Enhancement of sludge gravitational thickening with weak ultrasound

Gravitational thickening is the prevailing method to reduce sludge volume but the process is slow and usually requires addition of polyelectrolyte(s). This paper investigated the potential benefits of sonication on enhancing the sludge gravitational thickening with very low energy dose, so called “weak ultrasound”. Results showed that weak sonication significantly changed the sludge settlability and the main mechanism was release of the loosely bounded extracellular polymeric substances. The changes in sludge behaviors by sonication were strongly influenced by power density and sonication duration. Lower sound frequency was slightly better than higher frequency. Weak sonication (<680 kJ·kg^-1 DS) improved the sludge gravitational thickening while high ultrasonic energy deteriorated the process. Considering both the sludge thickening efficiency and energy consumption, the optimum conditions were 0.15 W·mL^-1, 7 s, and 25 kHz. Under such conditions, the energy dose was only 155 kJ·kg^-1 DS, much lower than literature reports, and the sludge settling time was shortened from 24 h to 12?h. Weak sonication could substitute expensive polyelectrolyte coagulant for sludge thickening. Combination of weak sonication and polyelectrolyte could further reduce the settling time to 6 h. The final water content of the thickened sludge was not changed after sonication or polyelectrolyte addition.     

浅析管道输油中水击的危害及对策

分析了水击产生的原因及危害,介绍了防止水击的有关自动化控制技术.     

Tourism effects on the environment and economic sustainability of sub-Saharan Africa

This paper integrates tourism, economic growth, and environmental issues in a multivariate format. Unlike recent research on this topic, a panel data of selected sample nations of sub-Saharan Africa is adopted by using cointegration and panel regression models. The current research discovers both long-run equilibrium and short-run dynamics between economic growth, tourism, energy use, and carbon emissions in sub-Saharan Africa. Furthermore, tourism and energy use show a highly significant direct impact on economic growth. In addition, tourism, energy use, and economic growth yield a highly significant positive effect on carbon emissions. Dissecting the region into oil producers and non-oil producers further suggests that the economic growth of sub-Saharan Africa has been accomplished by strong growth in tourism and energy use. However, there is highly significant evidence that in oil producing countries, CO₂ emissions are directly affected by energy use and economic growth and not by tourism. For non-oil producing countries, tourism and energy use but not economic growth incur a highly significant positive impact on carbon emissions.     

Combined biologic aerated filter and sulfur/ceramisite autotrophic denitrification for advanced wastewater nitrogen removal at low temperatures

An innovative advanced wastewater treatment process combining biologic aerated filter （BAF） and sulfur/ ceramisite-based autotrophic denitrification （SCAD） for reliable removal of nitrogen was proposed in this paper. In SCAD reactor, ceramisite was used as filter and Ca （HCO3）2 was used for supplying alkalinity and carbon source. The BAF-SCAD was used to treat the secondary treatment effluent. The performance of this process was investigated, and the impact of temperature on nitrogen removal was studied. Results showed that the combined system was effective in nitrogen removal even at low temperatures （8℃）. Removal of total nitrogen （TN）, NH4＋ -N, NO3-N reached above 90% at room temperature. Nitrification was affected by the temperature and nitrification at low temperature （8℃） was a limiting factor for TN removal. However, denitrification was not impacted by the temperature and the removal of NO3 -N maintained 98% during the experimental period. The reason of effective denitrification at low temperature might be the use of easily dissolved Ca（HCO3）2 and high-flux ceramisite, which solved the problem of low mass transfer efficiency at low temperatures. Besides, vast surface area of sulfur with diameter of 2-6 mm enhanced the rate of microbial utilization. The removal of nitrate companied with the production of SO42-, and the average concentration of SO27 was about 240mg.L^-1. These findings would be beneficial for the application of this process to nitrogen removal especially in the winter and cold regions.     

