development. This water management practice emphasizes all types of water including wastewater as valuable resources as opposed to burden to the environment. The collected wastewater from the building may be more than sufficient for the
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building use upon removal of pollutants and contaminants in the water. The recycled water can be used for toilet flushing, landscape irrigation, cooling water makeup and other cleaning purposes.
LEED, Leadership in Energy and Environmental Design, is the green building rating system developed and adopted by the U.S Green Building Council. At the time the Solaire project was originally planned and designed in 1999, LEED was not available for high-rise residential buildings. The BPC Authorities conducted extensive research and benchmarking to develop their own standards to attain a LEED certification with a level of Gold or above for the existing buildings and new buildings. The Solaire set an example and achieved a LEED Gold award in 2004 as the first green building in the U.S.
The NYC DEP has a comprehensive water reuse incentive program that offsets water reuse operational costs by providing a 25% reduction in rates for city water and sewer when at least 25% reuse is provided onsite. The Solaire building also received state tax incentives both for providing affordable housing and for offsetting the cost of some of the green building features in the design.
13.2 TECHNICAL CHALLENGES OF WATER QUALITY CONTROL
Treatment train for water recycling
The Solaire onsite wastewater treatment, storage and reuse system is located in the building’s basement, and includes a series of common-walled, cast-in-place, concrete tanks (Figure 13.2). The plant is designed to provide high-level removal of organic material (measured as biochemical oxygen demand or BOD), total suspended solids (TSS) and nitrogen using a membrane bioreactor. Blackwater from the toilets and greywater from sinks and showers in the building are collected in an aerated 36 m3(9500 gal) feed tank and flows to a trash trap to remove larger non-biodegradable solids (American Water, 2008). A three-stage biological system consisting of an anoxic tank, an aerobic tank, and a membrane filter removes BOD, TSS and nitrogen. Phosphorus removal capability is provided to the treatment plant by addition of chemicals (aluminum salt).
The treated water is then further disinfected by ultraviolet lights. Any remaining colour is removed using ozone. The storage tanks serve as reservoirs for the treated water, which is used as flush water, make-up water for the cooling towers, and for irrigation. After water is extracted, biological sludge is sent to the city through the sanitary sewer system to aid in the municipal treatment process.
In addition, stormwater is collected and beneficially reused at the Solaire. The rooftop garden design incorporates a storm water retention system that retains rainwater using a mat below the soil surface. The rainwater can be saturated within the mat when it rains. Once the mat is saturated, excess rainwater spills over into drains on the roof’s surface. The rainwater is then collected in a 38 m3 (10,000 gal) tank in the building’s basement and saved for reuse. The treated water is used for landscaping irrigation with the high-efficiency drip irrigation system just below the top of the soil throughout the roof garden.
The gardens on the rooftop also provide added thermal insulation for the building and help reduce the heat island effect in the city.
Water quality control and monitoring
Plant influent wastewater sample is taken routinely to measure the wastewater characteristics for BOD, TSS, total phosphorus, orthophosphate, and TKN (total Kjeldahl nitrogen, sum of organic nitrogen and ammonia nitrogen). The typical concentrations
Wastewater
Figure 13.2 The Solaire wastewater treatment and recycling system schematic (a) and a view of plant interior (b).
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of BOD and TSS measured in the influent are 146 mgO2/L and 190 mg/L, respectively. The average water quality is presented in Table 13.1.
The BOD and TSS concentrations in the treated wastewater effluent are typically less than 6 mgO2/L and 1 mg/L, respectively. The pH of treated water is maintained between 6.8 and 7.2 by adding sodium hydroxide (NaOH) to the aeration tanks. Treated water is stored in a 34 m3(9,000 gal) storage tank. Although not for potable purpose, the typical turbidity of the treated water is between 0.1 and 0.2 NTU which is even less than the EPA’s drinking water standard.
Main challenges for operation
Since the start-up of the system in 2003, Applied Water Management has worked closely with the building mangers to ensure the normal operation of this complex wastewater treatment and recycling system. They have continuously looked for opportunities to optimize and improve the efficiency and effectiveness of the system. However, there are still challenges for system operators to deal with such a compact and complex system while trying to minimize the impact on residents and the functioning of the building. The main challenges and lessons learned are briefly summarized below.
