No abstract

Wastewater impact on drinking water sources was assessed using several approaches, including analysis of three pharmaceuticals and personal care products (PPCPs) -primidone, carbamazepine, and caffeine -as indicators, and determination of precursor concentrations for the disinfection byproduct N-nitrosodimethylamine (NDMA) using formation potential (FP) tests. Samples were collected in 2006 and 2007 in rivers impacted by wastewater treatment plant (WWTP) discharges, at drinking water treatment plant (DWTP) intakes upstream or downstream from these discharges, and from two WWTP effluents in two watersheds. The levels [10th percentile ) maximum (median)] of primidone, carbamazepine, caffeine, and NDMAFP were 2-95 (7) ng ⁄ l, 2-207 (18) ng ⁄ l, 7-687 (78) ng ⁄ l, and 12-321 (35) ng ⁄ l, respectively. The highest concentrations of primidone, carbamazepine, and NDMA precursors were from one of the WWTP effluents, whereas the highest concentration of caffeine was detected in a river heavily impacted by treated wastewater discharges. The lowest concentrations of the three PPCPs were from a DWTP influent upstream of a metropolitan urban area with minimum wastewater impact. Temporal variations in PPCP and NDMAFP concentrations and streamflows in two selected watersheds were also observed. Furthermore, correlation analysis between caffeine or carbamazepine and primidone was evaluated. The results show that measurement of the two pharmaceuticals and NDMAFP tests can be used to evaluate wastewater impact in different watersheds, whereas caffeine results were more variable.

Enzyme‐linked immunosorbent assay (ELISA) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) were compared for analyzing microcystins in water. ELISA results of microcystin‐LR spiked into raw water samples were close to the spike concentrations, but method variability was ±25%. However, ELISA‐derived microcystin‐LA concentrations were two to three times higher than the spike concentrations obtained using the kit‐provided microcystin‐LR standards, indicating the need for variant‐appropriate ELISA standards. LC/MS/MS results agreed with spike concentrations for all variants in reagent water, but matrix suppression was observed in some raw waters. In bench‐scale studies, ozonated microcystins generated low‐level positive responses by ELISA and a protein phosphatase inhibition assay, even though microcystins were not detected by LC/MS/MS. These findings indicate that ELISA results—particularly in treated water—should be interpreted with caution because of the possibility of false‐positives, relatively high variability, and differential detection of some variants.

An evaluation of existing analytical methods used to measure contaminants of emerging concern (CECs) was performed through an interlaboratory comparison involving 25 research and commercial laboratories. In total, 52 methods were used in the single-blind study to determine method accuracy and comparability for 22 target compounds, including pharmaceuticals, personal care products, and steroid hormones, all at ng/L levels in surface and drinking water. Method biases ranged from <10% to well over 100% in both matrixes, suggesting that while some methods are accurate, others can be considerably inaccurate. In addition, the number and degree of outliers identified suggest a high degree of variability may be present between methods currently in use. Three compounds, ciprofloxacin, 4-nonylphenol (NP), and 4-tert-octylphenol (OP), were especially difficult to measure accurately. While most compounds had overall false positive rates of ≤5%, bisphenol A, caffeine, NP, OP, and triclosan had false positive rates >15%. In addition, some methods reported false positives for 17β-estradiol and 17α-ethynylestradiol in unspiked drinking water and deionized water, respectively, at levels higher than published predicted no-effect concentrations for these compounds in the environment. False negative rates were also generally <5%; however, rates were higher for the steroid hormones and some of the more challenging compounds, such as ciprofloxacin. The elevated false positive/negative rates of some analytes emphasize the susceptibility of many current methods to blank contamination, misinterpretation of background interferences, and/or inappropriate setting of detection/quantification levels for analysis at low ng/L levels. The results of both comparisons were collectively assessed to identify parameters that resulted in the best overall method performance. Liquid chromatography-tandem mass spectrometry coupled with the calibration technique of isotope dilution were able to accurately quantify most compounds with an average bias of <10% for both matrixes. These findings suggest that this method of analysis is suitable at environmentally relevant levels for most of the compounds studied. This work underscores the need for robust, standardized analytical methods for CECs to improve data quality, increase comparability between studies, and help reduce false positive and false negative rates.

N‐nitrosodimethylamine (NDMA) and other nitrosamines have been reported in drinking and recycled water at low parts‐per‐trillion levels, both as contaminants and disinfection byproducts. Many of these nitrosamines cause cancer in animals and are probable human carcinogens. In this study, three existing analytical methods were expanded, refined, and validated for the analysis of NDMA and seven other nitrosamines in potable, waste, and recycled water. Method detection limits for a solid‐phase extraction (SPE) method and a cartridge SPE (CSPE) coupled with gas chromatography–tandem mass spectrometry were 0.7–0.8 ng/L for NDMA and 0.3–1.4 ng/L for other nitrosamines. The micro‐liquid–liquid extraction (MLLE) method that was developed used less volume and was effective at analyzing the different sample matrixes but yielded higher detection limits (2–4 ng/L). NDMA was the only nitrosamine detected in potable water; however N‐nitrosodiethylamine, N‐nitrosomorpholine, N‐nitrosopiperidine, N‐nitrosodi‐N‐butylamine, and N‐nitrosopyrrolidine were present in other matrixes tested. The SPE methods and the MLLE method have been submitted for inclusion in the next revision of Standard Methods for the Examination of Water and Wastewater, and the CSPE method will be submitted for approval in the future.