二氧化氯消毒效果影响因素试验研究

通过对比实验,考察了二氧化氯、液氯和氯胺三种常用消毒剂对肠道菌的灭活效果,以及pH、温度、培养基稀释倍数等因素对二氧化氯消毒效果的影响.试验结果表明,二氧化氯消毒剂具有高效性和广谱性;pH值在6.0～9.0内变化,二氧化氯的消毒效果几乎不受影响;温度的升高会加强二氧化氯的灭菌效果;随着培养基稀释倍数的增加,粪肠球菌对二...     

生长环境对消毒剂灭活粪肠球菌影响效果的试验研究

通过改变培养基稀释度和培养温度以及添加无机生长元素（氯化钾、硫酸镁、三氯化铁）研究了自由氯、氯胺和二氧化氯对不同生长环境下所培养的粪肠球菌的灭活情况。结果表明，当粪肠球菌在100倍稀释的肉汤培养基上生长时，达到3log去除率氯和二氧化氯所需的0值分别增加了2．1和5．5倍，而氯胺所需的D值变化很小；将粪肠球菌的生长温度从22℃调整至44．5℃时，达到3log去除率氯胺所需的C≠值下降了2倍，自由氯和二氧化氯所需的C￡值则变化不大；在营养肉汤培养基中投加K＋（4mmol／L）、Mg2＋（0．4mmol／L）和Fe3＋（0．08mmol／L）后，粪肠球菌对自由氯和二氧化氯的抗性提高了，对氯胺的抗性则变化不大，达到3log去除率自由氯和二氧化氯所需的C￡值最大分别增加了约2．3和19倍。     

冻融和氯盐侵蚀耦合作用下的大掺量粉煤灰混凝土耐久性探讨

鉴于北方海洋环境十分恶劣,对混凝土的破坏严重,目前对于海工混凝土耐久性问题的研究主要集中在氯离子渗透、硫酸盐侵蚀、冻融作用等方面。其中,氯盐侵蚀和冻融作用对混凝土造成的破坏尤为严重,所以对海工混凝土进行抗冻、抗盐害的设计尤为重要。出于混凝土劣化的主导因素和经济性的考虑,在海工结构中,大掺量粉煤灰混凝土(High Fly Ash Content Concrete,简称HFCC)以其经济效益和环境效益被人们愈来愈重视。主要对氯盐和冻融耦合作用下的大掺量粉煤灰混凝土的耐久性进行了探讨。     

典型有机氮化物对卤乙酸生成量和耗氯量的影响

以自来水厂的滤后水为处理对象,研究了甘氨酸、半胱氨酸、赖氨酸、亮氨酸、天门冬氨酸和甲胺等6种典型有机氮化物对饮用水消毒过程中卤乙酸生成量和耗氯量的影响。结果表明,有机氮化物的存在会强化消毒过程中卤乙酸的生成,且卤乙酸生成量的增值与有机氮化物的含量呈正相关,同时与有机氮化物的性质和水体的pH有关;有机氮化物的存在还会使耗氯量增加,增值与有机氮化物含量成正比。有机氮化物强化卤乙酸生成的原因可能是:耗氯量的升高使得水中天然有机物与氯反应而生成的卤乙酸量增加;有机氮化物自身在氯化过程中生成了卤乙酸。     

自由氯、氯胺和顺序氯化对饮用水消毒效果的试验研究

研究了自由氯、氯胺和顺序氯化三种消毒方式对大肠埃希氏菌和粪肠球菌的灭活效果.结果表明,自由氯浓度越高,对细菌的灭活速率和最终灭活率越大;氯胺浓度越高,对细菌的灭活速率和最终灭活率越大;顺序氯化消毒效果优于单独使用自由氯或氯胺时的消毒效果.同时,还探讨了pH和温度对三种消毒方式的影响.     

氯盐环境下混凝土内钢绞线的锈蚀特性试验研究

预应力钢筋的锈蚀特性是研究预应力混凝土结构耐久性失效及防治的基础，为此，分别采用内掺盐和外浸盐两种方式在自然气候条件下作了如下三组混凝土内钢筋锈蚀的对比试验：钢绞线与热轧带肋钢筋、钢绞线与热轧光圆钢筋、钢绞线中心钢丝与热轧光圆钢筋。通过对锈蚀过程中锈蚀电流密度的测试以及试验完毕后的破形观察与称重对比和分析，得到如下结果：钢筋外表面锈蚀程度在面向保护层侧明显严重于背向保护层侧；钢绞线及其中心钢丝外表面锈蚀相对最不均匀，具有严重的局部锈蚀——坑蚀形态，带肋钢筋次之，光圆钢筋相对最均匀、全面；钢绞线内表面发生类似于空气中的相对全面、均匀的锈蚀；钢绞线的平均外表面锈蚀率小于热轧带肋钢筋的与热轧光圆钢筋的，但严重的局部锈蚀对其受拉性能极其不利。另外，还对上述锈蚀特性进行了电化学机理分析。     

