Variability of Non-Regulated Disinfection By-Products in Distribution

Chapter 18

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Variability of Non-Regulated Disinfection By-Products in Distribution Systems: Impact of the Storage Tank Christelle Legay,1 Patrick Levallois,2 Rocio Aranda-Rodriguez,3 Luda Dabeka,3 Joan Hnatiw,3 and Manuel J. Rodriguez*,1 1Centre

de Recherche en Aménagement et Développement, Université Laval, Pavillon Félix-Antoine-Savard, 2325 rue des Bibliothèques, Québec City, QC G1V 0A6, Canada 2Direction de la Santé Environnementale et de la Toxicologie, Institut National de Santé Publique du Québec, 945 avenue Wolfe, Québec City, QC G1V 5B3, Canada 3Exposure and Biomonitoring Division, Environmental Health Science Bureau, Health Canada, EHC, Tunney’s Pasture 0800C, bktOttawa, ON K1A OK9, Canada *E-mail: [email protected].

In this chapter, the spatial variability of non-regulated disinfection by-products (DBPs) in drinking water – haloacetonitriles (HANs), haloacetaldehydes (HAs), haloketones (HKs), chloropicrin (CP) and cyanogen chloride (CNCl) – was investigated in four distribution systems in the Québec City area. Attention was directed to the impact, on DBP levels, of water that is re-chlorinated in distribution system storage tanks. The results show that when there was a storage tank as part of the distribution system, flow through this led to an increase in targeted DBP levels except for CNCl for which levels were systematically lowest at sites located after the storage tank. However, for most DBP families, the variability within the storage tank was different from month to month. Moreover, the impact on DBP levels of water flowing through the storage tank differed between the four systems under study.

© 2015 American Chemical Society Karanfil et al.; Recent Advances in Disinfection By-Products ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

This study highlights that, as for regulated DBPs (trihalomethanes-THMs and haloacetic acids-HAAs), the selection of the sampling locations for non-regulated DBP monitoring represents a considerable challenge.


Introduction Disinfection by-products (DBPs) in drinking water are known to vary within distribution systems. Several factors may influence DBP variability, such as raw water source characteristics, the treatment applied and some distribution system characteristics (1–3). The variability of DBP levels within systems makes it difficult to monitor these compounds. Past studies have investigated the spatial variability of DBPs, but focused mainly on two prevalent families (trihalomethanes-THMs and haloacetic acids-HAAs) presently regulated in most industrialized countries. However, other non-regulated DBP families occurring at low levels in drinking water are considered as potentially of greater health concern than THMs and HAAs (4). These include, among others, haloacetonitriles (HANs), haloacetaldehydes (HAs), haloketones (HKs), and halonitromethanes (HNMs). A number of studies have focused specifically on the spatial variability of these DBPs within distribution systems where water is disinfected with chlorine (5–10). In Williams et al. (5) and Shin et al. (6), the spatial variability of DBPs within several systems was investigated through comparisons with the levels measured in finished water at the water treatment plant (WTP) and at only one site located in the system (in the middle or at the extremity according to the study). In Golfinopoulos et al. (7), finished water and a large number (eight) of sites were characterized within one distribution system. However, the variation of DBP levels between these sites was not really investigated. Koudjonou et al. (8) investigated the spatial variability of DBP levels within systems by sampling the finished water and water from three sites spatially distributed within each system, yet only one HA species was investigated in this study. Guilherme and Rodriguez (9) considered three sampling sites located in systems under study to investigate the spatial variability of three DBP families. However, the presence of DBPs in finished water was not measured. Moreover, it is important to note that in the above studies, the impact on DBP levels of water flowing through a distribution system storage tank (defined in this paper as the residence time added by the storage tank) was not investigated. Mercier-Shanks et al. (10) focused on the spatial variability of DBPs by sampling various sites spatially dispersed in one distribution system (which is also studied in this chapter), including two sites located after a storage tank with re-chlorination. In this study (10), the impact of water flowing through the storage tank was only briefly discussed, only one system was investigated and DBP families under study were limited (HANs, HKs and one HNM species). In this chapter, the spatial variability within systems of non-regulated DBPs (HANs, HAs, HKs, one HNM species and cyanogen chloride) was investigated for four distribution systems where water was disinfected with chlorine. The focus was on the impact, on these DBPs, of water flowing through distribution 342 Karanfil et al.; Recent Advances in Disinfection By-Products ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

system storage tanks (where re-chlorination was applied). The variation of this impact according to season was also investigated. Moreover, the evolution within distribution systems of the relationship between the levels of regulated (THMs) and non-regulated DBPs was estimated. To conclude, strategies were discussed to control and survey these non-regulated DBPs within distribution systems for monitoring or exposure assessment studies.

