The Helena, which opened in late 2005, is an apartment building that offers more than amenities, views, and nice finishes. Behind the $100 million tower’s gleaming glass and metal skin is a serious high-performance building. Its owner and designers say the Helena will annually use 65 percent of the energy and one-third of the potable water of comparable properties.
During the design phase of the building, which was ultimately to receive LEED Gold Standard rating (Leadership in Energy and Environmental Design) one of the criteria that was required was high levels of water recycling. The building's designers needed to find a system to treat the wastewater produced in the building to recycle quality water for reuse.
High levels of treatment are required in order to minimize the chemical addition requirements, especially at the cooling towers which were designed to use recovered wastewater. The system effluent discharge requirements were set at < 5mg/L BOD, < 5 mg/L Total nitrogen and <0.1 mg/L phosphorus.
Some other technologies were considered, such as a conventional SBR system, and MBBR systems, however, none were considered to answer all of the requirements as well as the DynaLift MBR system.
The membrane bioreactor technology was selected because this technology consistently offers the highest water quality. Since footprint and equipment access was also a major consideration, the Dynatec Hi-Rate system was selected. This system has the smallest footprint of any MBR. Because of the external membrane design, all equipment can be accessed and maintained without requiring high ceilings.
The Helena’s most space-intensive green feature is the blackwater recycling system, which reclaims about 43,000 gallons of wastewater each day. The processed blackwater, along with storm water, is used in the cooling tower, for flushing toilets, and for irrigation of the 12,000 square feet of green roofs. The system occupies about 5,000 square feet on the north side of the second and third floors, an area not suitable for apartments because of the proximity of an existing structure.
Due to high concentrations of mixed liquor and long SRT, sludge wasting is minimized. Wasting is carried out to the city sewer, together with screenings. No solids or liquid sludge leave the system other than by sewer discharge, ensuring that the system is odor free.
“Although the equipment added about 1.5 percent to the construction cost of the building, the square footage did not count against the tower’s allowable floor area ratio and made perfect use of space that would not generate revenue”, points out Bruce Fowle, FAIA, FXFOWLE senior principal. The system is sized to also handle the blackwater load of the Rose, an apartment building the developer plans for the site just to the west of the Helena.