Inactivation of f2 virus with ferrate (VI)

Water Research Vol. 14, pp. 1705 to 1717 Pergamon Press Ltd 1980. Printed in Great Britain

INACTIVATION OF f2 VIRUS WITH FERRATE (VI) THOM~ SCHn~K and THo~o,s D. WAITE Department of Civil Engineering, University of Miami, Coral Gables, FL 33124, U.S.A. (Received January 1980)

Abstract--Disinfection of f2 virus with iron(Vl) ferrate in buffered, distilled water and secondary treated sewage effluent has been studied. The relative resistance of ['2 virus and Escherichia coil to iron(VI) ferrate has also been examined in buffered, distilled water. Potassium ferrate was found to rapidly inactivate f2 virus at low concentrations at pH = 6, 7 and 8 in pure water systems, and also in secondary effluent. The disinfection reactions observed did not follow first order reaction kinetics, f2 Virus appeared to be equally, or less resistant to potassium ferrate than were most bacteria, including E. coil, in buffered, distilled water at the pH values tested, and also in secondary effluent, lron(VI) ferrate appears to be a good viricidal agent in raw water and wastewater.

INTRODUCTION

difficulties. Iodine can also form potentially dan-

Chlorination presently accounts for over 95 per cent of all municipal, potable-water dis.infection (Morris, 1971) and is also used extensively for wastewater disinfection. Although the record of chlorination is admirable, problems arising from its use have recently been recognized. Chlorine residuals have been found to be highly toxic and inhibitory to aquatic life (Collins & Deaner, 1973; Brungs, 1973; US EPA, 1975). Removal of these residuals (dechlorination) from disinfected wastewaters will greatly increase the cost of chlorine disinfection, Formation of potentially dangerous chlorinated organic compounds has been associated with the chlorination process (Rook, 1974; Bellar et al., 1974). Removal of the organic compounds (precursors) prior to disinfection or removal of the chlorinated organic compounds after disinfection will also greatly increase the cost of disinfection with chlorine, Combined chlorine compounds are known to be relatively poor disinfectants, especially against viruses (Kelly & Sanderson, 1958, 1960a; Clarke et al., 1964; Kruse, 1970; Oliveri et ai., 1971), In order to overcome this deficiency, breakpoint chlorination is usually required practice (Cookson & Robson, 1975). Since few waste treatment plants are presently designed for or operated at breakpoint chlorination, more stringent disinfection requirements could greatly increase the cost of disinfection with chlorine. Alternative disinfectants presently under investigation such as bromine, bromine chloride, iodine, chlorine dioxide, ozone and ultra-violet irradiation all have associated drawbacks. Bromine and bromine chloride behave similarly and form combined compounds of reduced disinfection effectiveness, especially against viruses (Lindley, 1966; .Iohannesson, 1968; Kruse, 1970; Mills, 1973). They also can form potentially dangerous halogenated organic compounds (Morris, 1975) and their residuals are toxic to some extent to aquatic life (US EPA, 1975). They are also dangerous chemicals, generating transportation and handling

gerous halogenated organic compounds (Morris, 1975).Present methods of chlorine dioxide generation technology result in the potential formation of chlorinated organic compounds (Symons, 1976) and also have drawbacks with respect to transportation and handling problems since chlorine gas is required for generation of chlorine dioxide. All of the alternative disinfectants mentioned above may be capable of inactivating pathogenic organisms over the expected variation in water and wastewater temperatures, quantities, and composition but at a relatively high cost. For these reasons, potassium ferrate has been investigated as an alternative to chlorination for the disinfection of water and wastewater. Before ferrate can be seriously proposed as an alternative to chlorine, the costs and toxicity of ferrate treatment as well as its effectiveness as a disinfectant against a variety of organisms under varied water and wastewater conditions must be determined. This report will deal with ferrates effectiveness as a viricidal agent. Ferrate (VI) ion has the molecular formula FeO4 ~-. Wood (1958) reported the redox potential of ferrate to vary from -2.2 V in acid to -0.7 V in base. Many metallic salts of ferric acid (MFeO4) have been synthesized (Waite, 1978b), potassium ferrate (K~FeO4) being utilized in this study. Aqueous solutions of potassium ferrate have a characteristic violet color. The overall decomposition of ferrate~I) ion in aqueous solution is described by: 2FeO~- + 3H20--~ 2FeO(OH) + 3/202 + 4OH-. Hydroxide ion and molecular oxygen are generated upon decomposition, and the decomposition rate is dependent upon pH, initial ferrate concentration, and temperature. The decomposition rate is also influenced to some extent by surface characteristics of the hydrous iron oxide formed upon decomposition. Ferrate is most stable in strong base, and Haire (1965) reported that ferrate stability is also highly dependent

