Academic literature on the topic 'Dichlorobromomethane'

The liquid Bacillus subtilis/microsome rec-assay method was applied to twenty chlorinated chemicals and fourteen aldehydes which may occur in chlorinated and ozonated waters. The results showed that substances could be classified into four categories: strongly DNA damaging, DNA damaging, not DNA damaging, and reverse. A new indicator, ‘rec-gram', was introduced to evaluate quantitatively the DNA damaging potential of substances. Bromoform, chloroform, dibromo-chloromethane, dichlorobromomethane, carbontetrachloride, tetrachloroethylene, and six other chlorinated chemicals showed direct or indirect DNA damaging potential. Heptachlor, trans-chlordane, p,p'-DDT, and three other chemicals showed the reverse effect with or without S9 activation. Trichloroethylene and pentachlorophenol showed neither DNA damaging potential nor the reverse effect. Acetaldehyde, benzaldehyde, formaldehyde, glyoxal, acrolein, acetylacetone, isophorone, and 3-methyl-2-butanone showed direct or indirect DNA damaging potential. Propionaldehyde, furfurol, and two other aldehydes showed the reverse effect with or without S9 activation. Carvone and n-valeraldehyde showed neither DNA damaging potential nor the reverse effect. On the rec-gram scale, hexachlorocyclopentadiene and hexachloropentadiene showed the strongest DNA damaging potential of the test substances. Seven chlorinated chemicals and aldehydes showed DNA damaging potential although they had been shown to be not mutagenic with the Ames system.

In this study, the changes in UV absorbance of water samples were characterized using defined differential UV spectroscopy (DUV), a novel spectroscopic technique. Chlorination experiments were conducted with water samples from Terkos Lake (TL) and Büyükçekmece Lake (BL) (Istanbul, Turkey). The maximum loss of UV absorbance for chlorinated TL and BL raw water samples was observed at a wavelength of 272 nm. Interestingly, differential absorbance at 272 nm (ΔUV272) was shown to be a good indicator of UV absorbing chromophores and the formation of trihalomethanes (THMs) resulting from chlorination. Furthermore, differential spectra of chlorinated TL waters were similar for given chlorination conditions, peaking at 272 nm. The correlations between THMs andΔUV272were quantified by linear equations withR2values >0.96. The concentration of THMs formed when natural organic matter is chlorinated increases with increasing time and pH levels. Among all THMs, CHCl3was the dominant species forming as a result of the chlorination of TL and BL raw water samples. The highest chloroform (CHCl3), dichlorobromomethane (CHCl2Br), and dibromochloromethane (CHBr2Cl) concentration were released per unit loss of absorbance at 272 nm at pH 9 with a maximum reaction time of 168 hours and Cl2/dissolved organic carbon ratio of 3.2.

Introduction. The problem of providing the population with drinking water with guaranteed quality, safety, and physiological usefulness is highly relevant for many regions of Russia. The use of chlorination for disinfection of the water is a potential cause of the formation of excess concentrations of organochlorine compounds in it, including trihalogenomethanes, which leads to elevated levels of carcinogenic risk. The study’s object was: data on the content in water of centralized water supply systems of carcinogenic organochlorine compounds - chloroform, dichlorobromomethane and chlorodibromomethane. Material and methods. information on the incidence of the population of malignant neoplasms; the results of an experiment to evaluate the effectiveness of the preliminary ammonization method. The paper used methods of health risk assessment, variation statistics, and mathematical modeling. Results. The use of preliminary ammonization in Taganrog prevents the formation of trihalogenomethanes and ensures the maintenance of an individual multi-route carcinogenic risk at an acceptable level (9.933 · 10-6). Systematic unreasonable hyper chlorination of river water without prior ammoniation is the main reason for the excess content of chlororganic compounds and the high level of individual carcinogenic risk in the Primorsky rural settlement of the Neklinovsky District - up to 3.234 · 10-3 in 2015. Modeling on the basis of experimental chlorination of natural water indicates the high efficiency of preliminary ammonization in the disinfection mode, which ensures the content of free total active chlorine in tap water in the range from 0.8 to 1.2 mg/l. Conclusion. The high efficiency of the application of preliminary ammonization of natural water to prevent the formation of trihalogenomethanes and reduce carcinogenic risk has been confirmed. The priority factor for the formation of excess amounts of organochlorine compounds in drinking water is its hyper chlorination. Promising measures to reduce the carcinogenic risk of trihalogenomethanes in tap water include the systematic monitoring of their content, the use of preliminary ammonization, the exact dosage of chlorine, the deep purification of the source water before chlorination, the replacement of primary chlorination with ultraviolet disinfection, and others.

Chlorine was accepted as an effective disinfectant for drinking water in early 1900s. Because of chlorination, chlorine has dramatically reduced the incidence of waterborne diseases. An unwanted side effect is the formation of harmful by-products upon chlorination. The most significant group of disinfection by-products formed during chlorination is the trihalomethanes (THMs). In this reason, European Union initiated the maximum contaminant level (MCL) of total concentration of THMs to 100 μg L-1. Because of this regulation, operational parameters of the WTP and raw water quality characteristics need to be studied in depth in order for THMs to be minimised. Statistical analysis is necessary for this purpose employing the parametric two-way ANOVA for the concentrations of chloroform (CHCl3) and dichlorobromomethane (CHCl2Br) and the analysis of variance on data ranks of chlorodibromomethane (CHClBr2) concentration. Chlorine dose, postchlorination, bromide levels, reaction temperature, reaction duration and dissolved organic carbon levels as well as pH of raw water, are the factors that affect the rate of THMs formation and the total THMs yield. Athens Water Supply and Sewerage Company (EYDAP SA), as the water supplier of a city with 3.5 million inhabitants, makes continuous attempts to improve water quality.

