THE EFFECTS OF AMINE STRUCTURE, CHLORAMINE SPECIES AND OXIDATION STRATEGIES ON THE FORMATION OF N-NITROSODIMETHYLAMINE

To comply with the increasingly stringent disinfection by-product (DBP) regulations in the United States, many water treatment plants have been switching from chlorination to chloramination in the last decade. Although chloramination reduces the formation of regulated DBPs such as trihalomethanes and haloacetic acids, it causes the formation of nitrosamines. Nitrosamines are a class of compounds that are probable human carcinogens, mutagens and teratogens at concentrations as low as 0.2 ng/L. In particular, N-nitrosodimethylamine (NDMA) is the most frequently detected nitrosamine in distribution systems in the United States. Although, nitrosamines are currently not regulated by the USEPA, they have been recently identified as a group of contaminants highlighted for possible regulatory action. Although several studies have investigated the formation mechanisms and important precursors for nitrosamines (especially NDMA), there is still much more to learn about their formation pathways. The main objective of this research was to systematically examine nitrosamines formation from amines to gain insight into the formation mechanisms of nitrosamines (especially NDMA) and examine the interactions of these precursors with different oxidants. Specifically, the research focused on: (i) the formation potential of nitrosamines from amino acids (AAs) under different disinfection conditions, (ii) the roles of tertiary structure on the formation of NDMA during chloramination, (iii) the importance of chloramine species in the NDMA formation, and (iv) the interaction of various precursors with different oxidants (chlorine, chlorine dioxide and ozone) and their consequent effect on NDMA formation. The research approach consists of three phases. First phase consisted of identifying the important nitrosamine precursors and understanding the effect of precursor structure on the conversion yield. Primary and tertiary amines were selected as the target compounds and results are presented in Chapters V and VI. Then in the second phase the roles of chloramine species in NDMA formation was examined as presented in Chapter VII. Finally, controlling NDMA formation, practically as critical as understanding the fundamentals of those reactions, was investigated using different oxidants in Chapter VIII. AAs were selected initially as nitrosamine precursors since they are rich in nitrogen, reactive and shown to form of other classes of DBPs (trihalomethanes, halonitromethanes, etc.). Nine AAs (alanine, aspartic acid, cysteine, glutamic acid, glycine, lysine, histidine, proline and serine) were selected based on their structures (i.e., acidity vs. basic, polar vs. nonpolar, hydrophilic vs. hydrophobic), and tested under different oxidation conditions for their formation of nitrosamines. NDMA yields of all nine AAs during chloramination were below the minimum reporting levels. However, during ozonation alone and ozonation followed by chloramination, the formation of several nitrosamines (including N-nitrosopyrrolidine and N-nitroso-di-n-butylamine) at very low molar conversion yields (25%). Espe cially, strategies for controlling the discharge of those types of contaminants would lead to decreases in NDMA precursor\u27s levels in source waters. (ii) The precursor\u27s structure also influences the chloramine species (mono- vs. di-) responsible for NDMA formation. The dominant chloramine species responsible for NDMA formation was found as dichloramine in selected natural waters. The utilities may opt to minimize the formation of dichloramine in their distribution systems (e.g., maintaining higher pH) to control NDMA formation. However, it should be noted that some NDMA formation may still be observed due to monochloramine. (iii) Pre-oxidation strategies can be an effective method for utilities to control NDMA formation as long as the formation of regulated DBPs (trihalomethanes, haloacetic acids, chlorite and bromate) are within the allowable limits. Chlorine has shown reduction in NDMA formation for most of the precursors (except polymers). On the other hand, chlorine dioxide and ozone may lead to decreases or increases in NDMA formation depending on the characteristics of the precursors. Preliminary testing is suggested for utilities for selecting the appropriate oxidant type, to optimum dose and contact times for controlling NDMA formation