1705

1706

THOMASSCHINKand THOMASD. WAITE

on the initial Fe(III) concentration which apparently accelerates decomposition. Studies on the stability of ferrate in aqueous solution have shown that dilute solutions of ferrate are more stable than concentrated solutions (Schreyer & Ockerman, 1951). Ferrate decomposition rate has also been found to decline markedly in the presence of phosphate, and at low temperatures (Wood, 1958; Schreyer & Ockeman, 1951 ; Wagner et al., 1952). Several researchers have determined that iron(VI) does not convert directly to iron(Ill) on decomposition, but passes through its +5 and + 4 oxidation states (Murmann, 1974; JezowskaTrezebiatowska & Wronska, 1957; Magee, 1961). Evidence that ferrate possessed significant disinfecting properties was first noted by Murmann & Robinson (1974). The first detailed disinfection studies were done by Gilbert (1975) utilizing Escherichia coli in buffered, distilled water. Below pH 8.0 the disinfecting ability of potassium ferrate was observed to increase markedly, however, steady and effective kills were also noted at pH values between 8.0 and 8.5. Disinfection efficiencies were observed to increase slightly as the pH increased above 8.0. Gilbert also observed that only a 5-fold increase in the molar concentration of ferrate was necessary to achieve the same degree of inactivation of E. coil in secondary effluent as was achieved against E. coli in buffered distilled water at pH 8.0. Waite (1978a) tested several organisms against potassium ferrate. Three members of the Enterobacteriaceae were tested and all reacted to potassium ferrate in a similar manner. All were rapidly and effectively inactivated in buffered, distilled water with a ferrate concentration of 10-SM at pH 7. Four gram positive organisms: Streptococcus faecalis, Streptococcus boris, Staphylococcus aureus and Bacillus cereus were also tested. The gram positive organisms were found to be far more resistant to ferrate than the gram negative organisms mentioned previously. At least one order of magnitude greater ferrate concentration was required to achieve the same degree of disinfection in the same period of time. Waite observed no consistent pattern of ferrate inactivation of E. coil increasing with decreasing pH between pH 8 and 6. While some correlation between temperature and E. coli inactivation rate constants was found, Waite reported that for temperature changes norreally encountered in water treatment, only a small effect on inactivation kinetics would be expected. The initial concentration of E. coli cells and the initial carbon content of the disinfecting medium (in the form of glucose; @2-200 nag 1-1 as C) had little effect on inactivation kinetics. It is interesting to note that retardant die-off kinetics were observed in all disinfection studies of Waite (1978a) and Gilbert (1975) at pH levels of 8.0 or below, Viruses are among the most difficult to remove organisms from water and wastewater, and are the smallest known pathogenic organisms, ranging from 1/100th to 1/2 g in diameter. The viruses of greatest

concern in water and wastewater treatment are the enteric viruses, and many of these viruses have been isolated from wastewater (Paul & Task, 1942; Kelly & Sanderson, 1960b; Clarke et al., 1967; Kelly & Sanderson, 1960b; Clarke et al., 1967; Malherbe & Strickland-Cholmley, 1967; Grabow, 1968; Sobsey, 1975), and surface waters (Metcalf & Stiles, 1968; Grinstein et al., 1970; Berg, 1971), and are presumed to exist in very low concentrations in drinking water (Shaffer, 1977). While these viruses are associated with numerous diseases (Mosley, 1965, 1967; McDermott, 1971; Taylor, 1974; Cookson, 1974), infectious hepatitis is the only epidemiologyically established waterborne viral disease (Mosley, 1967). Viruses can survive great lengths of time in clean and polluted water, often even longer than bacteria which are capable of reproducing in some of these waters (Clarke et al., 1964). Many researchers believe that waterborne viral diseases are not limited to the small number of documented hepatitis outbreaks (Berg, 1971; Goldfield, 1974; Sobsey, 1975), and therefore feel that complete virus removal from drinking water is justified. There is also a potential health hazard to downstream recreationalists and consumers when viruses are discharged from sewage treatment plants. Although water and wastewater treatment processes are effective to varying degrees for virus removal, complete virus removal does not usually occur. Therefore, disinfection is necessary to achieve or approach this goal (Berg, 1964, 1971). Due to inadequate virus detection methods, a lack of virus removal goals and standards, and an incomplete knowledge of the relationships between virus inactivation and variables of the disinfection process, complete virus removal from waters before use for drinking and recreational purpose cannot be guaranteed at the present time even with disinfection: AIthough complete virus removal may occur in some water and wastewater treatment plants, this is going on undetected and disinfection facilities are not presently designed for this purpose (Berg, 1971). There has been a great deal of concern expressed in recent literature for improved virus removal from water and wastewater. For the reasons mentioned above, the application of potassium ferrate as a water and wastewater disinfectant was examined here, with special reference to viruses. The effects of potassium ferrate concentration and time of contact were investigated over varied conditions of pH and organic content. The virus chosen as a model in this study was the f2 virus, which has been used as a model for previous disinfection studies due to its chemical and physical similarities to enteroviruses. Experimental evidence has shown that t"2 virus responds to chlorine and iodine similarly to enteric viruses (Olivierei et al., 1975), and based on limited available data, f2 virus appears to respond to chlorine in a manner similar to the infocfious hepatitis virus (Ofivierei et al., 1975) and poliovirus II (Cramer et al., 1976).

