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921.
Xu Z  Deng S  Yang Y  Zhang T  Cao Q  Huang J  Yu G 《Chemosphere》2012,87(9):1032-1038
Pentachlorobenzene (PeCB) in simulated flue gas was destructed by a commercial V2O5-WO3/TiO2 catalyst in this study. The effects of reaction temperature, oxygen concentration, space velocity and some co-existing pollutants on PeCB conversion were investigated. Furthermore, a possible mechanism for the oxidation of PeCB over the vanadium oxide on the catalysts was proposed. Results show that the increase of gas hourly space velocity (GHSV) and the decrease of operating temperature both resulted in the decrease of PeCB removal over the catalyst, while the effect of the oxygen content in the range of 5-20% (v/v) on PeCB conversion was negligible. PeCB decomposition could be obviously affected by the denitration reactions under the conditions because of the positive effect of NO but negative effect of NH3. The introduction of SO2 caused the catalyst poisoning, probably due to the sulfur-containing species formed and deposited on the catalyst surface. The PeCB molecules were first adsorbed on the catalyst surface, and then oxidized into the non-aromatic acyclic intermediates, low chlorinated aromatics and maleic anhydride.  相似文献   
922.
Ozonation as an advanced oxidant in treatment of bamboo industry wastewater   总被引:1,自引:0,他引:1  
Wu D  Yang Z  Wang W  Tian G  Xu S  Sims A 《Chemosphere》2012,88(9):1108-1113
The present study employed ozonation process to treat the bamboo industry wastewater (BIWW). The impact of ozone dosage and initial organic concentration on color, COD and TOC removal rates were studied along with characterization of the major organics in raw and treated wastewater. The results suggested the ozone dosage of 3.15 g h−1 (concentration 52.5 mg L−1) was suitable for the treatment. After 25 min ozonation of 1 L raw wastewater, the color, COD and TOC removal efficiencies were 95%, 56% and 40%, respectively, with an influent COD concentration of 835 mg L−1. The ratio of kg O3 kg−1 COD at 3.15 g h−1 was 2.8 (<3), revealing that ozonation was a cost effective process for tertiary treatment of BIWW. Longer oxidization time was required to achieve similar results for raw wastewater with higher COD concentration. The chromatogram from gel permeation chromatography revealed that ozonation resulted in the breakdown of high molecular weight compounds into lower molecular weight components but could not completely mineralize the organic matter. The majority of these compounds were identified in both raw and ozonated samples via GC-MS analysis. In addition to ester derivatives as the main intermediates of ozonation, 1-chloroctadecane, methyl stearate, benzophenone and α-cyperone were identified as the by-products of ozonation.  相似文献   
923.
Xie XM  Liao M  Yang J  Chai JJ  Fang S  Wang RH 《Chemosphere》2012,88(10):1190-1195
The effect of ryegrass (Lolium perenne L.) root-exudates concentration on pyrene degradation and the microbial ecological characteristics in the pyrene contaminated soil was investigated by simulating a gradually reducing concentration of root exudates with the distance away from root surface in the rhizosphere. Results showed that, after the root-exudates were added 15 d, the pyrene residue in contaminated soil responded nonlinearly in the soils with the same pyrene contaminated level as the added root-exudates concentration increased, which decreased first and increased latter with the increase of the added root-exudates concentration. The lowest pyrene concentration appeared when the root exudates concentration of 32.75 mg kg(-1) total organic carbon (TOC) was added. At the same time, changes of microbial biomass carbon (MBC, C(mic)) and microbial quotient (C(mic)/C(org)) were opposite to the trend of pyrene degradation as the added root-exudates concentration increased. Phospholipid fatty acid (PLFA) analysis revealed that bacteria was the dominating microbial community in pyrene contaminated soil, and the changing trends of pyrene degradation and bacteria number were the same. The changing trend of endoenzyme-dehydrogenase activity was in accordance with that of soil microbe, indicating which could reflect the quantitative characteristic of detoxification to pyrene by soil microbe. The changes in the soils microbial community and corresponding microbial biochemistry characteristics were the ecological mechanism influencing pyrene degradation with increasing concentration of the added root-exudates in the pyrene contaminated soil.  相似文献   
924.
This paper investigated the degradation kinetics of norfloxacin in a soil, and its effects on soil respiration and nitrogen transformation under different conditions. Compared to the sterile control, the degradation rates of norfloxacin in the non-sterile soil were greatly enhanced, suggesting that microorganisms played a major role in the degradation. Accelerated degradation for norfloxacin in the soil was observed with decreasing concentrations (30 mg/kg to 5 mg/kg) with its half-life decreasing from 62 days to 31 days. Amending swine manure into the soil and increasing the soil moisture level enhanced the biological degradation of norfloxacin. No obvious inhibition of norfloxacin on soil respiration was observed in the soil, while only slight effect on nitrogen transformation was found. The results suggested that norfloxacin at the reported environmental concentrations (<100 mg/kg) would have little effect on microbial activity and functions in the soils.  相似文献   
925.

