Amino Acids as Potential Precursors to Odorous Compounds in Tap Water during Spring Runoff Events.

The onset of spring runoff in northern climates and tap water odor events are difficult to predict because common water quality parameters cannot fully explain the intermittent odor events that occurred over past decades. Studies have shown that small polar water-soluble compounds, such as amino acids (AAs), leach first from ice/snowmelt. AAs are known to produce odorous compounds, such as aldehydes and chloroaldimines, upon chlorination. Therefore, we proposed that AAs may serve as markers for small and soluble organics that contribute to the odor of chlorinated tap water. Here, we studied the occurrence of AAs in source water collected at two water treatment plants and the odor profiles of tap water at >300 homes during the 2021 and 2022 spring runoff events. AA concentrations were at baseline levels (<100 ng/L) during the 2021 runoff but much higher (up to 5500 ng/L) in 2022 and associated with an escalation in odor complaints. AA concentrations peaked at the onset of the 2022 spring runoff and corresponded with the strongest reported odor intensities in tap water. We obtained high resolution MS and MS/MS spectra of chloroaldimines and confirmed the formation of chloroaldimines under chlorination of the six AAs detected in source water. The results indicate that AAs signal the onset of spring runoff and represent small polar water-soluble compounds that may contribute to tap water odor problems.

Analysis of free amino acids in natural waters by liquid chromatography-tandem mass spectrometry.

This paper reports a new analytical method for the analysis of 18 amino acids in natural waters using solid-phase extraction (SPE) followed by liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) operated in multiple reaction monitoring mode. Two different preconcentration methods, solid-phase extraction and concentration under reduced pressure, were tested in development of this method. Although concentration under reduced pressure provided better recoveries and method limits of detection for amino acids in ultrapure water, SPE was a more suitable extraction method for real samples due to the lower matrix effects for this method. Even though the strong cation exchange resin used in SPE method introduced exogenous matrix interferences into the sample extracts (inorganic salt originating from the acid-base reaction during the elution step), the SPE method still incorporates a broad sample clean-up and minimised endogenous matrix effects by reducing interferences originating from real water samples. The method limits of quantification (MLQ) for the SPE LC-MS/MS method in ultrapure water ranged from 0.1 to 100 µg L(-1) as N for the different amino acids. The MLQs of the early eluting amino acids were limited by the presence of matrix interfering species, such as inorganic salts in natural water samples. The SPE LC-MS/MS method was successfully applied to the analysis of amino acids in 3 different drinking water source waters: the average total free amino acid content in these waters was found to be 19 µg L(-1) as N, while among the 18 amino acids analysed, the most abundant amino acids were found to be tyrosine, leucine and isoleucine.

Which chemicals drive biological effects in wastewater and recycled water?

Removal of organic micropollutants from wastewater during secondary treatment followed by reverse osmosis and UV disinfection was evaluated by a combination of four in-vitro cell-based bioassays and chemical analysis of 299 organic compounds. Concentrations detected in recycled water were below the Australian Guidelines for Water Recycling. Thus the detected chemicals were considered not to pose any health risk. The detected pesticides in the wastewater treatment plant effluent and partially advanced treated water explained all observed effects on photosynthesis inhibition. In contrast, mixture toxicity experiments with designed mixtures containing all detected chemicals at their measured concentrations demonstrated that the known chemicals explained less than 3% of the observed cytotoxicity and less than 1% of the oxidative stress response. Pesticides followed by pharmaceuticals and personal care products dominated the observed mixture effects. The detected chemicals were not related to the observed genotoxicity. The large proportion of unknown toxicity calls for effect monitoring complementary to chemical monitoring.

Odour reduction strategies for biosolids produced from a Western Australian wastewater treatment plant: results from Phase I laboratory trials.

This study investigated sources of odours from biosolids produced from a Western Australian wastewater treatment plant and examined possible strategies for odour reduction, specifically chemical additions and reduction of centrifuge speed on a laboratory scale. To identify the odorous compounds and assess the effectiveness of the odour reduction measures trialled in this study, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS SPME-GC-MS) methods were developed. The target odour compounds included volatile sulphur compounds (e.g. dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide) and other volatile organic compounds (e.g. toluene, ethylbenzene, styrene, p-cresol, indole and skatole). In our laboratory trials, aluminium sulphate added to anaerobically digested sludge prior to dewatering offered the best odour reduction strategy amongst the options that were investigated, resulting in approximately 40% reduction in the maximum concentration of the total volatile organic sulphur compounds, relative to control.