Inactivation of 12 virus with ferrate (VI) EXPERIMENTAL PROCEDURE Materials

1707

Where N is the number of viable organisms, t is the time from initial contact between organism and disin-

Potassium ferrate was prepared in the laboratory by oxi- fectant, and k is a rate constant. In order for this first dation of ferric nitrate with chlorine gas according to the order rate equation to be valid, all parameters other method of Schreyer et ai. (19531 Samples of ferrate were than the number of organisms (such as the nature and then analyzed for purity by the chromite reduction method state of the organism, concentration of disinfectant, (Sdireyer et al., 1953),and only ferrate of greater than 90% opportunity for contact between the organism and the purity was utilized in the experiments. f2 Virus, E. colt K-13, and E. coil Strain B, were utilized disinfectant, and the nature and environmental conin this study. 12 Virus and its host, E. coil K-13 were ditions of the disinfecting medium) must remain conobtained from Dr Vincent Olivieri of the Johns Hopkins stant with time. A first order rate equation would University, and E. coil Strain B (which is resistant to attack yield a straight line plot on semi-log paper. It was by 12) was obtained from the American Type Culture Colevident in the above mentioned figures, that the data lection. Preparation of t2 required addition of 12 virus into an E. did not follow first order kinetics. Although the devicoli K-13 culture growing in Tryptone Yeast Extract Broth ation from Chick's Law has been described in the in the log phase of growth at 36-38°C to insure efficient literature as being due to organism clumping, (Katzeadsorption and penetration stages of the viral reproduction nelson et al., 1974; Sharp, 1976; Wei & Chang, 1975) cycle. After 12 viruses replicated in this culture, the large percentaga of resistant E. coil K-13 cells were carefully or organism heterogeneity (Gard, 1957; Withell, removed by centrifugation and heat treatment to prevent 1942), it is doubtful that these phenomena are of the remaining E. coli cells from interfering with the ferrate major importance here. The most probable reason for during disinfection studies, departure from first order kinetics, in this case, is due 12 Virus was assayed by plating out dilutions of an f2 to the rapid decomposition of ferrate in aqueous solusample on a lawn of host E. coil K-13 cells, f2 Viruses were counted by enumerating plaques that appeared in the tion. Thus, one of the parameters (disinfectant conopaque lawn of E. coli. centration) that should remain constant in order for E. coil strain B was cultured in nutrient broth and disinfection to follow first order kinetics, is not assayed by plating on nutrient agar. Individual colonies remaining constant with time, and the organisms, are were easily discernible and counted at the correct dilutions. A sterile 0.1 M NaOH-KH2PO4 buffering system was faced with a constantly decreasing concentration of used as the disinfecting medium for most of the tests, disinfectant. The importance of decreasing concenSecondary effluent obtained from the Chicago-North Side tration of disinfectant in disinfection studies has been Sewage Treatment Plant was used as the disinfecting t noted by other workers (Hiatt, 1964), (Olivieri et al., medium for the remainder of the experiments. 1971), and (Waite, 1978a). Ferrate decomposition in The organisms utilized in each experiment were prepared exactly the same way, as changes in the amount of the phosphate buffer system used in these experiments organism-suspending nutrient medium being added to the will be discussed in greater detail later in this section. reaction flask altered the results of the experiments. PotasFigure 8 is a plot of the Watson time-concentration sium ferrate disinfection results appeared to be especially relationship for f2 virus inactivation at pH = 5.9, 6.9 sensitive to changes in the amount of TYE broth present. Therefore, f2 virus stock samples were diluted 1:100 with and 7.8. The War.son time-concentration relationship sterile distilled water prior to each run to minimize any is an empirical relationship developed by Watson interfering effects of the TYE broth. E. coli Strain B cells (1908)and has been used to compare disinfectants as were washed with sterile buffer three times prior to addi- well as the relative resistances of organisms to each tion into the reaction flask to minimize any interfering other or to varied disinfecting conditions. This reeffects of the nutrient broth. Initial concentrations of the organisms ranged from approx. 10s-10~ cells or plaque lationship is: forming units ml-1. Disinfection tests with various concentrations of potasC't99 = K. sium ferrate were performed in sterile phosphate buffered Where C is the concentration of the disinfectant water and in secondary sewage effluent. Experiments in buffered water were run at pH 6, 7 and 8. Experiments (rag I-~), n is a constant known as the coefficient of were run on t2 virus alone and on a mixture of 12 virus and dilution, t99 is the contact time required for 99% inacE. coil Strain B. Use of this resistant strain of E. coil tivation of the organism, and K is a constant indicatallowed ferrate resistance comparisons to be made from ing the time required for 99% inactivation with experiments run in the same reaction flask, thus elimin- 1 mg 1-1 disinfectant. Figure 8 was prepared from dieating errors inherent when studies are carried out separately under slightly varied conditions. The ability of ferric off curves utilizing a linear regression analysis of the chloride to inactivate or aggregate t"2 virus and E. coli in initial slopes of Figs 1-5. sterile phosphate buffered water was also examined. Values for "K" and "n" from the Watson time-concentration relationship are reported in Table 1. The RESULTS AND DISCUSSION value of "n" is an indicator of the relative effect of Figures 1-5 show the disinfection kinetics of t2 reaction time and disinfectant concentration. If "n" virus and Escherichia coli strain B with potassium values are greater than unity, disinfectant concentration has a greater effect on the inactivation rate ferrate. In all cases, the data were plotted in semi-log than does time of contact. If "n" values are less than format, thus assuming that the disinfection kinetics unity, then contact time is more important. An "n" followed Chick's Law. (Chick, 1908) ,~alue near unity denotes approximately equal effects dN/dt = -RN. from each variable (Fair et al., 1971).

