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ABSTRACT: Inhalation is one of the main exposure routes to pathogenic microorganisms during wastewater reuse. An applicable method is introduced to assess the pathogenic microbial exposure from inhalation. Firstly, emission intensity of pathogenic microorganisms during reclaimed water spraying is determined by the concentration of pathogenic microorganisms in reclaimed water, spraying intensity and aerosolizing efficiency factor. The value of the aerosolizing efficiency factor is usually between 0.003 and 0.01. Then the concentration of pathogenic microorganisms in air is calculated by referring to the model of air pollutant dispersion and considering the microorganisms decay. The value of the microbial viability decay factor is between -0.23 s(-1) and 0 s(-1), and that of the environmental impact factor is between 0.016 and 73, varied by different kinds of microorganisms. And then the exposure from inhalation route can be finally attained by multiplying inhalation rate and exposure time. The daily average inhalation rate is 4.5-17 m3 x d(-1), and the hourly average inhalation rate is 0.3-3.2 m3 x h(-1), differentiated by age, gender, and activity of susceptible population. The method proposed in this study can be directly used to assess the pathogenic microbial exposure caused by reclaimed water used for agriculture irrigation, gardening, or fountain spraying.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 02/2009; 30(1):70-4.
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ABSTRACT: In recent years, the exploration and development of the effective methods of treatment and prevention to algal blooms, especially Microcystis aeruginosa blooms has been an important issue in the field of water environment protection. Allelochemicals (natural plant toxins) are considered promising sources of algicides to control algal blooms. The objective of this study is to determine the inhibitory effects and potential mechanisms of a well-known allelochemical gramine (N,N-dimethyl-3-amino-methylindole) on bloom-forming cyanobacterium M. aeruginosa. The results showed that this indole alkaloid effectively inhibited the growth of M. aeruginosa. The effective concentration causing a 50% inhibition at 3 d (EC(50, 3 d)) increased with the initial algal density (IAD) increasing. When IAD increased from 5x10(4) to 5x10(5)cellsmL(-1), the values of EC(50, 3 d) increased from 0.5 to 2.1mgL(-1). In the cells of M. aeruginosa, gramine caused an obvious increase in the level of reactive oxygen species (ROS). The lipid-peroxidation product malondialdehyde (MDA) increased significantly in gramine-treated cells. The effects of gramine on enzymatic and non-enzymatic antioxidants were in different manners. The activity of superoxide dismutase (SOD) was decreased after gramine exposure. The catalase (CAT) activity was increased after 4h but decreased from 60h. Both the contents and the regeneration rates of ascorbic acid (AsA) and reduced glutathione (GSH) were increased after 4h of exposure to gramine. However, only GSH content was still increased after 40h of exposure. These results suggested that the activation of antioxidants in M. aeruginosa played an important role to resist the stress from gramine at initial time, the inactivation of SOD is crucial to the growth inhibition of M. aeruginosa by gramine, and the phytotoxicity of gramine on M. aeruginosa may be due to oxidative damage via oxidation of ROS.
Aquatic toxicology (Amsterdam, Netherlands) 12/2008; 91(3):262-9. · 3.12 Impact Factor
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ABSTRACT: Removal of Cryptosporidium and Giardia under different reaction conditions, such as flocculent dosage, pH, temperature, were investigated to study the removal characteristic and mechanism of pathogenic protozoan in a flocculation process. The experimental results showed that after flocculation, there were not good linear relationships between average t potential of colloid in water samples and removal efficiency of the two kinds of microspheres, the surrogates of the pathogenic protozoan, or the residual turbidity (R = 0.49, 0.48, 0.65). But the linear relationship between the removal of the two kinds of microspheres was obvious (R = 0.99), and there were also good exponential relationships between the removal of microspheres and residual turbidity (R = 0.92,0.95). Sweep flocculation appeared to be an important mechanism for protozoan removal under the conditions in this study. The removal efficiency of Giardia was higher than that of Cryptosporidium under same reaction conditions.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 09/2008; 29(8):2287-90.
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ABSTRACT: The concentration of pathogenic protozoan (Cryptosporidium and Giardia) in water samples of different units in a full-scale wastewater treatment plant in Beijing was investigated periodically. The average concentrations of Cryptosporidium detected in untreated wastewater, primary sedimentation, secondary sedimentation, flocculation-sedimentation and sand-filtration effluent were 238, 179, 6, 1, 0.3 oocysts/L respectively, and the average concentrations of Giardia were 1568, 1048, 22, 4, 0.6 cysts/L respectively. The total removal efficiencies of Cryptosporidium and Giardia in this treatment process were 2.98 and 3.46 log respectively. Very little protozoan in wastewater could be removed by preliminary treatment process, the removal efficiencies were only 0.13 and 0.18 log respectively. Biological treatment unit had the highest removal efficiency, up to 1.50 and 1.67 log respectively. Advanced treatment process could enhance the removal of the protozoan effectively. The results also showed that the pollution level of pathogenic protozoan in the influent of wastewater treatment and reclamation plant was various according to the climate, high in dry seasons and low in rainy season.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 08/2008; 29(7):1955-60.
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ABSTRACT: Macrophytic allelochemicals are considered an environment-friendly and promising alternative to control algal bloom. However, studies examining the potential mechanisms of inhibitory allelochemicals on algae are few. The allelochemical ethyl 2-methyl acetoacetate (EMA), isolated from reed (Phragmites communis), was a strong allelopathic inhibitor on the growth of Microcystis aeruginosa. EMA-induced antioxidant responses were investigated in the cyanobacterium M. aeruginosa to understand the mechanism of EMA inhibition on algal growth. The activities of enzymatic antioxidants superoxide dismutase (SOD) and catalase (CAT), and the contents of non-enzymatic antioxidants reduced glutathione (GSH) and ascorbic acid (AsA) of M. aeruginosa cells were analyzed after treatments with different concentrations of EMA. Exposure of M. aeruginosa to EMA caused changes in enzyme activities and contents of non-enzymatic antioxidants in different manners. The decrease in SOD activity occurred first after 4 h of EMA exposure, and more markedly after 40 h. CAT activity did not change after 4 h of EMA exposure, but increased obviously after 40 h. The contents of AsA and GSH were increased greatly by EMA after 4 h. After 60 h, low EMA concentrations still increased the CAT activity and the contents of AsA and GSH, but high EMA concentrations started to impose a marked suppression on them. EMA increased dehydroascorbate (DHAsA) and oxidized glutathione (GSSG) contents during all exposure times. After 60 h, the regeneration rates of AsA and GSH (represented by the AsA/DHAsA ratio and GSH/GSSG ratio, respectively) were reduced by high EMA concentrations. These results suggest that the activation of CAT and the availability of AsA and GSH at early exposure are important to counteract the oxidative stress induced by EMA, and the inactivation of SOD may be crucial to the growth inhibition of M. aeruginosa by EMA.
Journal of plant physiology 01/2008; 165(12):1264-73. · 2.50 Impact Factor