Typically, wastewater treatment plants, especially with biological treatment processes, show better performance if the influent flow is relatively consistent. But because all the influent flow to the treatment plant is generated from the building residents only, the flow at the Solaire can vary significantly depending upon the time of the day and the occupancy of the building. For example, summer and part of the winter are typically the vacation seasons when the residents leave the building, resulting in low flows. Sometime the flow is so low that the bacteria responsible for the removal of contaminants in wastewater are in jeopardy of starving due to lacking of food (typically carbon sources). When that happens, the experienced operators add food (sometime dog food) to the wastewater to keep the bacteria healthy and ready to work when needed.
A major concern with the operation of a wastewater treatment plant in a building basement is the potential for adverse impact on the residents. These issues include odour and noise which are common for a conventional wastewater treatment plant, but at Solaire precautions have been taken to reduce the odor and noise. The plant has an enclosed blower and each tank is sealed only with a hatch for operator to access the tank for inspection and maintenance. In addition, the air from the head space of the feed tank is vacuumed and piped to a carbon adsorption system located in the basement, which is then exhausted above the roof level to eliminate chances of odor from the plant escaping and entering the apartment building.
The original plant design did not include biological phosphorus removal, but chemical removal of phosphorus is now provided to minimize scaling in the building cooling system that uses recycled water. In some instances, recycled water is blended with city water to augment the flow. An on-going research project is taking place by a team of scientists and operators from American Water, with an aim to optimizing phosphorus removal while minimizing the use of the chemicals and energy.
13.3 WATER REUSE APPLICATIONS
The treated water is beneficially reused in the apartment building (Krogmannet al.2007). Out of the 95 m3/d (25,000 gal/d) that are recycled, 34 m3/d (9000 gal/d) are used to flush toilets, 39 m3/d (11,500 gal/d) go to the cooling tower, and 22 m3/d
Table 13.1 Typical characteristics of raw wastewater and recycled water (treated effluent) of the Solaire.
Parameter Units Inlet raw wastewater Treated recycled water
pH – – 6.5–8.0
Biological oxygen demand, BOD mgO2/L 146 ,6
Total suspended solids, TSS mg/L 190 ,1
Total phosphorus mgP/L 6.9 ,1
Ortophosphates mgP/L 3.3
Total Kjeldahl nitrogen, TKN mgN/L 37
Turbidity NTU – ,0.2
Fecal coliforms cfu/100 mL – ,100
cfu/100 mL – ,1
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(6000 gal/d) are used for landscape irrigation. These applications of the treated wastewater required the approval from the City’s Health Department. The Solaire only uses reclaimed water for non-potable purposes and does not supply the water for other purposes to prevent cross-contamination and drinking the reclaimed water. The treated stormwater is stored and used for irrigation of the green roof and rain garden.
Evolution of the volume of supplied recycled water
The influent flow to the Solaire wastewater system is continuously metered and the monthly data relative to 2009 are shown in Figure 13.3 (American Water 2010). The monthly wastewater volume varies significantly and ranges from 2300 to 4200 m3. The low volume treated during the month of August 2009 was because the residents go on vacation during that period. Due to the beneficial reuse of the recycled water, the use of city potable water has been significantly reduced with only minor supplement when necessary. Figure 13.3 shows also the amount of city water needed to supplement flushing and cooling water use, which takes approximately only 15% of the total average water use.
13.4 ECONOMICS OF WATER REUSE
Project funding and costs
The Solaire project was initially financed through a construction loan and long-term financing. However, all the work was postponed after the September 11 World Trade Center attack in 2001. After the tragedy, all the financing had to be restructured. The new financing mechanism of the Solaire project used an innovative approach with public and private collaborations, including a private loan, and public sector grants from the New York State Energy Research and Development Authority (NYSERDA), the US Department of Energy, and the New York State Green Building Tax Credits.