Disinfection is an essential process in the treatment of municipal wastewater before the treated wastewater can be discharged to the environment. Hillsborough County's Northwest Regional Water Reclamation Facility (NWRWRF) in Tampa, Florida, currently uses ultraviolet (UV) light for disinfection. However, this method has proven expensive to implement and maintain, and may not be effective if the light transmission is poor. For these reasons, Hillsborough County is considering switching from UV light to sodium hypochlorite for disinfection. However, hypochlorite (chlorine) disinfection has disadvantages as well, such as the production of disinfection by-products (DBPs) such as trihalomethanes (THM) and haloacetic acids (HAAs), which may have adverse impacts on the quality of surface waters that receive the treated wastewater. Therefore, the objectives of this research are (1) to compare NWRWRF typical operating conditions and water quality to those of two nearby facilities (River Oaks and Dale Mabry Advanced Wastewater Treatment Plants) that currently employ chlorine disinfection, (2) to determine the chlorine demand of treated effluent from NWRWRF, (3) to quantify the DBP formation potential of treated effluent from NWRWRF, and (4) to determine the effects of temperature, reaction time, and chlorine dose on chlorine demand and THM formation. To inform laboratory experiments, the quality of final effluent was monitored at NWRWRF and at two nearby wastewater treatment plants that currently use hypochlorite for disinfection. At these two facilities, pH of 7.0-8.0, chemical oxygen demand (COD) of 12-26 mg/L, alkalinity of 200-250 mg/L as CaCO3, chlorine residual of 1.5-6.0 mg/L, and total trihalomethanes of 100-190 ix μg/L (mostly chloroform) were observed. Conditions at NWRWRF were similar to those at Dale Mabry and River Oaks AWWTP, suggesting that chlorine demand and THM formation at NWRWRF would be similar to those at the two AWWTP, if chlorination is to be used. THM experimental results agreed with this suggestion. Chlorine dose and temperature effects on the free chlorine residual and THMs production in NWRWRF filtered wastewater effluent were determined. Filtered effluent was collected and transported to USF laboratory where it was tested for 3 different chlorine doses (6 mg/L, 9 mg/L and 12 mg/L as Cl2) and 3 different temperatures (16°C, 23°C, and 30°C) at 7 different contact times (15, 30, 45, 60, 75, 90, and 120 min) in duplicate. The total number of batches prepared was: 3 different chlorine doses × 3 different temperatures × 7 different reaction times = 126 reactors. According to Florida Administrative code 62-600.440, total chlorine residual should be at least 1 mg/L after a contact time of at least 15 min at peak hourly flow. Also, according to Florida Administrative code 62-600.440, if effluent wastewater has a concentration of fecal coliforms greater than 10,000 per 100 mL before disinfection, FDEP requires that the product of the chlorine concentration C (in mg/L as Cl2) and the contact time t (in minutes) be at least 120. Results showed that free chlorine residual was always above 1 mg/L in 15 min contact time for all chlorine doses and temperatures tested in this thesis. However, to be conservative, thesis conclusions and recommendations were based on the more stringent regulation: C*t ≥ 120 mg.min/L, assuming that the number of fecal coliform in NWRWRF wastewater effluent exceeds 10,000 per 100 mL prior to disinfection. The analysis showed that free chlorine residual for 6 mg/L was below the FDEP standard at all temperatures. At 16 °C and 23 °C, chlorine doses of 9 and 12 mg/L resulted in an appropriate free chlorine residual above the FDEP standard. However, a chlorine dose of 12 mg/L was resulting in high residual, which means high THM would be expected. Therefore, at 16 x and 23°C, 9 mg/L would be preferable. At 30 °C, only the chlorine dose of 12 mg/L met the standard at all contact times. As expected, free chlorine residual decreased with an increase in temperature from 23°C to 30°C. Surprisingly, the residual at 16°C was lower than residual at 23°C. The production of THMs increased with higher contact time in all the experiments completed. Chlorine dose didn't have an effect on THM formation at 23°C, but it did at 30°C and 16°C, where THM concentrations were generally higher with the increase of chlorine dose. Temperature effect was noticed in most of the experiments, where THM production was usually higher at higher temperatures, except some cases where formation was similar for different temperatures. Chloroform, dichlorobromomethane, dibromochloromethane production ranges were respectively: 20-127 μg/L, 18-59 μg/L, and 3-7 μg/L. Bromoform concentrations were not observed in this experiment at any temperature or chlorine dose. According to Florida Administrative code 62-302.530, Criteria for Surface Water Quality Classifications, the Florida Department for Environmental Protection (FDEP) set the following limits for THM concentrations in wastewater effluent to be as the following; 470 μg/L for chloroform, 22 μg/L for dichlorobromomethane, 34 μg/L for dibromochloromethane, and 360 μg/L for bromoform. Experimental results on NWRWRF filtered effluent showed that only dichlorobromomethane exceeded the limits set by FDEP at about 30 min contact time for all temperatures and chlorine doses tested. However, according to Florida Administrative code 62- 302-400, proposed changes to the code have set higher DCBM limit of 57 μg/L. Chlorination would be recommended at NWRWRF if the DCBM regulated limit increases to 57 μg/L. The recommended chlorine dose would be 9 mg/L for water temperatures around 16-23 °C and 12 mg/L for water temperatures around 30 °C