A STUDY CONCERNING ZEOLITE APPLICATION IN DRINKING WATER TREATMENT AT PILOT-PLANT SCALE

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1 A STUDY CONCERNING ZEOLITE APPLICATION IN DRINKING WATER TREATMENT AT PILOT-PLANT SCALE Cristian Danielescu 1, Camelia Podaru 1, Daniela Sonea 1, Florica Manea 1, Ilie Vlaicu 2, Adina Pacala 2, Cristiana Cosma 3, Georgeta Burtica 1 1 Politehnica University of Timisoara, Sq. Victoriei no. 2, 36, Timisoara, Romania, 2 Aquatim Company, Str.Gheorghe Lazar no. 11, 381 Timosoara, Romania 3. National R&D Institute for Industrial Ecology-ECOIND, sos. Panduri no. 9-92, 5663 Bucharest, Romania cristian.danielescu@chim.upt.ro Introduction The presence of high concentration of iron and manganese in the groundwater requires their removal for drinking water. Their removal can be achieved by physicalchemical processes, e.g., oxidation followed by filtration. ClO 2 is commonly used as a preoxidant and primary disinfectant during water treatment, mainly as an alternative to chlorine for trihalometane control. Based on the literature, it was found as opportune substituting chlorine with chlorine dioxide (ClO 2 ), which has the distinct advantage of being a much stronger oxidant in comparison to chlorine. ClO 2 can be also used for the control of iron and manganese, of the taste and smell [1, 2]. In the last years, natural zeolites have been attracted attention as filtering properties for the sorption process, and Romanian zeolite with high content of clinoptilolite (about 68 %) have been exhibited a great affinity for high metals retaining [3]. The use of combined treatment of zeolite filtering with ClO 2 oxidation can be regarded as an alternative to conventional technology of groundwater drinking treatment. This paper aimed to evaluate the results the pilot plant technology consisted of two steps of filtering on zeolite with two different granulation intermediated by ClO 2 oxidizing. The technology performance was assessed based on the process/technology efficiency subjected to the residual iron, manganese and ClO 2 concentrations in the treated water. Materials and methods The experimental study was carried out on a pilot plant, containing two steps of filtering on zeolite by different granulation (1-5 mm for filter 1, and.4- mm for filter 2), intermediated by the oxidizing with chlorine dioxide. Figure 1. The technological scheme of the pilot plant Water resulting from the aeration stage of the existing conventional treatment with the

2 determined characteristics, e.g., mg/l total Mn and mg/l total Fe, was used as feed. In the technological flow, the columns which were used in the filtering were equipped with natural zeolite and then connected in series; the flow of the filter 1 was D 1 = L/h, and D 2 = L/h for the second filter. The inner diameter of the columns equipped with natural zeolite was d= 125 mm, and the height of the zeolite layer in the columns was H = 1 m. The zeolite from Mirsid (Romania) was used with clinoptilolite (68%, wt.) as major component and the following composition (%, wt.): 62,% SiO 2 ; 11,65% Al 2 O 3 ; 1,3% Fe 2 O 3 ; 3,74% CaO;,67% MgO;,72% Na 2 O; 3.3% K 2 O;,28% TiO 2. [3-7]. ClO 2 (chlorine dioxide) was prepared by OXIPERM module, using as reactants HCl, NaClO 2 solutions and water. The concentration of total and dissolved manganese and iron, and chlorine dioxide was determined. The standaridized determination methods were used, i.e., Romanian standards for iron and manganese [8] and American standard for chlorine dioxide. [9] The applied dose of ClO 2 was calculated taking in account the reaction stoichiometry, for both manganese and iron [1-13]. Mn ClO 2 +2 H 2 O MnO 2 (S) + 2 ClO H +. From the stoichiometry, 2.45 mg of chlorine dioxide are required to oxidizes 1 mg of soluble manganese. Fe 2+ + ClO H 2 O 4 Fe(OH) 3 (S) + Cl H +. From the stoichiometry, 1.2 mg of chlorine dioxide are required to oxidizes 1 mg of soluble iron. It was used three different dose son ClO 2 as three different ratio (1:1.5; 1:1; 1:.8) = x R ; x C Fe C 2. 5 ; R = 1.5; 1.;.8. D ClO 2 = diz Mndiz Results and Discussion The experimental results subjected to iron and manganese removal are presented comparatively for ClO 2 oxidation process and during complete technology, underlying the role of the second zeolite filtration step. Figures 2 and 3 present the comparison subjected to the total Mn removal during the oxidation step and entire pilot plant technology, at the different functioning time. R= 1.5 R=.8 R= Figure 2. Removal efficiency of total Mn during ClO 2 oxidation step. Figure 3. Removal efficiency of total Mn during complete technology For the Mn removal, the dose of ClO 2 had a strong influence, because the main quantity of Mn is eliminated through the process of oxidation with ClO 2. Moreover, the Mn removal continues also through retaining it on the second filter with zeolite (F2), but it has to emphasize that after a certain functioning time the F2 fouling

