LI B RARY OF THE UN IVE.RSITY OF ILLINOIS 628 no A- 9 • The person charging this material is re- sponsible for its return on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. University of Illinois Library E! SEP 6 1968 jKMB mjm~^ JQCT3 -, — r> i ~ T r " h - }fL i L161— O-1096 Digitized by the Internet Archive in 2013 http://archive.org/details/preliminaryinves01baum no. \ ENG *ING LIBRARY UNIVERSITY OF ILLINOIS URBANA, ILLINOIS/ CIVIL ENGINEERING STUDIES SANITARY ENGINEERING SERIES NO. 1 ft ENGINEERING UBRARY A PRELIMINARY INVESTIGATION OF THE EFFECTIVENESS OF A DIATOMITE FILTER IN THE REMOVAL OF RADIOACTIVE PHOSPHORUS FROM WATER By E. R. BAUMANN, H. F. ZOBEL, and H. E. BABBITT These Studies deal with current activities in the department of Civil Engineering. They serve as progress reports of major investigations, and in general as a means for disseminating information not readily adaptable for presentation in formal technical papers or bulletins. DEPARTMENT OF CIVIL ENGINEERING UNIVERSITY OF ILLINOIS URBANA, ILLINOIS November 1, 1951 Sanitary Engineering Series No. 1 A PRELIMINARY INVESTIGATION OF THE EFFECTIVENESS OF A DIATOMITE FILTER IN THE REMOVAL OF RADIOACTIVE PHOSPHORUS FROM WATER by E. R. Baumann, H. F. Zobel, and H. E. Babbitt November 1, 1951 The removal of radioactive substances suspended in water has been suggested by various investigators and by the Atomic Energy Commission. The advantage of removal by filtration lies in the concentration of the radioactive substances on the filter medium which may be disposed of more easily due to its smaller bulk, and the freeing of the water from radioactivity. The use of the conventional rapid sand filter for the removal of radioactivity from a public water supply may not be practicable because o r the bulk of radioactive wash water to be handled and, since the sand particles in the filter are not removed in the washing of the filter, it may become increasingly radioactive. In view of the method of operation of a diatomite filter in water purification, the relatively small proportion of water used in backwashing and the complete elimination of the used filtering medium, the use of a diatomite filter for the removal of radioactive substances from drinking water has been suggested. -3- The end of the funnel was inserted through a perforated stopper into a filtration flask and the arm of the flask was connected to a vacuum pump which was used to control the rate of filtration. A precoat of diatomac- eous earth was laid on the wire septum, and a measured quantity of water of known radioactivity was poured onto the filter at the start of a test. The liquid used in a test was an aqueous dilution of radioactive phosphorus (P~ z ) sufficiently concentrated to give 2,000 counts per minute under the standardized counting conditions shown in Fig. 3. The counting cylinder placed over the Geiger tube contained a standard volume of about 50 ml. of water. In the performance of a test 150 ml, of radioactive phosphorus solution giving 2,000 counts per minute was poured on the precoat on the septum .in the Buchner funnel. Tv.'enty five ml. of the solution were passed through the filter and discarded. The re- mainder of the solution was then filtered at a predeter- mined constant rate. The filtrate was then measured for radioactivity under the standardized conditions for counting shown in Fig. 3. The percentage reduction of radioactivity was taken as 100 times the ratio of the difference between counts before and after filtration to the counts before filtration, i.e. 2.000. of w-wo* -4- Activated carbon, and chemical coagulants, were added to different samples of water in some of the tests, in the expectation that the removal of radioactive substances might be increased thereby. In another series of tests an electric current was passed through the filter, as indicated in the equipment shown in Fig. 4. In the use of this apparatus the septum consisted of a flat, porous, stainless-steel disc. No filter aid was used. A small quantity of radioactive solution was passed through the filter and rejected before the test was started. Electrical currents of 22 and of 55 volts were passed between the electrodes shown, during different tests. The supply of radioactive liquid was held in the funnel shown in the figure, and the flow rates through the filter were controlled by the pinch cock shown on the rubber tube. Observations made during the tests are shown in Table 1. It may be assumed from an examination of the tabulated data that: 1. Tests 1 and 2 indicate that recirculation of liquid does not promote removal of radioactivity with diatomaceous earth precoat alone, since only about 12 to 13 per cent is removed. -5* 2. Tests 3 and 8c indicate that very slow filtration rates aid in removals, particularly when chemical methods are not employed. These low flow rates probably would be impracticable with large amounts of waste. 3. Tests 1,2, 5, 8a, 8b, 8d, and 15 indicate that the use of diatomaceous earth alone does not permit very good removals. 4. Tests 7,11,12,14, and to some extent 13, indicate the overall effectiveness of activated carbon in adsorption of radioactive phosphorus. 