This year marks the 10th anniversary of the installation of a water recycling system at the Solaire, a building in the Battery Park City development in New York City’s borough of Manhattan. The Solaire was the first “green” residential high-rise building in the United States and earned a gold rating on the Leadership in Energy and Environmental Design (LEED) scale devised by the U. S. Green Building Council (Washington, D.C.).
Since the Solaire, water recycling systems have been added in five additional Battery Park City buildings.
The systems are a testament to the evolution of urban recycled-water development. The evolution has included changes in regulations, project delivery methods, and technology. Perhaps the most significant changes are the broader acceptance of water recycling, institutional and public commitment to green technology, more modest carbon footprints, and the environment in general.
Keys to success
The project has been a success, not only as measured by the consistently high-quality effluent produced, a dramatic reduction in potable water demand, and user acceptance, but also by the awards it has won. Key ingredients that led to this success included the vision and dedication of the project proponents, including a city authority with foresight, a dedicated project champion, a committed developer, and an innovative engineer.
The New York City Department of Environmental Protection (DEP) recognized far in advance that its inexpensive water supply was neither going to support a growing demand forever nor be inexpensive forever. Following droughts in the 1960s and 1970s, DEP compared the cost of conservation programs and installing new water supply facilities. Conservation was the better alternative. Several conservation programs were instituted, including the incentives that made the Solaire more economically attractive.
Setting the standard
The Battery Park City Authority (BPCA) owns Battery Park City’s 37-ha (92-ac) site. Building owners enter long-term leases and agree to build according to BPCA environmental guidelines. Interestingly, the guidelines were written in the 1970s and 1980s to green building standards prior to the establishment of the LEED rating system.
The Solaire’s water recycling system consists of a membrane bioreactor followed by a multiple-barrier approach for disinfection. The membrane bioreactor is an activated sludge system enhanced for nitrogen removal with membranes that have an effective pore size of 0.4 µm. The disinfection system consists of an ozone generation and contacting system, used for oxidation and color removal, followed by an ultraviolet-light system for additional disinfection.
Effluent meets strict reuse standards established by the New York City Department of Health; these standards are similar to the highest-level reuse quality requirements established by many states. The water is reused for toilet flushing and cooling-tower makeup water.
Finished water from the storage tank circulates through the ozone and ultraviolet-light systems to maintain disinfection. Surplus wastewater — the system treats up to 94.6 m3/d (25,000 gal/d) — and solids are discharged to the municipal sewer.
Automatic potable-water fill valves provide a backup system to provide flush-water service even if the recycling system is out of service.
Challenge: Project delivery
The recycled-water systems had implications for almost all of the building’s systems. The mechanical, electrical, and plumbing engineer, as well as the architect, mechanical contractor, general contractor, building trades, and project manager all had to cooperate to enable the installation.
To provide the best results, the wastewater engineer generally acted as the design–builder, coordinating the integration of the recycling system into the building, being responsible for the specification and procurement of recycling system equipment, and working closely with the building trades. That the project’s designer also would operate these systems helped to provide integration and continuity from design through operation.
Challenge: Lack of regulations
In 2001, New York state had no recycled-water guidelines. Therefore, BPCA, DEP, the New York City Health Department, the building’s owners, and the design professionals cooperated to determine what standards, commissioning testing, and longer-term monitoring would be required. For the Solaire, a trial period evaluated the system, and adjustments were made to determine future operating parameters and monitoring requirements.
Today, system regulation continues to evolve as other regulatory and industry groups are engaged. The New York City Department of Buildings, Office of Technical Code Review, has since adopted official water reuse code requirements as part of an interim plumbing code. “Buildings Bulletin 2010-027,” which was drafted by the Building Sustainability Board, establishes water quality and system monitoring requirements. The interim bulletin is being adopted into the plumbing code as part of a routine triannual code update. It serves as a model for in-building water reuse systems.
Several changes in system design were needed as engineers and designers decided on new water quality requirements. Several scientific and applied site studies analyzed the systems at Battery Park City. As originally designed, the treatment system included space for an activated carbon adsorption system to remove color, which often accompanies membrane bioreactor effluent. By the time the system was constructed, this option was replaced by ozone, which had proven effective at oxidizing color at much lower life-cycle costs and provided an additional disinfection.
An example of cooperative development occurred when the Solaire’s heating, ventilation, and air-conditioning system showed phosphate buildup on the condenser tubes of a high-efficiency gas-absorption chiller. The Solaire’s combined rainwater and recycled-water system was designed to remove nitrogen but not phosphorus. After the discovery, phosphorus removal was implemented.
The next 10 years
These systems have convinced the New York City Buildings Department to allow additional reuse applications, including laundry cold-water supply and sidewalk washing.
Current research focuses on maximizing energy efficiency and optimizing the treatment processes. Research projects include investigating biological process modifications to reduce energy and chemical requirements and optimizing membrane configuration and aeration systems by using separate membrane and variable-speed process blowers to enable process blower control based on dissolved-oxygen levels.
Andre Zinkevich is a senior vice president, Ed Clerico is CEO, Bruce Douglas is a senior vice president, and Michael Zavoda is a managing engineer at Natural Systems Utilities (Hillsborough, N.J.).
©2012 Water Environment Federation. All rights reserved.