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Int J Env Health Eng 2012,  1:52

THMs assessment in Khuzestan rural water treatment plants

1 Environmental Technology Research Center; Department of Environmental Health Engineering, Ahwaz Jundishapur University of Medical Sciences, Ahwaz, Iran
2 Department of Environmental Engineering, Ahwaz Science and Research Branch, Islamic Azad University, Ahwaz; Khuzestan rural water and wastewater company, Khuzestan, Iran
3 Department of Environmental Health Engineering, Alborz University of Medical Sciences, Karaj, Iran
4 Department of Environmental Engineering, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran
5 Department of Environmental Engineering, Ahwaz Science and Research Branch, Islamic Azad University, Ahwaz, Iran

Date of Web Publication31-Dec-2012

Correspondence Address:
Hoda Amiri
Alborz University of Medical Sciences, Karaj
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Source of Support: Ahwaz Jundishapur University of Medical Sciences, Ahwaz, Iran, Conflict of Interest: None

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Aims: The trihalomethanes (THMs) concentration was investigated in some of rural water treatment plants in Khuzestan.
Materials and Methods: Fifteen of the water treatment plants with the same drinking water source (Karoon river) were selected for analysis of THMs to assess the levels and the relationship between THMs and total organic carbon (TOC), pH, temperature, chlorination dose, and free chlorine residue.
Results: THMs ranged from 1.8 to 219 mg/l in winter and 1.7 to 98 in summer, where the level in some treatment plants is higher than the Maximum Concentration Level (MCL). The ratio of total THMs levels was significantly correlated with temperature, pH, chlorination dose, and free chlorine residue, but negative correlation with TOC.
Conclusion: Epidemiological studies using total THMs levels should be considered in the analysis of water treatment plant's results, and regulatory check of this parameter with drinking water guidelines.

Keywords: Drinking water, Khuzestan, rural water treatment plants, THMs

How to cite this article:
Ahmadi M, Keyani A, Amiri H, Hasani AH, Sekhavatjoo MS, Takdastan A. THMs assessment in Khuzestan rural water treatment plants. Int J Env Health Eng 2012;1:52

How to cite this URL:
Ahmadi M, Keyani A, Amiri H, Hasani AH, Sekhavatjoo MS, Takdastan A. THMs assessment in Khuzestan rural water treatment plants. Int J Env Health Eng [serial online] 2012 [cited 2022 Nov 28];1:52. Available from:

  Introduction Top

Although chlorination is most widely used for disinfection of drinking water treatment plants, trihalomethanes (THMs) are formed as a result of chlorination of natural water. Only four THM compounds are normally found: chloroform (CHCl 3 ), bromodichloromethane (CHBrCl 2 ), dibromochloromethane (CHBr 2 Cl), and bromoform (CHBr 3 ). Additional chlorination by-products can be formed during the relatively slow organic reactions that occur between free chlorine and naturally occurring organic precursors such as humic and fulvic acids. The formation potentials of these additional by-products can also be determined, but different quenching agents and different analytical procedures may be needed. [1] There are various factors which significantly affect the formation of THMs such as pH, temperature, dissolved organic carbon (DOC), bromide concentrations, and operational factors like chlorine dose and contact time. [2] Many researchers have qualitatively and semi-quantitatively investigated the effects of these factors on THM formation. [3] Since THMs in nation's drinking waters have been related to cancer and reproductive outcomes, the presence of these compounds is of concern from the health-related aspect; epidemiological studies have recommended a probable link between chlorination and chlorination by-products with excess risk of bladder and rectal cancer. [4] Also recent epidemiological studies have also recommended that THMs may have negative acute reproductive effects, as well as spontaneous abortion, birth defects, and stillbirths. [5],[6] The most current toxicological and some epidemiological studies have recommended that the brominated THMs cause the greatest concern. [7] Therefore, new restrictive rules of surface water and the maximum level of total THM (TTHM) in the distribution systems are being imposed by the Safe Drinking Water Act and its amendments (SDWAA).The recommended maximum contaminant level (MCL) of THM is 80 μg/l. [8] Several studies have been carried out in the USA, Canada, EU, UK, Malaysia, Poland, Spain, and Finland to evaluate the distribution and determinants of THMs and HAAs. They reported that the THMs and HAA s levels during the chlorination of drinking water were related to disinfection processes and chemicals, water source, pH, temperature, concentration of chlorine residual, residence time, reaction time, humic and fulvic content, total organic carbon (TOC), and bromide content, and that these factors affected the various THMs and HAAs in different ways providing a potentially different mixture of THMs and HAAs in different regions. Also they found that the THMs concentration will increase with enhanced residual time, bromide, residue chlorine, TOC, and specific by-products in water distribution systems. [9],[10],[11],[12],[13],[14] Most municipal water supply systems in Khuzestan (southwest of Iran) use chlorination for water disinfections because it is extremely efficient and cost effective. As such the formation of THM during chlorination process is important and need to be monitored with the view to ensure the compliance of the guidelines set. However, little is known about the levels of THMs in drinking water in Khuzestan since to our knowledge no data have been published in the scientific literature. The aim of this study was to measure the THM levels in 15 rural water treatment plants in Khuzestan, Iran.