LEACHING OF DISSOLVED ORGANIC CARBON AND SELECTED INORGANIC CONSTITUENTS FROM SCRAP TIRES

An environmentally friendly method for the disposal of scrap tires is currently unavailable; as a result, ultimate disposal of used vehicle tires continues to be a major challenge around the world. In the United States (US), during the past two decades, scrap tires have been generated at the rate of approximately one tire per person per year (i.e., approximately 290 million new scrap tires every year). It is estimated that there are currently 2 billion tires stockpiled in the US. Due to various problems involved in the disposal of scrap tires, different alternatives for recycle and reuse have been examined; however, one concern is the leaching of different tire constituents (organic and inorganic) with time, and their subsequent potential harmful impacts on the environment. The main objective of this study was to perform a systematic investigation to examine the leaching of dissolved organic carbon and selected inorganic constituents from crumb rubber and tire chips under different water chemistry conditions: at three different pH values (4.0, 7.0 and 10.0) in distilled and deionized water, and in the stimulants of acidic rain water (pH 3.0), hard groundwater (pH 8.3) and soft groundwater (pH 6.3) These are the water chemistry conditions that are likely to be encountered during scrap tire (crumb rubber or tire chips) reuse applications. One hundred grams of crumb rubber (8x14 mesh size) or tire chips (1\u27_1\u27, 2\u27_2\u27, 4\u27_2\u27 and 6\u27_2\u27) were soaked and mixed in each leaching solution with a solid to solution ratio of 1:20 at room temperature for one month period. Samples were periodically collected and analyzed for selected inorganic constituents (sulfur (S), zinc (Zn), cadmium (Cd), chromium (Cr), arsenic (As), potassium (K), phosphorus (P), sodium (Na), manganese (Mn), iron (Fe), calcium (Ca), magnesium (Mg), aluminum (Al), copper (Cu), lead(Pb), selenium (Se), molybdenum (Mo) and nickel (Ni)), dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254) and dissolved nitrogen (DN). Toxicity Characterization Leaching Procedure test was also performed to assess the toxicity of the leachates. Results showed that the best condition for using scrap tire chips in environmental reuse applications was around the neutral pH conditions. Leaching of dissolved organic carbon and selected elements was minimal around the neutral pH values. pH was a more important parameter than conductivity of the solution in controlling the leaching of DOC and selected elements from scrap tires. The changes in conductivity did not have a significant impact on the leaching of organics or inorganics. When tire chips were exposed to acidic conditions, Fe by far was the most significant metal leaching from tires at very large quantities (up to ~800 mg/ 100 g tire). The presence of organics significantly increased the Fe concentrations in water (e.g., ~ 20 mg/L at pH 4) above its solubility. Mn was the second metal observed leaching at acidic conditions; however at amounts (2-5 mg/ 100 g tire) significantly lower than Fe. When the tire chips were exposed to basic conditions, the leaching of DOC significantly increased (reaching 27 mg/ 100 g tire). For crumb rubber, leaching of DOC reached up to ~120 mg/ 100 g tire, indicating that organic components in tires are more prone to leaching under basic conditions. Under the basic conditions, the leaching of inorganics, including Fe (\u3c1 mg/ 200 g tire) was significantly lower. As, Cd, Cr, Cu, Mo, Se, Ni and Pb were always below the detection limits for all conditions tested during one month of leaching experiments. The SUVA254 values of the leaching solutions remained in the range of 1.5 to 3.0 L/mg-m during the experiments. A gradual increase in the SUVA254 values after the first week was observed, indicating an increase in the fraction of aromatic carbons leaching from the tires over time. The presence of some aromatic compounds in the leachate solutions was confirmed with gas chromatograph coupled with tandem mass spectrometer scans. Some of these compounds (e.g., aniline, benzothiazole, benzothiazolone) have been also reported in previous studies. Analysis of DOC leaching data showed that the mass of DOC leached during the first 12 hr consisted of 40-50% of the leaching during the first week and 20-25% of the leaching during the four weeks of experiments. Although the cumulative DOC mass leached from tires depended on tire size and leaching solution, the leaching rate remained constant regardless of tire type and leaching solution composition. Analysis of leaching rate of four metals (Zn, Fe, Al, Mn) at acidic conditions showed a rapid initial leaching rate for Zn, followed by a slower but constant rate, while there was a constant rate of leaching for Fe, Mn and Al from the beginning of the experiments without showing any sign of slowing down. This observation was attributed to the release of the Zn from the rubbery portion of the tires due to the relatively similar leaching patterns observed for DOC and Zn. On the other hand, Fe, Al and Mn are probably coming from the wires in tire chips and showed a continuous and constant rate of dissolution. Crumb rubber showed significantly higher degree of leaching than tire chips for all detected constituents except Fe, since the main source of the iron in tire chip was the wires that were removed prior to preparing the crumb rubber. Among the tire chips that were within the particle size range of practical applications, leaching from 1\u27_1\u27 size tire chips, in general, was higher than the other particle sizes. The difference in leaching among other particle sizes (2\u27_2\u27, 4\u27_2\u27 and 6\u27_2\u27) was relatively small or negligible for most of the parameters monitored

