低C/N比水产养殖废水生物脱氮实验研究

随着短程硝化-反硝化理论研究的发展,在低C/N比条件下,实现污水的生物脱氮处理已成为可能。为此,设计了水产养殖用水的三级生物膜短程硝化-反硝化处理工艺,并对该工艺在去除模拟水产养殖废水主要污染物的作用进行了初步研究。研究结果表明,在进水pH值7.5~8.5,温度为28~32℃,溶解氧为0.5~1 mg/L,游离氨浓度为5~10 mg/L的条件下,模拟废水的COD、NH4+-N和TN的平均去除率分别达到94.4%、91.6%和70.1%;并且低C/N比对出水氨氮NH4+-N的去除率影响不大,NO2--N的平均浓度控制在5.2 mg/L以下,低于鱼类的耐受浓度。表明该短程硝化-反硝化工艺设计,可用于低C/N比水产养殖废水主要污染物的生物处理,尤其是可消除NO2--N对水产养殖的潜在威胁,基本达到养鱼回用标准。     

内电解法处理含N,N-二甲基乙酰胺工业废水

用内电解法处理含N,N-二甲基乙酰胺(DMAC)工业废水,研究pH、Fe∶C(体积比)、活性炭粒径和水力停留时间(HRT)等对该废水处理效果的影响,并确定最佳工艺条件。实验结果表明:在进水浓度维持在50 mg/L左右,最佳的工艺参数pH、Fe∶C和HRT分别为3.0、1∶1和60 min时,DMAC去除率高达到95%,处理水DMAC浓度小于5 mg/L。处理后废水的可生化性有明显的改善,BOD5/COD由0.21提高至0.66;而DMAC的去除基本符合二级动力学规律。     

Decomposition and oxidation of sodium 3,5,6-trichloropyridin-2-ol in sub- and supercritical water

Sodium 3,5,6-trichloropyridin-2-ol (STCP) is a necessary precursor compound for the production of chlorpyrifos and triclopyr, which are extensively used as pesticide and herbicide, respectively. In the process of STCP production, however, large amount of wastewater containing STCP is discharged, which causes increasingly environmental concerns. Therefore, it is of great significance to develop a rapid and effective method for the disposal of containing STCP contaminants. In this work, the thermal decomposition of STCP in sub- and supercritical water was investigated using a continuous tubular reactor. While STCP was stable below 280 °C, it could be effectively decomposed at elevated temperature. FT-IR spectra of the decomposition products indicated that the pyridine ring structure in the STCP molecule was stable even at temperatures up to 400 °C. The decomposition reaction was mainly caused by the substitution of Cl groups in the STCP molecule with OH groups, resulting in polyhydroxylated pyridines as the major decomposition product. Moreover, high pressure favored the substitution reaction. To completely decompose STCP into non-toxic or low toxic compounds, supercritical water oxidation (SCWO) was employed to evaluate the oxidation of STCP using H₂O₂ as an oxidant. It was found that STCP could be completely oxidized to H₂O, CO₂ and corresponding inorganic ammonium salts with an oxidation rate of 99%.     

Development of a SWAT Patch for Better Estimation of Sediment Yield in Steep Sloping Watersheds1

