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Managing Chloraminated Systems during Warm Weather:
Fast Response Early Boost (FREB) Approach
As more and more water treatment facilities convert from chlorine to chloraminated systems, it has become apparent that a large percentage, perhaps 63% or more of tanks with chloraminated water (AwwaRF, 2003, ISBN 1-58321-283-3, page xxi) experience unwanted nitrification and a loss of residual disinfectant during warm weather. Collaborations with SolarBee customers have helped to develop a management strategy to prevent this from happening. The current strategy outlined below, called the Fast Response Early Boost (FREB) approach, has provided effective control in chloraminated potable water tanks during warm months when these problems are most acute.
- SolarBee’s complete mixing cannot change water age in a tank, but it does make all the water in the tank essentially the same water age for treatment purposes. Preventing thermal stratification and associated variable water age is particularly important in chloraminated tanks, where the chloramine starts to break down into chlorine and free ammonia (i.e., auto-decomposition) with a water age of more than 5 days. When this happens, the tank can quickly lose its disinfectant residual, as described below, even if it is being mixed.
Mixing a potable drinking water reservoir has many known benefits, but sometime intervention beyond just mixing is required to keep the water quality high, such as: periodic boosting via an in-tank chemical injection system.
- When chloraminated water warms up to a temperature of 15°C (59°F), the ammonia oxidizing bacteria (AOB, also sometime called "nitrifying bacteria") begin to grow rapidly in the tank. AOB are 13 times more resistant to chlorine than most bacteria, and prefer to be attached to the sidewalls and/or reside in the bottom sediment. AOB are also likely present throughout the water column, since the residual chloramine in the entire tank can spiral down very fast when the water warms up. These bacteria quickly use up all free ammonia present in the water, and then appear to "pull" ammonia off of the chloramine molecule and consume that as well. This can cause the chloramine residual throughout the tank to disappear quickly. AOB oxidize ammonia first to nitrite (maximum contaminant level allowed is 1.0 mg/L) and then to nitrate (maximum contaminant level allowed is 10 mg/L). Usually the nitrite limit is the first to be violated, and the residual disinfectant falls below the minimum standard too. The killing effect of chlorine on AOB increases when water temperatures exceed about 25°C (77°F), so the worst problems occur between 15°C and 25°C.
- Consequently, when water temperatures in a chloraminated tank reach 15°C or higher, the tank should be monitored weekly or even more often. In northern climates these warm temperatures will only occur in summer, but in the southern US they can occur year-round. Important variables to monitor include combined and free chlorine, total and free ammonia, and nitrite/nitrate concentrations. SolarBee circulation creates uniform temperatures and water quality in the tank, making sampling truly representative of tank water.
- With the FREB approach, if the disinfectant residual drops by even 0.1 or 0.2 mg/L below the normal range, and if nitrites are also rising, the owner should immediately boost the chlorine through the SolarBee boosting system. Depending on how large the tank is, as few as 1-10 gallons of sodium hypochlorite (or whatever chlorine source the water agency prefers) may prevent a downward spiral in residual chlorine from occurring. Otherwise, if the owner waits until the chlorine residual becomes dangerously low before boosting, the tank may need to be taken offline, and/or deep-cycled, and/or taken through breakpoint chlorination with up to 200 gallons or more of a chlorine mixture needed to get an adequate chlorine residual established again.
- Frequent boosting with small doses of chlorine is far less costly than having a major problem occur in a tank. Major problems can often cost $10,000 to $20,000 or more to correct when considering labor (e.g., field crews, supervisors, fire protection coordination), lost water, chlorine costs, and potential liabilities associated with other methods used to solve the problem. These savings can quickly pay for a SolarBee.
- The SolarBee is the only potable water mixing system on the market today that provides the capability for Fast Response Early Boost (FREB), the most effective management approach to solve problems associated with chloraminated water in warm weather, because the SolarBee: 1) has a boosting attachment, and 2) keeps the tank de-stratified, usually to within 0.1°C, to minimize water age, and 3) allows for thorough chlorine mixing during the boost, and 4) quickly circulates the chlorine boost throughout the tank volume including all boundary layers (i.e., both bottom sediment layer and sidewalls).
 Glendale Water and Power has long been on the leading edge when it comes to water treatment in their plant and distribution system. Patrick Hayes uses chloramine as the main disinfection method, both to comply with DBP rules and to keep Glendale's water as fresh as possible. Over long retention times, chloramine can break down and cause unhealthy nitrification. To prevent this, Glendale installed SolarBee® long-distance water circulators in their storage tanks. The SolarBee® provides thorough mixing of the entire tank, keeping temperature stratification and stagnation to a minimum. And it constantly replaces the disinfectant at an boundary areas, thus helping to reduce nitrification. In addition, SolarBee® can also be used for boosting with chlorine or chloramines. It's important to note that solar-powered SolarBee® can do all this without using grid power. "Thanks to SolarBee®, we've seen significant improvement in sustaining our water quality," reports Mr. Hayes. You can, too, with SolarBee® in your potable, water tanks.
 The treatment plant and reservoir at Palmdale, California always strives to maximize water quality. Part of the challenge was blue-green algae that choked the reservoir all summer, giving the water bad taste and odor. At first, Greg Dluzak coped by dumping up to 2000 pounds of copper sulfate into the lake each week. But chemicals are costly – and they'll cause environmental problems down the road. Always open to innovative solutions, Palmdale installed seven SolarBee® water circulators on the reservoir, and three more in the storage tanks. SolarBee's near laminar flow worked wonders. "Those algae blooms were virtually eliminated and chemical treatments reduced to a minimum," reported Mr. Dluzak. In fact, the lake's water clarity doubled. Also, SolarBee® balanced the water temperature and improved the catch rate for sport fisherman. In the storage tanks, SolarBee's thorough mixing keeps temperature stratification and stagnation to a minimum, thus providing good chlorine residual and reducing the risk of disinfection byproducts. Thanks to SolarBee®, Palmdale's water is clear and clean. "SolarBee® keeps our water fresher than ever," beams Mr. Dluzak. It can do the same for you.
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