Formation of N-nitrosamines from chlorination and chloramination of molecular weight fractions of natural organic matter.

N-Nitrosamines are a class of disinfection by-products (DBPs) that have been reported to be more toxic than the most commonly detected and regulated DBPs. Only a few studies investigating the formation of N-nitrosamines from disinfection of natural waters have been reported, and little is known about the role of natural organic matter (NOM) and the effects of its nature and reactivity on the formation of N-nitrosamines. This study investigated the influence of the molecular weight (MW) characteristics of NOM on the formation of eight species of N-nitrosamines from chlorination and chloramination, and is the first to report on the formation of eight N-nitrosamines from chlorination and chloramination of MW fractions of NOM. Isolated NOM from three different source waters in Western Australia was fractionated into several apparent MW (AMW) fractions using preparative-scale high performance size exclusion chromatography. These AMW fractions of NOM were then treated with chlorine or chloramine, and analysed for eight species of N-nitrosamines. Among these N-nitrosamines, N-nitrosodimethylamine (NDMA) was the most frequently detected. All AMW fractions of NOM produced N-nitrosamines upon chlorination and chloramination. Regardless of AMW characteristics, chloramination demonstrated a higher potential to form N-nitrosamines than chlorination, and a higher frequency of detection of the N-nitrosamines species was also observed in chloramination. The results showed that inorganic nitrogen may play an important role in the formation of N-nitrosamines, while organic nitrogen is not necessarily a good indicator for their formation. Since chlorination has less potential to form N-nitrosamines, chloramination in pre-chlorination mode was recommended to minimise the formation of N-nitrosamines. There was no clear trend in the formation of N-nitrosamines from chlorination of AMW fractions of NOM. However, during chloramination, NOM fractions with AMW <2.5 kDa were found to produce higher concentrations of NDMA and total N-nitrosamines. The precursor materials of N-nitrosamines appeared to be more abundant in the low to medium MW fractions of NOM, which correspond to the fractions that are most difficult to remove using conventional drinking water treatment processes. Alternative or advanced treatment processes that target the removal of low to medium MW NOM including activated carbon adsorption, biofiltration, reverse osmosis, and nanofiltration, can be employed to minimise the formation of N-nitrosamines.

Determination of halonitromethanes and haloacetamides: an evaluation of sample preservation and analyte stability in drinking water.

Simultaneous quantitation of 6 halonitromethanes (HNMs) and 5 haloacetamides (HAAms) was achieved with a simplified liquid-liquid extraction (LLE) method, followed by gas chromatography-mass spectrometry. Stability tests showed that brominated tri-HNMs immediately degraded in the presence of ascorbic acid, sodium sulphite and sodium borohydride, and also reduced in samples treated with ammonium chloride, or with no preservation. Both ammonium chloride and ascorbic acid were suitable for the preservation of HAAms. Ammonium chloride was most suitable for preserving both HNMs and HAAms, although it is recommended that samples be analysed as soon as possible after collection. While groundwater samples exhibited a greater analytical bias compared to other waters, the good recoveries (>90%) of most analytes in tap water suggest that the method is very appropriate for determining these analytes in treated drinking waters. Application of the method to water from three drinking water treatment plants in Western Australia indicating N-DBP formation did occur, with increased detections after chlorination. The method is recommended for low-cost, rapid screening of both HNMs and HAAms in drinking water.

Simultaneous analysis of 10 trihalomethanes at nanogram per liter levels in water using solid-phase microextraction and gas chromatography mass-spectrometry.

