Factors affecting oxygen-transfer rates in headspace-gas respirometers.

Satisfactory measures of the biological-oxygen-uptake rate in headspace-gas respirometers can only be achieved if the rate of oxygen transfer from the headspace gas to liquid is greater than the rate of oxygen uptake by microorganisms. In the authors' study, factors potentially affecting oxygen-transfer limitations in headspace-gas respirometers were evaluated quantitatively. Tests were conducted to measure maximum-oxygen-uptake rates by operating a respirometer under various test conditions. Analysis of respirometric data indicated that limiting oxygen-transfer rates were related to mixing intensity, length of magnetic stirring bar, volume of sample, and oxygen content in the headspace gas. A multivariable model was developed to describe the overall contribution of these factors to the limiting oxygen-transfer rate. This model should be useful for estimating maximum-oxygen-transfer rates for essentially all headspace-gas respirometers.     

Comparison of methods for measurement of cooling tower drift

An international comparison of methods for measurement of cooling tower drift has been performed at the Massachusetts Institute of Technology. Participants from Belgium, the United States and the Federal Republic of Germany participated in measurements of a spectrum of test environments, which span the range of cases which would typically be encountered in operating cooling towers. The environments differed according to droplet mass flux, droplet size distribution and gas speed. A wind tunnel was built to provide the various test environments, and a special optical drift measurement system was built to permit simultaneous monitoring of the environment sampled in the tests. Cases tested included both mechanical and natural draft cooling tower environments.Among the types of instruments tested are the pulsed laser light scattering system (PILLS), sensitive paper and other sensitive surface droplet impaction systems, isokinetic drift mass flux measurement systems and photographic systems. The results indicate that the instruments tested vary widely in their capabilities, with droplet sizing instruments being more effective in low load, small droplet size spectrum situations, and isokinetic mass and chemical assay techniques being most accurate in high load, large droplet distribution cases. Instruments relying upon thermodynamic state measurements in most cases agreed mutually within an order of magnitude. Their major source of error is believed to arise in the measurement of the gas stream relative humidity. This quantity is necessary for inferring the drift mass flux from the measurement provided by such instruments, which is the mixture saturation deficit or excess. For these tests the relative humidity was typically ⩽ 98%.     

Comparison of three methods of particulate measurement in Chicago air

Simultaneous measurements of suspended particulate concentrations were taken in Chicago over an 8-month period with an integrating nephelometer, a 6-stage fractionating sampler, and a Hi-Vol air sampler. The correlation coefficient (r) between light scattering coefficient, b_scat, and the Hi-Vol measurements was 0.75. The light scattering coefficient was found to be highly correlated with the impactor stages which had cut-off diameters of 0.38 μm (r = 0.79) and 0.84 μm (r = 0.89). These associations were independent of relative humidity. In contrast, correlations between b_scat and all other size fractions, and with TSP, were greatly affected by relative humidity. Relatively strong relationships were also found between NO₂, O₃ and b_scat which support the contention that nephelometer measurements are a reflection of photochemical activity.     

非稳定状态下除磷过程的特点研究

为了研究非稳定状态下生物除磷的特点,采用序批式间歇反应器(SBR),通过不同的进水方式(连续进水和瞬时进水),系统地考察了进水体积、NOX-N、限制曝气等因素对除磷过程的影响。结果表明,在温度为(23±0.5)℃、pH为7.0～8.0时,厌氧搅拌期连续进水的比释磷量(单位质量污泥(以MLSS计)的释磷量(以PO43-P计))比瞬时进水时高出42.11%。在运行条件相似的情况下,厌氧搅拌期的比释磷量与每周期进水体积无关。相对于连续进水,瞬时进水更有助于促进微生物利用有机底物进行自身的生长。限制曝气对连续进水和瞬时进水的释磷过程都存在明显的影响,在DO小于0.1mg/L的情况下,2者的比释磷量相对非限制曝气时分别降低了57.14%和55.56%。在连续进水时,NOX-N的反硝化结束伴随着释磷速率的突然升高。利用贮存作用并不能每次都成功地抑制丝状菌污泥膨胀。     

Comparison of PM2.5 carbon measurement methods in Hong Kong, China

Samples from Hong Kong, China, were analyzed for organic carbon (OC), elemental carbon (EC), and total carbon (TC) by three thermal protocols (low-temperature IMPROVE and high-temperature STN and NIOSH) and two optical monitoring methods: reflectance and transmittance. Good agreement (+/-10%) for TC among the three protocols was observed for sample loadings of 1-55 microg m(-3). The two protocols using a reflectance pyrolysis correction showed best agreement for EC, with <20% differences found for approximately 80% of the samples. Hong Kong has a large diesel fleet, and for some heavily loaded samples the light transmittance was too low for quantitative detection, resulting in large uncertainties in the OC/EC split based on transmittance. Hong Kong experienced OC levels similar to those at US sites, but has much higher EC concentrations. OC/EC ratios range from 2 to 5 at two US sites and from 0.2 to 1.2 at three Hong Kong sites.     

