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781.
表面活性剂可以提高污泥发酵产生的挥发性脂肪酸的产量。经过污泥水解发酵产生的挥发性脂肪酸,既能作为生物除磷系统所需的优质碳源,使城市污水达到稳定深度除磷的要求,又减少了剩余污泥对环境的污染。将城市污水厂污泥生物转化为挥发性有机酸并用于生物除磷,丰富了污水生物处理和污泥处理与资源化等研究内容。 相似文献
782.
Abstract: A study was conducted to determine the effects of three land covers (sunn hemp –Crotalaria juncea, sudex, a sorghum‐sudangrass hybrid –Sorghum bicolor x S. bicolor var. sudanese, and common oats –Avena sativa) planted as vegetative filter strips on the reduction of sediment and nutrient loading of surface runoff within the Kaika‐Waialua watershed on the island of Oahu, Hawaii. Runoff samples were collected and analyzed for total suspended solids (TSS), total dissolved solids (TDS), phosphorous, and three forms of nitrogen (nitrate, ammonium, total nitrogen). Study results show that during seven out of 10 runoff events, the three cover crop treatments significantly reduced TSS as compared to the fallow treatment. Average removal efficiencies were 85, 77, and 73% for oats, sunn hemp, and sudex, respectively, as compared to the fallow treatment. Nutrient concentrations were low with phosphorous concentrations, lower than 1 (μg/ml) for all treatments, and total nitrogen (TN) concentrations below 7 (μg/ml) except in the sunn hemp treatment, where TN concentrations were less than 10 (μg/ml). Results of analysis of TDS showed that the cover crop treatments did not decrease dissolved solids concentrations in comparison with the fallow treatment. Analysis of nutrient concentrations in runoff samples did not detect any significant decreases in phosphorous, nitrogen, ammonium, or TN concentrations in comparison to the fallow treatment. However, a significant increase in TN concentrations in the sunn hemp treatment was detected and showed the nitrogen fixing capacity of sunn hemp. No treatment effects on runoff volume were detected, and runoff volumes were directly correlated with rainfall amounts showing no crops significantly impacted soil infiltration rates. These results were attributed to extremely low soil hydraulic conductivities (0.0001‐7 cm/day at the soil surface, 15 and 30 cm below the soil surface). This study showed that cover crops planted as vegetative filters can effectively reduce sediment loads coming from idle and fallow fields on moderately steep volcanically derived highly weathered soils. 相似文献
783.
Marco Tasin Anna-Carin Bäckman Marie Bengtsson Nélia Varela Claudio Ioriatti Peter Witzgall 《Chemoecology》2006,16(2):87-92
Summary. Host plant volatiles which attract insect herbivores for egg-laying are of principal interest with respect to insect ecology
and evolution. Direct applications concern population monitoring and control through behavioural manipulation. Identification
of behaviourally active plant secondary metabolites is essential also for plant breeding for insect resistance. Grapevine
moth females Lobesia botrana are attracted by upwind flight to green grape berries Vitis vinifera. The headspace of grape berries was collected on air filters. A solvent extract of these filters, released from a sprayer,
attracted females in the wind tunnel. The results demonstrate that volatile cues mediate attraction of grapevine moth females
to grape berries, and that headspace collections capture the essence of this odour signal. The air filter extracts were examined
by gas chromatography coupled with electroantennographic detection, and the compounds eliciting a consistent antennal response
in L. botrana females were identified by mass spectrometry. The headspace collection apparatus was calibrated for collection efficiency
of the active compounds. Their recovery rate ranged from 35 % for methyl salicylate to 83 % for (E,E)-α-farnesene. A synthetic ten-component blend was then formulated. The blend consisted of compounds eliciting an antennal
response, formulated in a blend ratio corrected for differences in collection efficiency. Subsequent wind tunnel tests showed
that female attraction to this synthetic ten-component blend was not significantly different from attraction to grape berries,
or to headspace collections of the same berries. At a release rate of 35 ng/h of the most abundant compound (E)-β-caryophyllene,
20 % of the test females approached the source of sprayed headspace collections and the ten-component synthetic blend, respectively.
In comparison, 100 g of green berries, releasing the main compound (E)-β-caryophyllene at a rate of ca. 4.7 ng/h, attracted
10 % of the females by upwind flight followed by source contact. 相似文献
784.
785.
Jackson MM 《Environmental monitoring and assessment》2006,116(1-3):363-382
The emission estimation of nine volatile organic compounds (VOCs) from eight organic liquids storage tanks companies in Dar-es-Salaam
City Tanzania has been done by using US EPA standard regulatory storage tanks emission model (TANKS 4.9b). Total VOCs atmospheric
emission has been established to be 853.20 metric tones/yr. It has been established further that petrol storage tanks contribute
about 87% of total VOCs emitted, while tanks for other refined products and crude oil were emitting 10% and 3% of VOCs respectively.
Of the eight sources (companies), the highest emission value from a single source was 233,222.94 kg/yr and the lowest single
source emission value was 6881.87 kg/yr. The total VOCs emissions estimated for each of the eight sources were found to be
higher than the standard level of 40,000 kg/yr per source for minor source according to US EPA except for two sources, which
were emitting VOCs below the standard level. The annual emissions per single source for each of the VOCs were found to be
below the US EPA emissions standard which is 2,000~kg/yr in all companies except the emission of hexane from company F1 which
was slightly higher than the standard. The type of tanks used seems to significantly influence the emission rate. Vertical
fixed roof tanks (VFRT) emit a lot more than externally floating roof tanks (EFRT) and internally floating roof tanks (IFRT).