Abstract: The watershed scale Soil and Water Assessment Tool (SWAT) model divides watersheds into smaller subwatersheds for simulation of rainfall‐runoff and sediment loading at the field level and routing through stream networks. Typically, the SWAT model first needs to be calibrated and validated for accurate estimation through adjustment of sensitive input parameters (i.e., Curve Number values, USLE P, slope and slope‐length, and so on). However, in some instances, SWAT‐simulated results are greatly affected by the watershed delineation and Digital Elevation Models (DEM) cell size. In this study, the SWAT ArcView GIS Patch II was developed for steep sloping watersheds, and its performance was evaluated for various threshold values and DEM cell size scenarios when delineating subwatersheds using the SWAT model. The SWAT ArcView GIS Patch II was developed using the ArcView GIS Avenue program and Spatial Analyst libraries. The SWAT ArcView GIS Patch II improves upon the SWAT ArcView GIS Patch I because it reflects the topographic factor in calculating the field slope‐length of Hydrologic Response Units in the SWAT model. The simulated sediment value for 321 subwatersheds (watershed delineation threshold value of 25 ha) is greater than that for 43 subwatersheds (watershed delineation threshold value of 200 ha) by 201% without applying the SWAT ArcView GIS Patch II. However, when the SWAT ArcView GIS Patch II was applied, the difference in simulated sediment yield decreases for the same scenario (i.e., difference in simulated sediment with 321 subwatersheds and 43 subwatersheds) was 12%. The simulated sediment value for DEM cell size of 50 m is greater than that for DEM cell size of 10 m by 19.8% without the SWAT ArcView GIS Patch II. However, the difference becomes smaller (3.4% difference) between 50 and 10 m with the SWAT ArcView GIS Patch II for the DEM scenarios. As shown in this study, the SWAT ArcView GIS Patch II can reduce differences in simulated sediment values for various watershed delineation and DEM cell size scenarios. Without the SWAT ArcView GIS Patch II, variations in the SWAT‐simulated results using various watershed delineation and DEM cell size scenarios could be greater than those from input parameter calibration. Thus, the results obtained in this study show that the SWAT ArcView GIS Patch II should be used when simulating hydrology and sediment yield for steep sloping watersheds (especially if average slope of the subwatershed is >25%) for more accurate simulation of hydrology and sediment using the SWAT model. The SWAT ArcView GIS Patch II is available at http://www.EnvSys.co.kr/~swat for free download.     

The South‐to‐North Water Transfer Project of China: Environmental Implications and Monitoring Strategy1

Abstract: In 2002, China launched the South‐to‐North Water Transfer Project after completing a 50‐year feasibility study. By 2050, the three‐route (i.e., East, Middle, and West) project will be capable of transferring 44.8 billion m³/year of water from the water rich Yangtze River to the arid north to alleviate water shortage and help secure a balanced social and economic development across the nation. However, diversion of such a large quantity of water could profoundly change the riverine environment of the upper Yellow River and the lower reach of the Han River, a tributary of the Yangtze River and the water supplying area of the project’s Middle Route, because of changes in the annual discharge. Secondary salinization seems inevitable in the water receiving areas of the North China Plain, and decrease in the discharge of the Yangtze River will result in seawater intrusion into the Yangtze Delta. This paper describes the project and discusses its environmental implications. Additionally, a long‐term monitoring strategy under the umbrella of the Chinese Ecological Research Network is proposed for environmental monitoring.     

Sustainable Water Resources Management in a Conflict Resolution Framework1

Abstract: A decision support system for sustainable water resources management in a water conflict resolution framework is developed to identify and evaluate a range of acceptable alternatives for the Geum River Basin in Korea and to facilitate strategies that will result in sustainable water resource management. Working with stakeholders in a “shared vision modeling” framework, sustainable management strategies are created to illustrate system tradeoffs as well as long‐term system planning. A multi‐criterion decision‐making (MCDM) approach using subjective scales is utilized to evaluate the complex water resource allocation and management tradeoffs between stakeholders and system objectives. The procedures used in this study include the development of a “shared vision model,” a simulated decision‐making support system (as a tool for sustainable water management strategies associated with water conflicts, management options, and planning criteria), and the application of MCDM techniques for evaluating alternatives provided by the model. The research results demonstrate the utility of the sustainable water resource management model in aid of MCDM techniques in facilitating flexibility during initial stages of alternative identification and evaluation in a basin suffering from severe water conflicts.     