CANON工艺中不同NH4+-N浓度条件下N2O释放特征

在温度为（30±1）℃,以人工配置无机高氨氮废水为进水的条件下,采用序批式生物膜CANON反应器（陶粒为填料）,研究了不同NH4+-N浓度条件下,CANON工艺脱氮过程中N2O的释放特征。研究表明：通过控制NH4+-N浓度分别为200、300、400和500 mg·L-1,获得了84.69%、80.58%、78.16%和90.09%的TN去除率,对应的TN去除负荷分别为1.42、1.48、1.52、1.82 kg·(m3·d)-1,CANON反应器脱氮性能非常稳定;反应过程中,对应的N2O释放总量分别为6.44、10.34、13.45、19.53 mg,即随着初始NH4+-N浓度的增加,N2O的释放总量逐渐增加;而N2O的释放率虽然也有增加,但增加幅度并不显著,占TN损失的比例分别为6.06%、7.00%、7.06%、7.15%;在一个反应周期内,N2O与NO2--N均呈现先升高后降低的变化趋势,但无因果关系。CANON反应器产生大量N2O 的主要原因,并非源于NO2--N的积累,也与FNA无关,而是羟氨积累造成的。     

生物脱氮好氧阶段不同反应过程N2O产量

在成功实现生活污水短程生物脱氮的基础上,采用体积为3 L的小试反应器,利用在线DO监测手段控制DO=1.0 mg·L-1,通过投加NaNO2的方式控制系统初始NO2--N=40 mg·L-1,以丙烯基硫脲（ATU）抑制NH4+-N的氧化过程,考察了生物脱氮好氧阶段不同反应过程中N2O的产生量。结果表明,除缺氧反硝化细菌的反硝化过程外,好氧条件下,氨氧化菌（AOB）能够以NH4+-N作为电子供体,NO2--N作为电子受体,进行反硝化脱氮过程,其反硝化产物为N2O。生物脱氮好氧阶段AOB的好氧反硝化和异养菌的缺氧反硝化反应中,N2O的产量分别占分别占进水总氮（NH4+-N+NO2--N）的7.23%和7.80%。好氧阶段NH4+-N和NO2-的氧化过程中,几乎没有N2O的产生。     

不同工况条件混合赤泥力学特性变化规律

在利用常规土工实验和XRF、XRD、SEM等微观测试手段分析了刚出厂混合赤泥化学成分、矿物组成、微观结构的基础上,通过无侧限抗压强度实验和固结排水三轴剪切实验对自然风干、浸水饱和、非饱和-饱和干湿循环3种工况条件下混合赤泥不同龄期力学特性的变化规律进行了研究。结果表明,自然风干试样的无侧限抗压强度和粘聚力要明显大于相同龄期浸水饱和试样和干湿循环试样,说明混合赤泥的强度形成与滤水过程有一定联系,且其强度的增长均主要集中在脱水龄期前70天内;混合赤泥在3种不同工况条件下无侧限抗压强度和粘聚力均有一定程度的增长,说明混合赤泥可在浸水环境下生成不可逆增长的具有水硬性的胶结矿物,使其在水环境中不发生崩解,可保证混合赤泥堆体在自然堆存过程中其力学特性满足安全堆载要求。     

Determination of ambient aerosol sulfur using a continuous flame photometric detection system. II. The measurement of low-level sulfur concentrations under varying atmospheric conditions

Principles involved in the measurement of sulfur concentrations using a flame photometric detector (FPD) are described along with factors other than sulfur which affect FPD response. Variations in inlet pressure and sample water vapor concentration are both shown to alter zero air response and instrument calibration to SO₂. Daily atmospheric fluctuations in barometric pressure and water partial pressure are found to significantly affect low-level (< 20 ppb) measurements. Possible solutions to these problems investigated in this paper include an inlet drying system, mass flow control and increased sensitivity through sulfur addition to the hydrogen stream. The FPD exhibits no detectable change in sensitivity up to an altitude of 1400 m when the mass flows of air and H₂ are held constant although a slight increase in baseline response is observed. The use of a 66 ppb SF₆-H₂ mixture results in a 13-fold increase in signal/noise at 1 ppb and lowers the limit of detection for sulfur to about 0.1 ppb.     

