固定化高效降解菌处理PTA废水的研究

研究了聚乙烯醇(PVA)加少量海藻酸钠及SiO2、CaCO3的方法固定高效菌处理PTA污水.结果表明,采用质量分数分别为PVA 10%、海藻酸钠0.3%、特种菌种10%、SiO2 3%、CaCO30.3%,用饱和硼酸溶液(pH为4.0)作为交联剂,制得的颗粒处理PTA废水时,废水COD负荷为2.91kg/m3·d时,CODcr、TOC、TA去除率均为85%以上;废水COD负荷为12.2kg/m3j·时,CODcr去除率仍为50%以上、TOC去除率为60%以上,当pTA废水pH从55降至35时,CODcr、TOC、TA去除率仍在86%以上.     

油田企业安全文化建设亟需解决的几个问题及对策

油田企业生产工作具有点多、线长、面广、庞杂、易燃易爆、有毒有害、高温高压、连续作业等特点,安全生产管理难度相当大,若稍有不慎,就会酿成大的事故.因此,避免或减少重大事故的发生是油田企业安全文化建设的重要目标.20世纪90年代,随着HSE管理体系引入中国,国内油田企业相继建立了HSE管理制度,并把HSE安全管理体系作为企业安全文化建设的主要载体.但油田企业安全文化建设仍存在误区,完全文化建设体系亟需进一步完善.     

Comparison of catalytic activity of two platinised TiO2 films towards the oxidation of organic pollutants

Two types of platinised TiO2 films, i.e., Pt-TiO2/ITO and Pt(TiO2)/ITO, were prepared by a procedure of dip-coating and subsequent photo-deposition, and photo-deposition and subsequent dip-coating, respectively. They were well characterized by DRS, XRD spectra, SEM microscopy and photoelectrochemical measurement. Their photocatalytic, dark catalytic and photoelectrocatalytic activities were investigated using formic acid as a model organic pollutants. Compared with pure TiO2/ITO film, the photocatalytic activity of the platinised TiO2 films were apparently improved. However, the improvement was considerably dependent on the preparation method of these films. Pt-TiO2/ITO not only possessed higher photocatalytic activity but also showed a dark catalytic activity towards HCOOH degradation. As a sequence, it was first emphasized that the dark catalytic effect of Pt-TiO2/ITO was partly responsible for degradation of formic acid in the photocatalytic oxidation process. Although the Pt(TiO2)/ITO film does not exhibit the dark catalytic activity, its photocatalytic degradation efficiencies towards HCOOH are higher than that of Pt-TiO2/ITO film. Therefore, in view of enhanced photocatalytic activity, the Pt(TiO2)/ITO was more favored than Pt-TiO2/ITO film.     

Statistical evaluation of an analytical IC method for the determination of trace level perchlorate

Trace level perchlorate analysis in water initiated a new development in the Ion Chromatography (IC) technology. Maintenance of a low detection limit may be highly affected by the operating conditions of the IC system. In this paper the homoscedasticity of the IC system within the calibration concentration range, the effect of the system drift on the calibration curve and the effect of the self regeneration suppressor (SRS) current on the detection limit were investigated. The experimental results were evaluated by statistical methods such as the Cochran test and the lack of fit test. The detection limits were obtained by two ways. One through method detection limit (MDL) and the other through detection limit from the calibration curve (DTC). The Cochran test results revealed the homoscedasticity of the IC system. The effect of system drift on the calibration curve was noticed by the lack of fit test. MDL yielded a lower but less reliable detection limit than DTC. An acceptable detection limit can be achieved under the lower SRS current (100 mA).     

Distribution and loadings of polycyclic aromatic hydrocarbons in the Xijiang River in Guangdong, South China

The Xijiang River is the major tributary of the Pearl River, South China, and is the major source water system for more than 4.5 million of urban population and 28.7 million of rural population. We initiated a systematic study on detection and quantification of organic pollutants in both water and suspended particulate matter (SPM) for samples collected in a span of 12 months. Our results showed that total concentrations of 15 polycyclic aromatic hydrocarbons (PAHs) varied from 21.7 to 138 ng l(-1) in water and from 40.9 to 665 microg kg(-1) in SPM. The organic carbon normalized distribution coefficients (K(OC)) computed for the PAHs were correlated well with their octanol-water partition coefficient (K(OW)). The estimated annual loadings of Ant, BaA, and BghiP and the total PAHs in the Xijiang River were 1620, 330, 177 and 19,400 kg, respectively. Further analysis of the data showed that combustion may be the major source of PAHs and that direct leakage of petroleum products may be insignificant.     