Occurrence and Formation of Disinfection By-Products in Indoor US Swimming Pools

Chlorination is commonly used to prevent the spreading of waterborne infectious diseases in swimming pools. This required disinfection practice also results in the formation of undesirable disinfection by-products (DBPs) from the reactions of chlorine with the organic matter (released by swimmers or present in the pool filling water) and inorganics (i.e., bromide). The main objective of this research was to improve our understanding of the occurrence and formation of different classes of DBPs (trihalomethanes [THMs], haloacetic acids [HAAs], halonitromethanes [HNMs], haloacetonitriles [HANs], and nitrosamines) in indoor swimming pools operational conditions in the U.S.. The results showed that the DBPs in the investigated 23 swimming pools were far higher than the drinking water regulation values in the U.S. Average THMs, HAAs, HANs, HNMs, and N-nitrosodimethylamine concentrations were 80 μg/L, 1541 μg/L, 19 μg/L, 5.4 μg/L, and 27 ng/L, respectively. An increase in organic matter released by the swimmers and bromide (from the filling water or electrochemical generation of chlorine) levels in the water increased the overall formation of DBPs. Increases in free available chlorine, pH, and water temperature were shown to enhance the formation of THMs and HAAs. These favorable conditions lead to rapid formation (i.e. 3-6 hours) of THMs and HAAs under swimming pool conditions

Coagulation-Ceramic Membrane Filtrati on for U.S. Surface Water Treatment Summary

The objective of this project was to conduct a systematic pilot-scale investigation of a hybrid coagulation-ceramic membrane treatment system to gain fundamental insights about necessary pretreatment conditions, fouling mechanisms, and contaminant removal capabilities, using two U.S. surface water sources. A two-phase plan was implemented for each of the three coagulants considered in this study: aluminum sulfate, aluminum chlorohydrate, and ferric chloride. The first phase involved the optimization of the coagulation pretreatment conditions that provided the best performance in terms of particle removal, organics removal, and membrane fouling. The second phase involved a comprehensive performance evaluation of the optimized system. The removal of precursors of selected regulated and emerging disinfection by-products as well as selected microorganisms and surrogates from the two U.S. surface waters was determined

ELEKTRO-EĞİRME YÖNTEMİYLE NANOFİBER TABAKALI HAVA FİLTRESİ ÜRETİMİ VE KARAKTERİZASYONU

Bu çalışmada, makro boyuttaki gözeneklere sahip farklı malzemelerin yüzeyi filtreleme performansını arttırmak amacıyla elektro-eğirme yöntemiyle nanofiber tabaka ile kaplanması amaçlanmıştır. Sadece mikrofiber filtreler yüzeyine kaplanan nanofiber tabakaların filtre olarak kullanılabileceği görülmüştür. Mikropartiküllerin filtrasyonunda kullanılan 25-85 g/m2 gramaj arasındaki mikrofiber filtrelerin yüzeyi, polimer solusyonu besleme debisi 21-30 ml/h, uygulanan gerilim 28-32 kV ve elektrotlar arası mesafe 19-23 cm aralığında elektro-eğirme deney parametreleri ile kaplanmıştır. Nanofiber tabaka ağırlığı 2-4 g/m2, nanofiber çapı 77-200 nm arasında değişen beş farklı hava filtresi numuneleri elde edilmiştir. Elektro-eğirme deney parametrelerindeki değişim ile nanofiber tabaka ağırlığı, nanofiber çapı ve yüzey morfolojisindeki değişmeler gözlenmiş ve üretilen numunelere etkisi incelenmiştir. Sonuçta, makro gözenekli malzemelerin nanofiber tabakalı filtre olarak kullanılamayacağı görülmüştür

