纤维素降解细菌筛选及降解特性分析

基于获得高效纤维素降解细菌的目的,通过LB培养基的培养以及刚果红培养基的筛选,从牛粪堆肥中筛选获得2株高效纤维素降解细菌。经鉴定,分别为枯草芽胞杆菌(Bacillus subtilis)和地衣芽胞杆菌(Bacillus licheniformis)。所筛选得到的菌种具有很高的滤纸降解能力,可在6d内使滤纸剧烈崩溃,振摇成均匀糊状;其中,地衣芽胞杆菌的羧甲基纤维素钠酶活峰值在发酵第4天达到峰值(237U/g)。     

Fenton氧化-序批式膜生物反应器耦合处理干法腈纶废水

采用Fenton氧化-序批式膜生物反应器(SBMBR)组合工艺处理干法腈纶废水。结果表明,在废水初始pH值为3.0,H2O2投加量为90.0 mmol/L,Fe2+投加量为20.0 mmol/L,反应时间为2.0 h的条件下,Fenton氧化预处理对腈纶生产废水的COD去除率达到47.0%以上,COD由1 091 mg/L降至560 mg/L,废水的BOD5/COD由0.32升至0.69,废水的可生化性得到显著提高。Fenton处理出水与丙烯腈废水等比例混合后,采用SBMBR进行生化处理,在水力停留时间为24 h,90 min缺氧/150 min好氧交替运行的条件下,COD、NH4+-N和TN的平均去除率分别为71.7%、97.2%和47.4%,碳源不足是限制TN去除效果的主要影响因素。在无外加碳源的条件下,组合工艺处理后出水COD和NH4+-N浓度分别为117 mg/L和1.7 mg/L,出水水质可以稳定达到国家一级排放标准(GB8978-1996)。     

Exposure to inhaled THM: Comparison of continuous and event-specific exposure assessment for epidemiologic purposes

Trihalomethanes (THMs) (chloroform, bromoform, dibromochloromethane, and bromodichloromethane) are the most abundant by-products of chlorination. People are exposed to THMs through ingestion, dermal contact and inhalation. The objective of this study was to compare two methods for assessing THM inhalation: a direct method with personal monitors assessing continuous exposure and an indirect one with microenvironmental sampling and collection of time–activity data during the main event exposures: bathing, showering and swimming. This comparison was conducted to help plan a future epidemiologic study of the effects of THMs on the upper airways of children. 30 children aged from 4 to 10 years were included. They wore a 3M^™ 3520 organic vapor monitor for 7 days. We sampled air in their bathrooms (during baths or showers) and in the indoor swimming pools they visited and recorded their time–activity patterns. We used stainless steel tubes full of Tenax^® to collect air samples. All analyses were performed with Gas Chromatography and Mass Spectrometry (GC-MS). Chloroform was the THM with the highest concentrations in the air of both bathrooms and indoor swimming pools. Its continuous and event exposure measurements were significantly correlated (r_s = 0.69 p < 0.001). Continuous exposures were higher than event exposures, suggesting that the event exposure method does not take into account some influential microenvironments. In an epidemiologic study, this might lead to random exposure misclassification, thus underestimation of the risk, and reduced statistical power. The continuous exposure method was difficult to implement because of its poor acceptability and the fragility of the personal monitors. These two points may also reduce the statistical power of an epidemiologic study. It would be useful to test the advantages and disadvantages of a second sample in the home or of modeling the baseline concentration of THM in the home to improve the event exposure method.     

Occurrence and fate of pharmaceutical products and by-products,from resource to drinking water

Among all emerging substances in water, pharmaceutical products (PPs) and residues are a lot of concern. These last two years, the number of studies has increased drastically, however much less for water resources and drinking water than for wastewater. This literature review based on recent works, deals with water resources (surface or groundwater), focusing on characteristics, occurrence and fate of numerous PPs studied, and drinking water including water quality. Through this review, it appears that the pharmaceutical risk must be considered even in drinking water where concentrations are very low. Moreover, there is a lack of research for by-products (metabolites and transformation products) characterization, occurrence and fate in all water types and especially in drinking water.     

Performance of different composting techniques in reducing oestrogens content in manure from livestock in a Vietnamese setting

Steroid oestrogens (SE) are released by humans and animals into the environment. In the Mekong Delta animal excrement is directly discharged into surface water and can pollute the water. Only a few animal production sites are currently treating the excrement in either biogas plants or vermicomposting systems. The concentration of SE in manures from pigs and cattle was monitored in the Mekong Delta, Vietnam. Fresh cow faeces had an oestrogen concentration of 3.3 ng E2 eq/g dry weight. The SE concentration in effluent from biogas plants fed with animal manures was 341 ng E2 eq/L. Most of the SE were in the solid phase (77.9–98.7%). Vermicomposting reduced SE to 95% of the original input.     

