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371.
Effects of inorganic nutrients on the regrowth of heterotrophic bacteria in drinking water distribution systems 总被引:2,自引:0,他引:2
Three laboratory-scale water pipe systems were set up to study the effects of adding three inorganic nutrients (ammonium, nitrate or phosphate) on biofilm formation in water pipes. The results showed that the effects of adding ammonium or nitrate on the biofilm formation were insignificant when levels below 0.1 mg N/l were added. Analogous results were observed when phosphate was added at levels below 0.005 mgP/l. However, as the addition of ammonium increased to 0.5 mgN/l, significant effects on biofilm formation were observed. Similar results were obtained phosphate was added at levels above 0.01 mgP/l. Batch tests were also conducted using water samples collected from a Taiwanese drinking water distribution system. The results indicated that the addition of ammonium, nitrate or phosphate to treatment plant effluent stimulates bacterial growth. In the distributed water of an urban area, the addition of nitrate or phosphate stimulated bacterial growth. The bacterial growth in the distributed water of a suburban area was not stimulated by adding any of these three inorganic nutrients. 相似文献
372.
I Chu D C Villeneuve V Secours V E Valli 《Journal of environmental science and health. Part. B》1990,25(2):225-241
Chlorinated diphenyl ethers (CDE's) are environmental contaminants that have been found in Great Lakes fish. Because of the paucity of toxicity data and potential for human exposure, the present short-term study was conducted to assess their potential toxic effects. Groups of 10 male and 10 female rats were administered the three CDE congeners (2,2',4,4',5-pentachlorodiphenyl ether (PCDE), 2,2',4,4',5,5'-hexachlorodiphenyl ether (HCDE), 2,2',3,4,4',6,6'-heptachlorodiphenyl ether (HPCDE] in diets at levels of 0.5, 5.0, 50 or 500 ppm for a period of 4 weeks. Decreased food consumption was observed with male and female rats fed the diet containing 500 ppm HPCDE. Treatment with the three isomers at the highest dose level produced an increase in liver weight in both sexes. While administration of PCDE produced an increase in hepatic aminopyrine demethylase activity, HCDE caused a significant increase in aminopyrine demethylase, aniline hydroxylase and ethoxyresorufin de-ethylase activities. HPCDE caused a significant increase in ethoxyresorufin de-ethylase activity. HPCDE at the highest dose level also caused a significant reduction in circulating lymphocytes in male rats. The 3 CDE's produced mild and adaptative histological changes in the liver and thyroid, but only HPCDE elicited mild changes in the thymus, bone marrow, and spleen. The above data indicate that HPCDE is immunosuppressive and that all three CDE isomers are considered to be moderately toxic in rats. The no-observable effects levels appear to be between 5-50 ppm in diet (0.36-3.0 mg/kg b.w.) for the three CDE's. 相似文献
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376.
采用厌氧复合床反应器与接触氧化、接触沉淀相结合的工艺,针对实船条件下可能出现的重启动、倾斜、海水及淡水海水交替冲洗厕所和水力负荷增加等情况,进行了特殊工况下船舶生活污水处理的试验研究。结果表明,该组合工艺在设计条件下(HRT为5h)重启动速度较快,可用于海水冲厕所产生的高盐度污水处理,耐受淡水海水交替变化的盐度冲击负荷变化能力较强,具有一定的水力负荷增加潜力,并且不受倾斜影响。 相似文献
377.
太湖流域经济增长与环境污染水平的关系研究 总被引:1,自引:0,他引:1
环境库兹涅茨曲线(KEC)是描述污染问题与经济发展之间关系的常用模型,一般情况下呈倒“U”形。通过对太湖流域1991-2005年的人均GDP与工业三废排放量之间的关系分析,研究发现,太湖流域的环境库兹涅茨曲线特征为增长的凹曲线,不同于传统的环境库兹涅茨曲线,同时分析了产生这一现象的原因,并从调整经济结构、转变增长方式、发展循环经济方面给出政策建议。 相似文献
378.
不同品种茶叶中锗含量的测定与研究 总被引:2,自引:0,他引:2
在苏木色精-偏钒酸胺体系中,锗可产生一灵敏的极谱催化波,峰电位为-0.57V(us SCE),检测下限为6.888×10^-11mol/l,线性范围为1.378×10^-10—1.102×10^-5mol/l。用催化极谱法测定茶叶中锗,兼具灵敏、准确、快速、简便、选择性好的优点,可用于茶叶样品中锗的定量测定。 相似文献
379.
Baoyu Gao Yongbao Chu Qinyan Yue Chunyan Kong Xiaona Wang 《Frontiers of Environmental Science & Engineering》2007,1(3):368-373
In order to investigate the characteristics of pure Nano-Al13, Nano-Al13 was separated and purified from a series of poly-aluminum chloride (PAC) solutions which had the same Al13 percentage but different total Al concentrations, by using column chromatography, ethanol-acetone resolving and SO2? 4/Ba2+ displacement. The Al13 species yield was characterized by Al-ferron timed complexation spectrophotometry and 27Al-NMR (nuclear magnetic resonance). The coagulation efficiency of Nano-Al13, PAC and AlCl3 in synthetic water was also investigated by Jar tests. The dynamic process and aggregation state of kaolin suspensions coagulating with Nano-Al13, PAC and AlCl3 were similarly investigated using a photometric dispersion analyzer 2000 (PDA2000). The experimental results indicated that the ethanol-acetone resolving method was simple and could separate the PAC solution at different concentrations, while column chromatography could separate PAC solutions at low concentrations. The SO4 2?/Ba2+ displacement method could separate PAC solutions at high concentrations. However, extra inorganic cation and anion could be added in the solution during separation. The coagulation efficiency and dynamic experimental results showed that Nano-Al13 with high positive-charged species was effective in removing turbidity and color. The dynamic process results showed that Nano-Al13 also had the best recovery capability after shearing compared with PAC and AlCl3 because the Nano-Al13 conformation is more effective in charge neutralization. 相似文献
380.
To test whether heterotrophic protists modify precursors of long chain n−3 polyunsaturated fatty acids (LCn−3PUFAs) present in the algae they eat, two algae with different fatty acid contents (Rhodomonas salina and Dunaliella tertiolecta) were fed to the heterotrophic protists Oxyrrhis marina Dujardin and Gyrodinium dominans Hulbert. These experiments were conducted in August 2004. Both predators and prey were analyzed for fatty acid composition.
To further test the effects of trophic upgrading, the calanoid copepod Acartia tonsa Dana was fed R. salina, D. tertiolecta, or O. marina that had been growing on D. tertiolecta (OM-DT) in March 2005. Our results show that trophic upgrading was species-specific. The presence of eicosapentaenoic acid
(EPA) and docosahexaenoic acid (DHA) in the heterotrophic protists despite the lack of these fatty acids in the algal prey
suggests that protists have the ability to elongate and desaturate 18:3 (n−3), a precursor of LCn−3PUFAs, to EPA and/or DHA. A lower content of these fatty acids was detected in protists that were fed good-quality algae.
Feeding experiments with A. tonsa showed that copepods fed D. tertiolecta had a significantly lower content of EPA and DHA than those fed OM-DT. The concentration of EPA was low on both diets, while DHA content was highest in A. tonsa fed R. salina and OM-DT. These results suggest that O. marina was able to trophically upgrade the nutritional quality of the poor-quality alga, and efficiently supplied DHA to the next
trophic level. The low amount of EPA in A. tonsa suggests EPA may be catabolized by the copepod. 相似文献