A new approach to evaluating the toxicity and genotoxicity of disinfected drinking water

The aim of this study was to evaluate the formation of toxic and genotoxic compounds in surface drinking waters treated with two widely used disinfectants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO(2)), and a new disinfectant, peracetic acid (PAA). For this purpose a pilot plant was set up to add these biocides continuously to pre-filtered lake water flowing into three different basins. During three seasonal experiments, short-term in vivo tests (with plant, fish and molluscs) and in vitro tests (with bacteria, yeast and human cells) were carried out to evaluate the formation of genotoxic disinfection by-products (DBPs). Gas chromatography/mass spectrometry (GC/MS) was used to identify DBPs produced during the different treatments, microbiological analyses were performed to test the biocidal activity of the disinfectants, and chemical analyses were carried out to evaluate the quality of the water. The pilot drinking water plant under study was useful in studying the toxicity and genotoxicity of disinfected drinking water with this combined chemical/biotoxicological approach. This paper describes the setting up of the pilot plant and sets out/reports the results of the microbiological and chemical analyses.     

一种评定高性能混凝土养护效果的新方法

本文提出了一种改进的表面吸水率试验用于评估混凝土的养护效果。养护的充分与否通过混凝土试件不同深度处的孔结构的差异来判定的方法。研究中利用高性能混凝土的自养护来对此方法的可行性进行了试验验证。试验结果表明：利用此方法测试的孔结构参数受养护条件的显著影响；养护措施不好的情况下，不同深度处混凝土试件的吸水率与孔结构参数差异显著；本方法操作简单、快捷，可以用来评价混凝土的养护效果。尤其适用于高性能混凝土。     

A new method for evaluating sulfur dioxide tolerance of certain trees

The paper proposes a new method for evaluating the tolerance of trees to SO₂ pollution stress, and grouping plants as indicators and controllers by tolerance index values. The index is calculated by a new arithmetic formula. The developed model is useful in identifying tolerant and susceptible plants to SO₂.     

A simple, inexpensive in situ method for assessing acute toxicity of effluents to fish

Test chambers for conducting in situ fish bioassays were constructed from 81. polyethylene bottles. Yearling fathead minnows (Pimephales promelas) and young-of-the-year bluegill (Lepomis macrochirus) demonstrated greater than 50% survival in the chambers after 65 days of exposure in a reservoir, river and creek. Fathead minnow survival was substantially greater than that of bluegils. The chambers provide a simple, inexpensive, sensitive technique to screen effluents for toxicity.     

A new and simple method for recuperation of enteroviruses from water

A new and simple method for recuperation of enteroviruses from water is described here. The sample to be analyzed, with a volume arbitrarily fixed to 101, is adjusted to pH = 3.5 with hydrochloric acid. It is then injected under low pressure (0.15 bar) by the lower end of a column containing glass powder (50 g). The calibration of the water's upward speed enables the glass powder to remain in dynamic suspension. Under these conditions, poliovirus is quantitatively adsorbed on the glass powder. The virus is then eluted from the glass powder with 50 ml of a glycine buffer (pH = 11.5) and thus concentrated 200 times in the final eluate. The total duration of operation does not exceed 2 h 30 mn. The recuperation efficiency is about 40–60% and does not depend on initial virus concentration in sample, and this, for virus concentrations ranging from 1 to 10⁴PFU/1.     

A method of calculating the pesticide partition between sediment and water for environmental systems

Pesticide values were calculated for natural systems in which the pesticides were partitioned between sediments and water. Two equations were evaluated that correlate the variables, surface area, pesticide concentration on the sediment and pesticide concentration in the water. The first, a linear equation, proved sufficiently accurate to calculate 45 or 48 data points to within one order of magnitude of the observed values. The second, a 7th degree polynominal was used on the same data set and resulted in a calculation of 46 of 48 values within one order of magnitude. Comparisons as to percent accuracy within the order of magnitude agreement revealed the linear equation was capable of reproducing the observed values to within 10 percent for 39 percent of the data set tested, and the 7th degree polynominal was capable of achieving this accuracy for 52 percent of the same data set. The correlation of surface area with pesticide partitioning illustrates the use of a readily measurable parameter (surface area) and pesticide concentration in the sediment to allow calculation of a non-measurable parameter (pesticide concentration in water). The utility of this work is an approximate calculation of pesticides in water at concentration ranges below the measurable limits of present day analytical equipment.     

