By Rainwater Management Solutions
Promoting sustainable rainwater harvesting practices will help solve stormwater and energy challenges throughout the world, according to the American Rainwater Catchment Systems Association (ARCSA). In an interview with World Water: Stormwater Management Editor-in-Chief Pamela Wolfe, ARCSA President David Crawford, and Secretary Neal Shapiro discuss the association’s expanded focus on stormwater, trends.
World Water has the mission of ARCSA evolved in the past decade to address not only water supply but also stormwater challenges as climate change effects such as severe rain events and prolonged drought have become more frequent and widespread?
Neal Shapiro: Besides rainwater harvesting for non-potable and direct-potable use, the ARCSA mission has evolved. It now includes and focuses on stormwater harvesting for mainly non-potable uses but also for potable as an indirect-use strategy. This is because there are more stringent water quality standards of NPDES (National Pollutant Discharge Elimination System) permits. These higher standards improve stormwater quality to protect water bodies, as well as collect local stormwater as a resource to expand supply in the face of less-traditional water resources. Why treat stormwater to a high level only to discharge it to a water body? It is more sustainable to use it in local supply. Although ARCSA has traditionally promoted harvesting rainwater falling on roofs – generally a cleaner resource requiring less treatment, and thus is more cost-effective – members see the need to broaden its efforts to include stormwater, such as rain that falls at grade or flows through pipes. This strategy increases opportunities to collect more precipitation for such uses as irrigation, flushing, fire protection, and vehicle washing, where potable water is unnecessary or in short supply.
WW: Stormwater is now considered an important component of the One Water approach that includes other water supply alternatives such as desalination and water reuse. Why has ARCSA expanded its focus on stormwater?
Neal: First, it’s important to be accurate in terminology for rainwater and stormwater management. As the collection of precipitation is a first-time use or application of this water, the accurate term to apply is “use,” not “reuse.” The latter is reserved for graywater and sanitary sewer water, which are reused a second time.
Also, Clean Water Act regulations continue to require additional and more expensive treatment of stormwater before discharging to surface water bodies. Consequently, the industry has reached a point where discharging this highly treated water is now a waste of a valuable resource. Plus, due to limited availability of less traditional water resources and changes in annual precipitation volume, collecting stormwater for local use, not discharging to a water body, is now an important supply management tool that supplements a community’s local water resources portfolio. In many areas, increasing local water supply reduces the need for imported water sources, which are often in short supply or subject to flow disruption. The One Water approach increases local water resources first, in addition to maximizing water efficiency and conservation, before looking to imported water or ocean water. In wetter climates, harvesting precipitation may not always be an economically viable solution now, but in areas that receive precipitation for only a few weeks of the year, building adequate rain-collection storage for use during dry periods can be exactly what a jurisdiction needs.
“THE RAINWATER AND STORMWATER TREATMENT INDUSTRY AND ITS TREATMENT TECHNOLOGIES ARE MATURE, EFFECTIVE, AND ALWAYS IMPROVING TO MEET NEW DEMANDS AND REGULATORY REQUIREMENTS, NATIONALLY AND GLOBALLY.” DAVID CRAWFORD, PRESIDENT OF ARCSA
WW: How is ARCSA promoting water harvesting?
David Crawford: Working with its partner the American Society of Plumbing Engineers (ASPE), ARCSA developed two important plumbing standards to promote rainwater and stormwater use, in association with the American National Standards Institute (ANSI) Standards 63 (rainwater) and 78 (stormwater). These documents assist plumbers, builders, and regulators in building collection systems to protect public health and deliver precipitation in a safe manner. ARCSA also has educational programs to assist plumbing and mechanical trade groups to become certified in designing, building, and inspecting such systems.
WW: What factors are driving the rainwater harvesting industry and how do they differ from the stormwater harvesting sector?
David: As people become more aware of the problems facing our centralized municipal inates effectively and disruptions in govern more control of their water systems by installing decentralized, onsite systems to ensure reliable, high-quality drinking and non-drinking water.
Neal: Changes to the NPDES permit program now require low-impact development strategies and green infrastructure (GI) solutions to collect and use precipitation (rather than treat and release to the environment). Whether rainwater or stormwater, municipalities have begun to require such solutions for private and public buildings. Besides requiring solutions during new construction, some municipalities have retrofit rebates such as government funds when they add precipitation collection systems on private properties. As municipal programs require and incentivize green infrastructure, the market is responding by providing solutions to meet the growing demand. The rainwater and stormwater harvesting markets are similar – although stormwater is more polluted in general and needs more advanced treatment systems to achieve the required water quality for various end uses. In addition to building permits that require precipitation harvesting, stricter water quality standards and the need to reduce combined sewer overflows have incentivized implementing precipitation harvesting strategies within stormwater management programs. In the United States (US) eastern region, combined sanitary and stormwater sewer systems prevail and older built-out urban centers with highly impermeable surfaces face significant polluted runoff problems. In this region, open space is a luxury or is simply nonexistent for building decentralized, concentrated precipitation collection systems. Yet, cities that do not have open space parcels are building green infrastructure including rain gardens, permeable paving, and specialized underground storage tree wells.
