Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 2, 1979 269
the nozzle became important at small heights; for example, at 2 cm the width was affected little by the concentration. Conclusions The investigation has demonstrated that the spreading characteristics of a film undergoing distillation cannot be ascertained from a knowledge of its ability to spread under non-mass-transfer conditions. Until it is possible to predict the complex contact angle-concentration relationships exhibited by binary systems experiencing distillation a t total reflux, the only means of determining the spreading behavior is by experiment at the appropriate conditions.
Nomenclature h = film length, mm 2 = film width, mm L i t e r a t u r e Cited Boyes, A. P.. Ponter, A. B., AIChE J., 18, 935 (1972). Fabre, S.,D . 9 . (Tech)Thesis No. 281,Ecole PolytechniqueFederale de Lausanne,
1977. Peier, W., Ponter, A. B., Fabre, S., Chem. Eng. Sci., 32, 1491 (1977). Ponter, A. B.,Davies, G. A., Beaton, W. I. Ross, T. K., Trans. Inst. Chem. Eng., 45, 345 (1967). Ponter, A. E., Boyes, A. P., Houlihan, R. N., Chem. Eng. Sci., 28, 593 (1973).
Received f o r review February 23, 1978 Accepted September 29, 1978
Application of Process Control Techniques to Radiation Treatment of Waste Water Shoji Hashimoto" and Waichiro Kawakami Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, Takasaki, Gunma, Japan 370- 12
The controllability of a radiation process for waste water treatment with the PID regulation of dose rate was examined and the effects of load variations on the stability of the process were discussed. Studies were carried out on radiation destruction of aqueous phenol solution in a continuous stirred tank reactor using cobalt-60 as a radiation source. An accurate controllabillty for load changes was demonstrated. Load status was shown to be expressed by two sets of parameters: (1) (inlet concentration)/(set point of effluent concentration)/(resiencetime) and (2) (rate constant of phenol destruction) (set point of effluent concentration)/(effective concentration of organics in the reactor). The allowable load changes for keeping the system stable were expressed by an equation using the two parameters, and the correctness of the expression was proved experimentally.
Treatment of waste water involving organics has frequently been carried out by the activated sludge process. The contents of the organics in the waste water often vary with time. As the biological process involves the growth and synthesis of a microbial community, the process has often led to unstable operation due to contamination of influent with biochemical toxics or by sudden load changes. On the other hand, ionizing radiation can easily degrade biochemical toxics such as phenol (Micic et al., 1975) and cyanide (Touhill et al., 1969) or nonbiodegradable substances such as dyes (Suzuki et al., 1976), PCB (Sawai, 1973), ABS (Sunada, 1970), etc. Radiation destruction of organics in aqueous solution takes place mainly through the reaction with active species, such as OH radicals, formed from water. For radiation treatment of waste water, an electron accelerator is a promising radiation source from the viewpoints of safety in handling and larger energy output compared with radioactive isotopes (Trump et al., 1975). When the electron accelerator is used as a radiation source, control of the effluent Concentration of organics is expected to be performed with high accuracy because the rate of radical formation is proportional to the dose rate which is easily variable by changing the irradiation current. Hence, an optimum operation is possible corresponding to the influent conditions and results in effective usage of radiation energy. Generally, waste water contains BOD substances in addition to biochemical toxics or nonbiodegradable 0019-7882/79/1118-0269$01.00/0
compounds. But it is not economical to apply the radiation process for decomposing all pollutants because the cost of radiation sources, such as an electron accelerator (Cleland, 1976) or cobalt-60 (Kukacka, 1965), and the operating cost, mainly due to fees of electricity or supplying the radioisotopes, are high. A cheaper radiation energy is required and it will lead to be more economical to justify using the radiation process together with a conventional process. For example, the waste water from petroleum or coal industries contains microbiologically toxic substances such as phenol in addition to BOD substances. For such cases, we can propose a combined process which removes BOD substances by biological treatment after destroying the toxics by radiation, because the irradiation will he expedient as a pretreatment process. And for the waste water from the dyeing or textile industry, which contains many BOD substances as well as biologically nondegradable dyes, a post-irradiation process would also be applicable for destroying dyes after removing ROD biologically. Especially in the former process, it is necessary to keep the toxics below a certain concentration in order further to operate the biological process satisfactorily. The purpose of this paper is to demonstrate an accurate controllability of the radiation process by using destruction of phenol as an example, and to present a method to determine the allowable load variation while keeping the system stable in a radiation process hy means of dose rate regulation. Although a cobalt-60 source was used as a convenience in this series of experiments, the results are 0 1979 American Chemical Society
270
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 2, 1979
_.r_ayi+Tload variations
dose rate
reactor
G'(P)
G I( P )
analyzer
GI ( P )
Figure 1. Block diagram of control system.