水质安全在线生物预警技术及研究进展

采用在线生物监测技术可以实现水体突发性污染事故的安全预警,并可根据受试生物的生物学指标变化对水体内多种污染物的综合毒性进行监测.水质安全在线生物预警技术通过低压电信号采集受试水生生物的行为生态学变化,并通过信号分析系统和设定的行为变化阈值,对水质状况进行分析.根据设定的预警方式,可以实现水质变化定性和半定量预警.     

A bioassay application for quantitative toxicity measurements, using the green algae Selenastrum capricornutum

This method, for use in the laboratory, requires a sample of only one litre, and is based on the measurement of growth inhibition of the unicellular alga Selenastrum capricornutum Printz. The assay involves making several dilutions in triplicate, enriching them with a known quantity of nutrients, and then introducing algae and incubating them until they reach the maximum standing crop. The resulting biomass is then compared with the theoretical biomass for each concentration, and the observed percentages of growth inhibition are plotted on “log-probit” graph paper to obtain the straight line of toxicity and from that the value of IC 50 (the concentration which inhibits algae growth by 50%); this value enables us to obtain an absolute measure of toxicity, expressed as a number of toxic units.     

Comparison of the toxicity thresholds of water pollutants to bacteria, algae, and protozoa in the cell multiplication inhibition test

Using analogous methods of the cell multiplication inhibition test, the toxicity threshold (TT) of 156 potential water pollutants was determined for model organisms of biological self-purification, i.e. bacteria of the species Pseudomonas putida, green algae of the species Scenedesmus quadricauda, and flagellate protozoa of the species Entosiphon sulcatum. From the number of 156 inorganic and organic pollutants tested, 23 exhibited a pronounced selective toxic action on bacteria of the species Pseudomonas putida, 47 on algae of the species Scenedesmus quadricauda, and 43 on flagellate protozoa of the species Entosiphon sulcatum. It is seen from the ratios found that a determination of the toxicity threshold of potential water pollutants for these three model organisms from the microbiological spectrum would provide a broader basis for assessing the damaging action of water pollutants to model organisms active in the biological self-purification of water. Ecotoxicological testing of potential water pollutants to evaluate their toxicity involving only one model organism of biological self-purification would give an incomplete and biased picture of the effects of pollutants.     

A sensitive seminested PCR method for the detection of Shigella in spiked environmental water samples

A rapid seminested polymerase chain reaction (PCR) method for the specific, sensitive detection of virulent Shigella spp. in spiked environmental water samples was developed. A set of primers specific for the invasion plasmid antigen gene (ipaH) of virulent Shigella spp. and enteroinvasive Escherichia coli produced a 620-bp fragment that was used as template for the seminested primer pair delineating a 401-bp fragment. By using agarose gel electrophoresis for detection of the seminested PCR-amplified products, a detection limit of 1.6 x 10(3) cfu S. flexneri was obtained with amplification reactions from crude bacterial lysates. The PCR procedure coupled with an enrichment culture incubated for 6 h detected as few as 1.6 S. flexneri organisms in pure culture. Treated sewage, ground, surface and drinking water samples collected from various sources were seeded with S. flexneri and incubated in GN broth for 6 h before detection by seminested PCR. A detection limit lower than 14 cfu/ml was achieved in some water samples. The results indicate that the described seminested PCR has the advantage of a rapid turnaround time and it fulfills the requirements of sensitivity and specificity for use in an environmental laboratory.     

Apparatus for control of poison concentration in toxicity studies with fish

In order to facilitate accurate maintenance of defined experimental conditions in studying the effects of water pollutants on fish, automatic apparatus is frequently used.

The equipment described here provides an automatic delivery of poison solutions to 14 aquaria; single poisons can be added at constant concentrations or poisons can be mixed or delivered in fluctuating or alternating concentrations.     

水质在线安全生物预警系统模拟预警及应用

水质安全在线生物预警系统可以实现水体突发性污染事故安全预警,根据受试生物生物学指标变化对水体内多种污染物的综合毒性进行监测。模拟预警结果表明,水质安全在线生物预警技术通过低压电信号采集日本青鳉的行为变化,并通过信号分析系统,结合行为变化阈值的设定,对水质状况进行综合分析,实现对污染水体的水质变化报警。     

一种节能节水的高层建筑中水供给新方案

介绍了一种针对高层中水供给的新方案,从该方案的设计思路出发,详细说明了该设计方案的工作流程和原理,给出了分层计算和成本估算,论证了该方案的可行性;最后总结了该设计方案在节能节水、降低对水泵要求等方面的特点,指出了该方案在中水供应设计中的应用前景。     

