Grantee Research Project Results
2001 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, 2000 through August 31, 2001
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 the study is to develop an integral 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:
An integrated model was developed to simultaneously predict bromate formation and C. parvum oocyst inactivation during ozone treatment of natural waters. The model consists of elementary chemical reactions that are responsible for ozone decomposition and bromate formation as well as a delayed Chick-Watson kinetic expression for ozone disinfection of C. parvum oocysts. This model has been evaluated experimentally with a laboratory-scale batch reactor, and a laboratory-scale flow-through ozone bubble-diffuser contactor using synthetic solutions. In addition, semi-empirical expressions considering the effect of natural organic matter (NOM) on relevant chemical and disinfection reactions have been incorporated into the model. The kinetic expressions were combined with empirical mass transfer correlations and the axial dispersion model to simulate the gas transfer and hydrodynamic characteristics in pilot- and full-scale ozone bubble-diffuser contactors. Figure 1 shows an example of the integrated model application to simulate the performance of one of the full-scale ozone contactors at Los Angeles Aqueduct Filtration Plant.
With the help of a recently purchased stopped-flow analyzer, bromamine decomposition kinetics were investigated under conditions when either NH 2Br or NHBr 2 was dominant. Experiments performed at different pH, buffer types, NH 3, and initial total bromamine concentrations enabled the formulation of the following reaction mechanism describing bromamine decomposition in the pH range of 6.6 to 9.4:
The first reaction, NH 2Br disproportionation, is an equilibrium reaction catalyzed by general acids in both directions. The catalysis species studied include H +, H 3BO 3, H 2PO 4 -, HPO 4 2-, and NH 4 +. The third order reaction rate constants for all these species were obtained by fitting experimentally obtained NH 2Br and NHBr 2 kinetic data to the model. The resulting catalysis rate constants correlated with their corresponding acid dissociation constants in accordance with the Bronsted-Pedersen relationship. Based on this relationship, the catalysis effect of carbonate species was predicted and later used in predicting bromamine decomposition under more realistic drinking water conditions. The second reaction, dibromamine decomposition, was base catalyzed. However, under the experimental conditions used, HPO 4 2- was the only species exerting any significant catalysis effects.
The proposed model fit the experimental data, under varying conditions such as pH, ammonia and initial bromamine concentrations. One potential application for this model is the prediction of bromamine decomposition in waters in which carbonate is the major buffer system. The applicability of the model was verified for such waters by comparing predictions to experimental data obtained at pH 9.38. The bromamine decomposition model also is providing the basis for the subsequent development of a broader model aimed at predicting the formation of cyanogen bromide in NOM-free water.
Future Activities:
Future research plans include the performance of additional experiments to assess the role of NOM in the formation of bromate. The kinetic information obtained from laboratory-scale experiments will be incorporated into the computer model. Model evaluation with full-scale ozone contactors will be attempted using data available either in the literature or developing new information through collaboration with water utilities.
The formation of BrCN from HCHO and NH 2Br remains challenging, and it is crucial to complete the model to predict BrCN formation. Because of the equilibrium reactions between the bromamines, pH will be narrowed down to the range of 8-10 for which case the amount of NHBr 2 is negligible. The major reactions are those involving HCHO, NH 2Br, and various intermediate species. Experiments will be performed with the stopped-flow system in two stages: one for fast equilibrium reactions, the other for slower decomposition reactions of the species formed from the initial fast reactions. The reaction between CN - and bromamines, the final step resulting in BrCN formation, also will be investigated. Even though this final reaction is predicted to be fast, the kinetic information is important for model development.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 23 publications | 8 publications in selected types | All 8 journal articles |
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Driedger AM, Rennecker JL, Marinas BJ. Inactivation of Cryptosporidium parvum oocysts with ozone and monochloramine at low temperature. Water Research 2001;35(1):41-48. |
R826830 (1999) R826830 (2000) R826830 (2001) R826830 (Final) |
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Rennecker JL, Driedger AM, Rubin SA, Marinas BJ. Synergy in sequential inactivation of Cryptosporidium parvum with ozone/free chlorine and ozone/monochloramine. Water Research 2000;34(17):4121-4130. |
R826830 (1999) R826830 (2000) R826830 (2001) R826830 (Final) |
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Supplemental Keywords:
bromate, chloramination, Cryptosporidium parvum, disinfection byproduct, drinking water, monochloramine, ozone, bromamine., 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.