Material and Methods Downloaded by UNIV OF CINCINNATI on May 30, 2016 | http://pubs.acs.org Publication Date (Web): August 24, 2015 | doi: 10.1021/bk-2015-1190.ch018

Case under Study This study was carried out in four distribution systems located in the greater Québec City area (Province of Quebec, Canada) supplying approximately 350,000 inhabitants. The main characteristics of these systems are presented in Table 1. These systems are supplied by surface water and all apply chlorine as their primary or secondary disinfectant. However, the type of surface water source (e.g., lake, river), type and efficiency of treatment applied before secondary disinfection (e.g., presence of ozonation or not), and distribution system characteristics (e.g., size, hydraulic regime, pipe characteristics) differ between the systems. Each distribution system includes at least one storage tank with a re-chlorination point. However, the re-chlorination strategy applied (injection location, dose) and water residence time in the storage tank vary between the systems (Table 1). The region under study is subject to important climatic variations during the year, with mean daily temperatures of ambient air ranging from -16.8°C to + 24.2°C (11), and different lengths of seasons (i.e., long winters and relatively short summers). These climatic variations can result in great temporal variations in raw water quality.

Water Sampling Bimonthly sampling campaigns were conducted between August 2006 and December 2007 (for logistical issues, data from the February 2007 campaign were not available). During these campaigns, four water samples were taken in each distribution system: at the finished water outlet the WTP and at three sites located within the distribution system. In order to investigate the impact of water flowing through the storage tank (that includes a re-chlorination step) at least one of these sites was not supplied by the storage tank and at least one was supplied by the storage tank. The DBP measurements included the analysis of HAs, HANs, HKs, chloropicrin (HNM species and noted CP), cyanogen chloride (CNCl) and THMs (Table 2). Free residual chlorine (FRC) concentration, temperature (T), pH, turbidity and ultraviolet absorbance at 254 nm (UV254) were also measured for each sample. 343 Karanfil et al.; Recent Advances in Disinfection By-Products ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

Table 1. Description of the Four Distribution Systems under Study Water source

Main treatment process

Storage tank characteristics Capacity

(m3)

Estimated water residence time

Location of re-chlorination

A

St. Lawrence Riverb

Pre-chlorination; PCTa; Post-ozonation; Post-chlorination

4,550

~ 1 day

Outlet

B

St. Lawrence Riverb

Pre-chlorination; PCTa; Post-chlorination

2,275

~ 1.5 days

Outlet

C

Chaudière River

Flocculation; Sedimentation; Inter-chlorination; Filtration; Post-ozonation; Post-chlorination

8,500

~ 4 days

Outlet

Dc

St. Charles Lake

PCTa; Post-ozonation; Post-chlorination

130,000

~ 3 to 5 days

Entrance and outlet

344


Systems

Complete physical-chemical treatment including sieving, coagulation-flocculation, sedimentation and filtration; different for systems A and B; c This system was studied previously by Mercier-Shanks et al. (10)

a

Karanfil et al.; Recent Advances in Disinfection By-Products ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