持续荷载和环境耦合作用下钢筋混凝土抗氯盐侵蚀试验研究

沿海混凝土结构长期处于持续荷载和侵蚀环境的耦合作用中。试验设计可持续施加拉/压应力的加载装置,对13根混凝土梁施加不同等级的荷载;同时对受力状态下的混凝土梁进行模拟海水干湿循环的侵蚀。通过试验,研究不同等级荷载和氯盐侵蚀耦合作用下混凝土梁抗氯盐侵蚀性能的变化规律。试验结果表明:(1)通过在梁的受压、受拉侵蚀面浇筑水池,以取水注水的方式来模拟干湿循环可以有效防止盐水对持荷装置的侵蚀,可使试验梁受力更稳定;(2)以施加荷载的大小占极限荷载的比例记做荷载水平λ。当λ=0.3时,受拉区混凝土开裂,各条裂缝最大宽度为0.04 mm,此时裂缝处氯离子浓度与不受力无裂缝混凝土内部氯离子浓度相近;当裂缝最大宽度为0.08 mm时,同深度处氯离子浓度较小幅度增加,影响氯离子传输速率的临界荷载裂缝宽度为0.04 mm。随着λ的增加,受拉区各位置氯离子浓度呈非线性增大,且距离裂缝越近,同深度处氯离子浓度越大;(3)λ<0.45时,混凝土梁受压区氯离子浓度随着荷载水平的增大而减小,当λ>0.45时,受压区氯离子浓度随着荷载水平的增大而增大;在压应力作用下,影响氯离子传输速率的临界λ=0.45。研究表明,荷载和氯盐侵蚀耦合作用对钢筋混凝土结构耐久性能具有巨大的危害,尤其是荷载裂缝处的氯盐侵蚀,实际工程中应采取相关措施加以防范。     

氯盐腐蚀下钢管混凝土方柱的承载力试验研究

对氯盐腐蚀下钢管混凝土方柱的承载性能进行试验研究。试验包含28个试件(17根短柱和11根梁),主要参数为腐蚀情况下的荷载比(0～0.75)及腐蚀状况(无腐蚀、完全腐蚀及部分腐蚀)。根据试验结果,对荷载及腐蚀对钢管混凝土和钢管性能的影响进行分析,并将按现有规范DBJ/T13-51-2010及EC4-2004计算的极限承载力与试验进行对比分析。     

干燥环境条件下大掺量矿物掺合料高强混凝土的抗冻性

用快冻法研究了单掺铝酸盐膨胀剂和钢纤维及其复合对大掺昔矿物掺合料混凝土抗冻性的影响.结果表明:大掺量矿物掺合料高强混凝土(HSC)具有较好的抗冻性,但是其抗冻性对养护环境相对湿度(RH)非常敏感,干燥养护条件下的冻融寿命仅有标准养护的38%～40%.单掺2%钢纤维在保证其抗冻性不变的基础上,可改善其抗冻性对养护环境RH的敏感性.单掺10%膨胀剂能够降低大掺量矿物掺合料HSC的抗冻性对养护环境湿度的敏感性,但是其冻融寿命降低了34%.此外,在改善大掺量矿物掺合料高强混凝土的抗冻性及其湿度敏感性方面,复合掺加膨胀剂和纤维的效果并不比单掺膨胀剂或纤维的效果更好.     

Free chlorine demand and cell survival of microbial suspensions

The utility of chlorine residual and chlorine demand as a surrogate for microbial contamination in the water distribution system was evaluated. The chlorine demanded by and cell survival of pure culture suspensions of Escherichia coli, Staphylococcus epidermidis, and Mycobacterium aurum were quantified in solutions with initial free chlorine concentrations of 0.20, 0.40, and 0.80 mg/L. The chlorine demand increased with initial concentration of cells and free chlorine for all species. At equivalent initial cell concentrations, chlorine demand was greatest for M. aurum, followed by S. epidermidis and E. coli. The chlorine contact time required for a 3-log inactivation of E. coli, S. epidermidis, and M. aurum was calculated as 0.032+/-0.009, 0.221+/-0.080, and 42.9+/-2.71 mg min/L, respectively. The ultimate chlorine demand and cell survival were directly proportional. No chlorine demand was observed at cell concentrations less than 10(5)CFU/mL for E. coli or 10(4)CFU/mL for S. epidermidis. M. aurum demanded chlorine at all initial cell concentrations including 10(3)CFU/mL, which was the detection limit of the cell quantification assay. Chlorine demand was determined to be a suitable surrogate indicator of the organisms studied and its utility may be enhanced in locations of the water distribution system that maintain a higher free chlorine residual.     

Treatment of anoxic pond effluent using crossflow microfiltration

The treatment of anoxic waste stabilization pond effluent was investigated using crossflow microfiltration in conjunction with dynamic membranes. The primary membrane used throughout the study was made of woven polyester, while the dynamic membrane was formed of manganese dioxide (MnO₂). Effluent from a lab-scale anoxic waste stabilization pond was treated with and without the addition of slug doses of polyaluminum silicate sulphate (PASS) as a coagulant. Removal of suspended solids, turbidity, COD and E. coli was found to be affected by feed turbidity and the addition of PASS. On the other hand, removal of Streptococcus faecalis and algal species was found to be 100% and was not affected by feed turbidity. This was attributed to their size which could be more than the pore size of the dynamic membrane. Addition of slug doses of PASS were found to have a positive effect on the permeate flux and quality, which was attributed to the influence of crossflow velocity on the agglomerated particles.     