The total capital cost of the Solaire project was US$114 million (Natural Resources Defense Council). The cost of the Solaire wastewater treatment and reclamation system was approximately $800,000. Along with energy efficient and other water efficient features in the building, the water recycling and reuse system help the project to meet stringent requirements to comply with the New York State Green Building Tax Credit, which was worth $2.8 million over five years. This tax incentive provided a means for the developer to offset some of the cost associated with the sustainable components through tax credits. Through its New Construction Program (NCP) NYSERDA provided a total of $628,079 to Solaire including a
$100,000 grant for LEED design assistance and energy modeling, a $319,079 incentive for the reduced use of electricity and $119,000 for commissioning of the project. NYSERDA also provided a $90,000 grant for the purchase of the photovoltaic panels. In conjunction with NYSERDA, the U.S. Department of Energy contributed $100,000 to the commissioning (U.S. Green Building Council).
Applied Water Management (a subsidiary of American Water at the time this report was prepared) designed, built and currently operates the wastewater treatment and reuse system. The treatment system has a highly automatic operation which requires the plant operators to spend only an average of 4 to 6 hours a week on plant maintenance and operation.
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Monthly volume, m3
Monthly volume of recycled water(flow at the treatment plant inlet)
Monthly volume of city water used to supplement flushing and cooling water
Figure 13.3 Monthly volumes of recycled water (measured at the plant inlet) and potable city water used to supplement flushing and cooling water in 2009.
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Pricing strategy of recycled water
The fee for use of public water and recycled water is not listed as a separate charge to the Solaire residents since there are no dedicated meters for each residential unit. Instead, the water use and sewer fee is included in the overall rental fee. The savings resulting from the reduced water use and sewer discharge are reflected in the overall savings in operation for the building.
Benefits of water recycling
The water recycling at the Solaire has demonstrated economic, social, and environmental advantages over the conventional approach adopted by typical public water systems. The primary benefits of the Solaire’s wastewater treatment and recycling system include:
Reduction of water demand from the City–as a result of water reuse for toilet flushing, cooling water, irrigation water to an adjacent park, the Solaire is able to save more than 50% of water from the public water supply system compared to conventional apartment buildings.
Reduction of the water fee from the City–although it was not the case initially, the City’s Water Department has a lower rate for the Solaire due to the decreased use of water.
Reception of grants and other incentives from public agencies to offset some of the capital investment.
Reduction of discharges of stormwater and wastewater to the City’s combined sewer system–stormwater runoff (approximately 650 m3 of water per year) is collected in a storage tank in the building’s basement to be used for irrigation of the rooftop gardens.
Avoided cost to upgrade and expand the City’s existing water and sewer systems due to the minimum impacts from the addition of the water demand and wastewater flow at Solaire.
Increased market value as the first green building in the U.S. that uses both a stormwater and blackwater reuse system.
As a model project to the other BPC buildings, the Solaire set up a series of standards and guidelines for the development of reuse systems for green buildings.
13.5 HUMAN DIMENSION OF WATER REUSE
Public education and communication strategy
Public involvement is one of the key components to the success of the Solaire project. The sustainable development concept was new to BPC in the early stage of the project. BPC Authorities organized a group of people to attend a USGBC meeting in the summer of 1999 in Chattanooga, Tennessee. Following the meeting, the BPC developed the initial Environmental Development Guidelines in one-year collaboration with a team of architects, engineers, and nongovernmental organizations (NGOs). External public organizations and city agencies were engaged to ensure that the guidelines would be accepted and embraced. It was challenging since the BPC Authorities had to educate and convince developers and construction contractors to build green buildings which were different from the well-developed conventional high-rise building guidelines. Through public involvement and outreach programs at a very early stage, BPC was able to identify key audiences and specific communities and offer information and opportunities for feedback.
Resident education is very important to the building management team. Staff members provide a tour for each person that moves into the Solaire, answering questions about green features and explaining the benefits and consequences of living in a green building. Hundreds of tours are given each year by the staff to educate the community and provide information on the project to the green building industry. Tours of the green roof and rain garden are also made available to residents and visitors.
The role of decision makers
The Solaire project received support from BPC Authorities, regulators and officials from the City and the State of the New York. During the opening ceremony of the building, George Pataki, the former Governor of the State of the New York spoke highly about Solaire:“This is sustainable living. This is environmentally sustainable living in a high-rise building in lower Manhattan. This is going to transform the way people live around the world”.