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THOMAS SCHINK and THOMASD. WAITE I

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Inactivation of 12 virus with ferrate (VI) I001~

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It can be seen in Fig. 8 and Table 1 that the inactiration of f2 virus is enhanced as pH decreases. The inactivation is especially enhanced by a decrease in pH from 6.9 to 5.9. Another noteworthy item observed from Fig. 8 is that the differences in inactiration rate between the different pH values decreased as the ferrate concentration was increased, Table 1 shows that I mg 1-1 of potassium ferrate inactivated 99% of f2 virus in 22 rain at pH 7.8,

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1712

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rapidly at a lower pH, and higher initial fcrrate conccntrations decompose more rapidly than lower initial concentrations. The effect of rapid decomposition of ferrate on viral inactivation is easily seen in Figs 1-3 as decreasing inactivation effectiveness with time. At lower pH values, the die-off rates decrease faster than at the higher pH values, but this is expected, since Figs 9 and I0 have shown that ferrate decomposes much more quickly at the lower pH values, Previous experiments with potasshun ferrate versus Escherichia coli (Waite~ 1978a) have shown that E. coli is only slightly more susceptible t0 potaw,ium fctraf¢ as the pH is decreased. On the ot!~r hand, our results (Fig. 8) have shown that f2 virus is much more suKeptible to potassium ferrate as the pH isdeereasecL To examine any difference in ~ f i t y to ferrate between f2 virus and E. co/i strain B, a Watson time-conoentrafion relationship plot of the data in Fig. 4 was made, and is shown in Fig. 11, The two organisms show esseatially ~th¢ same ~ l i t y to ferrate at pH = 6.9. Also on Fig. 11 is an overlay of

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the original Watson time-concentration plot (from Fig. 8) for f2 virus inactivation alone at pH = 6.9. Although a slight unexplained change in slope was noted, the inactivation rates of t"2 virus appear to be unchanged by the presence of E. coll. In Fig. 5, an overlay of the f2 virus die-off curve from Fig. 1 showing the inactivation of f2 virus without E. coil strain B present in the same flask shows that at pH = 5.9, the susceptibifity of f2 virus to ferrate does not appear to be affected by the presence of E. coll. Figure 12 shows a Watson time-concentration relationship for several organisms, including f2 virus, at pH = 7. This figure was adapted from previous research (Waite, 1978a) and Fig. 8. From this figure, t"2 virus is seen to be the least resistant organism to potassium fen'ate tested. Results from,this study have also shown that f2 virus and E. coii strain B are equally resistant to ferrate at pH = 6.9 (see Fig. 11). This slight difference is due to the fact that the virus is being compared to two ,different strains of E. coli and tests were performed by two different researchers. In

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Inactivation of t"2 virus with ferrate (VI) I0 " 4 ~.

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any event, it can be concluded that f2 virus is at least equally susceptible, if not more susceptible, to ferrate than is E. coli at pH = 7. Previous results for ferrate inactivation of E, coli at pH = 8.0 (Gilbert et al., 1976) reported a Watson time-concentration relationship "K" value of 15,8 min. The Watson time-concentration relationship "K" value reported in this study for f2 virus inactivation at pH 7.8 was 22min. This information, coupled with a comparison of Figs 4-8, also leads to the conclusion that f2 virus is approximately equally as susceptible to ferrate at pH = 8 as is E. coll. Another conclusion reached is that r2 virus is much less resistant to ferrate at pH = 6 than is E. coil Previous research (Shah & McCamish, 1972; Scarpino et aL, 1972; Cramer et aL, 1976) with other disinfectants has indicated that f2 virus is usually at least as resistant as is E. coll. I0 -:3 -

