排序方式: 共有14条查询结果,搜索用时 140 毫秒
1.
2.
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
3.
Suarez-Ojeda ME Guisasola A Baeza JA Fabregat A Stüber F Fortuny A Font J Carrera J 《Chemosphere》2007,66(11):2096-2105
This study examines the feasibility of coupling a Catalytic Wet Air Oxidation (CWAO), with activated carbon (AC) as catalyst, and an aerobic biological treatment to treat a high-strength o-cresol wastewater. Two goals are pursued: (a) To determine the effect of the main AC/CWAO intermediates on the activated sludge of a municipal WasteWater Treatment Plant (WWTP) and (b) To demonstrate the feasibility of coupling the AC/CWAO effluent as a part of the influent of a municipal WWTP. In a previous study, a high-strength o-cresol wastewater was treated by AC/CWAO aiming to establish the distribution of intermediates and the biodegradability enhancement. In this work, the biodegradability, toxicity and inhibition of the most relevant intermediates detected in the AC/CWAO effluent were determined by respirometry. Also, the results of a pilot scale municipal WWTP study for an integrated AC/CWAO-aerobic biological treatment of this effluent are presented. The biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) of main AC/CWAO intermediates allowed the classification of the intermediates into readily biodegradable, inert or toxic/inhibitory compounds. This detailed study, allowed to understand the biodegradability enhancement exhibited by an AC/CWAO effluent and to achieve a successful strategy for coupling the AC/CWAO step with an aerobic biological treatment for a high-strength o-cresol wastewater. Using 30%, as COD, of AC/CWAO effluent in the inlet to the pilot scale WWTP, the integrated AC/CWAO-biological treatment achieved a 98% of total COD removal and, particularly, a 91% of AC/CWAO effluent COD removal without any undesirable effect on the biomass. 相似文献
4.
Caliz J Montserrat G Martí E Sierra J Cruañas R Garau MA Triadó-Margarit X Vila X 《Chemosphere》2012,89(5):494-504
The involvement of the bacterial community of an agricultural Mediterranean calcareous soil in relation to several heavy metals has been studied in microcosms under controlled laboratory conditions. Soil samples were artificially polluted with Cr(VI), Cd(II) and Pb(II) at concentrations ranging from 0.1 to 5000 mg kg−1 and incubated along 28 d. The lowest concentrations with significant effects in soil respirometry were 10 mg kg−1 Cr and 1000 mg kg−1 Cd and Pb. However, only treatments showing more than 40% inhibition of respirometric activity led to significant changes in bacterial composition, as indicated by PCR-DGGE analyses. Presumable Cr- and Cd-resistant bacteria were detected in polluted microcosms, but development of the microbiota was severely impaired at the highest amendments of both metals. Results also showed that bioavailability is an important factor determining the impact of the heavy metals assayed, and even an inverted potential toxicity ranking could be achieved if their soluble fraction is considered instead of the total concentration. Moreover, multiresistant bacteria were isolated from Cr-polluted soil microcosms, some of them showing the capacity to reduce Cr(VI) concentrations between 26% and 84% of the initial value. Potentially useful strains for bioremediation were related to Arthrobacter crystallopoietes, Stenotrophomonas maltophilia and several species of Bacillus. 相似文献
5.
6.
Alfred L. Allen Jean Mayer Robert Stote David L. Kaplan 《Journal of Polymers and the Environment》1994,2(4):237-244
Eleven microorganisms were isolated from several temperate marine locations in the northeast Altantic coast of the United States and one tropical location in the Pacific Ocean (Hawaii) for the purpose of developing a rapid and accurate method of screening biodegradable materials for their susceptibility to mineralization. The materials evaluated in this study included chemically modified starch, amylose and pullulan, poly(3-hydroxybutyrate-co-valerate), (PHB/V), cellulose acetate, and a modified lignin/styrene. Some of the soluble, unmodified, biologically produced substrates such as starch, pullulan, and amylose mineralized rapidly. In general, the synthetic, insoluble polymers and the chemically modified polymers, such as acetylated and chlorinated amylose and pullulan, mineralized more slowly, although the ultimate mineralization of some of the substituted polysaccharides equaled or exceeded that of the unmodified substrate. The insoluble bacterial polyester, PHB/V, degraded rapidly after a short induction period. Initial respiration rate data, in general, could not be used as a predictor of ultimate mineralization. It was found that the cumulative level of carbon dioxide evolved signifies the minimum extent of biodegradation of the substrate, and the oxygen consumed is a good indicator of the maximum extent of substrate degradation.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts. 相似文献
7.