Regulators helped establish clear permitting pathways for the Solaire project. BPC Authorities negotiated with developers and NYC departments to achieve approval of certain green project features. BPC Authorities also provided oversight during each phase of the design and construction process. In addition, the developers received approvals from the City Health Department so that there were two review processes: one at the BPCA level and one at the City level. The NYC Health
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Department played an early role by visiting the plant during design and startup. The Solaire plant operators still send monthly sample results and quarterly and semi-annual reports to the NYC Health Department.
Public acceptance and involvement
The residents of the Solaire have fully embraced the green features provided in the building. Most of the people consider living in green buildings as a life style of the future. The use of recycled water and low flow fixtures have not caused any inconvenience to the residents, and to date, they have not complained about any operational issues of the wastewater treatment plant in their basement, although they have noticed that the temperature of the reuse water is different from the city water. Because the recycled water goes through all the treatment process within the building, the temperature of the reclaimed water is at about 20 to 25°C, which is about 5 to 10°C warmer than the city water.
13.6 CONCLUSIONS AND MAIN KEYS TO SUCCESS
The Solaire is one of six high-rise residential buildings in Battery Park City, an area adjacent to the Wall Street financial district, and is a leading example of urban environmentally sustainable development. The Solaire Apartments collect, treat, store and reuse the wastewater for toilet flushing, irrigation and cooling towers. This approach reduces the public water taken from the city’s water supply by over 50% and significantly decreases energy costs as less drinking water is pumped from the city’s treatment plant and wastewater is not transferred to the city’s wastewater treatment system. The rainwater collection system irrigates 930 m2 of rooftop gardens. Keeping with the “green” goal, the facility contains 50% recycled construction materials, consumes 35% less energy, and reduces peak demand for electricity by 65% using solar panel and other energy efficiency fixtures (American Water, 2008; Epstein, 2008).
The Solaire was a pioneer for green buildings as it was the first building to win the right to build on a site following the BPC Authorities Guidelines. It was also the first LEED certified residential high-rise building in North America with an integrated design for the site, facility, landscape, and water management. The Solaire set the goal for subsequent developers, becoming the green standard by voluntarily incorporating measures such as an onsite blackwater treatment plant with well-defined reclaimed water quality criteria.
In summary, some of the key factors that made the Solaire successful include the regulatory mandate for sustainable development by the BPC Authority, the public support through grants and incentives, the utilization of an emerging technology at that time–membrane bioreactor, and most importantly a team of people including the Solaire administration and Applied Water Management, who were open-minded to apply new technologies to meet innovation in green building development.
The following Table 13.2 summarizes the main drivers of this water reuse project as well as its benefits and challenges.
Table 13.2 Summary of lessons learned.
Reduction of the water fee from the City Reduction of discharges of stormwater and wastewater
Avoided cost to upgrade and expand the City’s existing water and sewer systems A show case of“green”building
Limited space in the building basement for the reuse system Relatively high energy intensity for the membrane bioreactors
Acknowledgements
The authors thank the staff of the Applied Water Management, a subsidiary of American Water, especially Don Shields, Andy Higgins, Jim Huntington and John Tekula, for their outstanding work on the success of the Solaire and other Battery Park City’s wastewater recycling systems. Special thanks to Michael Gubbins from the Solaire for his continued support of research and willingness to share information and expertise.
REFERENCES AND FURTHER READING
Carey H. (2005). The Solaire–Green by Design. Report of Battery Park City Authority. New York City.
Epstein K. (2008). NYC’s living lesson.High Performing Building, Summer Issue, 57–65.
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Krogmann U., Andrews C., Kim M., Kiss G. and Miflin C. (2007). Water mass balances for the solaire and the 2020 tower: implications for closing the water loop in high-rise buildings.Journal of the American Water Resources Association,43(6), 1414–1423.
Sustainable Water Resources Management, Volume 2: Green Building Case Studies. (2010). Report of Electric Power Research Institute.
Electric Power Research Institute, Alexandria.
The Solaire Annual Report. (2010). Report of American Water. American Water, Voorhees.
WERF. (2009). When to Consider Distributed Systems in an Urban and Suburban Context? Water Environmental Research Foundation,
WERF. (2009). When to Consider Distributed Systems in an Urban and Suburban Context? Water Environmental Research Foundation,