Contribution of N-Nitrosamines and Their Precursors to Domestic

Oct 23, 2015 - N-nitrosamines and their precursors are significant concerns for water utilities exploiting wastewater-impacted water supplies, particu...
43 downloads 8 Views 2MB Size
Subscriber access provided by University of Glasgow Library

Article

Contribution of N-Nitrosamines and Their Precursors to Domestic Sewage by Greywaters and Blackwaters Teng Zeng, and William A. Mitch Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b04254 • Publication Date (Web): 23 Oct 2015 Downloaded from http://pubs.acs.org on October 24, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

Environmental Science & Technology

1

Contribution of N-Nitrosamines and Their Precursors to

2

Domestic Sewage by Greywaters and Blackwaters

3

Teng Zeng1,2, William A. Mitch1,2,*

4

1

5

Stanford, California 94305, United States

6

2

7

Water Infrastructure (ReNUWIt), 473 Via Ortega, Stanford, California 94305, United States

Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega,

National Science Foundation Engineering Research Center for Re-Inventing the Nation’s Urban

8 9

AUTHOR EMAIL ADDRESS: [email protected]

10

CORRESPONDING AUTHOR FOOTNOTE:

11

William A. Mitch: Email: [email protected], Phone: 650-725-9298, Fax: 650-723-7058

12 13 14 15 16 17 18 19 20 21 22

ACS Paragon Plus Environment

Environmental Science & Technology

23

TOC ART

24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

ACS Paragon Plus Environment

Page 2 of 28

Page 3 of 28

48

Environmental Science & Technology

ABSTRACT

49

N-nitrosamines and their precursors are significant concerns for utilities exploiting

50

wastewater-impacted water supplies, particularly those practicing potable reuse of wastewater.

51

Previous efforts to identify specific precursors in municipal wastewater accounting for N-

52

nitrosamine formation have met with limited success. As an alternative, we quantified the

53

relative importance of greywater (i.e., shower, kitchen sink, bathroom washbasin and laundry)

54

and blackwater (i.e., urine and feces) streams in terms of their loadings of ambient specific and

55

total N-nitrosamines and chloramine-reactive and ozone-reactive N-nitrosamine precursors to

56

domestic sewage. Accounting for the volume fractions of individual greywater and blackwater

57

streams, laundry water represented the most significant source of N-nitrosamines and their

58

precursors, followed by shower water and urine. Laundry water was particularly important for

59

ozone-reactive N-nitrosamine precursors, accounting for ~98% of N-nitrosodimethylamine

60

(NDMA) precursors and ~70% of precursors for other uncharacterized N-nitrosamines. For the

61

other greywater streams, consumer products contributed additional N-nitrosamines and

62

precursors, but the remarkable uniformity across different products suggested the importance of

63

common macroconstituents. Consumption of a standard dose of the antacid, ranitidine,

64

substantially increased NDMA and its chloramine-reactive precursors in urine. Nevertheless,

65

nearly 40% of the American population would need to consume ranitidine daily to match the

66

NDMA loadings from laundry water.

67 68 69 70

ACS Paragon Plus Environment

Environmental Science & Technology

71 72

INTRODUCTION

73

To meet increasing water demands, utilities are exploring the use of source waters impacted

74

by municipal wastewater discharges or even the potable reuse of highly treated municipal

75

wastewater effluents.1 In addition to the occurrence of N-nitrosamines in municipal wastewater,2,

76

3

77

N-nitrosamines are probable human carcinogens with low nanogram-per-liter drinking water

78

concentrations associated with a 10-6 lifetime excess cancer risk.9 The U.S. Environmental

79

Protection Agency (USEPA) is considering regulation of N-nitrosamines as a group,10 and

80

California has established a drinking water notification level of 10 ng/L for N-

81

nitrosodimethylamine (NDMA) and two other N-nitrosamines.11 Thus, N-nitrosamines are a

82

significant concern for wastewater-impacted water supplies.5, 6

application of chloramines or ozone during treatment also promotes their formation.4-8 Several

83

Characterization of specific N-nitrosamine precursors and formation pathways has been a

84

research focus over the past decade.5, 6 Chloramination of secondary and tertiary amines forms

85

N-nitrosamines at comparable yields (i.e., ~2%).5, 12 Although secondary (e.g., dimethylamine)

86

and tertiary amines (e.g., trimethylamine) are human metabolites occurring in urine and feces,13,

87

14

88

significantly to N-nitrosamine formation in chloraminated wastewater effluents.4, 12 A subset of

89

tertiary amine-based moieties form NDMA at yields up to 90% upon chloramination and have

90

been hypothesized as an important source of NDMA precursors because some of these structures

91

occur in pharmaceuticals that may be microconstituents of domestic sewage (e.g., ranitidine and

92

methadone).15-17 Chloramination of quaternary ammonium compounds forms N-nitrosamines at

93

an order of magnitude lower yields than secondary and tertiary amines,18 but they have been

both are removed during activated sludge treatment, such that they do not contribute

ACS Paragon Plus Environment

Page 4 of 28

Page 5 of 28

Environmental Science & Technology

94

hypothesized to serve as N-nitrosamine precursors due to their occurrence as macroconstituents

95

of domestic sewage based upon their widespread usage as major ingredients of consumer

96

products (e.g., shampoos18) and of treatment polymers (e.g., cationic coagulation polymers19, 20).

