جستجوی مقالات مرتبط با کلیدواژه "تری هالومتان" در نشریات گروه "پزشکی"

Drinking water disinfection is an essential process for elimination of the microbial contaminations. Water disinfection by chlorine compounds can lead to formation of Trihalomethanes (THMs) as a disinfection by-products and carcinogenic effects. The aim of the study was investigation of potential risks assessment of THMs occurrence in drinking water in selected military centers in Tehran province.

This cross-sectional and descriptive study conducted in 2020. Thirty samples were collected from urban and groundwater sources. Free residual chlorine, temperature, pH and THMs of the samples were measured by conventional methods in which GC Mass measured THMs concentration. The hazard potential of THMs was calculated based on THQ, TR and PTDI indexes.

The average concentration of THMs in groundwater and urban water was 2.25 µg/L and 2.39 µg/L respectively. The THMs concentration had positive but non-significant correlation with free residual chlorine, temperature and pH. Provisional tolerable daily intake of groundwater and urban water was 0.10×10-3 and 0.11×10-3 mg/kg.day, respectively. The target hazard quotient for all selected centers was 0.001 and the target cancer risk for groundwater and urban water was 0.32×10-8and 0.34×10-8, respectively.

The results revealed that in selected centers, drinking water had not health risks from point of THMs concentration.

Among disinfection by products, trihalomethanes (THMs) are known as the main carcinogen compounds that it’s the major precursor is humic compounds. The aim of this study was to investigate the removal of humic compounds using Al and Fe compounds from Shahrchay river water.in Urmia city.
This study was done experimental. Experiments perform in jar test batch reactor in different values of pH, Al and Fe. Also THMs was measured under optimal removal conditions
The optimal dosages of ferric chloride, alum and PACl for removal of humic compound obtained, 10, 30 and 20 mg/L, respectively. The highest removal efficiency was related ferric chloride with 89 %, and removal efficiency for PACl and alum were 88% and 81%. But SUVA (specific ultraviolet absorbance) index decreased less than USEPA permissible limits (less than L/mg m 2) only with ferric chloride.
Ferric chloride can be used for removal of humic acid in water of Urmia Shaharchi river to decreased SUVA index in permission ranges. But the use of aluminum salts may lead to THM formation. Chlorinated treated water with Ferric chloride, approved reduction of the amount of trihalomethanes to USEPA permissible limits (ppb

Humic acid is a major agent in trihalomethanes (THMs) formation during chlorination process, which are known as carcinogens. The aim of this study were to investigate the removal of humic acid by three coagulants including PACl, alum and ferric chloride from water sources and their effect on zeta potencial.
This study was conducted experimentally in lab scale. Experiments were carried out in a batch reactor using a synthetic solution with humic acid concentration of 10 mg/l, pH 5, 7 and 9, and the coagulant dosages of 10, 20 and 30 mg/l (ferric chloride, alum and PACl, respectively). Also zeta potential and THMs formation reduction were evaluated under optimal condition for humic acid removal.
The results showed that under optimal dosages of the coagulants the highest removal efficiency was related to the ferric chloride with 89 %. Removal efficiency for PACl and alum were 88% and 81%, respectively. However, only the application of ferric chloride decreased the SUVA index down to the USEPA permissible limits (less than 2 L/mg m). Also in optimal condition pH, zeta potential and trihalomethanes values were gained more than 7, -15 mV and less than 50 ppb.
Ferric chloride can be used for treatment of water containing humic acid to decrease SUVA index down to the permission ranges. But the use of aluminum salts as coagulants may lead to THMs formation. Chlorinated water treated with Ferric chloride results in notable reduction in the amount of trihalomethanes (ppb

Organic matters enter to drinking water from a variety of sources, but one of the major sources of these compounds in aqueous solution can be decomposed plant and microbial residues. Chlorination is the most common method for water disinfection, the free chlorine in the water reacts with natural organic compounds and form disinfection byproducts. One of the dangerous byproducts is Trihalomethanes (THMs). These compounds are suspected to be carcinogenic for humans. In this study, 96 samples were taken from 4 points (Mianb Steghlal dam, output Minab water treatment plant, input and output of water treatment plant in Bandar Abbas) within 6 months. Parameters such as TOC, pH, temperature and chlorine residual were measured and used for prediction of THM formation by a methematical model. Results showed that Bandar Abbas drinking water has high TOC and THM formation potential is high. Minimum and maximum of THM was measured 14.78 and 84.86µg/l, respectively. Positive correlation was seen between concentrations of organic carbon and pH with THM formation. Increasing pH and TOC concentration in water, leads to increase of THM formation potential. Bandar Abbas drinking water has high potential to form THM, therefore, it is necessary to consider measures in this field.