  Materials and Methodes Top

Areas of study

Khuzestan Province is one of the 31 provinces of Iran. It is in the southwest of the country, bordering Iraq's Basra Province and the Persian Gulf. Fifteen rural water treatment plants with the same drinking water source (Karoon River) were selected to measure THM s [Table 1]. Water samples were taken for the analysis of various parameters such as THM s (μg/l) and its four compounds, TOC (μg/l), pH, temperature (˚C), chlorination dose (ppm), free chlorine residue (ppm) in summer and winter of 2009.
Table 1: Characteristics of Khuzestan rural water treatment plants

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Sampling and THM s measurement

Four THM s (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) were analyzed according to Standard Methods (Method number: 5710). [1] The THM samples were collected in 1-L glass (5710 A) bottles sealed with TFE-lined screw caps. As the sample has been chlorinated previously, they were collected with minimum turbulence and the sample bottles were filled completely and sodium thiosulfate solution (10%) was added to the bottles to avoid loss of THMs already present. A rapid and simple method for THM analysis by Purge and Trap coupled with a capillary column gas chromatograph was used to analyze the THM level in Iran mineral processing research center. The characteristics of GC and its operating conditions were shown in [Table 2]. The TOC analyzer (Shimadzu, model V CSH ) was used to analyze the value of TOC. Standard solution of THM species was purchased from Merck company and used without any purification.
Table 2: Characteristics of GC and operating conditions

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  Results Top

To our knowledge, this is the first published study that has measured THM levels in Khuzestan drinking water. A total of 30 samples were collected for the year 2009. The drinking water quality parameters are shown in [Table 3].
Table 3: Water quality parameters in selected Khuzestan rural water treatment plants (2009)

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Pearson's regression analysis was used to examine the correlation of THM with respect to TOC, pH, and chlorine dosage and residue chlorine [Table 4]. Using Pearson's correlation method, a low but definite with small negative relationship (r = -0.247) was obtained between THM formation and TOC for the drinking water treatment plant. A low correlation, definite with moderate relationship, was obtained between THM formation and pH. Also a significant relationship (r = 0.815) was obtained between THM formation and total chlorine dosage in both summer and winter.
Table 4: Relationship between THMs concentration with effective variables

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  Discussion Top

Statistical analyses were performed using analysis of variance (ANOVA) to check the relation between investigated parameters in winter and summer (α = 0.05). The value shows a significant difference between the two seasons. Also the mean value for the total THM s , CHBr 2 Cl, CHBrCl 2 , CHBr 3, and CHCl 3 was observed to be higher in winter compared to summer. However, CHBr 3 was found to be higher in summer compared to winter (P < 0.05). This is due to the water quality at different seasonal conditions and environment. As shown in [Table 3] and [Figure 1], the level of THM s in the number of water treatment plants in Khuzestan was higher than recommended MCL in both summer and winter, but these levels were set with national standards, [15] although high concentration was more significant in winter compared to summer. The THM S results were compared with WHO water quality guidelines using a statistical t-test. According to the result, there was significant difference between total THM s in winter and MCL of THM defined by WHO (P < 0.05), but no significant difference was observed between total THM s in summer and MCL of THM defined by WHO (P > 0.05). It seems it was due to various compounds of organic matter in winter. [3] . [Table 5] was used for compares THM standards in this study with different locales of world.
Figure 1: Average of THMs concentration in various rural water treatment plants in (a) winter and (b) summer

