Hassalo on Eighth

Biohabitats, GBD Architects, Glumac, PLACE Studio | Portland, Oregon

Introduction

HassaloonEighthisamixed-usedevelopmentlocated in Portland’s Lloyd EcoDistrict. The development includes three buildings with 657 housing units, over 50,000 square feet of retail space, and over 250,000 square feet of commercial office space. The project team developed a strategy to treat and reuse 45,000 gallons of greywater and domestic sewage on-site dailytoreinvigoratetheLloydDistrictwithoutstraining municipal and environmental resources. The project treats and reuses the wastewater to reduce strain on the city’s aging water infrastructure and to prevent sewage overflow into the Willamette River.

Norm

NORM is a system that uses biological processes and gravity to treat wastewater with minimal energy consumption. NORM stands for Natural Organic Recycling Machine and shares similarities to John Todd’s natural wastewater treatment system, the Living Machine. TheNORMsysteminvolvesseveralsteps.Wastewater is collected in the primary tanks, which connect to the sewer as an emergency overflow connection.

Biohabitats

The wastewater is pumped from the tanks to an anoxic reactor, which provides an oxygen-free environment to reduce the nutrient content of the wastewater. Next, the wastewater goes through trickling filters that are integrated into a park-like pedestrian corridor. In these filters, the wastewater is pumped over an organic medium that shelters microbes that devour the nutrients in the wastewater. This process allows for a high level of treatment in a narrow and tall silo, unlike conventional wastewater treatment plants that use large horizontal ponds. After that, the water is treated in a tidal wetland, a wood-chip wetland, and a dentrification reactor. Finally, it goes through a polishing tidal wetland, which creates flood conditions and drains similar to a tidal system, fostering naturally occurring microbial organisms that eat more nutrients. The wetlands are incorporated into the landscaping, with the primary treatment happening far below the pedestrian area; unpleasant smells are entirely avoided. Mechanical filters screen out fine particles, and ultraviolet and ozone systems eliminate lurking pathogens that mightbepresent,makingthewatersafeforreadyfor reuse in flushing toilets, running the buildings’ cooling systems, and irrigating the landscape. Any excess treatedwastewaterthatisnotusedisinjectedintodry wells to recharge the groundwater in the urban oasis that has negligible natural permeability, ensuring that no part of the wastewater is wasted.