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Addition of cations to a solution containing viruses could aggregate the negatively charged viruses through compression of the virus particles' diffuse counter-charge layer and/or by absorption and charge neutralization. Ferrate ion or one of its de composition products is positively charged and could aggregate the viruses. Because little or no inactivation was observed a few minutes after ferrate was added to the reaction flasks, the relatively stable breakdown products of ferrate (Fe 3 + and Fe 2 +) were not believed to cause virus aggregation. Experiments with ferric chloride as the disinfectant however were carried out to test this belief. Figure 6 has shown that 2.5 x I0 -s M ferric chloride (4 mg I - i ) had no effect on I"2 virus or E. coli at pH = 7. No testing was done at pH = 6, but the results are expected to be similar. Previous research had indicated that approx. 30 mg I - t ferric chloride T

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1714

THOMAS SCHINK and THOMAS D. WAITE

could remove 10% of 1"2 virus and 40 mg 1-1 could remove 98% (York & Drewry, 1974). Therefore, to achieve one order of magnitude of f2 virus inactivation 1.9x 10-¢M (30mg1-1) of ferric chloride would be required. The highest ferrate concentration used in our experiments against f2 virus was 5.0 x 10-SM, therefore any viral aggregation that may be taking place is probably not due to the relatively stable ferrate breakdown products, Fe 3÷ and Fe 2 +. This leaves only ferrate, Fe 6 *, or one of its relatively short-lived breakdown products, Fe s ÷ or Fe 4÷, as being capable of irreversibly (in our laboratory procedures) aggregating f2 virus. Whether or not ferrate or one of its breakdown products actually does aggregate f2 virus has not been determined and will require further research, Previous results utilizing potassium ferrate against Escherichia coil at pH = 7 in the presence of varying amounts of glucose (from 2 to 200 mg 1- ~ as C) have shown that glucose had no significant effect on ferrate inactivation kinetics (Waite, 1978b). However, other organic compounds would effect ferrate differently and could reduce ferrate before sufficient organism inactivation could take place. This is true to some extent with the organic compounds present in bacterial growth media and in primary and secondary sewage effluents. As noted previously ferrate was observed to react with the organic compounds present in the tryptone yeast extract broth used to prepare virus stocks. An order of magnitude dilution of this stock (containing broth) before addition to the reaction flask, resulted in approximately an order of magnitude less ferrate required to achieve a fixed percentage kill in a fixed period of time.

10- 5

Figure 7 has shown inactivation kinetics of f2 virus in secondary effluent utilizing various ferrate concentrations, while Fig. 13 compares Watson time-concentration relationships for ferrate inactivation of f2 virus in secondary effluent and in phosphate buffer at pH = 6.9-7.8. It can be seen that from one-half to one order of magnitude higher initial ferrate concentration is required to inactivate the same percentage of f2 virus in secondary effluent in the same amount of time as is required for f2 virus in phosphate buffer. Therefore, the organics present in the secondary effluent do exert a demand for the ferrate, and interfere slightly with the inactivation efficiency. This interfefence decreases as the initial ferrate concentration is increased. The slope of the line for disinfection in secondary effluent (Fig. 13) indicates that disinfection in secondary effluent is more sensitive to initial concentration than is disinfection in phosphate buffer solution, and also that disinfection in secondary effluent is more sensitive to initial concentration than to time of contact. This is explainable by the fact that pH was allowed to increase in the secondary effluent studies. With the studies done in phosphate buffer, sufficient buffering capacity was present to hold the pH constant. As pH increased in the secondary effluent, the ferrate was more stable allowing ferrate concentration differences more time to be effective. Previous research has been performed with ferrate against many types of bacteria in secondary effluent (Waite, 1978b). Table 2 has been adapted from this previous research as well as Fig. 13. Table 2 shows that t"2 virus is more easily removed from secondary effluent than are total bacterial populations. Only approximately 2 mg 1-1 ferrate was required to remove

I

!

200

c Z

olO

~4

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~ secondory effluent {~ phoephote buffer, pH 7.8

~P\\-~"

Z~ phosp,a,, bu,f.,, p.e.9

~ ~,~

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J 20

Ji

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z ,,, 0

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". . . . . L :0.2 l. . . . . .\ . . . IO IOO TIME FOR 99°/o INACTIVATION (rain) Fig~ 13: Watson t i n u P c o n c e ~ r ¢ ~ for f2,victlS ~ pH ,ffi 6.9 am~ 7~8 in phosplmt¢ buffer and in ~ ~ t .