3 occurred situation during which the F2 exit Mn concentration was higher than F2 enter Mn concentration. If the ClO 2 dose used was in an excess versus stoichiometric ratio (1.5), the concentration of total Mn in the final effluent was below the maximum allowance concentration- MAC, and the removal efficiency varied between %. For the stoichiometric ratio, the residual concentration was also below or equal with MAC, the removal efficiency varied between: %. ClO 2 dose corresponding to the deficit versus stoichiometric ratio did not lead to satisfactory results on the removal of manganese. The comparative results obtained for Fe removal under the same conditions are presented in Figures 4 and 5 and all results were satisfactory. It is necessary to notice that the most important concentration of total Fe is removal by F1 filtering, before the ClO 2 oxidation process. 1 R=1. R= Figure 4. Removal efficiency of total Fe during ClO 2 oxidation step. Figure 5. Removal efficiency of total during complete tehnology The comparative results presented in Figures 6 and 7 underline the role of F2 filter for the removal of residual ClO 2 concentration. IF2 EF2 ClO 2 (mg/l) ClO 2 (mg/l) R time (days) R time(days) 5 Figure 6 The variation of ClO 2 concentration before F2 filtering. Figure 7 The variation of ClO 2 concentration after F2 filtering

4 Compared with the ClO 2 concentration before F2 filtering, no presence of residual ClO 2 in the treated water above MAC (.8 mg/l ClO 2 ) was recorded, which informs about the F2 availability to retain ClO 2. Conclusion: Use of zeolite and ClO 2 as oxidant for drinking water treatment led to the residual concentration of iron and manganese below maximum allowable concentration (.2 mg/l for iron and.5 mg/l for manganese). In certain cases, the initial concentration of ClO 2 necessary to meet Romanian iron and manganese requirements has produced a residual concentration of ClO 2 higher than the maximum contaminant level (.8 mg/l), which was removed using F2 filter. For the removal of Mn, the dose of ClO 2 had a strong influence because the most important quantity of Mn was eliminated through the oxidation process with ClO 2. Moreover, the removal of Mn continues also through retaining it on the second filter with zeolite. ClO 2 dose did not influence the Fe removal for the studied pilot plant. Acknowledgments This work is supported by The Romanian National Research of Excellence Programs CEEX, PROAQUA - Grant 631/3.1.5, RIWATECH - Grant 62/3.1.5, PNII ZEONANO - SPP no.56/ References: [1] Schmidt, W., Using Chloride dioxide for drinking water disinfection by the application of the chlorite/chlorine process, Acta Hydrochimica and Hydrobiologica, 32, 1, (4) 48- [2] Neewman, J.,Zhou, P., Use of chlorine dioxide and ozone for control of disinfection byproducts, Water Intelligence on-line, 126 (4); [3] C.Orha, G.Burtica, F.Manea, A.Pop, The retaining capacity of the zeolite used in water disimfection, Bulletin of the Transilvania University of Brasov, ISSN , (6) [4] M. Sprynskyy, M. Lebedynets, A.P.Terzyk, P.Kowalczyk, J.Namiesnik, B. Busz, Amonium sorption from aqueous solution by the natural zeolite Transcarpathian clinoptilolite studied under dynamic condition, Journal of Colloidal and Interface Sciente 284 (5) [5] G. Tsitsishvili, T. Andronikashvili, G. Kirov, L.Filizova, Natural Zeolites, Ellis Horwood, [6] Swietlik J., Raczyk-Stanislawiak U., Polonia, Adsorbtion of NOM oxidated with clorine dioxide, on GAC, Water Research, (1) [7] Alvarez-Ayuso E., A. Garcia-Sanchez & X. Querol, Purification of metal electroplating waste waters using zeolites. Water Res. 37, (3) [8] Romanian standards for iron and manganese, Potable Water Low No.428/2 and 311/4 [9] United States Environmental Protection Agency (USEPA), National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts, [1] Kallis G., Butler D., The EU water framework directive: Mesures and implication, Water Policy, vol. 3, (1) ,. [11] Shi L., The Investigation on clorine dioxide purity determined by modifield by iodometric method, D, Shandong University, Jian, China Water Tratment Chlorine dioxide, (3).

5 [12] EPA, Alternative Desinfectants And Oxidants Guidance Manual, United States Environmental Protection Agency, Office of Water, EPA April (1999) 815-R99-14, Palint A. T., Analytical Control of Water Disinfection With Special Reference to differential DPD Methods for Chlorine, Chlorine Dioxide, Bromine, Iodine and Ozone, J.Inst. Water Eng. 28:139 [13] Enrico Veschetti, Giovanni Citti, Mario Belluati, Elena Borelli, Mario Colombino and Massimo Ottaviani, Water desinfection with ClO2 and NaClO: A Comparative Study in pilot plant-scale, Electronic Journal of Environmental, Agricultural and Food Chemistry.

CE 370. Disinfection. Location in the Treatment Plant. After the water has been filtered, it is disinfected. Disinfection follows filtration.

CE 370. Disinfection. Location in the Treatment Plant. After the water has been filtered, it is disinfected. Disinfection follows filtration. CE 70 Disinfection 1 Location in the Treatment Plant After the water has been filtered, it is disinfected. Disinfection follows filtration. 1 Overview of the Process The purpose of disinfecting drinking