5. Tests 13 and 14 indicate that the addition of stable isotopic material of the same element reduces the percentage removal. An increase in the amount of precoating material increases removal in such cases. 6. Test 12a indicates that ions once removed on carbon probably are not washed out by the passage of uncontaminated water. 7. Tests 12,13, and 14 indicate that activated carbon retains its effectiveness even when the precoating material is reduced to more practical proportions. 8. Tests 15 to 23 indicate that chemical precipitation and adsorption materially increase the effectiveness of precoat materials in the removal of radioactive components from water. The series of tests was conducted with distilled water and tap water since the utilization of these procedures would involve raw water. -6- 9, Test 29 indicates the percentage of removal by the septum itself, without filter aid or other help. 10. Tests 24 and 25 indicate that, with the electrical connections as shown on the chart, the removal of activity is less than that by the septum without any charge impressed on the electrodes. 11. Tests 26 and 27 indicate a time lag before effective removal is begun. 12, Test 23 indicates that a reversal of the electrodes from tests 26 and 27, with all other conditions remaining the same, decreases the per cent removal of the radioactivty by the septum. 13, Tests 30 and 31 were actually the same test conducted over a prolonged length of time with no change in the electrical nature of the test as it progressed. The samples were taken at the end of 10 and 45 minutes of filtration. Analysis indicates that some time lag is probably necessary before the electrical character of the solution is such that effective removal is possible. The highest percentage removals were obtained with ^he use of activated carbon which was as high as 100 per cent in some tests. Excellent percentages re- moval were obtained also by the use of a proprietary, diatomite, Crystal Flo. The use of coagulants in conjunction with J7.1535 greatly increased its effectiveness over that when coagulation was not used. . ■ •• . : -7- It is appreciated that the results of tests reported herein are indicative only of what may be done by the use of diatomaceous earths in the removal of radioactive phosphorus from water. Further tests are desirable on other isotopes, and observations on the characteristics of the back-wash water and of the used diatomites are also desirable. The successful use of diatomite filters in the removal of radioactive phosphours from water is indicated. Table 1 Effect of Diatomaceous Earth Filters on the Removal of Radioactive Phosphorus -from .VJater. "'1 % removai Test Precoat Filter apparatus Weight of Rate of radio*? No. Medium and notes coat _ T.b /sq.f t. .qpm/sq. ft. ac tivity 1 JM535 Complete precoat 1 12.3 Filter water re- circulated 15 min before sampling. 2 D4200 1 17.9 3 JM535 Buchner filter 1 0.16 93.0 apparatus 4 Crystal Flo. do. 1 0.58 88.4 5 JM535 do. 1 0.58 52.4 6 D4200 do. 1 0.39 72.4 7 Everpure do. 1 0.29 100 8a JM535 do. 1 1.20 52.2 8b do. do. 1 0.39 51.7 8c do. do. 1 0.03 85.6 8d do. do. 1 0.29 45.8 9 Sparkler pad Gravity flow through filter. Pad contained silver - 0.30 69.3 10 do. Contained finely divided silver - 0.80 74.5 11 do. Pad contained activated carbon - 0.80 100 12 Everpure# Commercial filter 0.15 0.70 97.3 12a do. Uncontaminated water No radioactivity carried to through cake of 12 filtrate from pad 13 do. Added one mole of stable 0.15 0.70 64.6 phosphate to stock 14 do. solution 0.34 0.70 81.7 :, ' ; '■ • . Test No. Chemical coagulant -8- Amt. of chem. Gr. per gal. % removal Precoat Flow of radio- Lb/sg.f t. gpm. activity. using J74535 as a precoat. Tests 15 to 23 were run on Buechner funnel apparatus. Tests 15 to 20 were run with distilled water plus radioactive phosphorus. Tests 21 to 23 were run with tap water and radioactive phosphorus 15 None 16 Ferric hydroxide 17 Calcium hydroxide 18 Aluminum sulphate 19 Bentonite 20 Aluminum sulphate 21 Ferric hydroxide 22 Calcium hydroxide 23 Aluminum sulphate Tests 24 to 31 show the effect of electric charges on the removal of radioactive phosphorus, using the apparatus shown in Fig. 4. Sign of Upper Middle Lower Notes elect- elect- elect- rode rode rode 1 0.50 0.80 6 K 1 0.50 0.80 95.6 1 0.50 0.80 96.9 1 0.50 0.80 98.5 1 0.50 0.80 89.4 1 0.50 0.80 74.4 1 0.50 0.80 92.1 1 0.50 0.80 89.8 1 0.50 0.80 97.8 Test Vol No. 24 22 25 22 26 22 27 22 28 22 29 30 55 31 55 Per cent removal of radioactivity, + + Made in one continuous operation + Filtration without electrical connec- tions. Steel plate only. + _- + 43.4 45.7 51.5 57.2 54.5 53.0 Tests run over period of 30 min. Samples taken at end of 10 & 30 min. 52.0 73.7 # contains activated carbon. Wafer t.: Septum o, , /v/ /e • ■Dfurry \# i u m |- -7 .^s_ fc filtered /Vo r ■/>■/ d> / /~ /o w c? -,+jBacA FlQ. /_ Common Mat hod of hi It ration 7& + o^s/Sfpsfor^ 76. -c Pppd*^o$ Used i o Tes fs /J//ou/or l*Oj Ce// " n dcs/jr far ^ "..._"" ::r. ; SSsX f 7g. 3" i GUI 7ft, nd Ce Qnot I Oe/oer 7c//? a r) - 1