电吸附对水中盐类、氨氮、COD的去除效果分析

电吸附技术作为高效、环境友好型的除盐、除氨氮技术，可应用与水的深度处理领域内。为了使污水回用达到工业用水的水质标准，对电吸附去除水中盐类、氨氮、COD的效果进行分析，结果表明，电吸附设备处理不同氨氮浓度的废水，对中低浓度的氨氮去除效果稳定，当进水氨氮浓度低于20 mg/L时，处理后出水氨氮浓度低于5 mg/L，COD浓度小于25 mg/L，达到回用标准；随着进水盐浓度的增大电吸附处理效果逐渐变差，在电导率低于2 500 μS/cm时除盐率在75%左右，氨氮去除率达到70%左右，COD去除率达到60%左右。经电吸附处理后的低氨氮浓度废水，TDS、氨氮浓度均可达到工业回用水标准。     

Supply Curves for Using Powder River Basin Coal to Reduce Sulfur Emissions

Abstract

Supply curves were prepared for coal-fired power plants in the contiguous United States switching to Wyoming's Powder River Basin (PRB) low-sulfur coal. Up to 625 plants, representing ～44% of the nameplate capacity of all coal-fired plants, could switch. If all switched, more than $8.8 billion additional capital would be required and the cost of electricity would increase by up to $5.9 billion per year, depending on levels of plant derating. Coal switching would result in sulfur dioxide (SO₂) emissions reduction of 4.5 million t/yr. Increase in cost of electricity would be in the range of 0.31-0.73 cents per kilowatt-hour. Average cost of S emissions reduction could be as high as $1298 per t of SO₂. Up to 367 plants, or 59% of selected plants with 32% of 44% nameplate capacity, could have marginal cost in excess of $1000 per t of SO₂. Up to 73 plants would appear to benefit from both a lowering of the annual cost and a lowering of SO₂ emissions by switching to the PRB coal.     

Influence of sediment composition on PAH toxicity using zebrafish (Danio rerio) and Japanese medaka (Oryzias latipes) embryo-larval assays

Due to hydrophobic and persistent properties, polycyclic aromatic hydrocarbons (PAHs) have a high capacity to accumulate in sediment. Sediment quality criteria, for the assessment of habitat quality and risk for aquatic life, include understanding the fate and effects of PAHs. In the context of European regulation (REACH and Water Framework Directive), the first objective was to assess the influence of sediment composition on the toxicity of two model PAHs, benzo[a]pyrene and fluoranthene using 10-day zebrafish embryo-larval assay. This procedure was undertaken with an artificial sediment in order to limit natural sediment variability. A suitable sediment composition might be then validated for zebrafish and proposed in a new OECD guideline for chemicals testing. Second, a comparative study of toxicity responses from this exposure protocol was then performed using another OECD species, the Japanese medaka. The potential toxicity of both PAHs was assessed through lethal (e.g., survival, hatching success) and sublethal endpoints (e.g., abnormalities, PMR, and EROD) measured at different developmental stages, adapted to the embryonic development time of both species. Regarding effects observed for both species, a suitable artificial sediment composition for PAH toxicity testing was set at 92.5 % dry weight (dw) silica of 0.2–0.5-mm grain size, 5 % dw kaolin clay without organic matter for zebrafish, and 2.5 % dw blond peat in more only for Japanese medaka. PAH bioavailability and toxicity were highly dependent on the fraction of organic matter in sediment and of the K _ow coefficients of the tested compounds. The biological responses observed were also dependent of the species under consideration. Japanese medaka embryos appeared more robust than zebrafish embryos for understanding the toxicity of PAHs following a sediment contact test, due to the longer exposure duration and lower sensitivity of sediment physical properties.     

Kinetic study of γ-hexabromocyclododecane orally given to laying hens (Gallus domesticus)

Introduction  

High concentrations of hexabromocyclododecane (HBCD) sometimes recorded in free-range hens' eggs are thought to be due to soil ingestion. Of the three stereoisomers of HBCD (α-, β-, and γ-HBCD), γ-HBCD is the main component in the commercial mixture, as well as in environmental matrices, whereas the isomer profile is α-dominated in biota. In fish and in mammals, this shift is thought to be due to a rapid elimination of γ-HBCD and to its bioisomerization to the more persistent α-HBCD. The aim of the current controlled study was to better understand the fate of ingested HBCD in laying hens. The isomer profile in soil being γ-dominated, excretion kinetics of γ-HBCD into egg yolk, and accumulation in liver and in abdominal fat were investigated.     

Comprehensive temperature monitoring in an in-vessel forced-aeration static-bed composting process

Comprehensive temperature monitoring was done in an in-vessel forced-aeration static-bed composting process using sewage sludge. The three layers that divided the compost pile horizontally showed different temperature distributions. The temperature of the top layer appeared not to be influenced by the ambient temperature. The temperature of the center area of the top layer was taken to be the representative temperature for evaluating composting start-up performance. The temperature of the bottom layer was strongly influenced by the ambient temperature, and the temperature of the center area of the bottom layer was taken to be the representative temperature for pathogen control as it was the minimum temperature in the reactor. Composting start-up performance was influenced by several factors when the ambient temperature was either below or above 20°C. When the ambient temperature was below 20°C, the time taken to reach 65°C (T ₆₅) was influenced by the temperature of inflowing air, but when the temperature was higher than 20°C, it was influenced by the ratio of sewage sludge to seed compost (F/S). T ₆₅ was least when F/S was 1–2. Received: January 9, 2001 / Accepted: October 10, 2001