10.6

I.o

Inactivation of t2 virus with ferrate (Vl)

1715

Table 2. Percentage removal in relation to fcrrate :dose (adapted from Wait¢, 1978b)

Ferrate dose (rag 1-1 as KzFeO4)

Total bacteria removed from secondary effluent in 60 min (%)

12 Virus removed from secondary effluent in 60 win (%)

3 7 36 54 72

-57 87 99 99.9

99 -----

99% of f2 virus in 60 min, while 54 mg 1-1 ferrate was required to remove 99% of total bacteria in 60 min. As mentioned previously, Gilbert (1975) found that only a 5-fold increase in molar concentration of ferrate was neo~ssary to achieve the same degree of inactivation of E. coli in secondary effluent as was achieved against E. coil in buffered distilled water at pH 8.0. This agrees well with the secondary effluent study shown in Fig. 13, indicating that the resistances of 12 virus a n d E. coil in secondary effluent are nearly equal, Comparisons of magnitudes of 12 kill from results of this study with results of other studies are difficult due to differences in equipment design, methods of f2 virus purification, and general laboratory procedures, However, comparison of our results with the results obtained using other disinfectants against f2 virus will be attempted, keeping in mind that the accuracy of those comparisons may be questionable, Estimates of the time required for 99% inactivation of t2 virus have been extracted from the results of Olivieri et al. (1975), Sc,arpino et ai. (1974) and from this study, and are presented in Table 3. It can be seen that ferrate is slightly more effective for f2 virus inactivation than either a mixture of HOCI and OCI-, or free bromine, and is more effective than free iodine. However, ferrate can be seen to be slightly less effectiv¢ for 12 virus inactivation than HOCI. The effective-

ness of bromine incroascs with decreasing pH (Lindley, 1966) as does iodine (Stringer et al., 1975), however, it should be remembered that 12 inactivation by fcrrate also increases markedly w i t h docrca,sing pH. A comparison can' be made between combined chlorine (formed in secondary effluent) and: fen,ate against 12 virus.: For this cue, t h e results utilizing ferrate in secondary effluent should be used in order that the combinations of chlorine with ammonia may be equalized l~y reactions of fcrrate with ammonia or other compounds present in the diluent. N o specific comparison can. be made between bromamines and forrate. It will be sufficient to state that bromamine has been found, to lack any viricidal capacity against 12 virus (Lindlcy, 1966). Iodine does not combine with ammonia and this may give iodinean advantage over chloramines and bromamines dilinll~ction is carried out in secondary effluent (Stringer et aL,~1975). A study utilizing prcreacted chlorine with filtered and autoclaved secondary effluent at p H = 7 reported that 27.5 mg 1- ~ of initial combined chiorine~residual inactivated 99% of' f2 virus in 68 min (Cramcr eta/., 1976).As shown in Fig. 13, 20 mg 1" L KzF¢O4 inactivated 99% of 12 virus in secondary effluent in approx. 1 min. These results show ferrate to be much more effective for the inactivation of the 12 virus than combined chlorine under the conditions mentioned above.

Table 3. Concentration and contact time requirements for 99% inactivation of 12 virus by several disinfectants in relatively pure water systems Results adapted from others

Disinfectant Iodine* Bromine* Chlorine*t Chlorine~§

Temperature (°C)

pH

27 0 10 5

7 7.5 7.5 6

Ferrate results Time fox 990 Dose inactivation (mg 1- ~) (min) 50 15 2 0.15

* Olivieri et al. (1975). t Approximately 1:1 mixture of HOCI and OCI-. :[ Scarpino et al. (1974). § Mostly HOCI.

8 2.5 12 1.0

Temperature (°C)

pH

24 24 24 24

7 7.5 7.5 6

Time for 99% Dose inactivation (mg l- 1) (rain) 1.0 15 2.0 0.4

53 1

6 1.0

1716

THOMASSCHINK and THOMASD. WAITE

At pH values lower than 7, combined chlorine disinfcction will improve due to the presence of a greater proportion of dichioramine.

