The PAE Living Building, located in Portland, Ore., at the heart of the city’s historic district, is the first fully certified Living Building in Portland, and the largest developer-driven commercial Living Building in the world.

To achieve Living Building certification, 100% of water needed for all building functions, including drinking water, is collected and treated on-site before being released back to the environment to complete the water cycle. The solutions that made this possible include a rainwater-to-potable treatment system, greywater collection and treatment system, nonpotable water supply system to flush fixtures and irrigation, urine-to-fertilizer nutrient recovery system, and a vacuum-flush toilet composting system for blackwater treatment.

The PAE Living Building design team’s intention was three-fold: achieve the Water Petal requirements of International Living Future Institute’s (ILFI) Living Building Challenge (LBC), find a way to decarbonize and provide a replicable roadmap for water use, and redefine what “waste” means.

Rainwater-to-Potable Water Systems

The PAE Living Building’s water story begins with rainwater falling onto the rooftop catchment system, allowing it to collect 100% of the water used on an annual basis. A Portland ordinance requires buildings in the downtown area to include a green roof. An exception to the ordinance was granted by the city to maximize the rooftop solar photovoltaic energy system and rainwater collection.

Rainwater collected on the roof drains into an internal gravity storm drain piping system, directing it down the five-story building, through a hydraulic jump prefilter on the ground floor, and into a 71,000-gallon, site-built concrete belowgrade cistern. The roof membrane, solar panels, storm drain piping and cistern lining systems are all NSF-rated for drinking water standards. 

Around 38 years of local rainwater data was used to calculate the cistern volume to ensure rainwater storage was adequate to provide capacity through the dryer summer months during the years with the lowest rainfall totals. 

The stored rainwater is pumped up to the ground floor mechanical room, where it is treated for potable water use at lavatories, showers, break room sinks and drinking/ice-making water. The rainwater treatment system consists of multibarrier filtration and disinfection systems including four stages of micron and membrane filters, UV filtration and a pH analyzer. 

The Oregon Department of Health required a chlorine injection system. Two 500-gallon potable water day tanks store the treated rainwater before it’s distributed to fixtures via a duplex variable speed booster pump system. 

To operate the rainwater-to-potable treatment system and provide safe, potable water to the building occupants, the system was required to obtain an Oregon permit to become a public water treatment facility. A licensed water treatment facility operator must be on-site daily to operate the system and confirm water quality testing to prove the water is safe to drink. The system must be operated manually to ensure safety. 

The two 500-gallon day tanks store enough water to last the building occupants one to two days, so the system generates fresh water in batches. Ultra-low-flow potable water fixtures keep the maximum daily potable water demand to a minimum of around 650 gallons per day. 

A caveat and major lesson learned related to drinking water is the use of chlorine in the treatment system. ILFI’s LBC Water Petal initiative directs water to be treated without the use of chemicals but allows exception if mandated by the State’s department of health who are licensing and permitting the public water treatment system to operate. To grant the exception, LBC allows chlorine injection at the source treatment system if chlorine is removed by 0.5-micron filtration before reaching any drinking water fixtures within the building. 

This allows the state requirements to be met with chlorine in the day tanks and distribution piping system, helping keep the supply system clean. The PAE Living Building features 0.5-micron filtration for hot and cold water in all break rooms. These filters, located under the break room sink for easy maintenance, ensure no chlorine enters the water supply to sinks, dishwashers, coffee makers, ice makers and drinking water outlets. 

Greywater Collection, Treatment and Reuse Systems

Once the potable rainwater is used at potable water fixtures on the upper floors of the building, it is again collected in a greywater gravity drainage piping system and routed down to the first-floor mechanical room. First-floor fixtures drain to an underground duplex sump pump system, then pumped back up to the greywater main drain in the first-floor ceiling space. Greywater then drains by gravity through a hydraulic jump pre-filter before entering the greywater treatment tank and system. 

It is important to note that break room sinks and dishwashers are also connected to the greywater collection and treatment system. Drainage from these fixtures is typically considered blackwater due to the presence of organic food waste. To minimize food waste entering the greywater treatment system, strainers are provided at kitchen sink drains along with training and signage encouraging occupants to discard food waste into the nearby composting bins. 

Regardless of the occupants’ actions, the greywater system is not technically a greywater treatment system due to the kitchen fixtures’ connection. This meant that the pathway for permitting this system under the current greywater recycling code provisions was a roadblock. Ultimately, the Oregon Department of Environmental Quality permitted the greywater system as a blackwater treatment system. 

This permit pathway is intended for utility-scale wastewater treatment plants with daily treatment volume in the order of hundreds of thousands of gallons per day. This is a little more than the 450 to 550 gallons/day anticipated in the building. Although the path to permitting this system was not the road most travelled, the expertise and familiarity of water treatment code pathways by the water treatment consultant Biohabitats lead the way to obtaining a permit. 

The wastewater treatment system consists of a textile filter pod that includes 25 square feet of textile media containing a suspended fabric fixed film filter using attached growth biological microorganisms. Wastewater is recirculated via a pump from the bottom of the tank and sprayed over the textile media through a pressure distribution system and nozzles at the top of the tank. 

