超声波参数对剩余污泥中SCFAs和EHCs释放的影响

考察了不同超声处理参数下剩余污泥中短链脂肪酸SCFAs和易水解组分EHCs的释放特性。结果表明:超声波作用下SCFAs的最大释放量为197.0 mg/L,超声时间对SCFAs释放影响显著;在超声时间为100 min内,声能密度小于0.6 W/mL时,EHCs释放随超声时间和声能密度的增加而提高;在相同能耗下,长超声时间、低声能密度的超声处理条件更有利于获得较高的EHCs,超声时间对EHCs释放的贡献度高于声能密度;释放的EHCs以糖类为主,经短时间水解酸化可生成较高浓度的SCFAs。     

Reliability analysis of pedestrian safety crossing in urban traffic environment

This paper describes the pedestrian safety crossing behaviour at signalized crosswalks in an urban traffic environment based on human reliability analysis. In our research, pedestrians’ waiting durations are modelled by a non-parametric and two parametric reliability models that recognize the effects of covariates. The covariates include pedestrian personal characteristics and urban traffic conditions in order to reflect the effects of human factors and internal environment comprehensively. The results indicate that most pedestrians show distinct time-dependent reliability but a few pedestrians are too impatient to wait for the lights changes.     

垃圾填埋场覆盖黄土的甲烷氧化能力及其影响因素研究

利用西安江村沟填埋场不同覆盖时间的临时覆盖黄土和新鲜黄土掺堆肥配置的土样,开展了甲烷氧化培养瓶试验,培养历时最长达22d,研究了不同覆盖时间的覆盖黄土和不同堆肥掺量的新鲜黄土的甲烷氧化能力,以及含水量对覆盖黄土甲烷氧化能力的影响,分析了甲烷氧化过程中各组分气体体积变化关系.研究结果表明:不同覆盖时间的覆盖黄土的甲烷氧化能力相差很大,覆盖3~5年的黄土最大甲烷氧化能力达26.05~53.95μg CH4/(g×h), 而未覆盖的新鲜黄土几乎没有甲烷氧化能力.在新鲜黄土中掺入堆肥,能有效提高其甲烷氧化能力,且在堆肥掺量小于50%时,土样的最大甲烷氧化能力与堆肥掺量呈正比例关系.含水量对覆盖土的甲烷氧化能力有很大影响,黄土甲烷氧化的最适宜含水量约为20% ~ 30%.在甲烷氧化过程中,甲烷氧化菌将CH4中约44%的碳氧化为CO2,其余碳转化为甲烷氧化菌胞内物质.实际工程中进行覆盖层设计时,需要根据填埋场实际产气量和覆盖层导气性确定与甲烷通量相匹配的甲烷氧化速率,进而合理确定堆肥掺量.     

不同好氧/缺氧时长联合分区排泥优化生活污水短程硝化反硝化除磷颗粒系统运行

采用生活污水接种人工配水下成熟短程硝化反硝化除磷颗粒,通过不同好氧/缺氧时长联合分区排泥优化调控短程硝化反硝化除磷系统运行.结果表明,调控好氧/缺氧时长联合分区排泥可实现系统的稳定运行.后期稳定期出水COD浓度在50mg·L^-1以下,出水TN浓度低于15mg·L^-1,TN去除率达83%左右并保持平稳,出水P浓度均在0.5mg·L^-1以下,平均去除率为93.72%.同时,分区排泥（70%顶部污泥和30%底部污泥）可作为筛选微生物的途径,维持了良好的亚硝化和除磷性能,使粒径分布更为集中,并保证氨氧化菌（ammonia oxidizing bacteria,AOB）和反硝化聚磷菌（denitrifying phosphate accumulating organisms,DPAOs）的生长优势.缺氧时长的增加提高了缺氧异养菌的生长速率,使得缺氧异养菌分泌出更多的EPS,确保了颗粒污泥性状的改善和后续维持稳定.     

STOCHASTIC FLOW DURATION CURVES FOR EVALUATION OF FLOW REGIMES IN RIVERS1

ABSTRACT: A stochastic estimation of low flow in the upper reaches of streams is needed for the planning, development, and management of water resources and/or water use systems. In this paper, the definition and development procedure for the stochastic flow duration curve is presented and applied to five catchments located in eastern Japan and to two catchments in western Thailand. The probability distribution of N‐year daily discharge data is extracted at various percentages of time for which specified discharges are equaled or exceeded in a water year. Such a distribution is usually represented with a straight line on log‐normal probability paper. However, some of the probability plots for the annual minimum daily discharge are best represented with a straight line on Weibull probability paper. The effectiveness of the stochastic flow duration curve defined for the evaluation of flow regime is illustrated through its application. The ten year probability for the discharge exceeded 97 percent of the time may be recognized as an index of low flow. The recession shape of the lower part of the flow duration curve is dependent on the strength of low flow persistence.     

