School A called a water treatment company to evaluate the school’s cooling towers. The school was interested in saving water, energy and in eliminating bacteria in the towers themselves. After completing a water audit, the company notified the school that the cooling towers were wasting over 6 million gallons of water a year, that dangerous chemical drums used to treat the water were hauled through the school during school time and that bacteria levels in the tower were dangerously high at more than 1 million per milliliter of water even though it was receiving traditional chemical treatment.
School B hired a water management company to evaluate their 81 schools for an alternative to chemical treatment for their cooling towers. A random elementary school cooling tower was selected and found to have poorly maintained and often inoperative chemical treatment equipment for their cooling tower. Bacteria counts in the tower were in the danger area. A closer daily inspection revealed that teachers used the shade of the tower to get children out of the sun. In addition, the mist from the top of the bacteria laden tower was regularly used to cool down students on hot days. When appraised of the health risk, the County School HVAC Director stopped all alternative chemical considerations for the towers. His budget did not have sufficient funds for that much corrective action and he didn’t want parents or staff to become alarmed. It was better that no one know. Children still use the tower for shade and its mist to cool off.
School C tested ozone as an alternative to chemical treatment for a cooling tower at an Elementary School. The Initial investigation, prior to ozone, showed that bacteria levels and calcium scaling in the towers to be in the danger area. Within two weeks of ozone system installation, bacteria levels were lower than the schools drinking water. After a year, the school had saved over 1.2 million gallons of water and over 2,000 lbs of phosphate. 41 more towers are now planned for ozone conversion with a total water savings of over 35 million gallons a year.
Air Conditioning and The Cooling Towers
Behind every large building in America there usually lies a Cooling Tower. The tower is the large metallic structure towards the back or on a roof top of these large buildings. The cooling towers insure air conditioning equipment work at optimum capacity. The Ac equipment send hot water to the towers which are designed to allow it to cascades down its sides. Here, heat is released before being pumped back into the building. This water had gained heat from the buildings air conditioning units and is now being cooled before it is sent back to the AC unit. Some towers operate 24 hours a day, 365 days a year.
Water is lost three ways from the tower; 1) through evaporation, 2) through drift or as a mist from a top fan and 3) through blowing down, where mineral and chemical laden water is discharged to the sewer. Fresh or make-up water is continually added to insure the AC works properly. A cooling tower can use anywhere from 50-90% of a buildings total water consumption to keep the AC units working correctly. Cooling towers are an energy efficient method to cool water when compared to air cooled towers which use large amounts of electricity. When treated properly, cooling towers can enhance a buildings environmental impact on the community.
Bacteria and Cooling Towers
Unfortunately, the Cooling Tower usually contains the largest store of bacteria on any school, hospital, hotel or office campus. Cooling towers act as huge incubators in that they operate at warm temperatures and provide water and food from airborne contaminants necessary for bacteria to grow unchecked. It is not uncommon to find over a 1million bacteria per milliliter of water growing in the tower. Cooling tower drift, from fans on the top of the tower, can create a mist or water aerosol to carry bacteria to areas around the tower. Traditional chemical treatment only poisons bacteria. Therefore, chemicals must be monitored extremely close and the chemicals changed often, to insure that bacteria are killed and that the health of people in close proximity to the tower is not endangered.
Legionellosis and The Cooling Tower
Legionellosis is a potentially fatal form of pneumonia. Caused by exposure to Legionella Pneumophila (Lp). Lp bacteria is the cause of many hospital acquired cases of pneumonia and can go undetected unless specifically targeted. Legionella can be found in high bacteria levels of cooling tower slime. Some have even been found in low levels of bacteria tower slime. In 2,001, the Center for Disease Control stated that 25,000 cases of Legionnaire’s Disease occur each year. Of these, 4,000 resulted in death. Many more resulted in hospitalization for pneumonia like symptoms.
Chemical Treatment Problems in Schools
Chemicals attempt to control tower bacteria by poisoning. But bacteria can build an immunity requiring the chemical companies to use different poisons to kill and control their growth. During blow down, this poison laden water is then poured down a school’s drains to be treated at the municipality’s water treatment plant before being discharged to the local river.
Compounding this problem is chemical delivery. In some cases, chemical drums must be brought through the school hallways and cafeterias to chemical pumps at the back of the school. Unfortunately, chemical company contracts are chosen on a yearly, low bid basis. There is no incentive for quality control or daily or weekly repairs or service. Chemicals are budgeted based on the lowest contract dollar with the least amount of chemicals necessary regardless of bacteria count.
On another note, if the building is a sensitive government facility, ‘hardening’ the facility against attack is further compromised. Trucks with chemical drums for tower treatment must be individually inspected for explosives and bio-hazards. Unfortunately, they have to be close enough for inspection where a fertilizer bomb could do significant harm.