Accumulation of copper in brown rice and effect of copper on rice growth and grain yield in different rice cultivars

A pot experiment with 38 commonly cultured rice cultivars showed that the effect of Cu (100 mg kg(-1)) on rice growth, grain yield and accumulation of Cu in brown rice varied greatly with different cultivars. Although the average Cu concentration in brown rice of the 38 cultivars was significantly increased (P<0.01) compared with the control, in none of the cultivars did Cu concentration in brown rice exceed the maximum permissible limit of 10 mg Cu kg(-1). This suggests that rice grown in Cu-contaminated paddy soil (100 mg Cu kg(-1)) will not adversely affect human health through the food chain. Because of the significant negative correlation between grain weight and Cu concentration in brown rice with the soil Cu treatment, screening for cultivars with low Cu accumulation in brown rice and high grain yield for Cu-contaminated areas is feasible. The present research led to the recommendation of three such cultivars: Jiahua, Zhenxian 866, Zhe 733. The average grain yield under Cu treatment (100 mg Cu kg(-1) soil) was significantly (P<0.01) reduced compared with the control. The decreases or increases of grain yields mainly resulted from the combined effects of the panicles per pot, spikelets per panicle and filled spikelets per panicle under the soil Cu treatment. Furthermore, there were significant (r=0.869, P<0.01) positive correlations between the RC (relative changes) of spikelets per panicle and filled spikelets per panicle under the soil Cu treatment.     

Effects of metsulfuron-methyl on the microbial population and enzyme activities in wheat rhizosphere soil

The effects of metsulfuron-methyl, a sulfonylurea herbicide, on the wheat soil microorganisms were evaluated by the methods of microbial inoculation culture, and the activities of three enzymes were measured using the colorimetric method. The tolerant microorganisms that can resist 500 microg x g(-1) metsulfuron-methyl in the counting culture medium were studied specially. Metsulfuron-methyl distinctly inhibited the common aerobic heterotriphic bacteria, but the effects on common fungi and common actinomycete were not evident. In the meantime, the number of tolerant fungi increased greatly in the rhizosphere after the application of metsulfuron-methyl in contrast to the significant decrease of the amount of tolerant actinomycete. It indicates that fungi might turn into the dominant microbial type and actinomycete is the sensitive factor in the soil polluted by sulfonylurea residues. The population of aromatic compounds-decomposing bacteria, aerobic azotobacter, and nitrite bacteria all increased in the earlier period, but the aerobic azotobacter decreased rapidly in number 30 days later, and the amount of nitrite bacteria also showed a temporary decrease with time 15 days later. However, the denitrifying bacteria just began to increase significantly after the crops had grown for 50 days. The amount of sulfur-oxidizing bacteria gradually decreased with the growth of crops, and so were the sulfate-reducing bacteria after metsulfuron-methyl application. To all types of microorganisms, there were more microbes in rhizosphere samples than those in nonrhizosphere except aerobic azotobacter. It means the growth of wheat root system can stimulate the growth of most microorganisms. The activities of hydrogen peroxidase and polyphenol oxidase in soil samples after metsulfuron-methyl application were notably lower than those in the control, and the difference of the activities between the samples of rhizosphere and nonrhizosphere was evident. On the contrary, the activity of dehydrogenase was not inhibited by the application of metsulfuron-methyl, and the rhizosphere effect was not obvious either.     

