Dissertation Entitled Investigation on Disinfection by Products (Dbps)
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Dissertation Entitled Investigation on disinfection by products (DBPs) degradation in water distribution systems by Mohsen Behbahani Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering ________________________________________ Dr Youngwoo Seo , Committee Chair ________________________________________ Dr Defne Apul , Committee Member ________________________________________ Dr Cyndee Gruden , Committee Member ________________________________________ Dr Dong-Shik Kim , Committee Member ________________________________________ Dr Ashok Kumar , Committee Member ________________________________________ Dr. Amanda Bryant-Friedrich , Dean College of Graduate Studies The University of Toledo May 2018 Copyright 2018, Mohsen Behbahani This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author An Abstract of Investigation on disinfection by products (DBPs) degradation in water distribution systems by Mohsen Behbahani Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering The University of Toledo May 2018 Disinfection by-products (DBPs) are ubiquitous by-products of disinfection process in water systems. It has been implicated that DBPs play a major role in deterioration of water quality and the increase of public health risks. Since the discovery of DBPs in 1974, there has been a lot of research works conducted to understand the formation and fate of DBPs in water systems. However, most of the previous studies focused on the formation of DBPs and our current understanding of DBP degradation is still limited especially in water distribution systems. The objective of this study is to investigate both abiotic and biological degradation of DBPs in water distribution systems. In the first objective, response surface methodology (RSM) was applied to investigate the degradation of major haloacetic acids (HAAs) in aqueous solutions using iron powder. The individual and combined effects of initial pH, iron dosage, and reaction time were considered as three major controlling factors. For all HAAs, the decrease of initial pH value and the increase of iron dosage improve degradation efficiency. The increase of reaction time was found to be influential on all HAA I degradation (except DCAA and TCAA). However, its effect was not as significant as that of the initial pH and iron dosage. Brominated HAAs showed higher degradation rates than chlorinated ones in similar experimental conditions. According to the ANOVA (analysis of variance) test outcomes, all the developed regression models could predict HAA degradation with high R 2 values which confirms the applicability of polynomial regression models for HAA removal estimation. The objective of second study was to evaluate the influence of water distribution system conditions (pH, total organic carbon, residual chlorine, and phosphate) on haloacetic acids (HAAs) biodegradation. A series of batch microcosm tests were conducted to determine biodegradation kinetics and collected biomass was used for real time quantitative reverse transcription polymerase chain reaction analyses to monitor how these drinking water distribution system conditions affect the relative expression of bacterial dehalogenase genes. It was observed that tested water distribution system conditions affected HAA biodegradation with different removal efficiencies (0-100%). HAA biodegradation was improved in tested samples with TOC (3 mg/L) and pH 8.5 compared to those of TOC (0 mg/L) and pH 7, respectively. However, slight improvement was observed with the increased PO 4 concentration (3.5 mg/L), and the presence of residual chlorine even at low concentration prohibited biodegradation of HAAs. The observed trend in the relative expression of dehII genes was compatible with the HAA biodegradation trend. Overall relative expression ratio of dehII genes was lower at pH 7, phosphate (0.5 mg/L), and TOC (0 mg/L) in comparison with pH 8.5, phosphate (3.5 mg/L), and TOC (3 mg/L) in the same experimental conditions. The objective of third chapter was to investigate the biodegradation of emerging II nitrogenous DBPs (N-DBPs). Considering the prevalence of dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) formation in water systems, these two DBPs were selected as target compounds in studying N-DBP degradation. DCAN biodegradation was observed at pH 6 and 7.5. However, the degradation efficiency was not statistically different at these pH values (P-values > 0.05). In contrast to pH 6 and 7.5, the hydrolysis (abiotic control) and biodegradation curves almost overlapped at pH 9. This observation indicates no potential biodegradation of DCAN at pH 