97

Efforts to identify specific precursors accounting for a significant fraction of N-nitrosamine

98

formation during chloramination have met with less success. While ranitidine has been detected

99

in U.S. wastewater treatment plant effluents with a mean concentration of 120 ng/L,21 it was

100

detected in only one out of 84 samples (at the 10 ng/L method reporting limit) in a nationwide

101

survey of wastewater-impacted streams.22 Methadone has been detected in a range of wastewater

102

effluents, but only accounted for a maximum of 3% of NDMA formation in wastewater-

103

impacted surface waters and a median of 13% of NDMA formation in one wastewater sample.17

104

On the other hand, ozonation of certain hydrazine, sulfamide, hydrazone and carbamate-

105

containing industrial chemicals can form NDMA at high yields.23 While efforts to attribute

106

NDMA formation during ozonation to specific industrial chemicals have achieved some success

107

in particular watersheds (e.g., anti-yellowing agents in Japan24, 25 and the fungicide, tolylfluanide,

108

in Germany26, 27), the dependence of such findings on the types of industrial discharges likely

109

render these precursors highly site-specific. Given the matrix complexity of wastewater, it is

110

likely that a wide array of compounds contribute to N-nitrosamine formation. However, the

111

relative importance of specific precursors during chloramination or ozonation remains unclear.

112

As an alternative to identifying specific precursors, the goal of this work was to compare the

113

loadings of N-nitrosamines and their precursors from different greywater and blackwater streams

114

to domestic sewage, including greywaters from tub showers, kitchen sinks, bathroom washbasins

115

and washing machines, and blackwaters from urine and feces. Particular emphasis was placed on

116

evaluating whether N-nitrosamine precursors derived from consumer products. Specifically, we

ACS Paragon Plus Environment

Environmental Science & Technology

117

quantified the ambient specific and total N-nitrosamine levels in four greywater and two

118

blackwater streams. We also quantified the levels of chloramine-reactive and ozone-reactive N-

119

nitrosamine precursors in these streams. Weighting these data by the percentage of domestic

120

sewage constituted by each stream, we estimated the fractional contributions of individual

121

streams to the overall loading of N-nitrosamines and their precursors to domestic sewage.

122

MATERIALS AND METHODS

123 124

Chemicals and reagents are described in the Supporting Information (see Text S1). Sample collection and processing

125

Greywater samples were collected from tub showers, kitchen sinks, bathroom washbasins and

126

washing machines by residents at two single-family houses on separate occasions. In order to

127

capture the variation in commercial formulations available on the market, at least five market-

128

leading brands of personal care (i.e., shampoos or handsoaps) or household cleaning products

129

(i.e., dishsoaps or detergents) were used for washing or cleaning activities (see Tables S1-S6 for

130

a product list). Each greywater and consumer product combination was evaluated once. For the

131

amount of consumer products applied and consumer practices (e.g., shower duration), the

132

residents followed their personal preferences. In contrast to previous studies measuring N-

133

nitrosamine formation from consumer products mixed with ultrapure water,18 we sought to gauge

134

the importance of consumer products relative to other components within the context of the

135

complex mixture generated under realistic usage conditions.

136

Shower water samples were collected from a stoppered tub after two daily showers where one

137

shampoo product was used along with the same type of bar soap. Kitchen water samples were

138

collected from a stoppered kitchen sink after manual washing of various loads of plates, bowls

139

and cutlery with one liquid dishwashing product. Bathroom washbasin water samples were

ACS Paragon Plus Environment

Page 6 of 28

Page 7 of 28

Environmental Science & Technology

140

collected in a stoppered bathroom washbasin after six handwashings with one handsoap product.

141

Laundry water samples were collected from the effluent of an Electrolux front-load washing

142

machine (model #EIFLW55HIW0, normal 52 min wash cycle set to warm water, medium soil

143

and high spin) washing a medium-size load of old, mixed white and colored clothes with one

144

detergent product but without any fabric softener product. One separate laundry water sample

145

was collected with mixed white and colored clothes washed with one fabric softener product but

146

without any detergent. Two additional laundry water samples were collected with white and

147

colored clothes washed separately without any detergent or fabric softener. For each greywater

148

stream, control samples without the application of consumer products were also collected (e.g.,

149

handwashings without using any handsoap). All samples were collected in high-density

150

polyethylene jars and returned to Stanford University within 24 h of collection, filtered through

151

0.7-µm pre-combusted glass fiber filters, and stored at 4 °C in the dark until use. While filtration

152

may remove particle-associated N-nitrosamines,4,

153

relevance to wastewater effluents.

