Grantee Research Project Results
2002 Progress Report: Integrated Approach for the Control of Cryptosporidium parvum Oocysts and Disinfection By-Products in Drinking Water Treated with Ozone and Chloramines
EPA Grant Number: R826830Title: Integrated Approach for the Control of Cryptosporidium parvum Oocysts and Disinfection By-Products in Drinking Water Treated with Ozone and Chloramines
Investigators: Mariñas, Benito J. , Minear, Roger A.
Institution: University of Illinois Urbana-Champaign
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 1998 through August 31, 2002 (Extended to March 31, 2003)
Project Period Covered by this Report: September 1, 2001 through August 31, 2002
Project Amount: $367,427
RFA: Drinking Water (1998) RFA Text | Recipients Lists
Research Category: Water , Drinking Water
Objective:
The overall objective of this research project is the development of process design recommendations for the simultaneous control of Cryptosporidium parvum oocysts and disinfection byproducts (DBPs) during ozone/chloramines sequential disinfection of natural waters. Because the main objective of this research project is to develop an integrated control strategy, the scope of work focuses on a limited number of selected DBPs (bromate, formaldehyde, and cyanogen halides) associated with the ozone/chloramines sequential disinfection process.
Progress Summary:
The reactive transport model previously developed was applied to a natural water (treated Ohio River water). The characteristic parameters that determine the reactions of natural organic matter (NOM) during ozonation were obtained from batch experiments. Flow-through experiments were performed to monitor dissolved ozone concentration, bromate concentration, and C. parvum survival ratio. In addition, a probe chemical, p-chlorobenzoic acid (pCBA) was used to estimate the overall exposure to hydroxyl radical during ozonation with respect to time. The reactive transport model thus developed was verified with actual experimental data in terms of the above four indicators.
Figure 1 presents experimental results obtained in terms of concentrations for dissolved ozone, pCBA, bromate, and the survival ratio of C. parvum oocysts plotted versus normalized cumulative volume of the total flow-through reactor. The operating conditions were: QL = 150 mL/min; QG = 15 mL/min; CG,in = 34 mg/L; T = 21°C (inlet) to 22°C (outlet), corresponding to an applied ozone dose of 3.4 mg/L. The model predictions for concentrations of dissolved ozone, pCBA, bromate, and C. parvum survival ratio using the parameters obtained from fitting independent batch data also are shown in Figure 1. The model prediction corresponded with experimental data. In addition, overall ozone gas transfer efficiency was measured to be 90.3 percent, which was consistent with the model prediction of 91.4 percent, thus validating the mass transfer model employed. The consistency between model and experimental data suggests that the model can be used to simulate the performance of flow-through ozone bubble-diffuser contactors using parameters from batch and semibatch testing. Model predictions with different applied gas-phase ozone also are shown in Figure 1. With increasing ozone dose there was the expected substantial increase in both bromate formation and C. parvum inactivation. However, the pCBA concentration profile, mirroring the hydroxyl radical exposure, showed little dependence on applied ozone concentration (ozone dose). Hence, the large increases in bromate formation and C. parvum inactivation with increasing ozone dose was apparently connected to the direct reaction with molecular ozone under these conditions.
Figure 1. Comparison of Profiles of (a) Ozone Concentration, (b) Normalized pCBA Concentration, (c) Bromate Concentration, and (d) Survival Ratio of C. parvum Oocysts, Measured Experimentally at Ozone Dose of 3.4 mg/L and Predicted With the ADR Model for Different Doses. (Numbers on the Lines Represent the Overall Ozone Dose in Model Prediction) (QL = 150 mL/min; QG = 15 mL/min; CG,in = 34.0 mg/L).
The proposed model is expected to provide a powerful tool to predict both C. parvum inactivation and bromate formation in flow-through ozone bubble-diffuser contactors. Once the parameters that determine the kinetics of ozone decomposition, bromate formation, and C. parvum inactivation are determined from bench-scale batch and semibatch tests, the model can be used to predict the performance in flow-through system. Further investigation in refining chemical reactions for NOM will enable the model to be utilized in more general cases.