Background, aim, and scope

The purpose of this study was to monitor and present the heavy metal concentrations in the blood of residents of areas near municipal waste incinerators (MWIs), who are more prone to environmental pollution. We also sought to compare and analyze the residents?? perception of environmental pollution as one of the factors affecting heavy metal concentrations in the blood using a survey about the perceived damage caused by the facilities. Since heavy metal levels in the blood can be affected not only by local environmental pollution but also by personal and occupational factors, heavy metal levels in the blood need to be verified and consistently monitored.

Methods

Residents who live within 300?m of MWIs in Seoul are acknowledged to be under indirect influence according to the Waste Disposal Act. A survey was given to 841 residents living within 300?m of a MWI from 2006 to 2009. The concentrations of heavy metals (lead, cadmium, and mercury) in the blood were measured in the 841 surveyed residents and in 105 residents in reference areas. Additionally, the perception of the damage caused by municipal waste incinerators was investigated using scores from 1 to 5 on a Likert scale.

Results

The measurements of the heavy metal concentrations in the blood showed that the mean concentrations of lead, cadmium, and mercury were 43.1, 1.7, and 1.3?ug/L, respectively. The blood levels of lead and cadmium were slightly higher in the group of the subjects who had resided the longest near the municipal waste incinerators. When compared with the domestic investigation by the Ministry of Environment, the concentrations of lead and cadmium were a little higher, while that of mercury was a little lower. Overall, there was no significant difference in the distribution of heavy metal levels in the blood among age groups. Additionally, the investigation of the perceived damage from municipal waste incinerators showed that the subjects  相似文献   
926.

Background, aim and scope

Lead (Pb) accumulation in soils affects plants primarily through their root systems. The aim of this study was to investigate early symptoms of the loss of membrane integrity and lipid peroxidation in root tissues and physiological adaptation mechanism to Pb in accumulating ecotypes (AE) and non-accumulating ecotypes (NAE) of Sedum alfredii under Pb stress in hydroponics.

Methods and results

Histochemical in situ analyses, fluorescence imaging, and normal physiological analysis were used in this study. Pb accumulation in roots of both AE and NAE increased linearly with increasing Pb levels (0?C200???M), and a significant difference between both ecotypes was noted. Both loss of plasma membrane integrity and lipid peroxidation in root tissues became serious with increasing Pb levels, maximum tolerable Pb level was 25 and 100???M for NAE and AE, respectively. Pb supplied at a toxic level caused a burst of reactive oxygen species (ROS) in root cells in both ecotypes. However, the root cells of AE had inherently higher activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), and lipoxygenase (LOX) in control plants, and the induction response of these antioxidant enzymes occurred at lower Pb level in AE than NAE. AE plants maintained higher ascorbic acid and H2O2 concentrations in root cells than NAE when exposed to different Pb levels, and Pb induced more increase in dehydroascorbate (DHA), catalase (CAT), and ascorbate peroxidase (APX) in AE than NAE roots.

Discussion and conclusion

Results indicate that histochemical in situ analyses of root cell death and lipid peroxidation under Pb short-term stress was sensitive, reliable, and fast. Higher tolerance in roots of accumulating ecotype under Pb stress did depend on effective free oxygen scavenging by making complex function of both constitutively higher activities and sensitive induction of key antioxidant enzymes in root cells of S. alfredii.  相似文献   
927.

