Dynamic Behavior of Water and Air Chemistry in Indoor Pool Facilities
Abstract
Swimming is the second most common form of recreational activity in the U.S. Swimming pool water and air quality should be maintained to allow swimmers, pool employees, and spectators to use the pool facility safely. One of the major concerns regarding the health of swimmers and other pool users is the formation of disinfection by-products (DBPs) in swimming pools. Previous research has shown that volatile DBPs can adversely affect the human respiratory system. DBPs are formed by reactions between chlorine and other compounds that are present in water, most of which are introduced by swimmers, including many that contain reduced nitrogen. Some of the DBPs formed in pools are volatile, and their transfer to the gas phase in pool facilities is promoted by mixing near the air/water interface, caused by swimming and pool features. Swimming pool water treatment processes can play significant roles in governing water and air quality. Thus, it is reasonable to hypothesize that water and air quality in a swimming pool facility can be improved by renewing or enhancing one or more components of water treatment. The first phase of the study was designed to identify and quantify changes in water and air quality that are associated with changes in water treatment at a chlorinated indoor pool facility. Reductions of aqueous NCl3 concentration were observed following the use of secondary oxidizer with its activator. This inclusion also resulted in significant decreases in the concentrations of cyanogen chloride (CNCl) and dichloroacetonitrile (CNCHCl2) in pool water. The concentration of urea, a compound that is common in swimming pools and that functions as an important precursor to NCl3formation, as well as a marker compound for introduction of contaminants by swimmers, was also reduced after the addition of activator. The second phase of this study involved field measurements to characterize and quantify the dynamic behavior of indoor air quality (IAQ) in indoor swimming pool facilities, particularly as related to volatile compounds that are transferred from swimming pool water to air. Measurements of water and air quality were conducted before, during, and after periods of heavy use at several indoor pool facilities. The results of a series of measurements at different swimming pool facilities allowed for examination of the effects of swimmers on liquid-phase DBPs and gas-phase NCl3. Liquid-phase NCl3 concentrations were observed to gradually increase during periods of high swimmer numbers (e.g., swimming meets), while liquid-phase CHCl3concentration was nearly constant in the same period. Concentrations of urea displayed a steady increase each day during these periods of intensive use. In general, the highest urea concentrations were measured near the end of each swimming meet. Measurements of IAQ dynamics during phase 2 of the study demonstrated the effects of swimmers on the concentrations of gas-phase NCl3 and CO2, especially during swimming meets. The measured gas-phase NCl3 concentration often exceeded the suggested upper limits of 300 µg/m3 or 500 µg/m3 during swimming meets, especially during and immediately after warm-up periods, when the largest numbers of swimmers were in the pool. Peak gas-phase NCl3 concentrations were observed when large numbers of swimmers were present in the pools; measured gas-phase concentrations were as high as 1400 µg/m3 .Concentrations of gas-phase NCl3 rarely reached above 300 µg/m3during regular hours of operation.
Degree
Ph.D.
Advisors
Blatchley, Purdue University.
Subject Area
Atmospheric sciences|Environmental engineering|Recreation
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