Evaluation of a respirometric test method to determine the heterotrophic yield coefficient of activated sludge bacteria 总被引:1,自引:0,他引:1
The heterotrophic yield coefficient of activated sludge bacteria is an important parameter in the field of wastewater degradation kinetics and the determination of degradation kinetics of defined chemicals. With the help of easily biodegradable organic compounds like glucose and acetate the respiration kinetics of degrading activated sludge bacteria was studied. The results of the respiration analysis were transformed to examine the degradation and respiration kinetics of municipal wastewaters at different food to microorganism ratios (F/M ratios). It was proved that the heterotrophic yield coefficient of aerobically degrading activated sludge bacteria could reliably be determined and that the heterotrophic yield coefficient was independent of the F/M ratio over a wide range. 相似文献
8.
This paper presents results of investigations on the influence of humic substances (humate, HS) on the biological treatment of wastewater containing heavy metals (Cr, Cu, Fe, Mn, Ni, and Zn). Respirometric studies indicated that the investigated system complied with the Haldane model for inhibitory wastes. Chemical analyses showed that, while the soluble COD removal was high (82%), only 7% of ammonia was oxidized to nitrate. An addition of HS (500 mg L−1) mitigated the inhibitory effect of the wastewater on the returned activated sludge. The system with HS complied with the Monod model for non-inhibitory wastes, and the removal of ammonia and metals was 99% and over 90%, respectively. It is suggested that an application of HS could be beneficial for treatment plants receiving wastewater streams containing heavy metals. 相似文献
9.
Biodegradation kinetics and toxicity of vegetable oil triacylglycerols under aerobic conditions 总被引:1,自引:0,他引:1
The aerobic biodegradation of five triacylglycerols (TAGs), three liquids [triolein (OOO), trilinolein (LLL), and trilinolenin (LnLnLn)] and two solids [tripalmitin (PPP) and tristearin (SSS)] was studied in water. Respirometry tests were designed and conducted to determine the biochemical oxygen demand (BOD) parameters of the compounds. In the case of the solid lipids, the degradation process was limited by their extremely non-polar nature. When added to water, PPP and SSS formed irregular clumps or gumballs, not a fine and uniform suspension required for the lipase activity. After 30 days, appreciable mineralization was not achieved; therefore, first-order biodegradation coefficients could not be determined. The bioavailability of the liquid TAGs was restricted due to the presence of double bonds in the fatty acids (FAs). An autoxidation process occurred in the allylic chains, resulting in the production of hydroperoxides. These compounds polymerized and became non-biodegradable. Nevertheless, the non-oxidized fractions were readily mineralized, and BOD rate constants were estimated by non-linear regression: LLL (k = 0.0061 h−1) and LnLnLn (k = 0.0071 h−1) were degraded more rapidly than OOO (k = 0.0025 h−1). Lipids strongly partitioned to the biomass and, therefore, Microtox® toxicity was not observed in the water column. However, EC50 values (<15% sample volume) were measured in the solid phase. 相似文献
10.
Variation in melanin patterns among individuals, populations, and species is common in fishes of the genus Xiphophorus. In the variable platyfish, Xiphophorus variatus, variation in metabolic rate is associated with melanin coloration and the color morphs appear to be physiological specialists adapted to particular environmental conditions. This study investigates whether a melanin polymorphism in the green swordtail, Xiphophorus helleri, is likewise associated with variation in metabolic rate. We measured metabolic rate as oxygen consumption rate of both adult male and juvenile X. helleri in static respirometers. The oxygen consumption rate does not differ significantly between the spotted and nonspotted morphs in either group, suggesting that-unlike in X. variatus-selection on metabolic rate is not involved in maintaining the polymorphism in X. helleri. We suggest that explanations need to be sought for the evolution of melanophore diversity in Xiphophorus that are pertinent to each melanin pattern polymorphism or groups of similar polymorphisms. 相似文献