Simulation of full-scale reverse osmosis filtration system for the removal of N-nitrosodimethylamine from wastewater

YesReverse osmosis (RO) is becoming one of the most promising technologies used in wastewater treatment because it offers high rate of contaminant rejection and lower energy consumption in comparison with other thermal treatment processes. Earlier research by the same authors in respect of a distributed one-dimensional mathematical model for a single spiral-wound RO membrane module based on the solution-diffusion model has been used in this paper to simulate the rejection of NDMA (N-nitrosodimethylamine) from wastewater in a series of seven RO elements full-scale treatment plant. Firstly, the applicability of this model has been evaluated using a simulation study and the results have been compared against experimental data gathered from the literature for a given plant. Secondly, further simulation and analysis studies are carried out to assess the performance of the plant for NDMA rejection and recovery rate under different operating conditions of feed pressure, flow rate, and concentration. For the studied RO configuration, it is concluded that a maximum of 55.1% NDMA rejection can be achieved, which confirms the remaining issue of lower NDMA rejection

Temporal variations of disinfection byproduct precursors in wildfire detritus

The Rim Fire ignited on August 17, 2013 and became the third largest wildfire in California history. The fire consumed 104,131 ha of forested watersheds that were the drinking water source for 2.6 million residents in the San Francisco Bay area. To understand temporal variations in dissolved organic matter (DOM) after the wildfire and its potential impacts on disinfection byproduct (DBP) formation in source water supply, we collected the 0-5 cm ash/soil layer with surface deposits of white ash (high burn severity) and black ash (moderate burn severity) within the Rim Fire perimeter in Oct 2013 (pre-rainfall) for five sequential extractions, and in Dec 2013 (∼87 mm cumulative precipitation) and Aug 2014 (∼617 mm cumulative precipitation) for a single water extraction. Water-extractable DOM was characterized by absorption and fluorescence spectroscopy and DBP formation tests. Both increasing cumulative precipitation in the field or number of extractions in the lab resulted in a significant decrease in specific conductivity, dissolved organic carbon, and DBP formation potential, but an increase in DOM aromaticity (reflected by specific UV absorbance). However, the lab sequential leaching failed to capture the increase of the NOx(-)-N/NH4(+)-N ratio and the decrease in pH and dissolved organic carbon/nitrogen ratio of ash/soil extracts from Oct 2013 to Aug 2014. Increasing cumulative precipitation, inferring an increase in leaching after fire, led to an increase in DOM reactivity to form trihalomethanes, haloacetic acids, and chloral hydrate, but not for haloketones, haloacetonitrile, or N-nitrosodimethylamine, which were more related to the original burn severity. This study highlights that fire-affected DBP precursors for different DBP species have distinct temporal variation possibly due to their various sensitivity to biogeochemical alterations

Annual banned-substance review: Analytical approaches in human sports drug testing.

A number of high profile revelations concerning anti-doping rule violations over the past 12 months have outlined the importance of tackling prevailing challenges and reducing the limitations of the current anti-doping system. At this time, the necessity to enhance, expand, and improve analytical test methods in response to the substances outlined in the World Anti-Doping Agency (WADA) Prohibited List represents an increasingly crucial task for modern sports drug testing programs. The ability to improve analytical testing methods often relies on the expedient application of novel information regarding superior target analytes for sports drug testing assays, drug elimination profiles, and alternative sample matrices, together with recent advances in instrumental developments. This annual banned-substance review evaluates literature published between October 2017 and September 2018 offering an in-depth evaluation of developments in these arenas and their potential application to substances reported in WADA's 2018 Prohibited List