b

The location of the raw water intake is


In each sampling location (public building, private residence or stores), samples were taken at the faucet of the restroom (except for the finished water samples taken at the WTP). Cold tap water was allowed to flow for approximately five minutes to obtain water from the distribution system and not stagnant water from the building pipes. Duplicate samples were collected in 60ml glass vials containing 1 mL of buffer solution (pH 4.1). In the field, 0.2 mL ascorbic acid solution (0.114M), used as quenching agent, were added to each bottle just before the sampling. The samples were stored at 4°C until the time of analysis. FRC and T were measured in situ at the same time as the DBP sample collection. 250 mL plastic bottles were used to collect and transport samples for laboratory analysis of the other parameters. Analytical Procedure As presented in Table 2, seven HA species (the sum represents HA7), four HAN species (the sum represents HAN4), two HK species (the sum represents HK2), CP, CNCl and four THM species (the sum represents THM4) were analyzed. The analysis of HANs, HAs, HKs, CP, CNCl and THMs was conducted in the Health Canada laboratory and described previously (12–14). Briefly, liquid-liquid extraction was performed with MTBE containing internal standards. The extracts were analyzed using a Varian 3800 gas chromatograph equipped with dual electron capture detectors. Two chromatographic columns were used: a DB-5 column (30 m x 0.32 mm id; film thickness 1 m) as the primary column, and a DB-1 column (30 m x 0.32 mm id; film thickness 1 m) for confirmation (15). The method detection limit (MDL) associated with each individual DBP under study is presented in Table 2. Measurements below the MDL were considered as equal to zero. Measurements of FRC were conducted using the DPD titrimetric method (Standard method 4500-Cl-F) with a DR-890 colorimeter from Hach. Water pH was measured with a Denver instrument AP15 pH/mV/FET meter. Turbidity was analyzed with a Hach 2100N Turbimeter. UV254 results were obtained by UV/visible spectrometry at 254nm (Hach DR5000) with 5 cm optical path quartz cells. Data Analysis In order to investigate the spatial variability of non-regulated DBP levels in the systems under study and, specifically, the impact of water flowing through the storage tank with re-chlorination, sampling sites were divided into three categories according to their location in each system. The first category included the finished water, for which samples were taken at the WTP (noted as “FW” in the tables and figures). The second category included the sampling sites located within the distribution system and directly supplied by the WTP, thus not supplied by a storage tank (noted as “Sup/WTP” in the tables and figures). The third category included only the sites supplied by a storage tank within the distribution system (noted as “Sup/S.tank” in the tables and figures). Depending on the system, the second and third categories might include one or two sampling sites. 345 Karanfil et al.; Recent Advances in Disinfection By-Products ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

Table 2. DBPs under Study DBPs

Abbreviations

MDL (µg/L)


HA7 (sum of the 7 HAs) Dichloroacetaldehyde

DCA

0.07

Trichloroacetaldehyde

TCA

0.06

Bromochloroacetaldehyde

BCA

0.05

Dibromoacetaldehyde

DBA

0.05

Bromodichloroacetaldehyde

BDCA

0.04

Chlorodibromoacetaldehyde

CDBA

0.06

Tribromoacetaldehyde

TBA

0.10

Trichloroacetonitrile

TCAN

0.04

Dichloroacetonitrile

DCAN

0.05

Bromochloroacetonitrile

BCAN

0.06

Dibromoacetonitrile

DBAN

0.05

1,1-dichloro-2-propanone

DCP

0.07

1,1,1-trichloro-2-propanone

TCP

0.06

Chloropicrin

CP

0.04

Cyanogen chloride

CNCl

0.07

Chloroform

TCM

0.41

Bromodichloromethane

BDCM

0.10

Dibromochloromethane

DBCM

0.08

Bromoform

TBM

0.09

HAN4 (sum of the 4 HANs)

HK2 (sum of the 2 HKs)

THM4 (sum of the 4 THMs)

MDL represents the method detection limit.

As previously mentioned, this chapter focused mainly on the impact of water flowing through a storage tank with re-chlorination on non-regulated DBPs. THMs were considered in order to determine the evolution within systems of the relationship between regulated and non-regulated DBPs. With this aim in mind, correlation analyses (Spearman rank correlation coefficients-rs) were conducted (using SPSS Version 22.0) between THM and non-regulated DBP levels and for each category of sampling sites previously described (i.e., FW, Sup/WTP and Sup/S.Tank). 346 Karanfil et al.; Recent Advances in Disinfection By-Products ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

Results and Discussion


DBP Occurrence in the Area under Study The finished water quality data (at the WTP) for the four distribution systems during the study period are presented in Table 3. DBP levels measured in each distribution system during the period under study are presented in Table 4. Irrespective of the system under study, the most abundant DBP family among those analyzed was HAs. As previously observed by Koudjonou et al. (8), statistically significant higher HA levels (significance level ρ

Variability of Non-Regulated Disinfection By-Products in Distribution

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