Effects of different sludge disintegration methods on sludge moisture distribution and dewatering performance

A key step in sludge treatment is sludge dewatering. However, activated sludge is generally very difficult to be dewatered. Sludge dewatering performance is largely affected by the sludge moisture distribution. Sludge disintegration can destroy the sludge structure and cell wall, so as change the sludge floc structure and moisture distribution, thus affecting the dewatering performance of sludge. In this article, the disintegration methods were ultrasound treatment, K₂FeO₄ oxidation and KMnO₄ oxidation. The degree of disintegration (DD_COD), sludge moisture distribution and the final water content of sludge cake after centrifuging were measured. Results showed that three disintegration methods were all effective, and K₂FeO₄ oxidation was more efficient than KMnO₄ oxidation. The content of free water increased obviously with K₂FeO₄ and KMnO₄ oxidations, while it decreased with ultrasound treatment. The changes of free water and interstitial water were in the opposite trend. The content of bounding water decreased with K₂FeO₄ oxidation, and increased slightly with KMnO₄ oxidation, while it increased obviously with ultrasound treatment. The water content of sludge cake after centrifuging decreased with K₂FeO₄ oxidation, and did not changed with KMnO₄ oxidation, but increased obviously with ultrasound treatment. In summary, ultrasound treatment deteriorated the sludge dewaterability, while K₂FeO₄ and KMnO₄ oxidation improved the sludge dewaterability.     

Two-year measurements of surface ozone at Dangxiong, a remote highland site in the Tibetan Plateau

Measurements of surface O3 and carbon monoxide(CO) were made from September 2009 to August 2011 at Dangxiong(30.48°N, 91.10°E, 4187 m a.s.l.), a remote highland site in a southern valley of the Nyainqêntanglha Mountains in the Tibetan Plateau, China. The monthly mean O3 mixing ratio ranged from 29.1 to 51.4 ppb, with an average of 38.5 ppb, and the maximum value was observed in May. The average diurnal cycle of O3 concentration showed a minimum in early morning and a maximum in the afternoon, with a broader "high platform" from the late morning to the late afternoon, and resembled that of surface wind speed. The concentration of surface O3 was highly significantly correlated with tropospheric column O3 over the regions surrounding Dangxiong and with that of surface O3 observed at a site north of the Nyainqêntanglha Mountains, suggesting a good regional representativeness of surface O3 at Dangxiong. In the afternoon when stronger winds blew, surface air showed distinct features of free-atmospheric air, with higher O3, lower CO, and lower relative humidity(RH). The negative O3–CO and O3–RH correlations in most months indicate a significant influence of air masses from the free troposphere. Trajectory analysis suggests that air masses originating from the south of the site make a negative net contribution to surface O3 and a positive contribution to CO and humidity, and those from the northwest sector contribute conversely to the respective quantities.     

Removal of tetracycline from aqueous solution by a Fe3O4 incorporated PAN electrospun nanofiber mat

Pollution of antibiotics, a type of emerging contaminant, has become an issue of concern, due to their overuse in human and veterinary application, persistence in environment and great potential risk to human and animal health even at trace level. In this work, a novel adsorbent, Fe₃O₄ incorporated polyacrylonitrile nanofiber mat (Fe-NFM), was successfully fabricated via electrospinning and solvothermal method, targeting to remove tetracycline (TC), a typical class of antibiotics, from aqueous solution. Field emission scanning electron microscopy and X-ray diffraction spectroscopy were used to characterize the surface morphology and crystal structure of the Fe-NFM, and demonstrated that Fe-NFM was composed of continuous, randomly distributed uniform nanofibers with surface coating of Fe₃O₄ nanoparticles. A series of adsorption experiments were carried out to evaluate the removal efficiency of TC by the Fe-NFM. The pseudo-second-order kinetics model fitted better with the experimental data. The highest adsorption capacity was observed at initial solution pH 4 while relative high adsorption performance was obtained from initial solution pH 4 to 10. The adsorption of TC on Fe-NFM was a combination effect of both electrostatic interaction and complexation between TC and Fe-NFM. Freundlich isotherm model could better describe the adsorption isotherm. The maximum adsorption capacity calculated from Langmuir isotherm model was 315.31 mg/g. Compared to conventional nanoparticle adsorbents which have difficulties in downstream separation, the novel nanofiber mat can be simply installed as a modular compartment and easily separated from the aqueous medium, promising its huge potential in drinking and wastewater treatment for micro-pollutant removal.     