The last stage of this research project regarding the formation of BrCN from HCHO and NH2Br is currently underway. Efforts were made to identify two inter-mediate species, CH2(OH)NHBr and {CH2(OH)}2NBr, which participate in the following sequence of reactions:
The third reaction only occurs when HCHO is in large excess. Different mass spectrometry techniques and experimental conditions were tested to identify these two species. Chemical ionization (CI) was found not to be powerful enough to ionize these two species and none of them was detected. Electron ionization (EI) always gave peaks for {CH2(OH)}2NBr at different probe temperatures ranging from 100 to 400°C. Electron spray ionization (ESI) MS was the only way to detect CH2(OH)NHBr. These analyses confirmed the presence of the two intermediate species and corresponding kinetic tests confirmed the proposed formation pathway. Initial spectrum and kinetic studies also confirmed that NHBr2 do not react at measurable levels with HCHO.
The various reactions of the proposed BrCN formation pathway will be investigated in three stages: the fast equilibrium reactions between HCHO and NH2Br, the somewhat slower decomposition reaction of the species formed from the initial fast steps, and the reaction between CN- and bromamines, the final step in BrCN formation pathway. The first two stages are still under investigation. The reactions between bromamines and cyanide ion were studied in a flow through cell encapsulated in a stopped-flow analyzer, and with a batch reactor. The pH ranges of 6 to 7 and 8 to 10 were selected to study NH2Br and NHBr2 reactions with CN-, respectively, by following the absorbance produced by bromamine, as well as the concentration of BrCN, the latter determined by gas chromatography. The two bromamines reacted with cyanide ion (CN-) according to the reactions:
with rate constants of 2.70 x 104 M-1s-1 for NH2Br and1.39 x 108 M-1s-1 for NHBr2. These values are about six orders of magnitude higher than those of the corresponding reactions between chloramines and CN-. The NHBr2 reaction was not acid-assisted. In contrast, the NH2Br reaction was general acid catalyzed, and affected by all acid species studied including H+, H2PO4-, HPO42-, H3BO3, and NH4+. The catalysis terms for these species were linearly correlated with their acid dissociation constants consistent with the Brønsted-Pedersen relationship. A model was developed to predict bromamine concentration profiles over time for the bromamine-cyanide system based on the above two reactions and bromamine decomposition reactions.
Future Activities:
The final research tasks will focus on the first two stages of BrCN formation: the fast equilibrium reactions between HCHO and NH2Br and the somewhat slower decomposition reaction of the species formed from the fast steps. Reaction rate constants will be obtained for each step. Ultimately, the formation of BrCN from NH2Br and HCHO will be predicted.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 23 publications | 8 publications in selected types | All 8 journal articles |
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Kim J-H, Rennecker JL, Tomiak RB, Marinas BJ, Miltner RJ, Owens JH. Inactivation of Cryptosporidium oocysts in a pilot-scale bubble-diffuser contactor. II: model validation and application. Journal of Environmental Engineering 2002;128(6):522-532. |
R826830 (2002) R826830 (Final) |
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Rennecker JL, Corona-Vasquez B, Driedger AM, Rubin SA, Marinas BJ. Inactivation of Cryptosporidium parvum oocysts with sequential application of ozone and combined chlorine. Water Science & Technology 2001;43(12):167-170. |
R826830 (2002) R826830 (Final) |
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Rennecker JL, Kim J-H, Corona-Vasquez B, Marinas BJ. Role of disinfectant concentration and pH in the inactivation kinetics of Cryptosporidium parvum oocysts with ozone and monochloramine. Environmental Science & Technology 2001;35(13):2752-2757. |
R826830 (2002) R826830 (Final) |
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Supplemental Keywords:
bromate, chloramination, Cryptosporidium parvum, disinfection byproduct, drinking water, monochloramine, ozone, cyanogen bromide, bromamines., RFA, Scientific Discipline, Water, Environmental Chemistry, Chemistry, Analytical Chemistry, Drinking Water, alternative disinfection methods, cryptosporidium parvum oocysts, public water systems, integrated approach, disinfection byproducts (DPBs), bromate formation, brominated DPBs, treatment, cyanogen halides, microbial risk management, chloramines, DBP risk management, drinking water contaminants, monochloramine, drinking water systemProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.