Purpose  

The oxone process for azo dye decolorization has drawbacks such as difficulties with reuse, risks of secondary pollution, and high costs associated with UV irradiation. This study aims to explore the use of oxone for decolorization in the absence of catalyst and under natural sunlight conditions (i.e., oxone/natural sunlight system) and evaluate the impacts of operating parameters (reagent dosage, initial methyl orange (MO) concentration, and initial pH) and coexisting substances (humic acid, NO3, metal ions) on the system’s decolorization efficiency.  相似文献   
928.
Bioaugmentation for the removal of polyaromatic hydrocarbons (PAHs) from wastewater using bacteria and yeasts is considered environment-friendly and a cost-effective technique. The effectiveness of this biodegradation system depends on the stability of inoculated microorganisms and the availability of nutrients. This study is aimed to investigate the removal of high molecular weight (HMW)-PAHs from biologically treated produced water using different biological systems. Three systems, inoculated with activated sludge (AS), the mixture of five yeast strains (MY), and the mixture of AS and the five yeast strains (SY), respectively, were constructed, and their performance for the removal of HMW-PAHs was compared over 10 weeks. The effluent of the biologically treated produced water from an oilfield was used as the influent after chrysene and benzo(a)pyrene were spiked as HMW-PAHs. Polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR-DGGE) and fluorescent in situ hybridization (FISH) techniques were used to examine the changes in the structures and abundances of the bacterial and yeast communities in these three systems. Only SY and MY systems were capable to remove chrysene (90.7 % and 98.5 %, respectively) and benzo(a)pyrene (80.7 % and 95.2 %, respectively). PCR-DGGE analysis confirmed that all of the five yeast strains inoculated remained in the SY and MY systems, while FISH results showed that the relative abundance of yeast in the SY and MY systems (10.6 % to 21.9 %, respectively) were significantly higher than AS system (2.3 % to 7.8 %, respectively). The relative abundances of the catechol 2,3-dioxygenase (C23O) indicated that the copy number ratios of benzene ring cleavage gene C23O in the yeast amended systems were much higher than that in the AS system. In this study, all of the three systems were effective in removing the low molecular weight (LMW)-PAHs, while HMW-PAHs including chrysene and benzo(a)pyrene were efficiently removed by MY and SY systems, not by AS system. The high HMW-PAHs removal in the MY and SY bioaugmentation systems possibly attributed to the inoculation of the mixed yeast culture. By combining the PCR-DGGE results with the FISH analyses, it was found that yeast probably consisting mainly of the five inoculated strains inhabited in the two bioaugmentation systems as a dominant population. The relatively higher performance of the SY system might be attributed to the suspended growth type which permitted a more efficient contact between microbial cells and contaminants. The bioaugmentation systems (SY and MY) were successfully established by inoculating with five nonindigenous yeast strains and demonstrated high performance in removal of HMW-PAHs.  相似文献   
929.

Introduction

The suitability of the application of ultrafiltration (UF) to harvest Chlorella sp. from the culture medium was examined. We investigated the effects of two improved UF system, forward air?Cwater flushing and backwash with permeate, on the concentration process.

Materials and methods

Backwash with permeate was selected as an optimization of the improved UF system, which was more effective for permeate flux recovery. Moreover, the hollow fiber UF system by adding periodical backwash with permeate was examined for Chlorella sp. harvesting.

Results and discussion

It was found that Chlorella sp. could be concentrated with high recovery in a lab-scale experiment. An overall algal biomass recovery of above 90% was achieved when the volume concentration factor was 10. For an original biomass of 1.3?±?0.05?g/L, 1?min backwash followed by 20?min forward concentrating was more effective, which resulted in a recovery of 94% and a high average flux of 30.3?L/m2/h. In addition, the algal recovery was highly correlated to the volume concentration factor and the initial biomass. A high concentration factor or a high initial biomass resulted in a low biomass recovery.  相似文献   
930.
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