STABLE
valid for an electron accelerator as a radiation source. Rate Expression of Phenol Destruction by Irradiation As previously reported (Kawakami and Hashimoto, 1974), radiation destruction of phenol proceeds by a first-order process for phenol concentration in an aqueous solution. The overall rate of the destruction is substantially proportional to the dose rate and inversely proportional to the initial phenol concentration, C,. The rate of phenol destruction r A in a batch system is therefore expressed by
kdCI
-
(1) CO where k d is the apparent rate constant, C is the phenol concentration, and I is the dose rate. A similar relation is also observed in radiation decoloration of aqueous dye solutions (Kawakami et al., 1977), and this may be a general feature in radiation destruction of organics in an aqueous system. The inverse proportionality in eq 1infers that the active species produced by the irradiation also react with products as with phenol, and the reactivity of the products is nearly the same as that of phenol. Then, the overall concentration of the reactants can be regarded to be constant while the reaction proceeds. When another substance coexists with phenol, the rate of phenol destruction can be presumed to be given by rA =
where CMo is the initial concentration of the coexistent, CA is the effective concentration of reactants, and 4 is the ratio of the reactivities of the coexistent and phenol with the active species. The reactivity of products of the coexistent with active species is assumed to be the same as that of the original material as seen in the phenol destruction. System Stability in Control of Radiation Process by Dose Rate Regulation A PID (proportional integral + derivative) feedback control system of waste water treatment is assumed as shown in Figure 1. The concentration of phenol in the effluent is continuously monitored by an analyzer. A delay time, t,, due to sampling devices and/or analyzer is assumed. The signal from the analyzer is transformed to a dose rate change by the dose rate regulator. When the radiation destruction of phenol is assumed to be carried out in a continuous stirred tank reactor and variations of inlet concentrations of phenol, CI, and coexistent, CMI, are also assumed, the mass balances with respect to the concentration of reactants can be expressed by
+
(3) (4)
where a , X = functions of load conditions, p = Laplace operator, S = sensitivity, and TI, TD = integral and derivative time. It is noted that the system stability does not change so long as the values of a and X remain constant even if the loads C,, T , I, Cm, and kd change; in other words, these two values are the parameters expressing the status of the load condition to the treatment process. T o maintain the system stable, it is necessary to satisfy the following two conditions. First, from the complex plane stability criterion for the open loop transfer function 1 - GO'w,) > 0 (6) must be satisfied. w, is the minimum frequency a t which the imaginary part of GoO'w) is zero (see Appendix). Secondly, from the power of radiation source, the maximum dose rate I H obtained in the process must be
I H > C,a/X
(7)
from eq 3 supposing CI >> C,. In other words, the system stability in the radiation treatment process of waste water depends on only the relations between the system parameters (S,TD, TI,IH,tl)and load conditions ( a ,A). As the sensitivity S is involved in eq 19 (Appendix) as a product with A, it is useful to consider that the load condition is expressed by two parameters, a and P (= SA). According to eq 19, the relation between a and p for the optimum settings (So,TIo,and Tm) in normal load conditions is plotted in Figure 2. The optimum settings were determined by the Ziegler-Nichols rules using the ultimate gain and period. Values used for calculation are shown in Table I. Even if a load status, which is expressed by a point P (a,p) in the a-p plane, deviated from the normal status P,(a,, &I, the system still remains stable so long as the point P is under the curve. The three straight lines through the point P, in Figure 2 show loci of the point P,
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 2, 1979
Table I. Values Used for Calculation of t h e Stability Criterion cs CIn
cM I kdn Tn tl
TC, TDo soa
In a
1.0 5.0 0. 4.0 X 16.5 1.6 2.6 0.64 8.5 x 103 6X lo3
-
271
6
ppm ppm PPm p p m rad-' min min min min rad m i n - ' p p m - I rad min-'
O p t i m u m settings calculated by Ziegler-Nichols rule. inside of the hot cell
outside of the hot cell
n
, L
I
1
#
l
,
60 m r ,
,
/
lower lim I
l
,
,
,
,
,
,
u
ELAPSES T I M E
Figure 4. Transient responses of phenol concentration and dose rate at start-up, residence time change, and set point change.