Photocatalytic Treatment of RDX Wastewater with Nano-Sized Titanium Dioxide (5 pp)

Background, Aim and Scope The polynitramines, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), are important military explosives and regulated toxic hazardous compounds. Production, testing and use of the compounds has resulted in numerous acres of contaminated soils and groundwater near many munitions facilities. Economical and efficient methods for treatment of wastewater and cleanup of soils or groundwater containing RDX and HMX are needed. This study focuses on the photocatalytic treatment of RDX wastewater with nano-sized titanium dioxide (nano-TiO2) under simulated sunlight, whose intensity and wavelength are similar to that of the real sunlight in Xi'an at noon. The objective is to determine the potential for RDX destruction with nano-TiO2 in aqueous solution. Materials and Methods: An activated carbon fiber (ACF) cloth-loaded with nano-TiO2 was put into the RDX containing solution, and the concentration of RDX was measured (by HPLC–UV) at regular time intervals under simulated sunlight. Results: The RDX degradation percentage of the photocatalytic process is higher than that of Fenton oxidation before 80 min, equivalent after 80 min, and it reaches 95% or above after 120 min. The nano-TiO2 catalyst can be used repeatedly. Discussion: The photocatalytic degradation kinetics of RDX under simulated sunlight can be described by a first-order reaction kinetics equation. The possible degradation mechanism of RDX was presented and the degradation performance was compared with that of biological method. Conclusions: It was demonstrated that the degradation of RDX wastewater is very effective with nano-TiO2 as the photocatalytic catalyst under simulated sunlight. The efficiency of the nano-TiO2 catalyst for RDX degradation under simulated sunlight is nearly identical to that of Fenton oxidation. Recommendations and Perspectives: To date, a number of catalysts show poor absorption and utilization of sunlight, and still need ultraviolet light irradiation during wastewater degradation. The nano-TiO2 used in the described experiments features very good degradation of RDX under simulated sunlight, and the manufacturing costs are rather low (around 10 Euro/m2). Moreover, the degradation efficiency is higher compared to that of the biological method. This method exhibits great potential for practical applications owing to its easiness and low cost. If it can be applied extensively, the efficiency of wastewater treatment will be enhanced greatly.     

137Cs budget during the period of 1960s in a small drainage basin on the Loess Plateau of China

A sediment profile with a thickness of 28.12 m in a failed reservoir in a small catchment of the Yuntaishan Gully in the Loess Plateau of China consisted of 44 flood couplets deposited during the period from 1960 to 1970 with total volume of 2.36 x 10(6)m(3). Specific sediment yields for a flood event varied from 300 t km(-2) to 14,400 t km(-2) and annual sediment yields varied from 2500 t km(-2) in 1966 to 40,000 t km(-2) in 1964 with a mean value of 12,700 t km(-2)a(-1) for the period. Average annual (137)Cs concentrations of the sediments increased from 0.92 Bq kg(-1) in 1960 to 4.82 Bq kg(-1) in 1963, then decreased to 1.53 Bq kg(-1) in 1970. The total (137)Cs activity in the reservoir sediments was 9.22 x 10(9) Bq, which accounted for 31.9% of the total (137)Cs fallout precipitation of 2.89 x 10(10) Bq within the catchment during the period. The proportion of the (137)Cs loss from the catchment to the (137)Cs fallout precipitation within the catchment in a year varied between 8.01% and 66.8%, and it was 20.9% for the peak (137)Cs deposition year of 1963 and 52.0% in 1964. By analysis of the (137)Cs budget in the catchment for the (137)Cs peak precipitation period from 1962 to 1964, the (137)Cs surface enrichment coefficient Gamma should be much less than 0.23. And for calculation of soil losses on the cultivated land in the inter-gully area by using the Mass Balance Model II, the value of Gamma should be 0.05-0.1.     

Influence of NOx on the activity of Pd/θ-Al2O3 catalyst for methane oxidation: Alleviation of transient deactivation

Alumina supported Pd catalyst（Pd/Al₂O₃） is active for complete oxidation of methane, while often suffers transient deactivation during the cold down process. Herein, heating and cooling cycle tests between 200 and 900 °C and isothermal experiments at 650 °C were conducted to investigate the influence of NO_x on transient deactivation of Pd/θ-Al₂O₃ catalyst during the methane oxidation. It was found that the co-fed of NO alleviated transient d...