Microorganisms In River Water Research Articles

Multiscale Study of Physical and Mechanical Properties of Sandstone in Three Gorges Reservoir Region Subjected to Cyclic Wetting–Drying of Yangtze River Water

Natural rock often suffers from cyclic wetting–drying involving different water types, and the resulting deterioration may differ from laboratory tests using distilled water or salt solutions. An inappropriate estimation of this deterioration effect may lead to fatal geological hazards and engineering failures. A multiscale study is conducted to investigate the physical and mechanical features of sandstone in Three Gorges Reservoir region (TGR sandstone) subjected to cyclic wetting–drying of Yangtze River water. During this study, three types of water, i.e., Yangtze River water, ionized water having similar ion compositions as the Yangtze River water, and distilled water, are used for comparison. The results show that the multiscale physical properties including mineral compositions (especially calcite and albite), micro-pore parameters, computed tomography values, and macro-mechanical parameters (i.e., Young’s modulus, uniaxial compression strength and tensile strength) are remarkably altered during the cyclic wetting–drying process. Significant correlations are found between these numerous multiscale properties. The results indicate that changes of mineral compositions and microstructure are the primary reasons for the deterioration of sandstone strength. The deterioration effect of distilled water on TGR sandstone is the least, while the effect of ionized water is the greatest, and that of river water being intermediate. These differences are ascribed to different chemical interactions, together with possible microorganism effects for river water, as microorganisms in river water potentially weaken the deterioration of cyclic wetting–drying of river water. In situ water is recommended for studying how rock properties are affected by water–rock interactions in real settings.

Drinking Water Treatment by Inductively Coupled Plasma System to Remove of Microorganisms in River Water

Inductively coupled plasma system was used in drinking water treatment system to kill the microorganisms in water such as total coliforms (TC), fecal coliforms (FC) and other coliforms (OC) from river water. The aim of this study was to investigate the effect of flowrate on removal efficiency (RE), death rate, and death yield and energy consumption of bacteria's. The frequency of the system was set at 4.6 MHz. The results show that the removal efficiencies and death rate of TC, FC and OC decreased with increasing flowrate. Compared to FC, the first-order reactions of TC and OC were lower in the following order: FC > OC > TC. The death yield of TC and OC significantly increased when the removal efficiency increased. The electromagnetic flux varied from 19.44 to 20.55 W/cm2 and the energy consumption was 0.26, 0.32, and 0.67 with flow rate at 20, 10 and 5 mL/minute, respectively. These results are very necessary to improve drinking water treatment.

Development of a whole community genome amplification-assisted DNA microarray method to detect functional genes involved in the nitrogen cycle.

A novel DNA microarray analysis targeting key functional genes involved in most nitrogen cycling reactions was developed to comprehensively analyze microbial populations associated with the nitrogen cycle. The developed microarray contained 876 oligonucleotide probes based on the nucleotide sequences of the nif, amo, hao/hzo, nap, nar, nirK, nirS, nrf, cnor, qnor and nos genes. An analytical method combining detection by the designed microarray with whole community genome amplification was then applied to monitor the nitrogen cycling microorganisms in river water and wastewater treatment sludge samples. The developed method revealed that nitrogen cycling microorganisms in river water appeared to become less diverse in response to input of effluent from municipal wastewater treatment plants. Additionally, the nitrogen cycling community associated with anaerobic ammonium oxidation and partial nitrification reactors could be reasonably analyzed by the developed method. However, the results obtained for two activated sludge samples from municipal wastewater treatment plants with almost equivalent wastewater treatment performance differed greatly from each other. These results suggested that the developed method is useful for comprehensive analysis of nitrogen cycling microorganisms, although its applicability to complex samples with abundant untargeted populations should be further examined.

Bacterial Degradation and Reduction in the Estrogen activity of 4-nonylphenol

Bacteria capable of degrading 4-nonylphenol (NP) were isolated and identified, and their ability to degrade NP was determined. The screening of microorganisms in river water and soil led to a collection of 23 strains of bacteria and five strains of fungi. Two strains of bacteria, identified as Pseudomonas sp. and Acidovorax sp., possessed great ability for degrading NP. The NP degradation rate of Pseudomonas sp. did not change with the NP concentration (50-100mg/L) . In contrast, the NP degradation rate of Acidovorax sp. increased with increasing NP concentration. Acidovorax sp. possessed the greatest NP degradation activity at 35°C. No NP degradation activity was observed for Pseudomonas sp. at temperatures higher than 30°C. Even when non-NP carbon sources such as glucose or sucrose were added, the NP degradation rates for both bacteria did not decrease. In addition, the estrogenic activity of NP decreased depending on the amount of NP residues determined by the yeast two-hybrid system.

Influence of tacticity and molecular weight of poly(vinyl alcohol) on crystallization and biodegradation of poly(3-hydroxybutyric acid)/poly(vinyl alcohol) blend films

The crystallinity and the profile of biodegradation by environmental microorganisms in river water were investigated for bacterial poly(3-hydroxybutyric acid) [PHB] blend films with stereoregular poly(vinyl alcohol)s [PVA] and low-molecular weight atactic PVAs. According to the DSC thermal analysis, the crystallization of PHB was found to be not suppressed by blending with highly isotactic PVA. This result is consistent with previous results obtained by using Fourier-transformed infrared spectroscopy, that is, PVA sample with higher syndiotacticity brings about higher suppression of crystallization of PHB. In the PHB/PVA blend system, the formation of small PHB crystals was found by wide angle X-ray scattering, even in the samples for which the melting endotherm of PHB was not detected by DSC. The biodegradation profile of these blend films depends strongly on the water solubility of the PVA component. The PHB blends with low-molecular weight atactic PVA, which shows higher water solubility than atactic PVA with higher molecular weight and stereoregular PVA, exhibited faster degradation compared to the PHB blends with high-molecular weight atactic PVA system. The biodegradability of the PHB blends with stereoregular PVA became extremely low, when the PVA composition in the blends became high.