The Fate of Enteric Bacteria in Relation to Suspended Particles in Sea Water

The investigation was carried out to determine the effect of suspended particles on the survival of selected enteric bacteria (i.e. Escherichia coli and enterococci) which are important indicators of faecal pollution in marine waters. Rates of bacterial removal under varying experimental conditions (i.e. particle concentration, sewage content, and degree of mixing) were determined. The combined effect of the factors concerned with the removal rate of bacteria was evaluated by statistical analyses carried out on the experimental data utilizing the 'complete factorial' experimental design, and a good correlation between bacteria and particles was obtained.     

二氧化氯对水中典型菌种的试验研究

研究了二氧化氯（ＣｌＯ２）对水中某些典型细菌的灭菌效果，考察了在消毒剂投量、ｐＨ值及接触时间等不同试验条件下，二氧化氯的灭菌效果．与液氯比较，二氧化氯的灭菌效果优于或与液氯相当．二氧化氯可在广泛的ｐＨ范围内有效地杀灭细菌．     

Ultraviolet inactivation of selected bacteria and viruses with photoreactivation of the bacteria

u.v. dose/survival response curves were developed for E. coli, S. faecalis, poliovirus and reovirus. The influence of photoreactivation on the bacterial curves was examined. A maximum photoreactivation of 3.4 and 2.4 log of u.v. inactivated E. coli and S. faecalis populations, respectively, was observed. When allowing for photoreactivation, the dose required for 99.9% inactivation of the bacteria was approximately twice that required when photoreactivation was not considered. Reovirus, a double-standard RNA virus, was found to be significantly more resistant to u.v. radiation than poliovirus, a single-stranded RNA virus. The viruses in general, were found to be more resistant to u.v. radiation than the bacteria.     

A new method for calculation of the chlorine demand of natural and treated waters

Conventional methods of calculating chlorine demand are dose dependent, making intercomparison of samples difficult, especially in cases where the samples contain substantially different concentrations of dissolved organic carbon (DOC), or other chlorine-consuming species. Using the method presented here, the values obtained for chlorine demand are normalised, allowing valid comparison of chlorine demand between samples, independent of the chlorine dose. Since the method is not dose dependent, samples with substantially differing water quality characteristics can be reliably compared. In our method, we dosed separate aliquots of a water sample with different chlorine concentrations, and periodically measured the residual chlorine concentrations in these subsamples. The chlorine decay data obtained in this way were then fitted to first-order exponential decay functions, corresponding to short-term demand (0-4h) and long-term demand (4-168 h). From the derived decay functions, the residual concentrations at a given time within the experimental time window were calculated and plotted against the corresponding initial chlorine concentrations, giving a linear relationship. From this linear function, it was then possible to determine the residual chlorine concentration for any initial concentration (i.e. dose). Thus, using this method, the initial chlorine dose required to give any residual chlorine concentration can be calculated for any time within the experimental time window, from a single set of experimental data.     

MD镇供水管网余氯衰减模拟

采用EPANET2建立了MD镇的管网水质模型,通过EPANET2的水质模拟分析与实际数据的对比,分析可能存在的问题。对可能存在的问题进行现场调查,进而对节点需水量和管壁衰减系数Kw进行调整,从而使模型中的模拟余氯与实测余氯相符。     

Mortality rates of autochthonous and fecal bacteria in natural aquatic ecosystems

Bacterial mortality has been investigated in freshwater (River Seine) and in marine (North Sea) systems using a method based on following the disappearance of radioactivity from the DNA of assemblages of bacteria previously labeled with tritiated thymidine. Measurement of bacterial mortality of autochthonous and various types of fecal bacteria allowed direct comparisons between their respective first-order mortality rates. Mortality rates obtained for the different types of bacteria in the River Seine were, respectively, 7.9-33.9 x 10(-3)h(-1) for Escherichia coli, 12.2-29.2 x 10(-3)h(-1) for S. faecium and 7.0-18.3 x 10(-3)h(-1) for the autochthonous bacteria. In the Belgian coastal waters, these rates were 4.6-27.3 x 10(-3)h(-1) for E. coli, 6.0-22.0 x 10(-3)h(-1) for S. typhimurium, 10.0-18.9 x 10(-3)h(-1) for S. faecium and 1.0-13.9 x 10(-3)h(-1) for autochthonous bacteria. In both environments, the overall mortality rates of autochthonous and the different fecal bacteria were in the same order of magnitude and overall mortality rates of E. coli were on average about twice as high for autochthonous bacteria. Grazing by protozooplankton was the dominant process of mortality for fecal and autochthonous bacteria in both environments. Except in a few situations, grazing by protozooplankton was responsible for more than 90% of the overall mortality rate of fecal and autochthonous bacteria in the river and in the coastal area.