Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 716-718
716
1.69 mol each of H 2 0 and C02 gives 75.71 L/min net change 18.93 L/min Total exhaust gas = 372.68 L/min. 2. Calculate number of moles of SO, represented by an 8.99 ppm drop in SO, 8.84 X lo4 L of SO, X 372.68 L/min = L of exhaust 3.29 X L of SO,/min
4. Calculation of ratio 1.31 X
mol of S03/min
4.71
mol of Mg/min
X
= 2.73
Registry No. SO2, 7446-09-5;SO3,7446-11-9;FeZO3,1309-37-1; MgO, 1309-48-4; A1203,1344-28-1; CaO, 1305-78-8.
(1)(3.35 X lo-,) L/min
1.29 X mol S03/min (0.0821) (300 K) 3. Calculation of moles of Mg injected. Putting 16.68 mL of KI-81 (15% Mg) in 1 L of fuel and injecting this at a rate of 9.5 mL/min gives about the desired rate. (Actually this is slightly above 10 gal/lOOO bbl because the original dilution was for a fuel use of 35 mL/min.) 16.68 mL of KI-81 0.5 mL 0.9 g XXX L min mL 15 g of Mg - 1.13 g of Mg 100 g of KI-81 min 4.71 X mol of Mg min n=
L i t e r a t u r e Cited Budesinsky, B. Anal. Chem. 1965, 37(9),1159. Hedley, A. B. J. Inst. Fuel 1967, 40, 142. Lay, K. W. J. Eng. Power 1974, 134. Levy, A.; Merryman, E. L. J. Eng. Power 1963, 229. National Bureau of Standards, "High Temperature Properties and Decomposition of Inorganic Salts. Part 1. Sulfates", NSBD7-NBS7, 1966. Reid, W. T. "External Corrosion and Deposits"; American Elseview Publishing Company, Inc.: New York, 1971. Reidick, H.; Reifenhauser, R. Combustion, 1980, 17. Rolker, J. VGB Krsftwerkstechnik 1973, 53, 333.
Received f o r review February 16, 1983 Accepted July 14, 1983
COMMUNICATIONS A New Water Disinfectant; A Comparative Study The N-chloramine compound 3-chloro-4,4dimethyC2-oxazolidinone (agent I) has been compared with several other antimicrobial agents as to its efficacy as a bactericide for treatment of water. The other agents tested included 1,3dichloro-5,5dimethylhydantoin,N-chlorosuccinimide, commercial HTH, and bleach (sodium hypochlorite). The species of bacteria included in the comparative study were Escherichia coli, KlebsEela pneumoniae , Roteus vubris, Salmonella chlolera-suis , Salmonella typhimurium, Serratia marcescens, Enterobacter cloacae , Staphylococcus aureus, Staphylococcus epidermidis , Pseudomonas aeruginosa , and Sphaerotilus natans In general, agent I requires somewhat longer contact time at a given concentration than do the other agents for complete kill, but it is much more stable in water solution than are the other agents.
.
Introduction
The most widely employed commercial disinfectant for drinking water is chlorine gas (Symons, 1977). While this agent is certainly an adequate disinfectant, it suffers several serious limitations. Being an extremely toxic gas, a ruptured metal cylinder or pipe in a treatment plant or a derailed railroad tank car transporting the gas could cause casualties. Chlorine gas has been shown to chlorinate organic impurities in water to produce toxic trihalomethanes (Vogt and Regli, 1981). Furthermore, chlorinated water remains disinfected for only a few hours due to rapid loss of total chlorine through vaporization from the water and reaction with foreign matter; chlorine is not a particularly stable agent in water. Other gaseous disinfectants such as ozone (Rice et al., 1981) and chlorine dioxide (Hoff and Geldreich, 1981) are being employed in some municipal treatment plants, but these agents are also toxic gases and suffer many of the same limitations as does chlorine. Clearly it would be desirable to develop a new water disinfection agent which would be of low volatility (e.g., a solid), stable in water and dry storage, and nonreactive 0196-4321/83/1222-0716$01.50/0
with organic impurities. Several agents which are being used for disinfection of small water supplies fit some of these qualifications. These include household bleach (5% NaOCl), calcium hypochlorite, trichloroisocyanuric acid, and hydantoin derivatives. Although these agents are adequate disinfectants, none of them is particularly stable in water or dry storage (Worley et al., 1983a,b). In fact, the storage of dry agents can be hazardous. Improperly stored calcium hypochlorite can lead to spontaneous fires, and bleach must be protected from light and high temperatures (White, 1972). It has been stated that N-chloramine agents do not react appreciably with organic material to produce toxic trihalomethanes (Vogt and Regli, 1981). However, it has also been suggested that chloramines are much weaker bactericides than is chlorine gas (Hoff and Geldreich, 1981). We believe that this generalized statement has been made prematurely and that there are N-chloramine agents which are strong disinfectants and which possess other attributes which render them of possible commercial use as allpurpose water disinfectants. One such agent, 3-chloro4,4-dimethyl-2-oxazolidinone (henceforth referred to as 0 1983 American
Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 4, 1983
Table I. Minimum Bactericidal Concentrations for Several Disinfectantsa bacteria agent ~b HY
717
NCS
HTH~ BL 1.0 0.2 0.2 0.2 8 .O Escherichia coli ATCC 25922 1.0 2.0 1.0 4.0 8.0 Klebsiella pneumoniae ATCC 13883 0.5 0.2 0.5 2.0 8.0 Proteus vulgaris ATCC 13315 2.0 2.0 2.0 2.0 8.0 Salmonella cholera-suis 8.0 2.0 2.0 2.0 8.0 Salmonella typhimurium ATCC 14028 0.5 0.5 2.0 8.0 10.0 Serratia marcescens ATCC 8100 1.0 0.5 0.2 1.0 8.O Enterobacter cloacae ATCC 23355 48.0 4.0 4.0 4.0 12.0 Staphylococcus aureus ATCC 25923 12.0 2.0 20.0 4.0 10.0 Staphylococcus epidermis ATCC 12228 8.0 2.0 4.0 4.0 8.O Pseudomonas aeruginosa ATCC 27853 12.0 2.0 4.0 8.0 8.0 Sphaerotilus natans Agent I, 3-chloroa These MBC values are given in ppm of total available chlorine following a contact time of 10 min. 4.4-dimethvl-2-oxazolidinone; HY. 1.3-dichloro-5.5-dimethylhydantoin; NCS, N-chlorosuccinimide;HTH, 65% calcium hypochloriie/35%inert materials; BL, household bleach.
broth with the appropriate bacteria and incubation for 18 h at 37 “C. The resulting suspensions of bacteria were then transferred to blood and MacConkey agars and incubated H~C, r o , for 18 h. Colony morphology was examined, and typical colonies were placed in tubes of sterile nutrient broth A N A o which were incubated for 18 h at 37 “C. Each suspension H3C I CI was then standardized to 900 X lo6 bacteria/mL (McFarland no. 3) in sterile distilled water. agent I A sufficient amount of each compound was added to by Kaminski and co-workers (1976). Recent experiments sterile distilled water to provide a concentration of 10 ppm in these laboratories have demonstrated that agent I is an available chlorine (assuming 100% dissociation); a standeffective bactericide in a laboratory water treatment plant ard iodometric titration was used to verify this concen(Burkett et al., 1981),that agent I is exceptionally stable tration (American Public Health Association, 1971). The in water and in dry storage (Worley et al., 1983a,b), that final pH values for these solutions were agent I (5.0, NCS agent I is apparently nontoxic to chickens drinking water (4.9), HY (5.4), HTH (5.6), and BL (6.1). A series of containing the agent at the 200 ppm level, and it detoxifies twofold dilutions of the stock solutions were made ranging aflatoxin (Mora et al., 1982). The cellular mechanisms of from 1:2 through 1:32. The resulting concentrations in action of agent I in inhibiting bacterial DNA, RNA, and ppm of available chlorine were 10, 5, 2.5, 1.2,0.6, and 0.3. protein synthesis have been addressed here also (Kohl et These solutions were all checked iodometrically for al., 1980). A general summary of the chemical and bioavailable chlorine immediately before use. One milliliter logical properties of agent I was presented at the Fourth of each bacterial suspension was added to 4 mL of each International Conference on Water Chlorination (Worley dilution of the agent being tested. This procedure resulted et al., 1983a). The purpose of the current work was to in a 20% dilution of the available chlorine for each test compare the efficacy as a bactericide of agent I to several run; this dilution is accounted for in the data listed in other common disinfectants. Table I. At contact time intervals of 10, 20, 30, and 60 min, l-mL aliquots of each test solution were removed and Experimental Section transferred to a sterile plastic Petri dish (Fisher Scientific). Agent I was synthesized and purified in these laboraThen 10 mL of nutrient agar was added to each plate; the tories according to the procedure of Kosugi and co-workers plates were allowed to solidify and were incubated for 7 (1976) although several modifications were effected which days at 37 “C. The plates were checked each day for increased the yield over that reported earlier. The purity growth. of agent I (NMR analyses) attained for this study was In the few cases (Table I) for which the 10 ppm available greater than 99%. The agent 1,3-dichloro-5,5-dimethyl- chlorine for a given agent was insufficient to kill a bachydantoin (HY) was prepared by chlorination of 5,5-diterium, successively higher concentrations of the agents methylhydantoin (Aldrich Chemical Co.). The remainder were tested until kill was achieved. Controls consisting of the agents were purchased commercially and used of 4 mL of sterile distilled water plus 1 mL of bacterial without further purification (N-chlorosuccinimide(NCS), suspension at 900x IO6 mL were always monitored. Also, Aldrich Chemical Co.; HTH, Olin Chemicals Corp.; HTH to ensure that the decomposition product of agent I (4,4is 65% calcium hypochlorite and 35% “inert ingredients”; dimethyl-Zoxazolidinone)did not inhibit bacterial growth, household bleach (BL), Clorox Company). The water a control