Ristoiu Dumitru, von Gunten Urs, Mocan Aurel, Chira Romeo, Siegfried Barbara, Haydee Kovacs Melinda, Vancea Sidonia
Faculty of Environmental Science, University Babes-Bolyai Cluj-Napoca, Cluj-Napoca, Romania.
Environ Sci Pollut Res Int. 2009 Aug;16 Suppl 1:S55-65. doi: 10.1007/s11356-009-0100-1. Epub 2009 Feb 14.
BACKGROUND, AIM AND SCOPE: After the discovery of chloroform in drinking water, an extensive amount of work has been dedicated to the factors influencing the formation of halogenated disinfections by-products (DBPs). The disinfection practice can vary significantly from one country to another. Whereas no disinfectant is added to many water supplies in Switzerland or no disinfectant residual is maintained in the distribution system, high disinfectant doses are applied together with high residual concentrations in the distribution system in other countries such as the USA or some southern European countries and Romania. In the present study, several treatment plants in the Somes river basin in Romania were investigated with regard to chlorine practice and DBP formation (trihalomethanes (THMs)). Laboratory kinetic studies were also performed to investigate whether there is a relationship between raw water dissolved organic matter, residual chlorine, water temperature and THM formation.
Drinking water samples were collected from different sampling points in the water treatment plant (WTP) from Gilau and the corresponding distribution system in Cluj-Napoca and also from Beclean, Dej and Jibou WTPs. The water samples were collected once a month from July 2006 to November 2007 and stored in 40-mL vials closed with Teflon lined screw caps. Water samples were preserved at 4 degrees C until analysis after sodium thiosulfate (Na(2)S(2)O(3)) had been added to quench residual chlorine. All samples were analysed for THMs using headspace GC-ECD between 1 and 7 days after sampling. The sample (10 mL) was filled into 20-mL headspace vials and closed with a Teflon-lined screw cap. Thereafter, the samples were equilibrated in an oven at 60 degrees C for 45 min. The headspace (1 mL) was then injected into the GC (Cyanopropylphenyl Polysiloxane column, 30 m x 53 mm, 3 microm film thickness, Thermo Finnigan, USA). The MDLs for THMs were determined from the standard deviation of eight standards at 1 microg/L. The MDLs for CHCl(3), CHBrCl(2), CHBr(2)Cl and CHBr(3) were 0.3, 0.2, 0.3 and 0.6 microg/L, respectively. All kinetic laboratory studies were carried out only with water from the WTP Gilau. The experiments were conducted under two conditions: baseline conditions (pH 7, 21 degrees C, 2.5 mg/L Cl(2)) to gain information about the change of the organic matter in the raw water and seasonally variable conditions to simulate the actual process at the treatment plant and the distribution system.
This study shows that the current chlorination practice in the investigated plants complies with the THM drinking water standards of the EU. The THM concentrations in all samples taken in the four treatment plants and distributions systems were below the EU drinking water standard for TTHMs of 100 microg/L. Due to the low bromide levels in the raw waters, the main THM formed in the investigated plants is chloroform. It could also be seen that the THM levels were typically lower in water supplies with groundwater as their water resource. In one plant (Dej) with a pre-ozonation step, a significantly lower (50%) THM formation during post-chlorination was observed. Laboratory chlorination experiments revealed a good correlation between chloroform formation and the consumed chlorine dose. Also, these experiments allowed a semi-quantative prediction of the chloroform formation in the distribution system of Cluj-Napoca.
CHCl(3) was the most important trihalomethane species observed after the chlorination of water in all of the sampled months. However, TTHM concentrations did not exceed the maximum permissible value of 100 microg/L (EU). The THM formation rates in the distribution system of Cluj-Napoca have a high seasonal variability. Kinetic laboratory experiments could be used to predict chloroform formation in the Cluj-Napoca distribution system. Furthermore, an empirical model allowed an estimation of the chloroform formation in the Gilau water treatment plant.
背景、目的与范围：在饮用水中发现氯仿后，大量工作致力于研究影响卤代消毒副产物（DBPs）形成的因素。不同国家的消毒实践差异显著。在瑞士，许多供水系统不添加消毒剂，或在配水系统中不维持消毒剂残留；而在美国、一些南欧国家和罗马尼亚等其他国家，配水系统中会使用高剂量消毒剂并保持高残留浓度。在本研究中，对罗马尼亚索梅什河流域的多个处理厂的加氯实践和DBP形成情况（三卤甲烷（THMs））进行了调查。还开展了实验室动力学研究，以探究原水溶解有机物、余氯、水温与THM形成之间是否存在关联。
从吉劳的水处理厂（WTP）不同采样点、克卢日 - 纳波卡的相应配水系统以及贝克莱恩、德日和日博WTP采集饮用水样本。从2006年7月至2007年11月，每月采集一次水样，并储存在用衬有聚四氟乙烯的螺帽封闭的40毫升小瓶中。加入硫代硫酸钠（Na₂S₂O₃）淬灭余氯后，水样在4℃保存直至分析。所有样品在采样后1至7天内使用顶空气相色谱 - 电子捕获检测器（GC - ECD）分析THMs。将10毫升样品装入20毫升顶空瓶中，并用衬有聚四氟乙烯的螺帽封闭。此后，样品在60℃的烘箱中平衡45分钟。然后将1毫升顶空气体注入气相色谱仪（美国热电菲尼根公司的氰丙基苯基聚硅氧烷柱，30米×53毫米，3微米膜厚）。通过1微克/升的八个标准品的标准偏差确定THMs的方法检出限（MDLs）。CHCl₃、CHBrCl₂、CHBr₂Cl和CHBr₃的MDLs分别为0.3、0.2、0.3和0.6微克/升。所有动力学实验室研究仅使用来自吉劳WTP的水进行。实验在两种条件下进行：基线条件（pH 7、21℃、2.5毫克/升Cl₂）以获取原水中有机物变化的信息，以及季节性可变条件以模拟处理厂和配水系统的实际过程。
本研究表明，被调查工厂当前的氯化实践符合欧盟的THM饮用水标准。四个处理厂及配水系统采集的所有样品中的THM浓度均低于欧盟饮用水中总三卤甲烷（TTHMs）100微克/升的标准。由于原水中溴化物含量低，被调查工厂中形成的主要THM是氯仿。还可以看出，以地下水为水源的供水系统中THM水平通常较低。在一个有预臭氧化步骤的工厂（德日），后氯化过程中THM形成量显著降低（50%）。实验室氯化实验表明氯仿形成与消耗的氯剂量之间具有良好相关性。此外，这些实验允许对克卢日 - 纳波卡配水系统中的氯仿形成进行半定量预测。
在所有采样月份中，水氯化后观察到CHCl₃是最重要的三卤甲烷种类。然而，TTHM浓度未超过欧盟规定的100微克/升的最大允许值。克卢日 - 纳波卡配水系统中THM的形成速率具有很高的季节性变化。实验室动力学实验可用于预测克卢日 - 纳波卡配水系统中的氯仿形成。此外，一个经验模型可用于估算吉劳水处理厂中的氯仿形成。