Combustion sources of particles: 2. Emission factors and measurement methods

Emissions from the combustion of biomass and fossil fuels are a significant source of particulate matter (PM) in ambient outdoor and/or indoor air. It is important to quantify PM emissions from combustion sources for regulatory and control purposes in relation to air quality. In this paper, we review emission factors for several types of important combustion sources: road transport, industrial facilities, small household combustion devices, environmental tobacco smoke, and vegetation burning. We also review current methods for measuring particle physical characteristics (mass and number concentrations) and principles of methodologies for measuring emission factors. The emission factors can be measured on a fuel-mass basis and/or a task basis. Fuel-mass based emission factors (e.g., g/kg of fuel) can be readily used for the development of emission inventories when the amount of fuels consumed are known. Task-based emission factors (g/mile driven, g/MJ generated) are more appropriate when used to conduct comparisons of air pollution potentials of different combustion devices. Finally, we discuss major shortcomings and limitations of current methods for measuring particle emissions and present recommendations for development of future measurement techniques.     

Comparison of experimental ponds for the treatment of dye wastewater under controlled and semi-natural conditions

This study compares the performance of simulated shallow ponds vegetated with Lemna minor L. under controlled and semi-natural conditions for the treatment of simulated wastewater containing textile dyes. The objectives were to assess the water quality outflow parameters, the potential of L. minor concerning the removal of chemical oxygen demand (COD) and four azo dyes (Acid blue 113, reactive blue 198, Direct Orange 46 and Basic Red 46) and the plants’ growth rate. Findings show that all mean outflow values of COD, total dissolved solids (TDS) and electrical conductivity (EC) were significantly (p < 0.05) lower within the outdoor compared to the indoor experiment except the dissolved oxygen (DO). The COD removal was low for both experiments. The outflow TDS values were acceptable for all ponds. The pond systems were able to reduce only BR46 significantly (p < 0.05) for the tested boundary conditions. Removals under laboratory conditions were better than those for semi-natural environments, indicating the suitability of operating the pond system as a polishing step in warmer regions. The mean outflow values of zinc and copper were below the thresholds set for drinking and irrigation waters and acceptable for L. minor. The dyes inhibited the growth of the L. minor.     

渗滤液氨氮在地下咸水环境中的迁移过程

海滨填埋场是沿海地区垃圾处理的一个重要选择,但其渗滤液泄漏引发的地下环境污染具有一定的独特性。以渗滤液中长时间保持高浓度的氨氮作为指标,通过构建砂箱实验,探讨咸水条件下氨氮在地下环境中的迁移转化过程。结果表明,在地下水环境中,渗滤液氨氮较易沿水流水平方向扩散,扩散速度随空间推移不断降低,从开始的4 cm/d降低到出水处的3.2 cm/d;其衰减率沿饱和区、过渡区、调整区依次增高;同时其衰减率随时间的增加不断降低,在实验的第15、25、35、45和55天,分别为100%、98.7%、95.6%、91.8%和83.5%。     

3种植物人工浮岛对生活污水水质动态净化特性的比较

在同等条件下开展了3种植物人工浮岛对生活污水水质处理比较研究,并对它们动态净化处理结果进行比较。结果表明,水体交换时间为7 d时,灯心草、菖蒲、美人蕉3种人工浮岛对总氮的平均去除率分别为48.4%、53.7%和59.3%;对总磷的平均去除率分别为59.3%、65%和69.3%;对COD的平均去除率分别为41.5%、40.5%和40.9%。显然美人蕉对总氮和总磷的去除效果最好,实验证明了美人蕉人工浮岛在对于生活污水处理中有广阔的应用前景。     

Intercomparison of measurement methods for black carbon aerosols

In this study, two method intercomparisons were performed. One thermal and two optical methods for the measurement of black carbon (BC) were applied to laboratory generated aerosols containing only BC. For the optical measurements, an aethalometer (Hansen et al., 1984. Science of Total Environment 36, 191–196) and an integrating sphere technique (Hitzenberger et al., 1996b. Journal of Geophysical Research 101, D14, 19 601–19 606) were used. The thermal method was described by Cachier et al. (1989a. Tellus 41B, 379–390). In an additional comparison, the integrating sphere was compared to a thermal optical technique (Birch and Cary, 1996. Aerosol Science Technology 25, 221–241) on ambient aerosol samples. The absorption coefficients were obtained from transmission measurements on filter samples for both the aethalometer and the integrating sphere. The BC mass concentration for the aethalometer was derived from this absorption measurement. The BC mass concentration for the integrating sphere, however, was obtained using an independent calibration curve. The agreement between the absorption coefficient σ_a obtained for the BC test aerosol on parallel filters with the aethalometer and the integrating sphere was satisfactory. The slope of the regression lines depended on filter type. A comparison between BC mass concentrations, however, showed that the aethalometer values were only 23% of those obtained by the integrating sphere technique indicating that for pure BC aerosols, the standard aethalometer calibration should not be used. Compared to the thermal method, the integrating sphere gave an overestimation of the BC mass concentrations by 21%. For the ambient samples, the integrating sphere and the thermal optical methods for BC mass concentration determination showed agreement within 5% of the 1 : 1 line, although the data were not so well correlated.     