Figure 3. Schematic diagram of experimental apparatus: 1,reactor; 2, lead shields; 3, cobalt-60 source; 4, servo-motor; 5, amplifier; 6, PID controller; 7, gas separator;8, fluorescence spectrophotometer; 9, phenol solution reservoir; 10, waste solution reservoir; 11,cylinder pump; 12, O2 cylinder.
when one of CI, T , and kd is changed and the others are maintained a t the normal values. The figures in the parentheses mean the ratio of load to the normal value. It can be seen that the system becomes unstable with increase of T and k d and decrease of CI, that is, with decrease of cy and increase of P. Experimental Section Apparatus. The arrangement of the experimental apparatus is shown in Figure 3. The main equipment in the hot cell is the reactor, the cobalt-60 source of 100 kCi which is plate type of 700 mm width and 300 mm height, and the dose rate regulator, and on the outside are the electric controller recorder, the cylinder pump, the gas separator, and the fluorescence spectrophotometer. The reactor itself is made of Pyrex glass and has about 330 mL volume. A draft tube is equipped in the reactor to promote mixing. The feed solution and gas feed lines are attached a t the top of the reactor. The dose rate regulator consists of a servomotor and two curved lead shields 50 mm thick which move around the reactor to regulate the aperture. All parts contacting the feed solution are made of Pyrex glass except polyethylene connecting tubing. Preparation of Solution and Analysis. Phenol, Guaranteed Reagent from the Wako Chemicals Co., Ltd., without further purification, was dissolved in distilled water to prepare the phenol solution. The phenol concentration was measured with a Hitachi fluorescence spectrophotometer, Type 203, a t an excited wavelength of 265 nm and absorption wavelength of 295 nm. Procedure. The phenol solution was prepared in the solution tank, through which was bubbled oxygen which is necessary for the destruction of phenol. The oxygensaturated solution was fed a t the required flow rate by the solution feed pump to the reactor, in which oxygen was again bubbled a t 200 mL min-l for mixing and for quick transportation of the solution to the outside of the hot cell. The irradiated solution was led to the gas separator together with oxygen, and then t o the analyzer. This
transportation caused a time delay of 1.6 min. When the solution flow reached steady state, the irradiation was started by placing the cobalt-60 source beside the reactor. The phenol concentration in the effluent was continuously sensed by the analyzer. The values of cy and P were varied by changing the solution feed rate, the effective concentration of organics, the sensitivity of the control system, and the final concentration set point. The effective concentration, CA,was changed by adding ethanol to the phenol solution as a coexistent substances. The concentration was calculated from the experimental results and was 12.5 ppm for the 20 ppm ethanol and 5 ppm phenol containing solution. Dose Rate Measurement. The dose rate in the reactor was measured by using the Victoreen ionization chamber, Model 575 A, which was calibrated by the glass dosimeter, Model DC 315 from Ohara Kogaku Co., Ltd. The relation between the aperture and dose rate was nearly linear, and the maximum and minimum values of dose rate were determined to be 6 X lo3 and 7 X lo2 rads min-', respectively. Results and Discussion A pair of typical response curves of the phenol concentration and dose rate is shown in Figure 4. The phenol concentration decreased immediately after the irradiation started with the dose rate at the upper limit (point A). It took the phenol concentration about 15 rnin t o decrease to 1ppm from 5 ppm. When the control was started (point B), the phenol concentration began to approach the set point (1ppm) with decaying oscillation. When