CO<Subscript>2</Subscript>-assisted removal of nutrients from municipal wastewater by microalgae <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and <Emphasis Type="Italic">Scenedesmus obliquus</Emphasis>     

R. Chaudhary  Y. W. Tong  A. K. Dikshit 《International Journal of Environmental Science and Technology》2018,15(10):2183-2192

Axenic culture of microalgae Chlorella vulgaris ATCC^® 13482 and Scenedesmus obliquus FACHB 417 was used for phycoremediation of primary municipal wastewater. The main aim of this study was to measure the effects of normal air and CO₂-augmented air on the removal efficacy of nutrients (ammonia N and phosphate P) from municipal wastewater by the two microalgae. Batch experiments were carried out in cylindrical glass bottles of 1 L working volume at 25 °C and cool fluorescent light of 6500 lux maintaining 14/10 h of light/dark cycle with normal air supplied at 0.2 L min^?1 per liter of the liquid for both algal strains for the experimental period. In the next set of experiments, the treatment process was enhanced by using 1, 2 and 5% CO₂/air (vol./vol.) supply into microalgal cultures. The enrichment of inlet air with CO₂ was found to be beneficial. The maximum removal of 76.3 and 76% COD, 94.2 and 92.6% ammonia, and 94.8 and 93.1% phosphate after a period of 10 days was reported for C. vulgaris and S. obliquus, respectively, with 5% CO₂/air supply. Comparing the two microalgae, maximum removal rates of ammonia and phosphate by C. vulgaris were 4.12 and 1.75 mg L^?1 day^?1, respectively, at 5% CO₂/air supply. From kinetic study data, it was found that the specific rates of phosphate utilization (q _phsophate) by C. vulgaris and S. obliquus at 5% CO₂/air supply were 1.98 and 2.11 day^?1, respectively. Scale-up estimation of a reactor removing phosphate (the criteria pollutant) from 50 MLD wastewater influent was also done.  相似文献   

Eco-friendly smart hydrogels for soil conditioning and sustain release fertilizer     

J. Pushpamalar  S. J. Langford  M. B. Ahmad  Y. Y. Lim  K. Hashim 《International Journal of Environmental Science and Technology》2018,15(10):2059-2074

In the agricultural industry, biomass waste generated along with the production of food, is transformed into value-added products. Also, the demand for the slow or control release fertilizer is increasing to reduce the cost of maintaining the agricultural land. These issues are tackled by converting biomass waste to a slow fertilizer release vehicle and biodegradable water retention material that could reduce the cost for fertilizer application and simultaneously preserved the soil from dryness. A series of carboxymethyl sago pulp (CMSP) hydrogels were prepared by electron beam irradiation. Slow release systems were evaluated by loading potassium nitrate (KNO₃) and ammonium nitrate (NH₄NO₃) into the CMSP hydrogels. These CMSP hydrogels endow slow release property, biodegradability and a soil moisture preservation property that could find greener application in agricultural industries. The results indicate that CMSP hydrogels have a great potential as an agent for slow release of fertilizers.  相似文献   

Photodegradation of dimethyl phthalate (DMP) by UV–TiO<Subscript>2</Subscript> in aqueous solution: operational parameters and kinetic analysis     

W. W. Jing  D. Q. Li  J. Li  X. F. Li  Z. H. Wu  Y. L. Liu 《International Journal of Environmental Science and Technology》2018,15(5):969-976

In this paper, the adsorption and degradation phenomenon involved in the photocatalytic degradation of dimethyl phthalates (DMPs) by titanium dioxide (TiO₂) was studied. A variety of operating variables were selected firstly. Then, it was proved that even for such weak adsorption properties molecules as DMP, adsorption was still an important prerequisite for photolysis. A surface-mediated reaction process was proposed that the photodegradation of DMP assisted by TiO₂ particles occurred primarily at the surface of the photocatalyst rather than in the homogeneous phase. According to Langmuir–Hinshelwood model, the adsorption constant determined from the dark adsorption was far less than that obtained in the light condition. Enhanced DMP adsorption on the surface of TiO₂ under irradiation was the possible reason for the improvement of photodegradation efficiency. Under the irradiation of light, a synergistic mechanism of adsorption and photocatalysis was responsible for DMP degradation. The quantitative analysis by adding scavengers indicated that ^·OH radical was primarily responsible for the photodegradation of DMP. It was further verified that ^·OH was produced much more from conduction band electrons rather than valance band holes toward photodegradation of DMP by adding foreign Cu²⁺.  相似文献   

Preservation of thermophilic mixed culture for anaerobic palm oil mill effluent treatment by convective drying methods     