Ozone a Safe Alternative to Chemical Treatment
Ozone is much safer than chemicals. Ozone is made from oxygen. Where oxygen is O2, ozone is O3. It is gaseous and only exist for a few minutes before converting back into oxygen. It can not be shipped and thus must be manufactured on site in a generator. Ozone generation systems are typically automatic requiring only a few minutes of monthly service. Once ozone is mixed in cooling tower water, the water can be reused and reused sometimes twice as long as chemically treated water can. This saves communities thousands of gallons of water per year per tower!
Ozone and Bacteria
Ozone is 500 times faster than chemicals in destroying bacteria. It burns up bacteria or oxidizes bacteria in thousandths of a second. And when finished, oxidizing, ozone reverts back into oxygen again. This keeps the environment around the tower safe and clean.
Ozonated Discharge Water
Water from chemically treated towers must be pumped to the Water Treatment Station and treated before being discharged. Ozonated discharge water can be discharged to streams because it is chemical free. This allows the school to avoid costly sewer fees. In addition, schools can send this water to irrigation lines on athletic fields, further reducing water usage and water bills. Environmentally speaking, if the school has a “Green Roof’, ozone tower water can be used to water the plants or in the case of open areas, be used to create decorative ponds or lakes.
A New 360o Approach to Procurement
Bid specifications for cooling tower water treatment should be weighted to its effect on the students, school and community. No longer should ‘the lower bid’ be the standard. Especially when we know that cost savings in water, sewer and energy can result in tremendous benefits for the school. Contracts should be reviewed with an eye on the complete effect, a 360-degree view point, of chemicals or their alternatives on staff, students, safety, the community, budgets, community water restrictions and water treatment plant loads. 5 areas should dominate the decision, 1) site safety, 2) water conservation, 3) reducing water and sewer cost, 4) bacteria control and 5) cooling water system protection against corrosion and scaling.
The Ideal Cooling Tower
The ideal Cooling Tower is one that is a safe, efficient and environmentally friendly. It is automatic, needs very little service and can be computer monitored from a remote site if necessary. The tower should be free from harmful bacteria levels.. The metal tower surfaces are neither corroding nor scaling and free from biofilm slime. The water in the tower basin should look pristine.
A Proactive Approach
A Hampton Roads, Virginia area school system chose ozone over chemicals for the countys’ schools cooling towers. The over riding reason was student, employee and building safety. Though they had no known cases of LD in the school system, they didn’t want any either. Ozone’s killing power on bacteria is documented as a thousand times faster than chemicals before it converts back into oxygen. Ozone was the only logical choice.
“Student and employee safety is most important to us,” said the Supervisor of Resource and Security Control. “Many of our cooling towers are near playgrounds.”
The Ozone System chosen was small and compact and was located near the towers in a near-by mechanical room. It made ozone 24 hours a day.
“In one of our middle schools, it would have been necessary to transport chemicals to the tower site through a cafeteria, up an elevator, down a classroom hallway, through the high school library, then the middle school library, across the boiler room, up a set of steps and around the back of the auditorium stage to a mechanical mezzanine, where we would have the chemical feeders installed for the rooftop mounted cooling towers. Obviously, we decided an on-site Ozone System was not only safer, but also a much more practical alternative.”
Increased Efficiency Converts to Energy, Water and Sewer Savings
Due to the bacteria free water and cleaner, safer towers, the Hampton Roads School System experienced increased efficiency of the air conditioning chiller equipment. The ozone eliminated scale build-up allowing the entire building’s HVAC system to operate at lower temperatures and pressures. An added benefit is that each school’s water source heat pumps also ran more efficiently due to the lower loop temperatures.
The Ozone System reduced total water usage. The school system estimates that 14 million gallons of water are saved annually because the water is cleaner longer before it has to be discharged. Once discharged, the school system saved more money by sending this chemical free water directly to drains and not the county sewer system.
The school system is a member of Businesses For the Bay. This is an environmentally active group supporting a cleaner Chesapeake Bay. With the removal of 14 million gallons a year of water from loads experienced at the Hampton Roads Water Treatment Plant, it was also estimated that ozone conversion reduced 2,100 lbs/yr of phosphates from being introduced into the treatment system. These phosphates would eventually make their way into the Bay and promote algae growth.
A Green School Community
In these days of disease elimination and energy and water conservation, communities must take a wide eyed approach to the largest user of community water, the cooling tower. Though it uses less energy than electric air-cooled systems, it can be a friend to a community under the correct treatment approach. Citizens must lobby their School Boards to investigate alternatives to chemically treating cooling tower water. For every 500 tons of cooling capacity, an ozone system can save the school almost a 1 million gallons of water a year. This is easy water to save especially in times of drought or area wide water restrictions. The ‘Greening’ of a community is a choice of proactive dynamics, how can we keep students safer and save water now for later?
For additional information on the use of ozone for the treatment of cooling tower water, contact Ron Basso, sales engineer, with Zentox Corporation at 757-369-9870 or by e-mail at info@zentox.com.
Established in 1997, Zentox is an industrial water services company located in Newport News, Va. The company specializes in green technologies and reconditions and treats process water for reuse, as well as for enhanced performance in a variety of industrial processes including water for evaporative cooling towers. The company applies a full range of technologies to develop solutions for a wide range of industries.