the residence time was decreased to 13.2 from 16.5 min (point C) by changing the solution feed rate, the dose rate increased and the concentration was maintained a t set point. When the set concentration, on the other hand, was changed to 1.5 ppm from 1.0 ppm a t point D, both the phenol concentration and the dose rate oscillated, indicating that the system was rather unstable. This instability was overcome by decreasing the sensitivity, for example, from 1.2 x lo4 to 5.0 X lo3 rads min-' ppm-l (point E). Other examples of transient responses of the phenol concentration and dose rate are shown in Figures 5 and 6. In these experiments, the PID control was started after continuous irradiation a t a constant dose rate to reach a steady state. The PID settings were calculated based on the Ziegler-Nichols rules by using the ultimate gain and period which were determined experimentally and were 2.0 X lo4 rads min-l ppm-l and 6 min, respectively. The values of cy and P in Figures 5a and 5b are 0.30 and 0.96 min-' and 0.20 and 0.96 min-l, respectively. It can be seen
272
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 2, 1979
E
B
-
a
k a
b
UNSTABLE
2.0
L
::I 0.4
a3
30min t ime
Figure 5. Examples of transient responses of phenol concentration and dose rate (stable). a, Load conditions: kd = 4.0 X lo-* ppm rad-'; CI = 5 ppm; CA = 5 ppm; T = 16.5 min; C, = 1.0 ppm; S = 1.2 X lo4 rad min-' ppm-' (a.= 0.30 min-'; p = 0.96 min-'). b, Load conditions: kd = 4.0 X lo4 ppm rad-'; CI = 5 ppm; CA = 12.5 ppm; T = 16.5 min; C, = 1.5 ppm; S = 2.0 X lo4 rad min-' ppm-' (a = 0.20 min-'; p = 0.96 m i d ) . h
ka
;; 20 - 1
a
-
P u v
OB
8C
0
8
0
@E
0
0
STABLE
0.2 a3 a4 a5 0.6 0.8 cl( 1 / m i n )
Table 11. Values Used for Simulation Study
cs
1.0
Ch
80
CMIn
100 0.2 3 x 10-4 25 1.0 1.27 0.316 8.10 x 105
@ Tn
b
tl
2.0 1-1
TI0
TDo
so h
0
*a?-
Figure 7. System stability and load status (comparison of experimental results with the calculated). Optimum controller settings: S = 1.2 X lo4 rad min-' ppm-'; TI = 3 min; TD = 0.75 min; 0,stable; 0 , unstable.
kdn
E P
*:
0
0.06 0.08ai
,
..
0
h
a
.
D .
ppm PPm PPm p p m rad-' mi n min mi n mi n rad min-I p p m - '
Table 111. Upper a n d Lower Limits of Load Variation and Dose Ratea
&
LH CI CMI kd 7
I a
30min time
,
Figure 6. Example of transient responses of phenol concentration and dose rate (unstable). a, Load conditions: kd = 4.0 X ppm rad-'; CI = 5 ppm; CA = 5 ppm; T = 16.5 ppm; C, = 1.0 ppm; S = 1.8 X lo4 rad min-' ppm" (a = 0.30 m i d ; p = 1.4 min-'). b, Load conditions: k d = 4.0 X 10"' ppm rad-'; cl = 5 ppm; CA = 5 ppm; T = 22.0 min; C, = 0.85 ppm; S = 1.8 X lo4 rad min-' ppm-' (a = 0.27 min-'; p = 1.2 min-').
in these cases that each recovery curve decays to a constant value and the system is stable. In the cases shown in Figure 6, the phenol concentration oscillated with constant (6a) or increasing amplitude (6b). The values of a and /3 for these unstable examples are 0.30 and 1.4 m i d and 0.27 and 1.2 min-', respectively. Figure 7 shows comparison summaries of the theoretical criteria for the system stability with all experimental results in various load conditions including experiments in Figures 4 to 6. The unfilled circles in this figure mean stable, and solid circles mean unstable. Points B, C, D, and E correspond to each case in Figure 4. The solid line is the calculated result. When the point lies below the curve, the system remains stable, and vice versa as described in the theoretical analysis. Figure 7 shows that the agreement of the calculations with experimental results is good. The load status P (0.20, 1.44) a t the point D in Figure 4 lies over the curve of Figure 7 . When the status was changed to P (0.20,0.60) by reducing the sensitivity (point
LL
200ppm ~ O O P P ~ 4x p p m rad-' 50 min 2.5 x l o s rad min-I
10 p p m 0 ppm 2X ppmrad-I 1 0 min 0 rad min-'
Tfac= 30 min.