D. T. Tan  S. K. Chin  P. E. Poh  Y. H. Lee 《International Journal of Environmental Science and Technology》2018,15(6):1211-1222

The generation of huge amount of liquid waste known as palm oil mill effluent is a major problem in oil palm industry. Meanwhile, anaerobic biodegradation of such organic effluent at thermophilic condition is a promising treatment technology due to its high efficiency. However, storage and transportation of thermophilic mixed culture sludge are challenging due to constant biogas generation and heating requirement. Hence, drying of thermophilic sludge was conducted to obtain dormant thermophiles and thus enables easier handling. In this study, thermophilic sludge was dried using heat pump at 22 and 32 °C as well as hot air oven at 40, 50, 60, and 70 °C. Subsequently, quality of dried sludge was examined based on most probable number enumeration, chemical oxygen demand, and methane yield. Average drying rate was found to increase from 3.21 to 17.84 g H₂O/m² min as drying temperatures increases while average moisture diffusivity values ranges from 5.07 × 10^?9 to 4.34 × 10^?8 m²/s. Oven drying of thermophilic mixed culture resulted in highest chemical oxygen demand removal and lowest log reduction of anaerobes at 53.41% and 2.16, respectively, while heat pump drying resulted in the highest methane yield and lowest log reduction of methanogens at 53.4 ml CH₄/g COD and 2.09, respectively. To conclude, heat pump at 22 °C was most suitable drying technique for thermophilic mixed culture as the original methane-producing capability was largely retained after drying, at a slightly lower yet still comparable chemical oxygen demand removal when palm oil mill effluent was treated with the rehydrated culture.  相似文献   

Soil wettability in ground engineering: fundamentals,methods, and applications     

S. D. N. Lourenço  Y. Saulick  S. Zheng  H. Kang  D. Liu  H. Lin  T. Yao 《Acta Geotechnica》2018,13(1):1-14

Wettability is a fundamental property controlling the extent of wetting in flat and granular solids. In natural soils, wettability affects a wide variety of processes including infiltration, preferential flow and surface runoff. In mineral processing, wettability is paramount in enhancing the efficiency of separation of minerals from gangue. The manipulation of surface wettability is equally crucial in many industrial applications. For instance, superhydrophobic surfaces are those on which water drops roll off easily and as such are used for self-cleaning applications. Therefore, while wettability is strongly cross-disciplinary, its evolution has been discipline-specific with a direct extrapolation or transfer of concepts, approaches, and methods to ground engineering unlikely to remain valid. This paper synthesizes relevant aspects from surface chemistry, materials science, mining engineering, and soil science, and discusses their implications within the context of new granular materials that resist wetting, for use in barriers or ground improvement and, in unsaturated soils, where the effects of wettability have been documented.  相似文献   

Hydro-thermal coupled analysis for health monitoring of embankment dams     

Tewodros Y. Yosef  Chung R. Song  Ki-Tae Chang 《Acta Geotechnica》2018,13(2):447-455

Measuring and analyzing internal dam temperature may provide insight into evaluating the integrity of earthen dams. Temperature in a dam, with the advent of modern distributed temperature sensing (DTS) technique, is conveniently measured. The analysis of the temperature is conducted based on a hydro-thermal coupled analysis technique. In this study, DTS-based temperature data and VS2DHI (a finite difference code for analyzing two-dimensional heat transport in porous media) were used to analyze the hydro-thermal coupled behavior in a dam. The results of this analysis show that the temperature variation in an earthen dam is closely related to seepage conditions. Additionally, a localized high-temperature (26 °C) zone found in the measured data of the dam, which raised concern to engineers on site, is explained through either hot water infiltration into the foundation layer or lower permeability of the foundation layer than the magnitude that appeared in the design document. These findings demonstrate that hydro-thermal coupled analysis has the potential for evaluating the integrity of earthen dams.  相似文献   

The measurement of soil gases and shallow temperature for determination of active faults in a geothermal area: a case study from Ömer–Gecek,Afyonkarahisar (West Anatolia)     

Ahmet Yıldız  Can Başaran  Metin Bağcı  Ayla Gümüş  Feyzullah Ekrem Çonkar  Yusuf Ulutürk  Hüseyin Ali Yalım 《Arabian Journal of Geosciences》2018,11(8):175