9. The production of DCAA at different concentrations as the end-product of DCAN degradation via both hydrolysis and biodegradation may implicate that the mechanism of DCAN biodegradation is similar to DCAN hydrolysis. TCNM was also found to be biodegradable at all tested pH values and the order of biodegradation was pH 6 > pH 7.5 > pH 9. The results of statistical analysis also showed significant differences in TCNM biodegradation (P-value <0.05) between pH 6 and 9, and pH 7.5 and 9. The TCNM biodegradation pathway includes the formation of considerable amounts of DCNM (as TCNM degradation by-product) which demonstrates that reductive dehalogenation is the major degradation mechanism. III This work is dedicated to all of my family members especially my wife, without whom none of my success would be possible. I am also grateful of my parents who supported and encouraged me all this time and for many comforts in their life they sacrificed for me. IV Acknowledgement I would like to express my sincere acknowledgement to all the people who helped make this dissertation possible. First of all, I wish to thank my PhD adviser, Dr Youngwoo Seo for all his support, encouragement, and guidance in the last few years. I also appreciate my committee members – Dr Defne Apul, Dr Cyndee Gruden, Dr Dong- Shik Kim, and Dr Ashok Kumar for their very constructive and helpful insights, comments, and suggestions. Special thanks to Ms Tamara Phares and Dr Boren Lin for providing guidance and instructions for molecular biology and gene expression analysis. I would like to thanks my colleagues and friends Dr One Choi, Dr Sang-hoon Lee, Farhad Batmanghelich, Lei Li, Lijia Liu, Youchul Jeon, Joe Calvilo, Zahra Nabati and all the other persons who helped me to finish this work. Finally, I acknowledge the National Science Foundation for providing financial support (CBET: 1236433) V Contents Abstract:………………………………………………………………………………….. I Acknowledgement……………………………………………………………………….V Contents ………………………………………………………………………………...VI List of Tables …………………………………………………………………………...IX List of Figures …………………………………………………………………………...X List of Abbreviations ………………………………………………………………...XIII 1. Overview……………………………………………………………………………….1 2. Literature Review ……………………………………………………………………..4 2.1. Aged water distribution systems……………………………………………..4 2.1.1. Corrosion…………………………………………………………….. 5 2.1.2. Biofilm in drinking water distribution systems…………………….6 2.2. Disinfection by-products (DBPs)……………………………………………..9 2.2.1. Types of DBPs……………………………………………………….10 2.2.1.1. Carbonaceous DBPs………………………………………..10 2.2.1.1.1. HAA Speciation and Toxicity……………………..10 2.2.1.1.2. THM Speciation and Toxicity……………………..12 2.2.1.2. Nitrogenous DBPs…………………………………………..13 2.2.2. DBP Regulations…………………………………………………….18 2.2.3. DBP stability and degradation in water distribution systems…….19 2.2.3.1. Abiotic degradation of DBPs………………………………20 2.2.3.2. Biological degradation of DBPs……………………………26 2.2.3.2.1. Biological degradation of HAAs…………………..26 2.2.3.2.2. Biological degradation of THMs……………….…31 2.2.3.2.3. Biological degradation of N-DBPs……………...…33 3. Research Objectives …………………………………………………………………37 4. Investigation of haloacetic acid (HAA) degradation by iron powder: Application of response surface methodology……………………………………………………….…41 4.1. Introduction……………………………………………………………….…41 4.2. Materials and Methods……………………………………………………...44 4.2.1. Materials………………………………………………………….…44 4.2.2. Batch Experimental Procedure………………………………….…44 VI 4.2.3. Analytical Methods……………………………………………….…45 4.2.4. Experimental design and data analysis………………………….…45 4.3. Results and Discussions……………………………………………………...47 4.3.1. Characterization of Iron Powder………………………………..…47 4.3.2. Development of regression model equations………………………50 4.3.3. Regression model validation……………………………………..…54 4.3.4. 3D surface plots for evaluating effects of experimental factors on HAA degradation…………………………………………………...58 4.3.5. Kinetics of HAA degradation by iron powder………………….…64 4.3.6. Evaluation of developed HAA removal models using data from Literature……………………………………………………………66 4.4. Conclusions………………………………………………………………..…67 5. Understanding the impact of water distribution system conditions on the biodegradation of haloacetic acids and expression of bacterial dehalogenase genes……………………………………………………………………………………..69 5.1. Introduction……………………………………………………………….…69 5.2. Materials and Methods……………………………………………………...71 5.2.1. Chemicals……………………………………………………………71 5.2.2. Bacterial Enrichment and Isolation………………………………..72 5.2.3. Batch biodegradation tests……………………………………….…73 5.2.4. Analytical methods……………………………………………….…74 5.2.5. Bacterial genomic DNA extraction, RNA isolation and reverse Transcription…………………………………………………...…...75