E in Figure 41, the load status moved below the curve and the system became stable. Simulation Studies The controllability of the radiation process by dose rate regulation was further examined by simulation studies using a digital computer. In these studies, calculations were also performed on the destruction of phenol, and the inlet concentration of phenol and the coexistent organic matter, the residence time, and the apparent rate constant of destruction were varied. Values used for calculation are shown in Table 11. The step-like load variations were supposed to be given a t random. The selection of kind of load, its value, and load variation time were determined by using three random numbers x , y , and z generated in computation as follows kind of load 0 Ix < 0.25 apparent rate constant 0.25 5 x < 0.50 inlet phenol concentration 0.50 Ix < 0.75 inlet concn of the coexistent residence time 0.75 Ix values of the load L = LL + y(LH - LL) loading interval Td
= Tfa&
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 2, 1979
273
Table IV. Kind and Value of Disturbance
min
min-'
4, min-'
crit. value OfO, min-'
27 5 275
100 104 105 107 107 132 142 164
3.0 x 10-4 3.0 x 10-4 3.0 x 3.0 x 10-4 2.82 x 1 0 - ~ 2.74 x 1 0 - 4 2.91 x 10-4 3.17 x 3.27 x 3.31 x
25.0 20.7 20.7 20.7 20.7 20.7 20.7 29.2 29.2 29.2
3.2 3.9 4.3 4.3 4.3 4.3 6.3 4.4 4.4 0.59
2.4 2.4 2.4 2.3 2.2 2.1 2.2 1.9 1.9 1.6
3.6 4.0 4.2 4.2 4.2 4.2 5.4 4.3 4.3 2.1
255 42.2 42.2 42.2 42.2 42.2 103 103
139 134 126 96.1 91.3 82.8 75.2 76.5
3.32 X 3.32 x 3.33 x 10-4 3.04 x 2.95 x 2.80 X 2.66 X 2.59 x 10-4
29.2 29.2 29.2 29.2 35.0 27.3 27.3 27.3
1.0 1.0 1.0 2.0 1.6 2.1 2.1 3.1
1.9 2.0 2.1 2.6 2.6 2.7 2.9 2.7
2.4 2.4 2.4 2.9 2.7 3.0 3.0 3.5
values o f load after disturbance occurs no. initial 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17
kind and value of disturbance
CI I ppm 80.0
= 20.7 CI = 8 8 . 1 k d = 2.17 X
T
2.71 x i o - 4 3.35 X CI = 129 T = 29.2 CMI = 275 CI = 17.1 CI = 30.1 CMI = 255 CMI = 42.2 k d = 2.49 X c, = 5 7 . 4 r = 35.0 r = 27.3 CMI = 103 CI = 8 5 . 3 hd = kd =
80.0 88.1 88.1 88.1 88.1 129 129 129 17.1
CMI,
CAY
ppm
ppm
k d , ppm/rad
100 100
100
100 100 100
30.1 30.1 30.1 57.4 57.4 57.4 57.4 85.3
'p
P
4 r
r -
u n
am w -
2 -
0
D
O 0
1
2 ELAPSED TIME (hrl
3
a,
100
100 100 100
4
Figure 8. Simulation studies on responses of phenol concentration and dose rate to random load variations.
where x , y , and z vary within the range from 0 to 0.999, LL and LH are the lower and upper limit values of load, and Tec is a time factor for the loading interval. These values are shown in Table 111. The load is assumed to be maintained constant until the same kind of load is applied again. The concentration of phenol in the reactor was calculated based on eq 3 and 4 using the Runge-Kutta method. The results are shown in Figure 8. The irradiation a t the normal operating condition was continued for 30 min in the first stage. The first variation of the load (residence time) was applied 30 min after start (point 1). The load variation points are designated by the arrows and are numbered. The kind and value of each disturbance are summarized in Table IV. In this table, the load conditions CY and /3 and the critical value of /3 calculated for the same value of CY using eq 20 (Appendix) were also shown. In this table, CA and kd do not vary immediately a t the load change. This is because the load change is assumed to occur in the influent, and it takes time for washing out the fluid in the reactor. I t can be seen from Figure 8 that the dose rate followed the load variation, and the effluent concentration is kept substantially constant at the set point for about 1.5 h. The dose rate attained the upper value (2.5 X lo5 rads min-') and the phenol concentration is slightly higher than the set point after the sixth disturbance is introduced. The load conditions do not satisfy eq 7 and are beyond the ability of the radiation source in this point. The phenol concentration oscillates after the twelfth disturbance is introduced. This is because /3 is very close to the critical value, especially a t the 14th and 16th
load conditions T,
points, as seen from Table IV. Conclusion The radiation destruction of organic substances was supposed to be used for pre-treatment of waste water to remove toxics, and the controllability of the radiation process was studied on the control of destruction of phenol by the PID dose rate regulation. An accurate controllability was obtained for various load changes, and the load status was shown to be represented by the two parameters CI/C,/T and Cskd/CA. The stability criterion for the load change was calculated and shown to agree with the experimental results. Acknowledgment We are indebted to Mr. M. Washino for his valuable discussion. Appendix Derivation of the Open Loop Transfer Function and the Stability Criterion. By replacing C = C, 6C, CI = CI, + ~ C ICMI , = C + , + ~ C M k,j I , = kdn + 6kd, 7 = 7, + 67 and I = In+ 61 to linearize eq 3 and 4 a t a normal load conditions (CIn, CMIn,kdn, T,, I,) and a t a certain effluent concentration (C,), and applying the Laplace transformation
+
is derived, where
The open loop transfer function of the control system, as shown in Figure 1, is given by
274
Ind.