Comparison of endotoxin levels and gram-negative bacteria under different conditions in microbial laboratories and a biowaste site

In this study, we assessed airborne endotoxin levels in university laboratories, hospital diagnostic laboratories, and a biowaste site. We also investigated indoor and outdoor sampling, sampling site, type of ventilation system, presence of open biowaste boxes, weather, and detection of Gram-negative bacteria (GNB). A total of 69 air samples were collected from 11 facilities in three institutions. Average total airborne endotoxin levels ranged from <0.01 to 10.02 EU m⁻³, with an overall mean of 1.03 EU m⁻³. Endotoxin levels were high in window-ventilated facilities, in facilities in which GNB were detected; levels were also high when it was rainy (all ps < 0.05). Endotoxin levels were significantly correlated with humidity (r = 0.70, p < 0.01). The presence of HVAC; humidity; and the presence of open biowaste boxes affect endotoxin levels in laboratories.     

生物表面活性剂合成条件的优化及提取方法

利用油平板筛选法和排油圈法从辽河某油田的土壤样品中分离筛选高效的生物表面活性剂产生菌, 通过16S rRNA基因序列分析对所筛选菌株进行鉴定。采用L16(45)正交实验对所筛选菌株合成生物表面活性剂的条件进行优化。比较5种提取方法对发酵液中生物表面活性剂的提取效果。共分离得到17株菌,其中菌株A3、As和Y产表面活性剂的能力最强。16S rRNA基因序列分析表明,这3株菌均为假单胞菌属(Pseudomonas)。菌株A3、As、Y和 A3-As混合菌的生物表面活性剂提取量较优化前有明显的提高,其产量分别是优化前的8.4倍、6.4倍、5.6倍和5.7倍,其中,菌株As的生物表面活性剂产量最高,可达20.55 g/L。对于3种纯菌和A3-As混合菌而言,5种提取方法中均以CHCl3萃取的量最高;而对其他混合菌,5种提取方法的差别并不显著。菌株A3、As、Y均属于高效的生物表面活性剂产生菌,具有很好的应用前景。     

Degradation of herbicides in two sandy aquifers under different redox conditions.

We examined the potential for complete degradation (mineralisation) of the four [ring-U-14C]herbicides mecoprop, isoproturon, atrazine, and metsulphuron-methyl in two sandy aquifers representing aerobic, denitrifying, sulphate-reducing, and methanogenic conditions. Slurries with sediment and groundwater were set-up aerobically or anaerobically in the presence of the electron-acceptor prevailing at the sampling site, amended with 25 microg l(-1) herbicide, and incubated at 10 degrees C. Considerable mineralisation was only observed in sediment from the plough layer incubated aerobically. Here, 30% of 14C-mecoprop was recovered as 14CO2 after 15 days and 15% of isoproturon was recovered as 14CO2 after 267 days. Only 7% of mecoprop was recovered as 14CO2 after 313 days in sediment from the aquifer below sampled at 1.95-3.00 mbs (m below the surface). In denitrifying and methanogenic slurries, 3% of 14C added as mecoprop was recovered as 14CO2. Isoproturon was not mineralised except in the aerobic plough layer, and atrazine and metsulphuron-methyl were not mineralised under any of the conditions applied.     

Shewanellasp．XB缺氧反硝化降解苯酚

苯酚的生物降解一直受到关注。以苯酚为惟一电子供体,研究了Shewanellasp．XB对苯酚的缺氧降解特性。研究结果表明,在反硝化条件下,当C／N为13．3时,苯酚可以完全降解,NO2--N积累量很少。另外,当加入氧化还原介体,如核黄素3μmol／L、AQDS0．01mmol／L、AQS0．05mmol／L和LQ0．01mmol／L时,苯酚降解速率分别为不加介体时的1．45、1．77、1．67和1．63倍。当以氯化铵代替硝酸盐时,苯酚也能进行厌氧发酵降解。另外,菌株XB反硝化降解苯酚可能是厌氧和好氧降解的混合过程。     

Effect of reducing conditions on sludge melting process

The objective of this study was to compare the effects of CO/CO(2) reducing conditions with those of air oxidizing conditions on the pouring temperature of the sludge melting process and the heavy metal leachability of the resultant sludge slag. Synthetic sludge ash composed of SiO(2), CaO and Al(2)O(3), as well as sewage sludge ash generated from a laboratory incinerator was employed. The experimental results indicated that the pouring temperatures are significantly reduced under the reducing conditions of CO/CO(2), or 24 and 77 degrees C lower than under air conditions for synthetic and sludge ash, respectively. The heavy metal leaching tests further indicate lower heavy metal concentrations present in the leachate under the reducing conditions, notably an order of magnitude lower in Zn. However, X-ray diffractogram indicates similar peaks for these two slags produced under different conditions.