Research and application of kapok fiber as an absorbing material: A mini review

Kapok fiber corresponds to the seed hairs of the kapok tree (Ceiba pentandra), and is a typical cellulosic fiber with the features of thin cell wall, large lumen, low density and hydrophobic- oleophilic properties. As a type of renewable natural plant fiber, kapok fiber is abundant, biocompatible and biodegradable, and its full exploration and potential application have received increasing attention in both academic and industrial fields. Based on the structure and properties of kapok fiber, this review provides a summary of recent research on kapok fiber including chemical and physical treatments, kapok fiber-based compositematerials, and the application of kapok fiber as an absorbent material for oils, metal ions, dyes, and sound, with special attention to its use as an oil-absorbing material, one predominant application of kapok fiber in the coming future.     

Experimental study of NO2 reduction in N2/Ar and O2/Ar mixtures by pulsed corona discharge

Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the total NO oxidation rate in the plasma atmosphere. In this study, NO2 reduction was experimentally investigated using a non-thermal plasma reactor driven by a pulsed power supply for different simulated gas compositions and operating parameters. The NO2 reduction was promoted by increasing the specific energy density （SED）, and the highest conversion rates were 33.7%, 42.1% and 25.7% for Ar, N2/Ar and O2/Ar, respectively. For a given SED, the NO2 conversion rate had the order N2/Ar 〉 Ar 〉 02/Ar. The highest energy yield of 3.31 g/kWh was obtained in N2/Ar plasma and decreased with increasing SED; the same trends were also found in the other two gas compositions. The conversion rate decreased with increasing initial NO2 concentration. Furthermore, the presence of N2 or O2 led to different reaction pathways for NO2 conversion due to the formation of different dominating reactive radicals.     

自然富硒土中Se对不同水稻籽粒吸收Cd的影响

通过水稻盆栽试验,在高低两种自然富硒土壤上种植3种水稻。结果发现,水稻籽粒Se含量与土壤中Se含量呈正相关,而土壤硒含量过高会降低水稻籽粒的产量。在添加Cd下,高富硒土种植的博优998、秋优998、金稻优998等水稻籽粒Cd含量比低富硒土分别降低了26.99%、10.28%、13.48%,说明土壤中适量的Se对水稻籽粒吸收Cd有拮抗作用。另外,秋优998富集Se、Cd的能力最强,生物产量最低,金稻优998达到富硒效果,而富集Cd的能力最弱,且生物产量较高,在筛选品种时,应优选金稻优998。     

生态化工产业发展影响因素分析——以山东省化工行业为例

在收集和分析对生态工业发展研究的文献基础上,将影响生态化工产业发展的因素归纳为3大因素:直接因素、间接因素和机制性因素,6个二级指标,分别是自然因素、经济因素、技术因素、产业因素、社会因素、政策法规,同时针对全国第一化工大省山东省不同类型、不同地域的11家化工企业进行了实地调研,并对问卷调研数据进行了基于SPSS软件的克朗巴哈α系数的信度分析以及主成分分析,结果表明问卷具有良好的信度,并按各二级指标中所含因素的重要程度确定了影响生态化工产业发展的12个主要因素,在此基础上提出了化工产业生态化发展的建议,为化工产业生态化建设提供相应的理论支撑。     

生物质絮凝剂在水处理中的应用研究进展

在水处理中,絮凝剂必不可少且种类繁多,现以无机及有机高分子絮凝剂使用最为广泛。但随着大众对于环境及水健康的关注度增大,其二者的毒性及难降解性使得大家将目光转向可实现无污染排放的绿色化絮凝剂-生物质絮凝剂。笔者在此就综述应用价值较高的几类生物质絮凝剂的研究进展,以期为理论研究和工程实践提供指导。     

昆明市大气PM_(10)污染分析与防治对策研究

通过分析昆明市建成区PM10污染水平、时空变化、气象影响、与PM2.5的关联性,提出相应的防治对策和措施。     

两种不锈钢在冷却塔冷凝酸液中的耐蚀性能

目的分析304不锈钢和316L不锈钢在电厂冷却塔内海水及烟气形成的模拟冷凝酸液环境中的耐蚀性能。方法利用浸泡试验和电化学试验方法测试两种不锈钢在模拟冷凝酸液中的腐蚀形貌、腐蚀率和极化曲线。结果 304不锈钢在模拟冷凝酸液中的耐蚀性能较差,其腐蚀率及钝态稳定性受冷凝酸液pH值的影响较大;316L不锈钢在模拟冷凝酸液中的耐蚀性能较好,其腐蚀率及钝态稳定性受冷凝酸液pH值的影响较小。结论 316L不锈钢在冷却塔冷凝酸液中的耐蚀性能明显优于304不锈钢。