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Table 5: Toxicological information and standards/guideline related to THMs (mg/l) in various locales of the world[15-17]

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Effect of TOC

Most investigators reported that THM formation rises with increasing soluble organic material content in natural water. The rate of THM formation will enhance as a result of TOC consumption and the results fitted to first-order reaction. [18],[ 19] In fact with adequate residue chlorine, the formation of THM will increase by higher available TOC. In comparison to studies previously reported about the positive impact of TOC on THM formation in drinking water, the statistical analysis showed a negative impact of TOC [Table 4]. This result is in accordance with Matamoros et al, who investigated THM formation in wastewater treatment plants in NE Spain. As they reported that while various factors can effect TOC on TTHM formation potential, it is noticeable that the differences in the type and concentrations of the TOC present in drinking water are significant to its formation too. [20]

Effect of pH

According to the findings, the rate of THM construction increases with pH. [21] As Adin et al, reported, [22] pH has two effects: decreasing THM formation as a consequence of low pH and correspondingly increasing THM formation as a consequence of high pH. [22] This is due to the reality that the initial reaction is dependent on HClO concentration, which is associated with pH. The lower the pH, the higher the HClO concentration resulting in alters to higher concentration of humics. The formation of THM chiefly depends on the last step of THM attack, which is the base-catalyst as with the THM reaction. Other investigators also pointed this effect, [23] who reported decreased THM formation as a result of lowering the pH.

Effect of chlorine dosage and residue chlorine

According to the finding of Gallard and Gunten, long-term chlorine demand and the formation of THM have a significant relationship and could be described by second-order kinetics. [24] As Malliarou et al, reported, many investigators confirm the fact that the ratio between total THM and total HAA levels was significantly correlated with temperature, pH, free, and total chlorine. Because of various parameters' influence on the formation of THMs and HAAs, the correlation was commonly moderate to weak. [9]

  Conclusions Top

The level of THM in a number of water treatment plants in Khuzestan is higher than MCL in both summer and winter, although high concentration was more significant in winter compared to summer. Based on the validation results obtained, it would appear that using Pearson's method of correlation, the organic matter measured as TOC showed a negative correlation with the formation of THM. A positive correlation was obtained for pH, temperature, chlorination dose, and free chlorine residue. Due to the fact that very little data about THM are currently available for the drinking water treatment plant in Khuzestan, Iran, this study is extremely useful for people to care more for their water drinking quality.

  Acknowledgment Top

The authors are grateful to Khuzestan rural water and wastewater company for financial support of this project.