How good is modelling of microbial survival in fluvial systems?

In natural and man-made environments microorganisms encounter a number of positive (growth) and negative (toxic and predatory) influences which affect their survival. Understanding microbial survival and potential for regrowth is important for risk assessment in a variety of water types and settings. However, the behaviour of microorganisms in fluvial systems cannot be completely simulated in the laboratory. We have previously studied the survival of several microorganisms in river water in the laboratory and in situ. Frequently our results were variable when sampling sites were separated temporally and spatially. In order to further understand why such differences may occur, we examined the effect of transient nutrient plugs on microbial survival and regrowth in parallel in two model systems with different characteristics: a flow-through hollow fibre diffusion (HFD) system and static diffusion chambers (DC). We focused on the behaviour of Escherichia coli because of its widespread use as an indicator. Results showed a different response of E. coli to transient presence of nutrients in the two systems; both systems responded to nutrient spikes but the HFD system responded more rapidly. For 1h and 2h nutrient spikes, the peak populations in the HFD system were seen 5h (62% net increase) and 8h (650% net increase) after nutrient addition, respectively. In the DC the corresponding figures were 7h (18.5% net increase) and 12h (300% net increase) hours. However, decline in microbial numbers was more rapid in the HFD than the DC system. When this was tested further with repeated short nutrient plugs (10min), the net growth in the CD system was higher than in the HFD. The main question that arises from these studies is under what conditions, if any, does the rapid response HFD model become more relevant for field conditions?

How good is modelling of microbial survival in flu vial systems?

In natural and man-made environments microorganisms encounter a number of positive (growth) and negative (toxic and predatory) influences which affect their survival. Understanding microbial survival and potential for regrowth is important for risk assessment in a variety of water types and settings. However, the behaviour of microorganisms in fluvial systems cannot be completely simulated in the laboratory. We have previously studied the survival of several microorganisms in river water in the laboratory and in situ. Frequently our results were variable when sampling Sites were separated temporally and spatially. In order to further understand why such differences may occur, we examined the effect of transient nutrient plugs on microbial survival and regrowth in parallel in two model systems with different characteristics: a flow-through hollow fibre diffusion (HFD) system and static diffusion chambers (DC). We focused on the behaviour of Escherichia coli because of its widespread use as an indicator. Results showed a different response of E. coli to transient presence of nutrients in the two systems; both systems responded to nutrient spikes but the HFD system responded more rapidly. For 1h and 2h nutrient spikes, the peak populations in the HFD system were seen 5h (62% net increase) and 8h (650% net increase) after nutrient addition, respectively. In the DC the corresponding figures were 7h (18.5% net increase) and l2h (300% net increase) hours. However, decline in microbial numbers was more rapid in the HFD than the DC system. When this was tested further with repeated short nutrient plugs (10min), the net growth in the CD system was higher than in the HFD. The main question that arises from these studies is under what conditions, if any, does the rapid response HFD model become more relevant for field conditions?

Development for Biodegradation Test for Organic Compounds by Microorganisms in River Water and Mutagenesis of Their Metabolites.

A method for the mutagenicity test of biodegradation products produced by microorganisms in river water was developed for the screening of the degradation of organic compounds in an environment. Microorganisms in river water were collected on the membrane filter, which was prepared by autoclaving for three times at 2-minute intervals to remove the surface-active agents coated on the filter. The modified Davis medium was suitable for the medium for the biodegradation test taking into account the growth of microorganisms, the preferential utilization of the chemicals as nutrients, and the effect of the medium component on Ames test following the biodegradation test. While the mutagenicity of 4-nitroquinoline-1-oxide disappeared during incubation with microorganisms, 8-nitroquinoline was shown to be mutagenic after incubation for 3 d, suggesting the conversion of 8-nitroquinoline to mutagenic metabolites.

A method for monitoring mineralization of 14C-labeled compounds in aqueous samples

Previously reported laboratory methods for measuring the rate of 14CO 2 release from an aqueous sample require a series of replicate growth flasks. At chosen times, some of these are sacrificed in order to quantitate the 14CO 2 released. The method presented here requires only one culture flask containing 200 ml of sample with labeled substrate, and one control-replacement flask containing 200 ml of sterile sample with labeled substrate. At each sampling time, 1 40 th of the liquid and headspace gas is removed from the modified 500 ml Erlenmeyer culture flask for 14CO 2 recovery. This method was used to study the mineralization of labeled amino acids, starch, n-hexadecane and anthracene by microorganisms in river water, and of n-hexadecane and n-hexadecanoic acid by microorganisms in sewage effluent.

Effect of upgrading a municipal wastewater effluent on pollution indicator and other microorganisms in river water

Effect of upgrading a municipal wastewater effluent on pollution indicator and other microorganisms in river water

The Effects of Heavy Metals on the Microorganisms in River Water

The Effects of Heavy Metals on the Microorganisms in River Water