Cookson J. T. Jr (1974) Virus and water supply. J. Am. War. Wks Ass. 66, 707. Cookson J. T. Jr & Robson C. M. (1975) Disinfection of wastewater effluents for virus inactivation. In DisinfecLongley et al. (1974) had shown 6.5 ~ag 1- ~ applied tion Water and Wastewater (Edited by John J. D.). Ann ozone to inactivate 99% of 12 virus in 15 min in Arbor Science Publishers, Ann Arbor, MI. secondary effluent. F r o m Fig. 13, it is evident that Fair G. M. et al. (1971) Elements of Water Supply and 6 mg 1-1 K2FeO4 inactivated 99% of f2 virus in Wastewater Disposal, 2nd edition. Wiley, New York. Gilbert M. B. (1975) A study of the potential of potassium approx. 13 rain in secondary effluent. While it is not fcrrate (VI) as a disinfectant and general oxidant for use possible to draw any concrete conclusions from this, in water and wastewater treatment. Masters Thesis, Unlit does appear that potassium ferrate is as effective versity of Miami, December. against f2 virus in secondary effluent as is ozone. Gilbert M. B. et al. (1976) An investigation of the applicability of ferrate ion for disinfection. J. Am. War. Wks Ass, 68, 495. CONCLUSIONS Goldfield M. (1974) Epidemioiogic aspects of waterborne viral disease. Presented at the International Conference 1. Potassium ferratc rapidly inactivates 12 virus at on Viruses in Water, Mexico City, Mexico. low concentrations at pH = 6, 7 and 8 in pure water Grabow W. O. K. {1970) The virology of waste water treatment. 2. 675. systems, and also in secondary effluent. Grinstein S. et al. (1970} Virus isolations from sewage and 2. The ¢a'lectivenesS of ferrate against t2 virus was from streams reccqving effluents of sewage treatment shown to increase as pH decreased. The increase in plants. Bulletin WHO. 42. fcrrate effectiveness was especially evident for the Hiatt C. W. (1964) Kinetics of the inactivation of viruses. drop in p H from 7 to 6. Baet. Rev. 28, 150. Jezowska-Trzebiatowska B. & Wronska M. (1957) Cong. 3. 12 Virus appears to be equally or less resistant to int. Chim. Pure Appl. 16e, Paris (1957). ferrate than are most bacteria in phosphate buffer at Johanneson J. K. (1968) Anomolous bactericidal action of pH values between 6 and 8, and also in secondary bromamin. Nature lgl, 1799. effluent with a n initial pH near neutrality. Katzenelson E. et al. (1974) Inactivation kinetics of viruses and bacteria in water by use of ozone. J. Am. War. Wks 4. One half to one order of magnitude greater Ass. 66, 725. ferrate concentration is required to inactivate bacteria Kelly S. M. & Sanderson W. W. (1958) The effect of chloand viruses in secondary effluent. Thus, ferrate nne in water on enteric viruses. Am. J. publ. Htth 48. aPtw~rs to be Ices affected by changes in the organic 1323. content of the disinfecting medium than are chlorine Kelly S. M. & Sanderson W. W. (1960a) The effect of chlorine in water on enteric viruses---II. The effect of cornor bromin~ It also appears that potassium ferrate is bined chlorine on poliomyelitis and coxsackie viruses. less affected,,by changes in temperature and pH than Am. J. publ. Hlth ~0, 14. is chlorine. Kelly S. M. & Sanderson W. W. (1960b) The density of 5. Ferrate has possible applications as a wastcwater enteroxaruses in sewage. J. War. Pollut. Control Fed. 32, 1269. disinfectant. Ferrate has been shown to more etfecKnocke K W. et al. (1967) Nachweis yon Reo-Viren in tivcly inactive 12 virus in secondary effluents than Abwassem Zentbl. Bakt. Parasitkde 203)417. combined chlorine and combined bromine. Ferrate Kruse C W. (1970) Halogen action on bacferenee on also has the advantage that it has no residual Which is Disinfection, ASCE. harmful to aquatic life, as do chlorine and bromine Lindley A. C. (1966) The activity of bromine against f2 bacteriophage and its host Escherichia coil K-12 under residuals, various aqueous conditions. Masters Thesis, The Johns Hopkins University, June. Acknowledgement--This work was supported by the Longley, K. E. et al. (1974) Enhanceracnt of terminal disinNational Science Foundation, Grant No. ENV76-83897. fection of a wastewater treatment system, in Virus Sur. viral in Water and Wastewater Systems (Edited by REFERENCES Malina & Sagic), Water Resources Symposium No. 7. Center for Research in Water Resources, University of Bellar T. A. et al. (1971) An integrated approach to the Texas, Austin. problem of viruses in water. J. Sanit. Enong Die. Am. Soc. McDermott J. H. (1971) Virus and water quality: occurCir. Engrs 97, 867. rence and control-conference summary. Proceedings of Berg G. (1964) The virus hazard in water supplies. J. New The Thirteenth Water Quality Conference, University of E~l. War. Wks Ass. 78, 79. Illinois. BergG. (1971) An integrated approach to the problem of Magee J. S. (1961) The kinetics of the decomposition of viru~u~ in water, J. Sanit. Engno Die. Am. Soc. Cir. Enors potassium tetraoxoferrateO/I) in aqueous solution. D. 97~,867. Abstr. Brungs W. A. (1973) Effects of residual chlorine on aquatic Malherb¢ H. H. & Strickland-Cholmley M. (1967) Quantilife. J. War. PoUut. Control Fed. 45° 2180. tative studies on viral survival in sewage puritic,ation Chick H. (1908) An investigation of the laws of disinfection, processes. In Transmission of Viruses by the Water Route J. HyO. 8, 92. (Edited by Berg G.). Interscicnce, London. Clarke N. A. et al. (1964)Human enteric viruses in water: Metcalf T. G. & Stiles W. C. (1968) Viral pollution of source survival and removability. In Advances in Water shellfish in estuary waters. J. Sanit. Engna Die. Am. Soc. Po. Uution Research, Vol. 2, p. 523. Cir. Engrs 94, 595. Collins H, F. & Dcaner D. G. (19_73) Sewaga chlorination Mills J. F. (1973) The chemistry of bromio¢ chloride in versus toxicity--A dilemma? J, Envir. Enang Die. Am. waste water disinfection. Am. Chem. $oc. Die. Enong Soc. Cir. Enors 99, 761. Chem. 13, 137. .

