Environ. Sci. Techno/. 1985, 19, 1192-1195
Interference in the Bactericidal Properties of Inorganic Chloramines by Organic Nitrogen Compounds Roy L. Wolfe, N. Robert Ward, and Betty H. Olson” Environmental Analysis, Program in Social Ecology, University of California, Irvlne, California 927 17
The interference of nitrogenous organic compounds on the bactericidal activity of chloramines w a ~ examined. The amino acid glycine (0.1-0.5 mg/L as nitrogen) was supplemented into water samples obtained from a finished water reservoir to artificially increase the levels of organic nitrogen. Inactivation rates of total count bacteria were markedly slower with chloramines (1.6 mg/L; Cl,-N, 3:l w/w; pH 8) when preammoniation and concurrent application methods were compared to preformed chloramines. Levels of glycine as low as 0.1 mg (as nitrogen)/L reduced the bactericidal activity with the preammoniation procedure. No decrease in the bactericidal properties was observed when preformed chloramines were assayed in the presence of glycine. Significantly, the inorganic chloramine residuals (ammonia derived) and organic chloramine residuals (glycine derived) could not be distinguished by amperometric or ferrous ammonium sulfate-diethyl-pphenylenediamine titration techniques. Hence, residual measurement by conventional analytical techniques may not indicate the true Ievel of disinfection potential of chloramines. The presence of nitrogenous organic compounds in water may significantly reduce the microbicidal activity of inorganic monochloramines by interfering with the formation and stability of this disinfectant. This interference results primarily from two sets of chemical reactions that lead to a progressive increase in the levels of organic N-chloro compounds and a corresponding decline in inorganic monochloramine. The initial distribution of organic and inorganic chloramines is determined by the concentrations and relative chlorination rates of organic nitrogenous compounds and ammonia (1). If the organic N compounds bind more rapidly with chlorine than ammonia, higher levels of organic chloramines will initially be formed. This kinetically determined distribution is followed by reaction toward equilibrium which frequently favors the formation of organic chloramines (2). As such, the expected level of inorganic chloramine residual may not be achieved during chloramine formation or the level of inorganic chloramine may decrease with extended residence time in the distribution system. Significantly, many organic chloramine compounds, particularly the chlorinated amino acids, have little or no bactericidal activity ( 3 , 4 ) . Compounding this problem is the inability of current analytical techniques that measure combined chlorine residuals to distinguish between inorganic and many forms of organic chloramines ( 2 , 5 ) . To our knowledge, there is no experimental evidence to date to verify that nitrogenous organic compounds reduce the disinfectant activity of inorganic chloramine as a direct result of preferential binding and exchange reactions. We report on a series of experiments designed to demonstrate interference in the bactericidal properties of inorganic chloramines by glycine when preammoniation and concurrent addition application techniques are used. This information is particularly pertinent for water treatment facilities using source water with elevated levels of interfering nitrogenous organic compounds because the amount of “active” inorganic chloramine in water cannot be quantified. 1192
Environ. Sci. Technol., Vol. 19, No. 12, 1985
Unfortunately, knowledge of the types and concentrations of nitrogenous organic compounds in surface waters is limited (2,s). However, the presence of amino acids and other primary amines such as peptides are thought to be among the most environmentally significant forms of organic nitrogen in water supplies due to their ubiquity and their interference with inorganic chloramine formation. In general, the concentrations of free amino acids in fresh water varies from a few to several hundred micrograms per liter (7). Gardner and Lee (8) found approximately 20 pg of several amino acids/L in moderately eutrophic lake water whereas Zygmuntowa (7) observed 50-200 pg of free amino acids/L in highly eutrophic pond water. Hutchinson (9) reported that free amino N, peptides, and nonamino N averaged 74,171, and 194 pg/L, respectively, in 15 Wisconsin lakes. The concentrations of free amino N in these lakes ranged from 20 to 1 2 1 pg/L, whereas the levels of peptide N ranged from 70 to 300 pg/L. Although not stated, the nutrient status of the lakes most likely ranged from moderately oligotrophic to highly eutrophic. The degree of eutrophication in lake water is important because it will influence the amount of nitrogenous organic compounds present (10). By comparison, the concentration of free amino nitrogen in sewage effluents can be expected to be an order of magnitude greater than the levels found in oligotrophic fresh waters. Isaac and Morris (11)estimate that free amino nitrogen ranges from 200 to 750 pg/L in domestic sewage effluent. Our research findings during May and June 1982 in a finished water reservoir suggested that nitrogenous organic compounds interfered with disinfection when preammoniation and concurrent application techniques were utilized to form inorganic chloramine. In these studies, we noted that the total count bacteria were inactivated significantly ( p < 0.05, df = 16, using linear regression analysis) more slowly at pH 8 when preammoniation and concurrent application techniques were used than when preformed inorganic chloramines were employed. Some of these data are presented in Table I. Organic amine containing compounds present in the San Joaquin Reservoir water were implicated as the interfering agents because the residual chloramine concentrations, determined by amperometric and ferrous ammonium sulfate-diethyl-pphenylenediamine (FAS-DPD) titration procedures, were identical regardless of disinfection application techniques. To test indirectly that organic amine compounds were interfering with inorganic chloramine formation and disinfection, two experiments were conducted in which the amino acid glycine was supplemented into the San Joaquin Reservoir water to artifically increase the level of organic nitrogen. These studies were conducted at 22 “C in sterile, 1-L beakers. Water samples were collected from the San Joaquin Reservoir between May and July 1982. The San Joaquin Reservoir (capacity 3 000 acre-ft) is a finished water reservoir maintained by the Metropolitan Water District (MWD) of southern California and is utilized for short-term storage. Generally, the water received by the reservoir is a blend of California State Project Water and Colorado River water, treated at the Robert B. Diemer treatment plant. This water has received full treatment
0013-936X/85/0919-1192$01.50/0
0 1985 American Chemical Society
Table I. Evidence of Interference in the Inactivation of Total Bacterial Populations from the San Joaquin Reservoir Using Different Chloramine Application Techniques residual sample date 5/6/82 5/17/82d 5/20/82
treatmenta
Xob
XI2
preform preamm conc preform preamm conc preform preamm conc
4.02 f 0.03 (100)' 4.02 f 0.03 (100) 4.02 f 0.03 (100) 3.66 f 0.06 (100) 3.66 f 0.06 (100) 3.66 f 0.06 (100) 3.98 f 0.03 (100) 3.98 f 0.03 (100) 3.98 f 0.03 (100)
2.62e (4.0) 3.55 f 0.13 (34.0) 3.42 f 0.19 (25.1) 2.48e (6.0) 2.73 f 0.19 (1117) 2.83 f 0.20 (14.7) 2.55 f 0.31 (3.7) 3.19 f 0.15 (15.9) 3.09 f 0.09 (12.9)
XZSb 1.45 f 0.17 (10.27) 3.44 f 0.21 (24.3) 3.28 f 0.34 (18.3) 0 (
