. This approach would make these systems more cost-effective to maintain and operate, reducing the largest cost of any construction project. Source: Making the Utility Case for Onsite Non-potable Water Systems
- Help building users connect to water. People living and working in buildings that treat and re-use their own water supply tend to be more aware of their water use and what they’re putting in the drains. They tend to conserve more water and behave in ways the prevent pollution. Source: Puttman Infrastructure tour of Hassalo on 8th
- Enhance quality of life. Onsite water treatment systems that use plants are preferred, since they are easiest to maintain and have the lowest energy demand. Plants reduce crime, lowers traffic speeds, improve well-being, and more. Source: Green Cities: Good Health
- Create a space for art. Onsite water systems have tanks, ponds, and other structures that have been integrated into the landscape and buildings in tasteful and attractive ways.
- Avoid big public expenses and rate increases for water customers. Dispersed systems can be blended with existing systems. This avoids large outlays that get passed on to water customers and further reduces the need to expand municipal water systems. . Source: Environmental Protection Agency Water Reuse and Recycling: Community and Environmental Benefits
- Blending water supplies costs less than having a single supply. Utilities with more than two sources of water can deliver water at a lower cost. Across the U.S., onsite water systems are being built for profit. Public bureaus should plan for onsite water systems to be mixed with existing systems. This will result in savings to water customers.
- Saves money on the maintenance and re-building of existing water systems. The cost to fix existing centralized water systems increases every year. At the same time, federal investment declines. “The total investment gap through 2025 is expected to be $105 billion, and $152 billion, by 2040 if left unaddressed. This doesn’t include replacing more than 7.3 million lead service pipes, which adds at least $30 billion to the investment gap.” Onsite water systems localize water systems and reduce the need to upgrade existing systems. For instance, less water in sewer pipes means existing smaller pipes don’t need to be replaced. Source: American Society of Engineers
- Reduce algae blooms and other low river flow impacts. Low river flows are a problem, because the river is too hot. Algae grows too fast and reduces oxygen levels in the water, harming animals that live in the river. Using water more than once leaves more water in nature, so low river flows occur less often (Source: Environmental Protection Agency). Trout Unlimited shows how harvesting rain can solve timing problems to reduce draws during low flow periods.
- Protect rivers that have too many nutrients. Nutrients are natural, but any material that exceeds natural levels can pollute a river. Many typical “waste”water treatment plants discharge nutrients and warm water to rivers. Re-using water can reduce or fully divert “waste”water from going into a river. On the other hand, nutrient-rich water is great for growing food, keeping water and nutrients onsite as plants take them up.
- Reduce and prevent pollution during rain storms. Re-using stormwater and “waste”water lowers the amount of pollution that flows into any river. Where existing combined sewer pipes carry both types of water, overflow of polluted stormwater and poop into rivers occurs less often. Source: Environmental Protection Agency
- Minimize flooding. One way to minimize floods is to capture stormwater runoff in a tank of pond and release it slowly away from the site. This practice has been an accepted method for decades at the site scale. “Active” harvesting of rain can further improve on this approach. These systems draw water from the tank or pond to be re-used on the site. This frees up space to store water in the next storm, which shrinks the size and cost of storage. These have proven to be even more effective for to reduce runoff and promote a cleaner surface water supply. Source: Environmental Protection Agency
- Enhance local water supply to protect surface water, groundwater, and wetlands. Re-using water reduces the need to draw on water from the ground and surface. These waters connect to each other and to wetlands via water flowing in the ground. Source: Environmental Protection Agency
- Protect watershed health with small-scale approaches. Conventional municipal systems often draw a lot of water from one place and pump and convey it a long way. After people use it once, those large volumes of water are conveyed long distances, treated, and released to a completely different watershed. Sometimes this is a good thing that restores flows at the lower end of the river system. It’s just as likely that plants and animals in both places are harmed by too much water at the low end (i.e. flood) and drying out (i.e. drought) at the top of the river system. Onsite water systems can capture, treat, use, re-use, and release water all within a small, local area, much smaller than a watershed. This helps maintain local water balance to reduce floods and droughts. Source: Eco-environmental impact of inter-basin water transfer projects: a review
- Reduce energy use. At over 8 pounds per gallon, water is heavy. Any time water must be pumped (which occurs in almost every system at some point) energy must be used. Most onsite water systems convey and pump water a very short way, so they use much less energy than typical centralized systems. Source: Environmental Protection Agency
- Reduce fire damage to buildings. Planting anything from flowers to trees is a great way to help reverse local and global climate change. Irrigating (i.e. watering) plants with re-used water conserves drinking water supplies. In some drought-struck areas, it’s illegal to water landscapes with drinking water, so this approach means we can help reverse climate change and have beautiful landscapes. More wet and cool (i.e. irrigated) soils slow the spread and intensity of fires. Source: United States Department of Agriculture, Forest Service
- Reduce resources used in the treatment process. Conventional water systems treat all water to the same level, whether we’re drinking it or flushing toilets with it. Instead of treating all water to a single standard that we can drink, onsite waters are treated to a level that accounts for their end uses and disposal points (e.g. water draining from a municipal “waste”water treatment plant to a river versus irrigation on land). This is called “fit for purpose” water.
- Diversify a community’s water sources. Many places buy water from outside of their own area (i.e. they import water). Onsite water re-use systems provide a local water supply that costs less than imported water. Having more than one or two sources of water helps a community bounce back faster when their water supplies are impacted. Source: Environmental Protection Agency
- Be ready for emergencies. Onsite water systems often include storage ponds and tanks dispersed throughout a community. These smaller systems are less complex than conventional water treatment systems, so they’re easier to repair. Also, when water is harvested onsite from buildings, water doesn’t need to be conveyed via buried pipes, which break in fire and earthquake events.