Afyonkarahisar is a very important geothermal province of western Anatolia and has low and medium enthalpy geothermal areas. This study has been carried out for the preparation of distribution maps of soil gases (radon and carbon dioxide) and shallow soil temperature and the exploration of permeable tectonic regions associated with geothermal systems and reveal the origins of radon and carbon dioxide gases. The western district of the study area is characterized by the high radon concentration (168.30 kBq/m³), carbon dioxide ratio (0.30%), and soil temperature (21.0 °C) values. Fethibey and Demirçevre faults, which allow the circulation of geothermal fluids, have been detected in the distribution maps of radon, carbon dioxide, and shallow depth temperature and the directions of the curves in these maps correspond to the strikes of Demirçevre faults. The effect of the fault plays an important role in the change of carbon dioxide concentration along the W-E directional geological section prepared to determine the change of soil gas and shallow depth temperature values depending on lithological differences, fault existence, and geothermal reservoir depth. On the other hand, it was determined that Rn²²² concentration and soil temperature changed as a function of geothermal reservoir depth or lithological difference. Tuffs in Köprülü volcano-sedimentary units are the main source of radon due to their higher uranium contents. Besides, the carbon dioxide in Ömer–Gecek soils has geothermal origin because of the highest carbon dioxide content (99.3%) in non-condense gas. The similarities in patterns of soil temperature, radon, and carbon dioxide indicate that the variation in soil temperatures is related to radon and carbon dioxide emissions. It is concluded that soil gas and temperature measurements can be used to determine the active faults in the initial stage of geothermal exploration successfully.  相似文献   

基于GF-2影像西藏桑耶地区岩性-构造遥感解译     

侯德华  张立国  王硕  王金贵  程州 《中国地质调查》2018,5(5):66-73

西藏桑耶地区位于青藏高原中南部,区内切割强烈,地势陡峻,属于高山峡谷区。为提高区域地质调查野外工作效率,在调查中率先开展了遥感解译研究。在充分收集已有资料的基础上,通过对GF-2卫星数据进行预处理和影像增强,结合野外验证建立了各地质要素的遥感解译标志,实现了区内不同地层岩性、侵入岩、断裂和褶皱等地质要素的提取,最终编制了研究区1:5万遥感地质解译图,为区域地质调查提供了数据支撑。结果表明: 各地质要素在GF-2数据上均有良好反映,完全满足1:5万尺度的遥感地质解译和编图的需要,充分显示出该卫星数据在区域地质调查等工作中具有良好的应用前景。  相似文献   

大连地区雷暴时空变化特征及其严重年大气环流背景分析     

王秀萍  金巍  王岩  侯彦泽  高磊 《气象与环境学报》2019,35(2):61-68

利用1961—2013年大连地区3测站逐日地面雷暴观测资料及1948—2016年NCEP/NCAR再分析月平均资料,采用线性趋势估计和合成分析方法分析了大连地区雷暴日数的时间和空间分布规律,并进一步探讨雷暴严重年5—9月平均大气环流背景特征。结果表明:大连地区雷暴具有明显的地域特征,空间分布主要呈现北部内陆地区多,南部沿海地区少的特点;除2月外,各地其余月份均可发生雷暴,7月和8月达到高峰值,雷暴集中发生在5—9月,雷暴具有较强的季节性,夏季6—8月最多,冬季很少出现雷暴;年平均雷暴日数总体呈减少趋势,其中北部的减少趋势尤为显著;雷暴初日多出现在4月,终日多出现在10月,初日较终日稳定,无论初日和终日均以北部地区较南部地区稳定,各地雷暴初日显著提前,终日推迟不显著,但仅有大连终日推迟趋势显著;雷暴初日和终日北部地区对应的候平均气温阈值分别为-1℃和10℃,南部(东部)地区对应的候平均气温阈值分别为6℃(-1℃)和3℃(8℃);多雷暴年,高层500 hPa蒙古低涡异常偏强,副热带高压偏西偏北,低层850 hPa偏南风水汽输送和大连上空整层垂直上升运动均异常偏强,这些有利于雷暴日数的增多,而少雷暴年与多雷暴年特征基本相反。  相似文献   

东北地区气温演变的一致性与局地性特征研究     

侯依玲  刘鸣彦  赵春雨  王涛 《气象与环境学报》2019,35(2):69-76

选取中国东北区域162个气象站1961—2015年地面气温资料,采用多种统计方法分析了近55 a东北地区气温的一致性和局地性演变特征。结果表明:东北地区年平均气温存在较为良好的空间一致性,"全区一致型"气候类型为东北地区最主要气候形态;第一旋转载荷向量时间系数呈上升趋势亦存在较明显2—7 a的周期,说明北部地区气温受全球变暖、ENSO等大尺度气候背景影响显著; 1961—2015年北部区域以0. 34℃/10 a的升温率高于南部区域的0. 26℃/10 a,但1980年后增温趋势减慢;年平均气温的概率曲线随年代整体向高值区移动,北部区域冬季增暖较为显著,南部区域冬夏均较为明显,春秋季节可能有缩短趋势。  相似文献