Allan Browning And Matthew Schnepf 2013-09-21 03:51:42
Green building is focused on increasing how efficiently facilities use energy, water and materials, while reducing their impact on people’s health and the environment. Often overlooked, the water treatment program for buildings’ HVAC systems can play a major role in meeting green objectives. Effective water treatment is essential preventative maintenance to protect buildings’ water systems from corrosion, deposits and microbiological growth. In many facilities, the water treatment program can be engineered to significantly improve system protection as well as energy and water efficiency. Steps can be taken to reduce chemical usage and associated handling concerns—or more sustainable chemicals can be used with equivalent or improved results. Most important to note: water treatment can have a significant impact on meeting green objectives. Energy and Water Efficiency The return on investment (ROI) for green building is closely linked with increased energy and water efficiency. In a typical office building, energy used to operate HVAC systems accounts for 60 percent of all utility costs—and water can easily total 5 percent of these costs. Although water treatment is a small fraction of utility costs, results received from water treatment programs have a far-reaching impact in terms of operating costs, resource conservation and reducing greenhouse gas (GHG) emissions. Table One shows the impact even minor waterside deposits in building heating and cooling systems can have on energy use and cost. For example, a mere 0.005” thick biological deposit (slime) on the chiller condenser tubes translates into over $16,000 per year in increased energy costs for a building’s cooling system operating at an average 500-ton load. Equally dramatic is the increase in GHG emissions. The carbon dioxide produced when fossil fuels are burned to generate energy is a major source of GHG emissions. For example, the increased electricity usage associated with a 0. 005” biological deposit results in 192 tons of GHG emissions. Improving the water treatment program to keep chiller heat transfer surfaces clean reduces energy use as well as a building’s carbon footprint. For facilities seeking LEED® for Existing Buildings: Operations & Maintenance (LEED-EBOM) certification by the U. S. Green Building Council® (USGBC), energy efficiency is vital. Energy efficiency, as measured by EPA’s ENERGY STAR® rating system, constitutes the largest single category of points in LEED-EBOM. Federal agencies are also focusing on energy efficiency and have been directed to reduce energy usage per square foot of building space by 2 percent annually through 2015 versus the 2006 baseline usage. A high-performance water treatment program that maximizes energy efficiency by keeping HVAC-system waterside surfaces clean helps increase a facility’s energy efficiency and improve its ENERGY STAR rating. Similarly, cooling towers are oft en the biggest water consumer in commercial buildings and frequently are not operated to maximize water efficiency. In many cases, cycles of concentration can be increased to reduce the tower bleed. Table One shows that increasing cycles of concentration from three to five in a building’s cooling water system operating at an average 500-ton load reduces annual water usage by over 1.6 million gallons. At a water cost of $6 per one thousand gallons, this means an annual cost savings of over $10,000. Alternate makeup water sources, like air-handler condensate, harvested rainwater, or grey water, can also be used to decrease fresh water usage. Boilers and closed loops can also create water saving opportunities with the added bonus of energy savings and reduced GHG emissions. The major boiler operating cost is for fuel to heat the water to boiling in order to make steam. Anything that can be done to maximize heat transfer efficiency and minimize wasted boiler water will reduce fuel costs. Additionally, making sure the boiler tubes have clean heat transfer surfaces will ensure efficient operation and minimize energy use. Closed loops should be maintained to minimize water loss. While they are typically not a large consumer of water or energy, maintenance on these systems should not be overlooked. Even a small leak in a closed loop can increase energy usage, water usage and GHG emissions. Minimizing Chemical Usage Water treatment measures that help reduce chemical usage also support green building. Pre-treatment and filtration equipment oft en optimize a water treatment program’s results while reducing chemical requirements at the same time. Feed and control equipment precisely apply treatment chemicals to ensure an accurate amount is used. This same equipment can benchmark chemical and water usage. Concentrated treatment chemicals also provide significant green benefits by reducing packaging, transportation costs and chemical handling requirements. Sustainable Chemicals Many people believe sustainability equals free from chemicals, but that is not entirely accurate. Operating a building sustainably involves using water, energy and chemicals in the most efficient and effective way. Currently, there is not a credible organization with standards to certify water treatment chemicals as green. However, certain chemicals and technologies are considered more environmentally responsible than others. For example, treatment chemicals that more readily degrade when discharged into the environment are less hazardous to manufacture. Also those that use or have lower usage/packaging requirements can be considered sustainable. Solid water treatment systems in particular offer several benefits over traditional liquids. Solids contain less hazardous chemicals, and because they decrease packaging materials, they reduce both landfill waste and shipping weight. This, in turn, reduces energy and carbon dioxide emissions associated with product delivery. Combined with ease of use, these factors make solids an attractive alternative to liquid chemicals. While it is important to minimize chemical usage and use sustainable chemicals, it is essential that green water treatment programs provide similar or better results in terms of system protection and energy/water efficiency. Otherwise, environmental benefits from reducing chemical usage will be offset by increased energy, water and material usage. Green Water Treatment The following actions are hallmarks of an effective water treatment program supporting green building objectives: Maintain clean heat transfer surfaces. Consider pretreatment equipment, filtration, chemical cleaning and treatment program upgrades to maintain and restore optimum heat transfer efficiency. Maintain the minimum blowdown rate consistent with good deposit control in boiler and cooling tower systems. Install equipment upgrades that allow reduced blowdown. Eliminate any uncontrolled leaks in all types of HVAC systems that will cause an increased use of water, fuel and chemicals ¡ Consider alternate makeup water sources like harvested rain water, air-handler condensate or grey water. Install automatic feed and control systems that precisely apply treatment chemicals. Installation of feed and control equipment that uses tracing chemicals or water meters are examples. Use web-enabled, data-logging controllers to monitor and log key treatment and system parameters. Use concentrates to minimize handling, packaging and shipping requirements. Consider solid water treatment technologies. The water treatment program for a buildingfs HVAC system is integral to the operation of energy, water and resourceefficient facilities. Obtaining optimum results from a water treatment program has huge economic payoffs and helps meet green building objectives. When developing and implementing an HVAC water treatment program, the impact on the environment, effects on employees and the work place and use of natural resources are all important considerations. Sustainable building operations can assist in reducing overall operating costs while creating a less hazardous workplace and a healthier environment. Allan Browning is director of technical marketing for Chem-Aqua And Matthew Schnepf is a corporate engineer for Chem-Aqua.
Published by Facilities Engineering Journal. View All Articles.