Assessment Tools for Urban Catchments: Developing Stressor Gradients1

Abstract: This is the first in a series of three articles designed to establish empirically defined biological indicators and thresholds for impairment for urbanized catchments, and to describe a process by which the biological condition of waterbodies in urbanized catchments can be applied. This article describes alternative gradients of urbanization for assessing and selecting a nationally applicable biological index (article 2 – Purcell et al., this issue ) and defining the potential of biological communities within a gradient of cumulative stressors (article 3 – Paul et al. this issue ). Gradients were designed to represent the most prominent mosaic of stressors found in urban settings. A primary urban gradient was assembled based on readily obtained information of urbanization to include three broad‐scale parameters: percent urban land use/land cover, population density, and road density. This gradient was used as the standard by which alternative urban gradients, which included fine‐scale instream chemical and hydrologic parameters, were assessed. Five alternative gradients were developed to provide numerous environmental management options based on availability of data from water program resources. The urban gradients were developed with the intent that they be applied throughout the country; therefore, data from three different regions of the United States (Mid‐Atlantic, Midwest, and Pacific Coast) were used to validate the urban gradient model. Our study showed that a relatively straightforward stressor gradient consisting of human population density, road density, and urban land use is useful in providing a framework for developing relevant biological indicators and evaluating the potential of biological communities as a basis for assessing attainment of designated aquatic life use.     

温度与秸秆比例对牛粪好氧堆肥的影响

为了研究不同C／N比值在不同温度条件下牛粪堆肥30d时的全量养分和有机质的含量情况,提出了以新鲜牛粪和苜蓿秸秆混合物为堆料,在添加1％的生物腐熟剂的基础上,对堆肥温度及C／N比进行调控,并进行交叉实验。结果表明,（1）采用培养箱进行好氧发酵时,在温度为30℃和45℃的环境下堆肥最佳,温度过低或过高都会影响堆肥。（2）牛粪高温好氧堆肥时,添加一定比例的苜蓿秸秆可以调节堆料的C／N比值、含水量,缩短堆肥时间,其中牛粪与秸秆比例为1：l混合堆肥效果较好。（3）堆肥30d时,堆料的TN、TP和TK含量较堆肥初期都有所增加,有机质含量有所降低是因为矿化和释放养分造成的,且各含量均符合国家有机肥标准。     

Effect of common food preservatives on mycelial growth and spore germination of Fusarium oxysporum

Abstract

The growth and spore germination inhibition of Fusarium oxysporum f.sp. radicis‐cucumerinum by the common food additives: acetic acid, formic acid potassium sorbate, propionic acid, sorbic acid, and the fungistatic agent sec‐butylamine was examined in vitro. The inhibitory efficacy of these chemicals decreased in the following order: sorbic acid, potassium sorbate, propionic acid, acetic acid, sec‐butylamine and formic acid. At pH 6.4, the ED₅₀ value for mycelium growth was: 976 ppm for sorbic acid, 1292 ppm for potassium sorbate, 2435 ppm for propionic acid, 3805 ppm for acetic acid, 3962 ppm for sec butylamine and 4668 ppm for formic acid. The ED₅₀ value for spore germination was: 225 ppm for potassium sorbate, 1201 ppm for sorbic acid, 1402 ppm for propionic acid, 1600 ppm for sec‐butylamine, 1957 ppm for acetic acid and 2485 ppm for formic acid.     

氧化亚氮形成的微生物学分子机制研究进展

1　氧化亚氮 (Ｎ2 Ｏ)的形成Ｎ2 Ｏ是继ＣＯ2 、ＣＨ4之后的第三大温室气体 ,它能破坏大气中的臭氧层 .在过去的 2 0～ 30年间 ,Ｎ2 Ｏ以每年 0 .2 %～ 0 .3%的速率增长 ,并且有进一步增长的趋势[1 ] .地球上人类和其他生物的活动是Ｎ2 Ｏ产生的主要来源 ,而微生物是其中最重要的生物源 .微生物产生Ｎ2 Ｏ的机理主要是通过硝化作用和反硝化作用过程进行的 ,如图 1所示 .反硝化过程中Ｎ2 Ｏ的形成 :硝化过程中Ｎ2 Ｏ的形成 :图 1　Ｎ2 Ｏ的形成Ｆｉｇ.1　ＦｏｒｍａｔｉｏｎｏｆＮ2 Ｏ　　催化反硝化过程的酶有 4种 :硝酸还原酶 (Ｎａｒ)、亚…