“WHY TREAT STORMWATER TO A HIGH LEVEL ONLY TO DISCHARGE IT TO A WATER BODY? IT IS MORE SUSTAINABLE TO USE IT IN LOCAL SUPPLY.” NEAL SHAPIRO, SECRETARY OF ARCSA
WW: What US cities or regions are adopting stormwater harvesting? Is this trend limited to arid regions to augment water supply resources or other water-rich regions to manage flood risk and reduce nutrient loads to receiving waters?
David: We are seeing a big surge across the US of communities that realize the benefits of water harvesting, including the states of Virginia, Minnesota, Ohio, and Texas, and the US capital city of Washington DC, just to name a few. The contamination of drinking water wells is also driving the public to explore alternative water resources.
Neal: Having worked in stormwater field in southern California for 20 years, I have observed a growing trend to directly use treated stormwater to help meet stricter water quality standards and develop a local water resource. A stormwater harvesting strategy solves two major management problems: It helps meet water quality requirements and supplies a local water resource, thereby solving permit compliance and water supply challenges. The traditional solution – treating and releasing stormwater back to surface water bodies – addressed only water quality requirements, wasting a water resource, which is an unsustainable strategy. Instead, the newer dual paradigm shift provides a sustainable solution. Collecting rainwater and stormwater for local use may be prevalent in the arid western region because of water supply challenges in contrast to the wetter eastern and Pacific Northwest regions. In dry regions, there is a more urgent need to collect precipitation for direct use and indirect groundwater recharge. Santa Monica, California is planning to build its first sanitary sewer-mining project in the next few years in conjunction with a large stormwater collection system, called the Sustainable Water Infrastructure Project (SWIP). In the last few years, the city has completed a number of unique stormwater collecting projects – one at a local park, using treated water for spray irrigation and restroom flushing, and another using a large storage tank under a beach parking lot adjacent to the Santa Monica Pier to collect stormwater and local brackish water for use.
WW: What technologies are enabling harvested rainwater to be used for more applications in industry, irrigation, toilet flushing, and even for drinking?
David: The rainwater and stormwater treatment industry and its treatment technologies are mature, effective, and always improving to meet new demands and regulatory requirements, nationally and globally. Generally, a typical effective treatment train for precipitation, depending upon where rain lands or flows, is composed of the following five steps, which can vary depending upon locale, and local plumbing and water quality requirements:
- Collecting plumbing system for precipitation runoff
- Pre-treatment and storage
- Multiple filtration systems depending upon end uses and short-term storage (if necessary)
- Disinfection and short-term storage (day storage)
- Delivery plumbing (with cross-connection prevention and inspection) to end uses with residual disinfection (sometimes required by local jurisdiction). Through this effective process, including prefiltration and disinfection, precipitation water quality has raised significantly. Leaving one of the steps out can make the difference of whether a system can produce high-quality water or not.
The image shows a 6-million-liter (1.6 million gal) stormwater tank under construction at the Santa Monica Pier. Water will be used for irrigation and Photo by Neal Shapiro, City of Santa Monica
WW: What role does real-time monitoring have in making stormwater harvesting systems more effective?
Neal: Real-time monitoring is a newer outgrowth of technical advances to manage and maximize stormwater storage and use. Often (such as in the west), when it rains, it truly pours – intensive rain events with high-volume rainfall in a short time, as well as actually exceeding the planned storage capacity, as rainfall averages seem to be changing dramatically. To better manage supply and demand with shorter, more intensive rain events, real-time monitoring is a solution. This strategy monitors storage levels and the rain event. If the storage capacity maximum is reached for the anticipated and predicted rainfall, the system is automatically drained to make room for the new rainwater or stormwater. The key to maximizing effective use of the stored water is to have a downstream use of the released water, such as an infiltration zone. Using a sudden release of stored precipitation for irrigation or some other direct use would probably exceed that demand and be impractical. Though one could overwater a large turf area, if available downstream, to get the water into the ground if a traditional ponding or infiltration area is not available. Certainly, good water storage and use planning is needed when using real-time monitoring for stormwater management.
WW: GI solutions such as rainwater and stormwater harvesting on residential and commercial properties are being implemented in more cities, to capture rainfall where it falls. What is the impact of GI on the quality of water resources?
Neal: GI solutions collect rainwater and stormwater for onsite treatment and use via passive treatment in general. For example, infiltration through soil media recharges groundwater where aquifers are accessible. Or via active collection (storage tanks), water can be treated (such as rapid treatment through proprietary systems) and used in irrigation, flushing, fire-fighting, and cleaning. GI systems remove water pollutants when precipitation runoff is collected, treated, and used, and thereby removed from entering surface water bodies.