Trihalomethanes (THMs) are major group of chlorinated by products, potentially hazardous and carcinogenicity of these compounds was recognized. The purpose of this study was survey on THMs concentration in Ahvaz drinking water. A descriptive cross-sectional study was based on 36-week sampling program during the winter, spring and summer of 2011 in water distribution network of the No. 1 and No. 2 water treatment plants (WTP1 and WTP2) in Ahvaz city was conducted. Sampling in the distribution networks was taken from finished water and three points of distribution networks. THM species analyses carried out by gas chromatograph system (GC/µECD) with head space technique. SPSS software was used for data analysis. One-way ANOVA test was used for THMs average comparison between seasons and sampling point and T-test was used for comparison between two distribution networks. In this study, the total THMs determined in winter, spring and summer ranged from 20.5-86µg/L, 18.92-66.06µg/L and 17.35-174.75µg/L respectively. According to this study, only in 6 samples the total THMs concentration exceed the U.S.EPA MCL (80 µg/L) and only in 3 samples exceed from the Iran standard and WHO guideline (∑THM/WHO guideline≤1). Average values of the total THMs in summer were 1.4 and 1.6 times higher than winter and spring respectively. Furthermore, brominated THMs were dominant species.

Trihalomethanes in the form of chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform.are a group of compounds that can form when the chlorine used to disinfect drinking water reacts with naturally occurring organic matter. Potential hazards and carcinogenic characteristics of THMs have already been recognized. Therefore, current study attempted to measure concentration of these compounds in output (drinking water) of Jlalieh water treatment plant. In this study concentrations of trihalomethanes with chloroform index have been measured in the output of Jalalieh water treatment plant in 2009. Monthly water sampling carried out in morning. Samples were taken to the lab and sodium thiosulfate was used for de-chlorination of the water samples. Samples were analyzed in a time span of less than 6 hours using a GC set. The average concentration of chloroform in input crude water of Jalalieh water treatment plant was equal to 7.42 µg/l. The average pH value in input and output of water treatment plant was equal to 7.92, and 7.87, respectively. The average concentration of chlorine in input and output of water treatment plant was equal to 0.73 mg/l, and 0.94 mg/l, respectively. Although concentration of free chlorine was 0.94 mg/l in output treated water, however, the chloroform concentration in output treated water was lower than the permissible value (200 µg/l) recommended by WHO for drinking water. The highest concentration of THMs was found in April.

Yazd province is located in the central desert part of Iran in which water scarcity was one of the most important problems. This has been recently solved to some extent, due to the approved channel project of water transferring from Isfahan to Yazd. Chlorination is usually used in the last stage of water treatment for disinfection in the networks, treatment plants, storages and channel stations. The possibility of carcinogen lateral composites formation is expected by tri-halo-methanes (THMs) due to the reactions occurs between the natural organic materials and free chlorine available in water. Based on the established standard by the country, the permissible limit of THMs in water is 200 mg/L. In this research, in addition to the amount of THMs and their distribution in Yazd water transferring channel and the city water network system, the important parameters and their correlations with THMs formation were discussed.

In a year of sampling period, the concentrations of THMs including the four major components of chloroform, bromoform, bromo di-chloro methane and di-bromo chloro methane during all seasons were measured using gas chromatograph and analyzed. This was done for 11 stations including Zayande-rood Basin River and Isfahan water treatment plant up to Yazd Shehneh storage, stations and inline equalization tanks and also five regions of Yazd city network.

According to the results, the maximum rate of THMs (51.14 mg/L) during the sampling period in summer for Yazd city network and in ancient context of Jamea Mosque district was found. In addition, the minimum concentration of THMs was 1.60 mg/L in winter for the domestic network of the city which was related to Azad Shahr district. The Average total amount of THMs during sampling periods in all stations was 12.26 mg/L.

SPSS and Excel softwares were used to analyze the research data in the descriptive and inferential manner. Both statistical methods (Simple correlation coefficient, Pearson and Spearman correlation test)) with 5% significant level were considered for data analysis. The results indicated that no significant difference existed between these parameters and national and international standard scales. These rates were generally desirable and lower than standard limit which indicates acceptable operation in the treatment system and storages in the channel line of Isfahan to Yazd. Furthermore, it was obtained that there is a correlation between THMs rates and effective parameters in producing confidential values such as 95%and 99%for the residue chlorine and heat respectively. Finally the distribution and diffusion plan of THMs in transferring line and civic network of Yazd were drawn.