Grantee Research Project Results
2000 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, 1999 through August 31, 2000
Project Amount: $367,427
RFA: Drinking Water (1998) RFA Text | Recipients Lists
Research Category: Water , Drinking Water
Objective:
The overall goal of this project is the development of process design recommendations for the simultaneous control of Cryptosporidium parvum oocysts and disinfection by-products (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:
Additional experiments were performed to investigate the effect of disinfectant concentration and pH on the inactivation kinetics of C. parvum oocysts with ozone, monochloramine, and ozone/monochloramine at 20?C. Experimental results revealed that the CT (product of disinfectant concentration and contact time) required to achieve a certain level of inactivation was unique, and therefore that the CT concept was valid for both single disinfectant and sequential disinfection processes under the range of experimental conditions investigated. No pH dependence was observed for primary inactivation with ozone in the pH range of 6 to 10, or primary and secondary inactivation with monochloramine at pH values of 8 and10. In addition, oocyst resistance to chemical disinfectant attack was found to vary among oocyst lots as well as with oocyst aging within a given lot.
As a tool for the optimization and design of the ozone disinfection process, an integrated model has been 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 lab-scale batch reactor, and a lab-scale flow-through ozone bubble-diffuser contactor using synthetic solutions. In addition, semi-empirical expressions taking into account the effect of natural organic matter 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. The model has been evaluated with pilot- and full-scale data obtained from water utilities. The full-scale evaluation has shown that the model is a promising tool for process design optimization.
The formation of cyanogen halides (XCN), DBPs associated with O3/NH2Cl sequential disinfection, has been studied. Initial results have demonstrated the formation of BrCN in the presence of bromide ion. A mechanistic study was performed to resolve the possible formation pathways for XCN, which will aid the modeling and help to devise treatment strategies to diminish its formation. The reaction between NH2Br and HCHO, the initiation reaction for a BrCN formation pathway, was studied extensively during this period. BrCN formation in this system competed with other reactions, including the decomposition of NH2Br, and the reaction between HCHO and NH3. The decomposition of NH2Br was found to involve many reactions with the overall rate affected by pH, [NH3]/[HOBr] ratio, initial NH2Br concentration and temperature. Experimental data have been obtained and efforts are currently directed at developing a model to describe this reaction. Interferences by the competing reaction between HCHO and NH3, will be minimized by using relative low [NH3]/[HOBr] ratios. The experiments will be performed with a sequential mixing stopped-flow system, and the experimental results will be analyzed with a kinetic model. Additional experiments have also shown that another possible competing reaction, HCHO oxidization by NH2Br to form HCOOH, does not appear to occur in this system, even though it is thermodynamically favorable. UV spectral evidence suggests that the formation of BrCN first goes through several fast equilibrium reactions followed by relatively slower steps. Membrane Introduction MS (MIMS) will be used to further confirm the formation of intermediates.
Future Activities:
Research plans for the next reporting period include the performance of additional experiments to assess the role of natural organic matter in the formation of bromate at temperatures in the range of 5 to 25?C. Experiments will be performed with both batch and flow-through reactors. The kinetic information obtained from these 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. Future efforts will also focus on the quantitative study of the fast equilibrium reactions and subsequent slower reactions between monobromamine and formaldehyde. By controlling the experimental conditions, NH2Br will be the only competition reaction considered in the system. After a clear understanding for this system is obtain, a more realistic system consisting of pre-ozonated water dosed with NH2Cl and Br- will be investigated.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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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, Corona-Vasquez B, Driedger AM, Marinas BJ. Synergism in sequential disinfection of Cryptosporidium parvum. Water Science and Technology 2000;41(7):47-52. |
R826830 (2000) 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 by-product, drinking water, monochloramine, ozone., 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.