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101.
Pambrun V Marquot A Racault Y 《Environmental science and pollution research international》2008,15(7):592-599
Background, aims, and scope Sometimes, urban wastewaters convey a more or less significant part of toxic products from industries or the craft industry.
Nitrifying activity can be affected by these substances, implying higher ammonia concentrations in the outlet effluent and
contributing to toxicity for the aquatic environment. Moreover, the more stringently treated wastewater standards now require
a reliable treatment for nitrogen. One of the key issues is the identification of the inhibition behavior of nitrifying bacteria
facing a toxic substance. This new understanding could then finally be integrated into models in order to represent and to
optimize wastewater treatment plants (WWTP) operation in cases involving ‘toxic scenarios’.
Materials and methods The toxic substances studied in this work, cadmium and 3.5-dichlorophenol (3.5-DCP), are representative of chemical substances
commonly found in municipal sewage and industrial effluents and symbolize two different contaminant groups. The effects of
Cd and 3.5-DCP on nitrification kinetics have been investigated using respirometry techniques.
Results IC50 values determination gives concentrations of 3.1 mg/L for 3.5-DCP and 45.8 mg/L for Cd at 21 ± 1°C. The variation to
low temperature seems to have no real effect on IC50 for DCP, but induces a decrease of cadmium IC50 to 27.5 mg/L at 14°C.
Finally, specific respirometric tests have been carried out in order to determine the potential effect of these toxic substances
on the nitrifying decay rate b
a
. No significant effect has been noticed for Cd, whereas the presence of 3.5-DCP (at IC50 concentration) induced a dramatic
increase of b
a
at 20°C. The same behavior has been confirmed by experiments performed in winter periods with a sludge temperature around
12°C.
Discussion The target substances have different modes of action on activity and mortality, notably due to the abilities of the contaminant
to be precipitated, accumulated, or even to be progressively degraded. Studies realized at low temperature confirmed this
assumption, and put in evidence the effect of temperature on toxic substances capable of being biosorbed. However, the change
in the sludge sample characteristics can be pointed out as a problem in the investigation of the temperature effect on nitrification
inhibition, as biosorption, bioaccumulation, and predation are directly linked to the sludge characteristics (VSS concentration,
temperature) and the plant operating conditions (loading rates, sludge age, etc.).
Conclusions This work brings new understandings concerning the action mode of these specific contaminants on nitrifying bacteria and,
in particular, on the role of temperature. The experiments lead to the determination of the IC50 values for both toxic substances
on biological nitrification. The inhibition mechanisms of Cd and 3.5-DCP on nitrifying activity have been simply represented
by a non-competitive inhibition model.
Recommendations and perspectives Other experiments carried out in a continuous lab-scale pilot plant should be done with a proper control of the operating
conditions and of the sludge characteristics in order to better understand the mechanisms of nitrification inhibition for
each contaminant. Finally, these first results show that toxic substances can have an effect on the growth rate but also on
the decay rate, depending on the characteristics of the toxic substance and the sludge. This eventual double effect would
imply different strategies of WWTP operation according to the behavior of the contaminant on the bacteria. 相似文献
102.
自催化法合成聚天冬氨酸 总被引:1,自引:0,他引:1
以马来酸酐和乙酸铵为原料,在微波条件下用自催化法合成了聚天冬氨酸(PASP)。通过正交实验确定了最佳合成条件:n(乙酸铵):n(马来酸酐)=1.2,微波功率为1200W,反应时间为10min。在最佳合成条件下,PASP的收率为91.6%,PASP的黏均相对分子质量约为1.5×10^4。经红外光谱表征和核磁共振氢谱测试结果表明,PASP的各种主要官能团表现明显。当Ca^2+质量浓度为250mg/L、PASP加入量为3mg/L时,PASP的阻垢率达到95%,表明PASP具有较好的阻垢性能。 相似文献
103.