28

dissolved N-nitrosamines are of greater

154

Urine and fecal water samples were obtained from five adult volunteers who had no known

155

gastrointestinal symptoms and had balanced meals at regular times. Sample collection and

156

handling protocols were reviewed and approved by the Stanford University Institutional Review

157

Board (Protocol Number 32245). Five volunteers who indicated no pharmaceutical use

158

contributed one set of first-voided morning urine and feces samples. In addition, two of these

159

volunteers consumed one Zantac® 150 tablet (contains 150 mg of ranitidine) at bedtime and then

160

contributed first-voided morning urine and feces samples. Urine samples were collected using

161

sterilized SAFE-D-Spense containers, while feces samples were collected using sterilized

162

Commode specimen collection systems. All samples were returned to Stanford University within

ACS Paragon Plus Environment

Environmental Science & Technology

163

6 h of collection. Whole urine samples were diluted into 6 L of tap water exhibiting a chloramine

164

residual to simulate a single urinal flush, filtered through 0.7-µm glass fiber filters, and stored at

165

-20 °C in the dark until use. Whole feces samples were homogenized with tap water in a

166

weight:volume ratio of 1:1 in a Waring laboratory blender, mixed with ~12 L of tap water to

167

simulate a single toilet flush, and centrifuged at 8,000 g for 10 min. The supernatant (i.e., fecal

168

water) was sequentially filtered through 2.7-µm and 0.7-µm glass fiber filters and stored at -20

169

°C in the dark until use. Greywater and blackwater samples were analyzed for basic water quality

170

parameters (see Text S2 for additional details), and each sample was split and chloraminated or

171

ozonated in duplicate.

172

Chloramination and ozonation tests

173

Previous research on chloramine-reactive precursors has mostly employed formation potential

174

tests, but the extreme chloramination conditions may overestimate the importance of precursors

175

that may not lead to meaningful N-nitrosamine formation under typical treatment conditions.

176

Instead, we employed Uniform Formation Condition (UFC) tests mimicking practical

177

chloramination conditions (designated as the “NH2Cl” samples). When needed, ultrapure water

178

was added to the sample to target a constant final volume of 500 mL for the analysis of specific

179

N-nitrosamines or 1 L for the analysis of total N-nitrosamines (TONO). The overall dilution of

180

matrix components (e.g., dissolved organic carbon (DOC), nitrogen species, etc.) was maintained

181

consistent across chloramination and ozonation tests (see Text S3 for additional descriptions).

182

These dilution factors were accounted for such that the N-nitrosamine concentrations are

183

reported as the concentrations in the raw greywater samples or in the urine or fecal water

184

samples after dilution into 6 L or 12 L of tap water, respectively. Chloramination was initiated by

185

adding an aliquot of freshly-prepared preformed monochloramine solution into the sample

ACS Paragon Plus Environment

Page 8 of 28

Page 9 of 28

Environmental Science & Technology

186

(buffered at pH 8.0 with 4 mM borate) to achieve an initial concentration of 5 mgCl2/L.

187

Chloraminated samples were held in the dark for 3 d at room temperature (typically 23±1 °C)

188

and the residual chloramines (typically 1.0±0.4 mgCl2/L) were quenched with ~31 mg/L ʟ-

189

ascorbic acid. We further applied ozone reactivity tests on a second set of samples (designated as

190

the “O3” samples). Ozonation was initiated by mixing an aliquot of ozone solution with the

191

sample to achieve an initial ratio of 0.8 mg ozone per mg DOC. This ozone dose was chosen

192

based on a literature review of typical doses employed for trace organic contaminant removal,

193

pathogen inactivation, and membrane fouling control.7, 29-34 Ozonated samples were held in the

194

dark at room temperature until no ozone residual was detectable.

195

Chloraminated and ozonated samples were analyzed following a modified USEPA Method

196

521 protocol for nine specific N-nitrosamines, including NDMA, N-nitrosomethylethylamine

197

(NMEA),

198

butylamine, N-nitrosopyrrolidine (NPYR), N-nitrosopiperidine (NPIP), N-nitrosomorpholine

199

(NMOR) and N-nitrosodiphenylamine. Samples were also analyzed for TONO using a

200

chemiluminescence method.8, 35, 36 A third set of untreated samples (designated as the “Raw”

201

samples), along with tap water blanks, were processed and analyzed following the same protocol

202

to quantify the background levels of N-nitrosamines. Specific and total N-nitrosamine

203

concentrations in raw, chloraminated and ozonated tap water samples were below the method

204

reporting limits (i.e.,