By Rick Andrew
Water reuse has been a topic of growing interest over the last decade or so. Water shortages and sustainability initiatives have contributed to this interest, with increased opportunities for water treatment equipment manufacturers, engineers and dealers resulting. There are two standards related to water reuse receiving increasing recognition by various states and plumbing codes: NSF/ANSI 350 Onsite Residential and Commercial Water Reuse Treatment Systems and the related standard, NSF/ANSI 350-1 Onsite Residential and Commercial Graywater Treatment Systems for Subsurface Discharge.
Overview
Essentially, the scope of these standards can be viewed in terms of input types, applications and reuse purposes. These scopes determine the challenge-water type, which in turn determines the test environment. In all cases, testing is extensive, with a 26-week/six-month test period being required to make sure the equipment will function under a variety of use conditions for an extended period of time.
Input types
The standards address situations in which all of the wastewater (graywater and blackwater) are being reused. This includes laundry, bathing, toilet flushing…everything. This is obviously the most demanding type of scenario for reuse treatment, because all of the wastewater is being treated. Additionally, the standards address scenarios in which only the graywater is being reused. Graywater essentially excludes toilet flushing wastewater (blackwater). For purposes of NSF/ANSI 350 and NSF/ANSI 350-1, graywater is defined as laundry water and bathing water. Further, the standards include requirements for reuse systems targeting only laundry water or only bathing water reuse. Each of these reuse scenarios has real-world applications that provide reuse and enhance the sustainability of the water infrastructure, so it is important to include requirements for all of them.
Applications
Applications include both residential and commercial. For purposes of NSF/ANSI 350 and NSF/ANSI 350-1, residential is up to 1,500 gpd. A residential application also requires a treated effluent quality that is slightly lower than that necessary for a commercial application. Commercial applications include those systems of any daily treatment capacity that meet a commercial-effluent quality and all treatment systems providing more than 1,500 gallons of treated effluent per day.
Possible end uses
NSF/ANSI 350 addresses general non-potable reuse applications such as toilet and urinal flushing and subsurface irrigation. NSF/ANSI 350-1 addresses subsurface irrigation only and excludes other reuse applications. By having both versions of the standard, states can decide which scope they would prefer to regulate through codes using either of these. NSF/ANSI 350-1 was initially developed specifically for the state of Washington, but of course, other states are free to reference it in their codes as well.
Challenge water and test environment
Under NSF/ANSI 350 and NSF/ANSI 350-1, the input type and application are what drive the type of challenge water, which in turn is what drives the test environment. For example, residential wastewater applications are tested at a wastewater treatment plant that is specially configured to be a test site. The test system is installed at the test site and actual wastewater is diverted to it as the challenge water. This wastewater must have a 30-day average TSS of 100-350 mg/L and five-day biochemical oxygen demand (BOD5) of 100-300 mg/L. Commercial wastewater applications, on the other hand, are tested on location where they will be utilized.
Reuse systems for graywater applications up to 1,500 gpd are tested in a laboratory using a specific recipe of simulated graywater, whereas systems for graywater applications greater than 1,500 gpd are tested on location where they will be used. Figure 1 describes the requirements for the graywater-application challenge water. Residential reuse applications involving laundry water only are tested in a laboratory using laboratory-created, simulated laundry water, whereas all commercial laundry reuse treatment systems are tested on location where they will be used. 
Finally, reuse systems for bathing water only applications up to 1,500 gpd are tested in a laboratory using a specific recipe of simulated bathing water, whereas systems for bathing water applications greater than 1,500 gpd are tested on location where they will be used. Figure 2 describes graphically the input types, applications, challenge water and test environment and reuse applications covered under NSF/ANSI 350 and NSF/ANSI 350-1.
Codes, regulations and the standards
Having been published in 2011, these standards are gaining recognition in various codes and regulations, adding to their importance and building a foundation for establishing reuse as a more common approach to water utilization. Recognition of these standards includes:
• The state of Washington’s adoption for their regulations
• The International Association of Plumbing and Mechanical Officials (IAPMO) and International Code Council (ICC) inclusion of NSF/ANSI 350 in their draft plumbing codes
• Canada, Australia and some European countries have expressed interest in the standard(s). Canada will likely reference NSF/ANSI 350 rather than creating a duplicate standard.
A growing opportunity
Increased acceptance, improved and enhanced understanding of equipment and capabilities, and growing desire for sustainable practices drives the opportunity for equipment manufacturers, distributors, dealers and installers in the area of water reuse. NSF/ANSI 350 and NSF/ANSI 350-1 contribute to this opportunity by providing a framework to establish effective performance of these systems for a variety of input types, applications and end uses.
About the author
Rick Andrew is NSF’s Director of Global Business Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: Andrew@nsf.org