using this unchlorinated precursor to agent I in employed in this study for solutions of the agents and for the presence of Escherichia coli was run also. The agent bacterial suspensionswas deionized, distilled, and sterilized being tested was considered to have been effective in killing (autoclaved at 15 lb pressure for 30 min). The pH of the a given bacterium if no growth was detected after 7 days. water was typically ca. 4.6 before adding the agents. All Results pH determinations were made with an Orion Research The minimium bactericidial concentration (MBC) for Microprocessor Ion Analyzer/901 (Orion Research Inc.). each agent for each bacterium is presented in Table I. All The bacteria employed in this study were obtained eiof the data in Table I refer to the shortest contact time ther from Difco Laboratories (“Bactrol Disk”) or from the (10 min) studied. The data for longer contact times (20, Department of Microbiology at Auburn University. All 30, and 60 min) have not been included in the table, but media used in this investigation were purchased from Difco of course the MBC values were generally lower for the Laboratories and were prepared and sterilized according longer contact times. Also, the MBC values can be conto the directions supplied by the manufacturer. Bacterial sidered to be upper limits because no attempts were made growth was established by inoculation of sterile nutrient agent I), has been studied extensively in these laboratories. Agent I was first prepared and shown to be bactericidal
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 22,
No. 4, 1983
in this preliminary study to render the water or glassware “chlorine demand free”. Table I shows that all of the agents tested were bactericidal at low concentration of potentially available chlorine. With a few exceptions the N-chloramine agents (agent I, HY, and NCS) exhibited lower MBC values than did the hypochlorites. This is probably a result of the presence of small amounts of organic load in the water which will affect agents exhibiting primarily “free chlorine” to a greater extent than N-chloramines. It is notable that agent I was the poorest bactericide tested for destruction of Staphylococcus aureus with 48 ppm total available chlorine necessary a t a 10 min contact time. The reason for this will be addressed in the next section. However, it was observed that agent I will kill this bacterium at the 8 ppm total available chlorine level if the contact time is extended (actual colony counts using a Quebec Colony Counter (American Scientific) were too numerous to count at 10 min, 4043 colonies/mL at 20 min, 2268 colonies/mL a t 30 min, and no growth a t 60 min). Furthermore, it should be noted that the decomposition product of agent I (4,4-dimethyl-2-oxazolidinone) does not kill Escherichia coli at the concentration (32 ppm) and long contact time (60 min) tested.
Discussion The reason for longer contact times being necessary for agent I than for the other agents tested for some of the bacteria must be related to its great stability in water. Recent work in these laboratories has shown that agent I suffers no significant loss of available chlorine in a demand-free system over a period of months, while the other agents tested all lose a large percentage of their available chlorine through vaporization or decomposition over a period of a few weeks. The action of agent I in water solution is shown in eq 1. Liquid chromatography studies
I
CI
I
H
in these laboratories have demonstrated that the equilibrium in (1) lies very far to the left with only ca. 1% dissociation. Furthermore, it has been demonstrated that agent I is much more stable than NCS in the presence of a denaturant (Kosugi et al., 1976). Agent I will continue to exhibit bactericidal properties in the presence of horse serum, while NCS is rapidly denatured. An obvious explanation for the remarkable stability of agent I relative to the other compounds tested is related to its chemical structure. The presence of the two electron-donor methyl groups a t the 4 position of the oxazolidinone ring must destabilize the anion center developing at the nitrogen when the C1+ is released to form hypochlorous acid. In effect this greatly stabilizes the N-Cl bond causing agent I to be a “slow-release” agent in a demand-free system. As the HOC1 is used up in killing bacteria or in vaporization or reaction with organics in the system, the equilibrium will be maintained by slow formation of additional HOC1. The other agents tested in this study tend to release chlorine rapidly because of their chemical structures and thus kill bacteria quickly (short contact times), but do not remain effective nearly as long as does agent I.
The agent HY contains one chlorine structurally similar to NCS and one structurally similar to agent I. The
a.
H3Ck