饮用水常规工艺处理高藻原水的应对措施

在以引滦水为原水的饮用水常规处理工艺中,针对高藻原水采取了生物控制、预氯化、强化混凝、对过滤单元进行适当调整等几项措施。两年多的实际生产运行表明,这几项措施有效控制了高藻原水对生产工艺的影响,显著降低了藻类数量,使出水浊度保持在较低范围内（〈0．3NTU）,保证了良好的出厂水水质。     

钢筋混凝土连梁震后安全性鉴定新方法试验研究

以钢筋混凝土剪力墙结构为研究对象,通过对4片连梁的低周往复加载试验,记录了每级控制位移下的损伤现象,并计算了对应的损伤指数,建立了构件典型损伤现象和损伤指数的对应关系,从而对钢筋混凝土剪力墙结构进行损伤鉴定。     

A review of catchment management in the new context of drinking water safety plans

By managing a catchment effectively, the range and amount of contaminants entering waters used for public water supply can be reduced, with resultant benefits for both water companies and consumers. Consequently, catchment management is increasingly being recognised as being at the heart of the water environment. An overview of current and previous catchment management initiatives is given, along with the European Landscape Convention, which could be used as a vehicle for the implementation of a national catchment management strategy. The adoption of the drinking water safety plan approach is strongly advocated by the World Health Organisation, and effective catchment management underpins this approach. Effective management of our catchments will also make a significant contribution to meeting our obligations under the Water Framework Directive, by helping to address the serious issue of diffuse pollution from agriculture.     

A method for evaluating the mechanical performance of thin-walled titanium tubes

A method which was developed to compare the stress–strain properties of three types of thin-walled, commercially pure titanium tubes is presented. The tubes were of types intended for use in large heat-exchanger applications and were to be subjected to significant plastic deformation during subsequent assembly processes. It had been anticipated that small differences in chemical composition and tube-drawing treatment would produce quite different characteristics. It is known that the properties of titanium can exhibit considerable degrees of anisotropy, especially for wrought products; although axial properties of the materials could be evaluated using standard test equipment and procedures, a novel testing system had to be designed to allow the circumferential properties to be assessed. Significant differences between tube types were observed and anisotropic material behaviour was apparent.     

基于安全系数的隧道二次衬砌支护设计新方法

通过Phase2软件,对圆形隧道开挖过程中围岩的变形和衬砌结构内力进行了分析,确定了满足收敛约束法原理的二衬支护时机和满足安全系数为1.4的支护方案,并给出了其具体的应用步骤,该分析方法为定量设计和改进隧道二衬支护方案提供了新思路。     

Chronic toxicity of the Sava River (SE Europe) sediments and river water to the algae Pseudokirchneriella subcapitata

The Sava River, the largest and most commercially valuable water body in the riparian countries, receives inputs of organic and inorganic compounds from a variety of domestic and industrial activities that may affect the health of human beings and wildlife. In this work, the chronic toxicity of sediment, sediment porewater and surface water from the Sava River and connecting tributaries to the freshwater algae Pseudokirchneriella subcapitata was assessed to characterise the potential impact on aquatic organisms. Samples of different environmental matrices were either tested directly (porewater) or subjected to pre-concentration (sediments and surface water) prior to testing in a 72 h growth inhibition assay using P. subcapitata. The results show that a combination of pre-concentration and bioassay testing was able to characterise the toxic potential and to identify several compartment-specific "hot spots" along the Sava River. Based on the resulting data, a crude risk assessment identified that some of the locations may represent a risk to algae. Additional testing using multiple species and exposure phases is required to conduct a thorough risk assessment, however.     

A toxicity testing system for exposing small invertebrates and fish to short square-wave concentrations of chlorine

We describe a flow-through toxicity testing system which can be manipulated to deliver a “square-wave” chlorine concentration curve for short exposure times to small invertebrates and fish. The system consists of a series of test containers, each with dual input delivery lines (dilution water alone or toxicant plus dilution water), a syringe pump for addition of toxicant to one of the two delivery lines, a constant head tank, and reservoir tanks. Control of valves on the delivery lines and on the test chamber drains caused chlorine concentration to rise to the target value in 1 min and to fall below detection limits (0.01 mg 1⁻¹) in 2 min at the beginning and end of the exposure period, respectively. Using this system, we determined the toxicity of 30- and 60-min exposures of total residual chlorine (85–95% free residual to Daphnia magna and Gambusia affinis. The 30- and 60-min LC 50 values were 0.097 and 0.063 mg 1⁻¹, respectively, for Daphnia and 1.59 and 0.84 mg 1⁻¹, respectively, for Gambusia. Use of this (or a similar) system can provide the readily comparable data base which is important for developing chlorine criteria for power plants.