  References Top

1.APHA, AWWA, WPCF. Standard methods for examination of water and wastewater. 21 st ed Washington DC, USA: American Public Health Association; 2005.  Back to cited text no. 1
2.Nikolaou AD, Golfinopoulos SK, Arhonditsis GB, Kolovoyiannis V, Lekkas TD. Modeling the formation of chlorination by-products in river waters with different quality. Chemosphere 2004;55:409-20.  Back to cited text no. 2
3.Golfinopoulos SK, Arhonditsis GB. Quantitative assessment of trihalomethane formation using simulations of reaction kinetics. Water Res 2002;36:2856-68.  Back to cited text no. 3
4.Fayad N. Seasonal variations of THMs in Saudi Arabian drinking water. J Am Water Works Assoc 1993;85:46-50.  Back to cited text no. 4
5.Klotz JB, Pyrch LA. A case control study of neural tube defects & drinking water contaminants. New Jersey: Department of Health & Senior Services; 1998.   Back to cited text no. 5
6.Waller K, Swan SH, DeLorenze G, Hopkins B. Trihalomethanes in drinking water& spontaneous abortions. Epidemiology 1998;9:134-40.  Back to cited text no. 6
7.U.S. Environmental Protection Agency. Federal Register, 40 CFR Parts 141 & 142. Tusday, March 31 1998;63:15673-92.  Back to cited text no. 7
8.Salvato JA, Nemerow ML, Agardy FJ. Environmental engineering. 5 th ed. New Jersey: John Wiley & Sons, INC; 2003.  Back to cited text no. 8
9.Malliarou E, Collins C, Graham N, Nieuwenhuijsen MJ. Haloacetic acids in drinking water in the United Kingdom. Water Res 2005;39:2722-30.  Back to cited text no. 9
10.Abdullah MP, Yew CH, Ramli MS. Formation, modeling and validation of trihalomethanes (THM) in Malaysian drinking water: A case study in the districts of Tampin, Negeri Sembilan and Sabak Bernam, Selangor, Malaysia. Water Res 2003;37:4637-44.  Back to cited text no. 10
11.Dojlido J, Zbiec E, Swietlik R. Formation of the haloacetic acids during the ozonation and chlorination of water in Warsaw water works(Poland). Water Res 1999;33:3111-8.  Back to cited text no. 11
12.King WD, Dodds L, Armson A, Allen AC, Fell D, Nimrod C. Exposure assessment in epidemiologic studies of adverse pregnancy outcomes and disinfection byproducts. J Exposure Anal Environ Epidemiol 2004;14:1-7.  Back to cited text no. 12
13.Villanueva CM, Kogevinas M, Grimalt JO. Haloacetic acids and trihalomethanes in finished drinking waters from heterogeneous sources. Water Res 2003;37:953-8.  Back to cited text no. 13
14.Nissinen TK, Miettiene IT, Martikainen PJ, Vartiainen T. Disinfection by-products in Finnish drinking water. Chemosphere 2002;48:9-20.  Back to cited text no. 14
15.U.S.E.P.A. Drinking Water Standards and Health Advisories, 12 th ed. Office of Water U.S. Environmental Protection Agency Washington, DC, EPA 822-S-12-001; 2012.   Back to cited text no. 15
16.WHO. Guidelines for Drinking-water Quality, 4th ed. WHO Library Cataloguing-in-Publication Data, Switzerland; 2011.  Back to cited text no. 16
17.Mazloomi S, Nabizadeh R, Nasseri S, Naddafi K, Nazmara S, Mahvi AH. Efficiency of domestic reverse osmosis (RO) in removal of trihalomethanes (THMs) from drinking water. Iran. J. Environ. Health. Sci. Eng 2009;6:301-306.  Back to cited text no. 17
18.Babcock D, Singer P. Chlorination and coagulation of humic and fulvic acids. J Am Water Works Assoc 1979;71:149-52.  Back to cited text no. 18
19.Trussell AR, Umphries MD. The formation of trihalomethanes. J Am Water Works Assoc 1978;70:604-12.  Back to cited text no. 19
20.Matamoros V, Mujeriego R, Bayona JM. Trihalomethane occurrence in chlorinated reclaimed water at full-scale wastewater treatment plants in NE Spain. Water Res 2007;41:3337-44.  Back to cited text no. 20
21.Steven AA, Slocum CJ, Seeger DR, Robeck GC. Chlorination of organics in drinking water. J Am Water Works Assoc 1976;68:615-20.  Back to cited text no. 21
22.Adin A, Katzhendler J, Alkaslassy D, Rav AC. Trihalomethanes formation in chlorinated drinking water: a kinetic model. Water Res 1991;25:797-805.  Back to cited text no. 22
23.Peters CJ, Young RJ, Perry R. Factors influencing the formation of Haloforms in the chlorination of humic materials. Environ Sci Technol 1980;14:1391-5.  Back to cited text no. 23
24.Gallard H, Gunten UV. Chlorination of natural organic matter: Kinetics of chlorination and of THM formation. Water Res 2002;36:65-74.  Back to cited text no. 24


  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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