SETTING AN EFFECTIVE TMDL: SEDIMENT LOADING AND EFFECTS OF SUSPENDED SEDIMENT ON FISR1

ABSTRACT: The Agricultural Drainage and Pesticide Transport model was used to examine the relationship between fish and suspended sediment in the context of a proposed total maximum daily load (TMDL) in two agricultural watersheds in Minnesota. During a 50‐year simulation, Wells Creek, a third‐order cold water stream, had an estimated 1,164 events (i.e., one or more consecutive days of estimated sediment loading) and the Chippewa River, a fourth‐order warm water stream, had 906 events of measurable suspended sediment. Sublethal thresholds were exceeded for 970 events and lethal levels for 194 events for brown trout in Wells Creek, whereas adult nonsalmonids would have experienced sublethal levels for 923 events and lethal levels for 241 events. Sublethal levels were exceeded for 756 events and lethal thresholds were exceeded for 150 events in the Chippewa River. Nonsalmonids would have experienced 15 events of mortality between 0 and 20 percent in Wells Creek. In the Chippewa River, there were 35 events of mortality between 0 and 20 percent and one event in which mortality could have exceeded 20 percent. The Minnesota Pollution Control Agency has proposed listing stream reaches as being impaired for turbidity at 25 NTU, which is approximately 46 mg suspended sediment/1. We estimated that 46 mg/1 would be exceeded approximately 30 days in a year (d/yr) in both systems. A TMDL of 46 mg SS/1 may be too high to ensure that stream fishes are not negatively affected by suspended sediment. We recommend that an indicator incorporating the duration of exposure be applied.     

IMPACT OF COAL SURFACE MINING AND RECLAMATION ON SURFACE WATER CHEMICAL CONCENTRATIONS AND LOAD RATES IN THREE OHIO WATERSHEDS1

ABSTRACT: Information is lacking on the watershed scale effects of mining and reclaiming originally undisturbed watersheds for coal on surface water chemical concentrations and load rates for a variety of constituents. These effects were evaluated on three small, geologically dissimilar watersheds subjected to surface mining in Ohio. Comparisons were made between phases of land disturbances using ratios of average concentrations and load rates: Phase 1 (natural), subphases of Phase 2 (mining and reclamation), and subphases of Phase 3 (partial reclamation and final condition) using 4,485 laboratory analyses of 34 constituents. Average concentration and load rate ratios were categorized into three classes—minor, moderate, and substantial. Mining and reclamation (M/R) affected flow duration curves in different ways‐baseflow changes were variable, but high flows generally increased. The average concentration ratios for all sites were classified as 15 percent “minor,” 36 percent “moderate,” and 49 percent “substantial” (average ratio of 2.4.) Generally load rate ratios increased due to mining and reclamation activities (average ratio of 3.3). Minor, moderate, and substantial impacts were found on average for 7 percent, 23 percent, and 70 percent, respectively, of load rate ratios. The impact of M/R on average load rates was not necessarily the same as on average concentrations due to changed hydrology and can be opposite in effect. The evaluation of the impacts of M/R requires knowledge of changing hydrologic conditions and changing supplies and rates of release of chemicals into streams. Median sediment concentration ratio is an indicator of average constituent load rate ratio of a wide variety of chemical constituents and is useful for development of best management practices to reduce chemical loads. The site at which diversion ditches were not removed during final reclamation sustained large chemical load rates, and removal of diversions at the other mined site reduced load rates. Revegetation of poorly reclaimed areas decreased chemical load rates. Chemical load rates were sensitive to geology, mining, and reclamation methods, diversions, and changing hydrology, concentration flow rate regressions, and watershed areas.     

STREAMFLOW CHARACTERISTICS OF SMALL WATERSHEDS IN THE BLUE MOUNTAINS OF OREGON1

ABSTRACT: Streamflow data for water years 1978–84 were evaluated to identify streamflow characteristics for 13 small watersheds (0.46–7.00 mi²) in the Blue Mountains of eastern Oregon and to determine differences among grazing intensities and vegetation types. The ranges for mean annual water yields, peak flows, and 7-day low flows for the 13 watersheds were 5.5–28.1 inches, 2.0–34.7 cfsm, and 0.006–0.165 cfsm, respectively. Two classes of vegetation were evaluated: (1) western larch-Douglas-fir (nine watersheds) and (2) other (four watersheds representing fir-spruce, lodgepole pine, ponderosa pine, and mountain meadow). The means for annual peak flows and the slopes of the flow.duration curve were significantly different (p=0.05) for the two vegetation classes; differences in mean annual water yield were marginallysignificant(0.05< p <0.10). After they were adjusted for precipitation, the means for annual water yield, peak flows, and slopes of the flow-duration curve were significantly different for the two vegetation classes; differences in the means for annual 7-day low flows were marginally significant. The western larch-Douglas-fir group had somewhat lower water yields but, overall, tended to have more favorable streamfiow characteristics including lower peak flows, higher low flows, and more evenly distributed flow regimes (flatter flow-duration curves) than the “other” class. Four levels of grazing intensity had no effect on streamilow characteristics.     

水库地震的地震动特性

利用新丰江、黄壁庄、喀什、龙羊峡、官厅、刘家峡和陡河等水库地震的近场地面运动资料，给出了水库地震地震动的峰值加速度衰减关系、频谱特性和持续时间。分析结果表明，较：天然地震而言，水库地震的地面运动峰值加速度高，衰减快；地震动反应谱特征频率高，持续时间短；场地卓越周期以坚硬基岩的最短，硬土次之，软土最长。研究得到的水库地震的地震动衰减关系和频谱特性可为水工结构的抗震设计和加固提供借鉴。     

新疆伊犁州2次6级地震加速度记录特征对比分析

分析了伊犁州2次6级地震地震动峰值不对称比、持时、峰值衰减特征和规律,选取5个典型台站的加速度记录,其中2个台站获得了较大加速度峰值,仪器烈度达VIII度,另外3个台站在2次地震中都获取记录,一个位于伊犁河谷、一个位于北天山山前、一个位于南天山山前,分别进行了地震动反应谱和傅氏谱比特征的对比分析。通过对2次地震强震动记录特征研究,探讨新疆伊犁州地区中强地震的强震动特征。