酰胺类除草剂的广泛使用对水生生态环境构成了潜在风险。为探究其对藻类的毒性作用,以铜绿微囊藻为对象,分别从藻类生长和氧化损伤效应角度探讨了甲草胺、乙草胺和丁草胺对铜绿微囊藻的毒性影响。实验结果显示,酰胺类除草剂对藻类的影响存在明显的滞后效应和剂量–效应关系,低浓度暴露组刺激藻类增长,高浓度表现为抑制作用;3种酰胺类除草剂增加了铜绿微囊藻的氧化压力,并随着暴露时间的延长和浓度的增加而增强。其中,藻体内过氧化脂质降解产物丙二醛(MDA)含量明显增加,同时超氧化物歧化酶(SOD)和过氧化物酶(POD)活性也显著增强。经96 h暴露后,甲草胺(32.0 mg·L~(-1))、乙草胺(32.0 mg·L~(-1))和丁草胺(15.0 mg·L~(-1))暴露溶液中相对MDA含量分别为138%、204%和154%,相对SOD活性分别为116%、87%和115%,相对POD活性分别475%、278%和627%。结合生物量及氧化损伤效应实验结果可知,3种除草剂对铜绿微囊藻的毒性大小顺序为丁草胺乙草胺甲草胺。 相似文献
104.
磺胺类兽药对土壤微生物数量的影响 总被引:5,自引:0,他引:5
采用室内培养的方法,研究磺胺类兽药(磺胺二甲基嘧啶、磺胺甲噁唑)污染对土壤微生物数量(细菌、真菌、放线菌、固氮菌、兼气性固氮菌、硝化细菌、亚硝化细菌、反硝化细菌及氨化细菌)的影响.结果表明,磺胺类兽药对土壤细菌数量有一定的激活作用,其最大激活率在700%以上.兽药对土壤真菌数量的影响主要呈现抑制作用,其最高抑制率为92.9%.兽药对土壤放线菌数量有一定的抑制作用,对土壤固氮菌数量则有一定的激活作用.兽药对土壤兼气性固氮菌数量的影响表现为较低浓度时(10 mg.kg-1)抑制,而较高浓度时(50 mg.kg-1)则激活.兽药对土壤硝化细菌、亚硝化细菌、反硝化细菌及氨化细菌有一定的激活作用,其中对硝化细菌的最大激活率可达1000%以上. 相似文献
105.
The inhibitory efficiency of anionic copolymers and the effect of the biocides sodium hypochlorite, glutaraldehyde, and tris(hydroxymethyl)nitromethane on the precipitation behavior of calcium fluoride (CaF2) were studied. The efficiency of polymeric inhibitors was traced from conductivity measurements by using half-life (t1/2) method. X-ray diffraction parameters have been measured for calcium fluoride scale minerals. An anionic copolymer (K-798) acts as one of the best inhibitors for the precipitation process of the calcium fluoride in water as compared to K-775. It is assigned to the fact that the copolymer (K-798) contains both sulfonic acid and sulfonated styrene groups while the polymer (K-775) having only the sulfonic acid group. It was further observed that the biocides have no appreciable effect on the performance of the anionic polymeric inhibitors. 相似文献
106.
过氧化氢酶活性及活性抑制的紫外分光光度测定 总被引:66,自引:3,他引:66
在体内实验条件下,测定了鲤鱼肝脏过氧化氢酶的活性。实验结果表明,过氧化氢酶的紫外分光光度法是可靠的,活性抑制结果表明,对-二硝基苯对鲤鱼肝脏过氧化氢酶无有明显的抑制作用。鲤鱼肝脏过氧化氢酶可作为一项指标用于生态毒理学研究。 相似文献
107.
采用活性炭吸附和两级Fenton氧化组合工艺对高盐度对氨基苯酚生产废水进行了处理实验研究。结果表明,p H值对活性炭去除有机物的影响较小。当活性炭投加量为4 g/L时,TOC去除率61%。分级加药可以有效提高Fenton氧化对有机物的去除效率。在温度为25℃、p H为3、30%H2O2投加量为3%(V/V)、Fe2+/H2O2摩尔比为0.05时,两级Fenton氧化处理后,出水TOC降至150 mg/L以下。此外,Fenton氧化后形成氢氧化铁污泥颗粒粒径为4.5μm,经过聚丙烯酰胺(PAM)絮凝之后,污泥的粒径明显增加,过滤特性改善。PAM絮凝效果依赖于溶液的p H值,当p H超过10后会失去作用,故在使用过程中需要严格控制溶液的p H值。 相似文献
108.
109.
对山海关滨海盐生植物及盐生植被景观和群落配置情况进行实地调查并参考历史文献,发现山海关滨海湿地共有盐生种子植物26科44属51种。结合山海关海岸带的气候、土壤理化性质及土地覆盖和利用的现状,选择乔、灌木类盐生植物3种,藤本类盐生植物1种,中生草本盐生植物5种,旱生草本盐生植物2种,湿生植物4种,共计15种作为滨海地区盐碱地改良和植被恢复的野生植物种类。 相似文献
110.