The use of IFRT and EFRT should be encouraged especially for storage of petrol which had highest atmospheric emission contribution.
Model predicted atmospheric emissions are less than annual losses measured by companies in all the eight sources. It is possible
that there are other routes for losses beside atmospheric emissions. It is therefore important that waste reduction efforts
in these companies are directed not only to reducing atmospheric emissions, but also prevention of the spillage and leakage
of stored liquid and curbing of the frequently reported illegal siphoning of stored products. Emission rates for benzene,
toluene, and xylene were used as input to CALPUFF air dispersion model for the calculation of spatial downwind concentrations
from area sources. By using global positioning system (GPS) and geographical information system (GIS) the spatial benzene
concentration contributed by organic liquid storage tanks has been mapped for Dar-es-Salaam City. Highest concentrations for
all the three toxic pollutants were observed at Kigamboni area, possibly because the area is located at the wind prevailing
direction from the locations of the storage tanks. The model predicted concentrations downwind from the sources were below
tolerable concentrations by WHO and US-OSHA. The highest 24 hrs averaging time benzene concentration was used for risk assessment
in order to determine maximum carcinogenic risk amongst the population exposed at downwind. Established risk for adult and
children at 2.9×10-3 and 1.9×10-3 respectively, are higher than the acceptable US-EPA risk of 1×10-6. It is very likely that the actual VOCs concentrations in some urban areas in Tanzania including Dar-es-Salaam City are much
higher than the levels reported in this study when other sources such as petrol stations and motor vehicles on the roads are
considered. Tanzania Government therefore need to put in place: an air quality policy and legislation, establish air quality
guidelines and acquire facilities which will enable the implementation of air quality monitoring and management programmes. 相似文献
786.
以紫外灯为光源,采用P25型TiO2光催化降解空气中的苯。为保证TiO2的高分散性、增加其在铝板上的附着牢固性,加入了聚乙烯醇和硅溶胶,这在一定程度上增加了催化剂对光能的利用率,但也造成了催化剂活性的降低。实验结果表明:苯的光催化降解反应属一级动力学反应;苯降解率随初始苯质量浓度的增加而减小,随反应面积的增大而增大,在253.7 nm波长光源下的降解效果优于365.0 nm;苯降解所得的气相产物主要为CO2和CO;随使用次数的增加,催化剂失活现象逐步显现;双氧水对催化剂的再生效果优于去离子水。 相似文献
787.
采用两级移动床生物膜反应器(MBBR)预处理高挥发酚含量的石化厂汽提净化水,考察了HRT和DO对废水中挥发酚和COD去除效果的影响。实验结果表明:在两级MBBR总HRT为10 h、MBBR中部废水DO 为1~3 mg/L的条件下, 装置连续运行处理ρ(挥发酚)=110~201 mg/L、COD=644~1 827 mg/L、BOD5/COD=0.15~0.69的废水,两级MBBR处理后出水平均ρ(挥发酚)为17.6 mg/L,挥发酚去除率达87.9%;平均COD为745 mg/L,COD去除率为32.7%;出水BOD5/COD平均为0.68,表明经过两级MBBR处理后,废水的可生化性有所提高,有利于废水的后续生化处理。 相似文献
788.
剩余污泥超声预处理后水解酸化特性 总被引:1,自引:2,他引:1
为探讨剩余污泥超声预处理后的水解酸化特性,考察了0.6 W/mL、5 min和1 W/mL、5 min 2种超声预处理条件下污泥水解酸化过程有机质、氮、磷的释放情况。实验结果表明,2种超声预处理均可促进污泥水解酸化,并且0.6 W/mL比1 W/mL的超声预处理更有利于SCOD的释放、VFAs的产生以及氮和磷的释放;水解酸化初期,超声预处理比未经超声预处理的污泥在有机质、氮、磷释放率上差异非常明显,随着水解酸化的进行,有机质和氮释放率差异仍很明显,而磷释放程度逐渐接近;经0.6 W/mL超声预处理,污泥水解酸化3 d后,SCOD释放率、VFAs浓度、TN释放率和NH4+-N释放率分别是未经处理污泥的1.85、2.63、1.85和1.41倍,而TP和PO43--P释放率较未经处理污泥仅分别多2.44和1.23个百分点。研究表明,控制适宜的声能密度、超声时间和水解酸化进程是超声预处理强化剩余污泥水解酸化效果的关键。 相似文献
789.
2018年9月20—29日,开展了南京市环境空气非甲烷烃(PAMS)原清单中57种挥发性有机物的手工和在线比对监测,监测项目主要包括碳氢化合物、卤代烃和含氧挥发性有机物。通过对VOCs 3 h均值、日均值和主要污染物指标等进行比对,分析在线监测数据与手工监测数据的相关性。测试结果表明,两种方法得到的3 h均值的差异度(1.43)和相关系数(0.897),日均值的差异度(2.16)和相关系数(0.946),呈现出差异度不显著、高度线性相关的特征。同时,进一步分析了监测数据产生偏离的原因,建议加强环境空气手工监测的质控管理,强化在线监测设备的运维管理,推进环境空气挥发性有机物监测的合理、有序发展。 相似文献
790.
针对用4-氨基安替比林直接光度法测定未经处理的生活污水中,预蒸馏后仍有悬浮物存在这一现象,进行了预处理后蒸馏和预蒸馏后用中速定量滤纸过滤的对比实验。结果证明预处理后蒸馏和预蒸馏后过滤均能达到消除悬浮物的目的。 相似文献