Trihalomethanes are predominantly formed during disinfection of water via reactions of the oxidant with natural organic matter. Even though chlorinated and brominated trihalomethanes are the most widespread organic contaminants in drinking water, when iodide is present in raw water iodinated trihalomethanes can also be formed. The formation of iodinated trihalomethanes can lead to taste and odor problems and is a potential health concern since they have been reported to be more toxic than their brominated or chlorinated analogs. Currently, there is no published standard analytical method for I-THMs in water. The analysis of 10 trihalomethanes in water samples in a single run is challenging because the iodinated trihalomethanes are found at very low concentrations (ng/L range), while the regulated chlorinated and brominated trihalomethanes are present at much higher concentrations (above µg/L). An automated headspace solid-phase microextraction technique, with a programmed temperature vaporizer inlet coupled with gas chromatography-mass spectrometry, was developed for routine analysis of 10 trihalomethanes i.e. bromo-, chloro- and iodo-trihalomethanes in water samples. The carboxen/polydimethylsiloxane/divinylbenzene fiber was found to be the most suitable. The optimization, linearity range, accuracy and precision of the method are discussed. The limits of detection range from 1 ng/L to 20 ng/L for iodoform and chloroform, respectively. Matrix effects in treated groundwater, surfacewater, seawater, and secondary wastewater were investigated and it was shown that the method is suitable for the analysis of trace levels of iodinated trihalomethanes in a wide range of waters. The method developed in the present study has the advantage of being rapid, simple and sensitive. A survey conducted throughout various process stages in an advanced water recycling plant showed the presence of iodinated trihalomethanes at ng/L levels.

Breakpoint chlorination and free-chlorine contact time: implications for drinking water N-nitrosodimethylamine concentrations.

North American drinking water utilities are increasingly incorporating alternative disinfectants, such as chloramines, in order to comply with disinfection by-product (DBP) regulations. N-Nitrosodimethylamine (NDMA) is a non-halogenated DBP, associated with chloramination, having a drinking water unit risk two to three orders of magnitude greater than currently regulated halogenated DBPs. We quantified NDMA from two full-scale chloraminating water treatment plants in Alberta between 2003 and 2005 as well as conducted bench-scale chloramination/breakpoint experiments to assess NDMA formation. Distribution system NDMA concentrations varied and tended to increase with increasing distribution residence time. Bench-scale disinfection experiments resulted in peak NDMA production near the theoretical monochloramine maximum in the sub-breakpoint region of the disinfection curve. Breakpoints for the raw and partially treated waters tested ranged from 1.9:1 to 2.4:1 (Cl(2):total NH(3)-N, M:M). Bench-scale experiments with free-chlorine contact (2h) before chloramination resulted in significant reductions in NDMA formation (up to 93%) compared to no free-chlorine contact time. Risk-tradeoff issues involving alternative disinfection methods and unregulated DBPs, such as NDMA, are emerging as a major water quality and public health information gap.

Detecting N-nitrosamines in drinking water at nanogram per liter levels using ammonia positive chemical ionization.

Detection of N-nitrosamines in water supplies is an environmental and public health issue because many N-nitrosamines are classified as probable human carcinogens. Some analytical methods are inadequate for detecting N-nitrosodimethylamine (NDMA) at low ng/L concentrations in water due to poor extraction efficiencies and nonselective and nondistinctive GC/MS electron ionization techniques. Development of a selective, sensitive, and affordable benchtop analytical method for eight N-nitrosamines, at relevant drinking water concentrations was the primary objective of this project. A solid-phase extraction method using Ambersorb 572 and LiChrolut EN was developed in conjunction with GC/MS ammonia positive chemical ionization (PCI). Ammonia PCI shows excellent sensitivity and selectivity for N-nitrosamines, which were quantified using both isotope dilution/surrogate standard and internal standard procedures. Method detection limits for all investigated N-nitrosamines ranged from 0.4 to 1.6 ng/L. Applying our extraction method to authentic drinking water samples with dissolved organic carbon concentrations of 9 mg/L, we were able to detect N-nitrosodimethylamine (2-180 ng/L) as well as N-nitrosopyrrolidine (2-4 ng/L) and N-nitrosomorpholine (1 ng/L), two N-nitrosamines that have not been reported in drinking water to date. With high recoveries of standards and analytes, the described internal standard method offers a valuable new approach for investigating several N-nitroso compounds at ultratrace levels in drinking water.