Eng.
Chern.
Process Des. Dev., Vol. 18, No.
2, 1979
Go = GI(P)G,(P)GI(P)
(13)
where G,(p), Gl(p) are transfer functions of the dose rate regulator and analyzer. As G,(p) is given by (6Z/In)/ (6C/Cs) and 6 1 is equal to S(1+ 1 / T g + TDp)GC, eq 14 is obtained.
Gl(p) is expressed by Gl(p) = e+@
(15)
At steady state under the normal load conditions CIn = -cs+ 7n
kdnCsIn
7n
CAn
(16)
is obtained from eq 3. Substituting eq 9, 14, 15, and 16 into eq 13 leads to
CMo= initial concentration of the coexistent, ppm Co = initial concentration of phenol, ppm C, = effluent concentration setting,, ppm 6C, 6c1,~ C M 6kd, I , 67, 61 = deviations from the normal values Go = open loop transfer function G1, G2, GB,G4 = transfer functions given by eq 9, 10, 11,and 12 G, = transfer function of the dose rate regulator GI = transfer function of the analyzer I = dose rate, rads min-' Z H = maximum dose rate, rads min-' kd = apparent rate constant of phenol destruction, ppm rad-' L = value of load LL,LH = lower and upper limit values of load p = Laplace operator r A = rate of phenol destruction, ppm min-' S = sensitivity, rads min-' ppm-' So, TIo, TDo = optimum controller settings t = time, min Td = loading interval, min Tf,, = time factor for loading interval, min TI, T D = integral and derivative time, min tl = delay time of analysis, min x , y, z = random numbers Subscript n = index for normal operation condition
where Cskdn
An = CAn
To maintain the system stable, the following condition must be satisfied according to eq 6. Sx[1(cy/wC) + (w,TD- ( ~ / ~ c ~ (wJJ ~ ) +) I(a/wc) l ~ ~ X~ (w,TD - (l/wcTJ) - 11 sin ( 4 I / [ w , + (cy2/w,)I > -1 (20) where X and cy are defined by eq 18 and 19 for new load conditions, and w, is given as the solution of eq 21.
tan (wet,) =
Greek Letters (Y = parameter defined by eq 19, min-'
p
= AS, min-' X = parameter defined by eq 18, ppm rad-' 7 = residence time of fluid in the reactor, min 4 = ratio of reactivities of phenol and the coexistent with the
active species a solution of eq 21, min-' Literature Cited w, =
Ciebnd. M. R., preprint presented at the Meeting of European Society of Nuclear Methcds in Agricutture, Subgroup I b on "Waste Irradiation", Germany, 1976. Kawakami, W., Hashimoto, S., preprint presented for the 8th Autumn Meeting of the Society of Chemical Engineers, Japan, 8-308,1974. Kawakami, W., Hashimoto, S., Nishimura, K., Miyata, T., Suzuki, N., Envlron. Sci. Techno/., 12, 189 (1978). Kukacka, Nucleonics, 23 (l),74 (1965). Land, E. J., Ebert, M., Trans. Faraday Soc., 63, 1181 (1967). Micic, 0.I., Nenadovic, M. T., Markovic, V. M., International Symposium on the Use of High-level Radiation in Waste Treatment Status and Prospect, IAEA-SM-194/402 (1975). Sawai, K., Genshifyoku Kogyo, 19 (IO), 29 (1973). Sunada, T., Genshlryoku Kogyo, 16 (1I),68 (1970). Suzuki, N., Nagai, T., Hotta, H., Washino, M., Bull. Chern. SOC.Jpn., 49, 600
(1976).
Nomenclature C, CI = concentration of phenol in the reactor and in the influent, pprn C A = effective concentration of organics, ppm CMI= concentration of the coexistent, ppm
Touhill, C.J., Martin, E. C., Fujiira, M. P., Olesen, D. E., Stein, J. E., Macdonneli, G., J . Water Polltit. Control Fed., 41 (2),R 44 (1969). Trump, J. G., Wright, K. A,, Merriii, E. W., Sinskey, A. J., Shaik, D., Sommer, S., IAEA-SM 194/503,International Symposium on the Use of High Level Radiation in Waste Treatment, Munich, West Germany, 1975.
Received for review March 7, 1978 Accepted November 10, 1978