Inactivation of f2 virus with ferrate (el) Morris J. C. (1971) Chlorination and disinfection-state of the art. J. Am. Wat. Wks. Ass. 63, 769. Morris J. C. (1975) Formation of halogenated organics by chlorination of water suppfies. USEPA. Mosley J. W. (1965) Transmission of Viral Diseases by Drinking Water. Intcrscience, London. Mosley J. W. (1967) Transmission of Viral Diseases by Drinking Water. In Transmission of Viruses by the Water Route (Edited by Berg C.). Interscience, London. Murmann R. K. & Robinspn P. R. (1974) Experiments utilizing FEO~- for purifying water. Water Res. g, 543. Murmann R. K. (1974) The preparation and oxidative properties of ferrate (FeO+2-). NTIS Publication PB-238-057. Olivieri V. P. et al. (1971) Inactivation of virus in sewage. J. sanit. Engng Die. Ant Soc. Cir. Engrs 97, 661. Olivieri V. P. et al. (1975) The comparative mode of action of chlorine, bromine, and iodine on f2 bacterial virus. In Disinfection Water and Wastewater (Edited by Johnson J. D.). Ann Arbor Science Publishers, Ann Arbor, MI. Oiivieri V. P. et al. (1975) The comparative mode of action of chlorine, bromine, and iodine on t"2 bacterial virus. In Disinfection Water and Wastewater (Edited by Johnson, J. D.). Ann Arbor Science Publishers, Ann Arbor, MI. Paul J. R. & Task J. D. (1942) Occurrence and recovery of the virus of infantile paralysis from sewage. Am. J. publ. Hlth 32, 235. Rook J. J. (1974) Formation of haioforms during chlorination of natural waters. J. Wat. Treat. Exam. 23, 234. Scarping P. V. et al. (1974) Effectiveness of hypochlorous acid and hypochlorite ion in destruction of viruses and bacteria. In Chemistry of Water Supply, Treatment and Distribution (Edited by Rubin), p. 359. Ann Arbor Science Publishers, Ann Arbor, ML Schreyer J. M. & Ockerman L. T. (1951) Stability of the ferrate(VI) ion in aqueous solution. Analyt. Chem. 23, 1312. Schreyer J. M. et al. (1953) Potassium ferrate, lnorg. Synth. 4, 164. Shaffer P. T. B. (1977) Virus detection methods-comparison and evaluation. In Virus and Trace Contaminants in Water and Wastewater (Edited by Borchardt et al.), p. 21. Ann Arbor Science Publishers, Ann Arbor, MI.

w.a, 14]I 2-.--~

1717

Shah P. C. & McCamish J. (1972) Relative resistance of poliovirus I and coliphage f2 and t2 in water. Appl. Microbiol. 24, 658. Sharp D. G. (1976) Virion aggregation and disinfection of water viruses by bromine. US EPA Office of Research and Development, May. Sobscy M. D. (1975) Enteric viruses and drinking water supplies. J. Am. War. Wks Ass. 67, 414. Stringer R. P. et al. (1975) Comparison of bromine, chlorine and iodine as disinfectants for amoebic cysts. In Disinfection Water and Wastewater (Edited by Johnson, J.D.). Ann Arbor Science Publishers, Ann Arbor, MI. Symonds J. M. (1976) Interim treatment guide for the control of chloroform and other trihalomethanes. Water Supply Research Division, Municipal Environmental Research Laboratory, Office of Research and Development, USEPA, June. Taylor F. B. (1974) Viruses+what is their significance in water supplies? J. Ant Wat. Wks Ass. 66, 306. USEPA (1975) Office of Research and Development, Disinfection of Wastewater, July. Wagner W. F. et al. (1952) Factors affecting the stability of aqueous potassium ferrate(VI) solutions. Analyt. Chem. 24, 1497. Waite T. D. (1978a) Inactivation of Salmonella sp., Shigella sp., Streptococcus sp. and 1"2 virus by iron(VI) fcrrate. Paper presented at 1978 annual AWWA Conference, Atlantic City, N J, June. Waite T. D. (1978b) Management of wastewater residuals with iron(VI) ferrate. First Annual Research Report to the National Science Foundation, March. Watson H. E. (1908) A note on the variation of the rate of disinfection with change in the concentration of the disinfectant. J. Hyg. g, 536. WCI J. H. & Chang S. L. (1975) A multi-poisson distribution model for treating disinfection data. In Disinfection Water and Wastewater (Edited by Johnson, J. D.), p. 11. Ann Arbor Science Publishers, Ann Arbor, MI. Withell E. R. (1942) The significance of the variation in shape of time-survivor curves. J. Hyg. 42, 124. Wood R. H. (1958) The heat, free energy and entropy of the ferrate(VI) ion. J. Am. chem. Soc. M}, 2038. York D. W. & Drewry W. A. (1974) Virus removal by chemical coagulation. J. Am. Wat. Wks. Ass. 66(12), 711.