Wastewater then percolates via gravity for filtering and cleaning by naturally occurring microorganisms living in the media. As the wastewater continues to be filtered by the biological media in the main part of the tank, a portion of the treated wastewater fills the discharge side of the tank for final filtering and distribution to the nonpotable water supply system. The tank, media and pumping flow rates were designed to handle up to twice the anticipated greywater demand to ensure the system is resilient in effectively handling peak flows. 

A set of duplex variable-speed pumps in the discharge tank pressurize the nonpotable distribution system and force the treated wastewater through in-line polishing stages of filtration, including 30-micron bag filters, UV disinfection and a hydropneumatic tank. 

Due to unexpected high iron content caused by cast-iron drainage piping leeching into the wastewater as it drained, additional filtration including recirculating ozone and a carbon filtration system polished the water to acceptable nonpotable water quality standards. From this point, the nonpotable water is distributed up through the building to supply water closets, urinals, and irrigation. 

Nutrient Recovery: Blackwater Systems

The PAE Living Building hosts a first-of-its-kind and scale multistory vacuum-flush composting toilet infrastructure. Eighteen “vacuum on demand” (VOD) flush toilets are distributed around the building along with five distributed VOD vacuum pumps, all connected to ground-floor composters. Similar to fixtures found on airplanes (but quieter), the toilets use vacuum power rather than swirling water to extract waste. 

Whenever one of the toilets gets flushed, the VOD vacuum pump kicks on to evacuate the bowl, macerate the waste as it flows through the pump, then direct it down the building to an underground atmospheric collection tank at the composters in the first-floor mechanical room. 

Norway’s Jets Vacuum AS manufactured the toilets. They have an adjustable flush flow rate only requiring between 0.11 to 0.22 gallons/flush (gpf) — between 83% and 92% less than code minimum 1.28 gpf toilets. Traditional modern toilets typically use about 1.6 gpf, while older fixtures can use as much as six gallons per flush. 

The Jets VOD system is among the most water-efficient water flushing toilet systems commercially available in the world, which is paramount when combining with a composting system. The less water, the better when it comes to composting. 

All the VOD pump outlet piping is routed separately back to the ground floor mechanical room where it combines into an underground atmospheric collection tank. Waste from the collection tank is pumped via duplex self-priming macerating pumps into a piping manifold system which distributes the waste to the composters. 

An automated control system determines which composter should receive the contents to ensure that waste is distributed equally among all the composters. Equal loading of the composters is extremely important to ensure they will all fill at the same rate so that maintenance and removal of compost can be performed for all 20 composters at the same time. 

Composter maintenance involves the addition of wood chips and manual turning of tines to mix the compost on a regular basis. Wood chips add carbon to the system to promote an aerobic environment within the composters. The processed solid compost is then manually removed every 18 to 24 months from the units and transported off-site for beneficial use as fertilizer. 

Liquid and solid waste travel from the vacuum-flush toilets to the composters. Liquid leachate collected at the composters passively drains by gravity out through the bottom of the units. The leachate drains combine and flow into an underground 2,000-gallon collection tank. Liquid leachate is very nutrient-rich and is pumped out of the tank as it approaches maximum capacity and transported off-site for use as fertilizer. 

The building also includes 14 hybrid waterless urinals, which divert approximately 9,400 gallons of urine annually to a dedicated 1,000-gallon underground urine tank for nutrient recovery. At regular intervals as the urine tank approaches capacity, urine is pumped out and processed by a fertilizer production system, which resides on-site in the first-floor mechanical room. 

The system converts or removes 98% of the nutrients in the processed liquid. The system produces a commercial retail-quality liquid ammonium fertilizer as well as struvite, a phosphorus-rich powdered fertilizer. The fertilizer products are commercially available for purchase at www.nutrientrecoveryservices.com. 

“Most fertilizer production right now is heavily fossil-fuel-based and trucked all over the country,” notes Pete Muñoz, PE, of Biohabitats. “The fact that this building is creating a local fertilizer is amazing and adds a whole different dimension to decarbonizing our communities.” 

The Future

With far-reaching goals for providing a roadmap for water use in Living Buildings, the PAE Living Building is an attempt to close the water cycle. By collecting rainwater, treating it on-site all the way through the waste process, the building proves what can be possible, while providing some lessons learned. The water systems’ design set out to be a replicable solution for future net-zero water use buildings. 

Future net-zero water systems’ designs should aim to use more passive systems and reduce energy-intensive plumbing systems. Water treatment requires a significant amount of space either within the building or on the exterior site. 

The PAE Portland Living Building was able to achieve this despite being land-locked in a downtown urban property. While its water systems’ designs may be replicable to an extent, the site and geology of future net-zero water buildings will have the biggest impact on the most practicable design solutions.

Luke Hendricks, PE, CPD and GPD, is a meticulous and driven mechanical engineer with PAE. His extensive experience includes the installation and design of plumbing, fire protection and mechanical systems at many of the West Coast’s top health care and commercial institutions, including the PAE Living Building. Hendricks is passionate about promoting sustainability through design and streamlining the building and design process for owners.