Potential shift of bacterial community structure and corrosion-related bacteria in drinking water distribution pipeline driven by water source switching

• Bacterial release from aged pipe sections under extreme conditions was quantified. • Released bacterial community structure exhibited large variation after transition. • Risks from transition reduced significantly with cleaner source. As a result of pollution in the present water sources, cities have been forced to utilize cleaner water sources. There are few reports regarding the potential shift of bacterial community structure driven by water source switching, especially that of corrosion-related bacteria. Three types of finished water were used for simulation, the polluted source water from the Qiantang and Dongtiaoxi Rivers (China) was replaced by cleaner water from Qiandao Lake (China). Here, we discussed the transition effects through three simulated reactors. The bacterial characteristics were identified using the high-throughput sequencing and heterotrophic plate count method. It was observed that the level of culturable bacteria declined by 2–3 orders of magnitude after water source switching. The bacterial community released from the pipeline reactor was significantly different under different finished water, and it exhibited large variation at the genus level. Porphyrobacter (58.2%) and Phreatobacter (14.5%) clearly replaced Novosphingobium, Aquabacterium, and Cupriavidus as new dominant genera in system A, which could be attributed to the lower carbon and nitrogen content of the new water source. Although corrosion-inhibiting bacteria decreased after switching, they still maintained dominant in three reactors (6.6%, 15.9%, and 19.7%). Furthermore, potential opportunistic pathogens such as Sphingomonas were detected. Our study shows that after transition to a high quality water source, the total culturable bacteria released was in a downtrend, which leads to a great reduction in the risk of bacterial leakage in the produced drinking water.     

Motivations for the use and consumption of wildlife products

The dominant approach to combating the illegal wildlife trade has traditionally been to restrict the supply of wildlife products. Yet conservationists increasingly recognize the importance of implementing demand-side interventions that target the end consumers in the trade chain. Their aim is to curb the consumption of wildlife or shift consumption to more sustainable alternatives. However, there are still considerable knowledge gaps in understanding of the diversity of consumer motivations in the context of illegal wildlife trade, which includes hundreds of thousands of species, different uses, and diverse contexts. Based on consultation with multiple experts from a diversity of backgrounds, nationalities, and focal taxa, we developed a typology of common motivations held by wildlife consumers that can be used to inform conservation interventions. We identified 5 main motivational categories for wildlife use: experiential, social, functional, financial, and spiritual, each containing subcategories. This framework is intended to facilitate the segmentation of consumers based on psychographics and allow the tailoring of interventions—whether behavior change campaigns, enforcement efforts, or incentive programs—to the specific context in which they will be used. Underlining the importance of consumer research and collaborating with local actors is an important step toward promoting a more systematic approach to the design of demand reduction interventions.     

企业安全管理信息化探讨

介绍了企业安全管理信息化过程所涉及的一些重要环节,分析了影响安全管理信息化建设成功的各种因素(如企业的领导者、员工、安全管理制度、网络安全)。企业安全管理信息化的成功实施将有助于提高企业安全管理的质量和水平。     

中孔活性炭对水溶液中Cr3+的吸附

采用模板法和氢氧化钾化学活化法制备出不同中孔率的中孔活性炭并用于水中Cr3+的静态吸附,探讨了中孔活性炭吸附Cr3+的影响因素.实验结果表明,当溶液pH为6.0、吸附温度为50℃、吸附时间为120min、活性炭加入量为2.0g/L以及活性炭中孔率为80.0％～90.0％时.中孔活性炭对溶液中Cr3+的去除率达到98.5％.分别采用Langmuir和Freundlich方程拟合活性炭对Cr3+吸附的等温线,发现Langmuir等温吸附模型对活性炭吸附Cr3+拟合程度更好.活性炭中孔率的增大有利于提高Cr3+的平衡吸附量,但同时还受到活性炭表面酸总量的影响.吸附Cr3+前、后活性炭的FTIR谱图表明,Cr3+与活性炭表面含氧官能团发生了离子交换反应.     

超滤膜系统污染物的形貌及组成分析

通过SEM、能谱、FTIR以及电感耦合等离子体质谱的分析方法对被污染超滤膜面的无机污染物、有机污染物和微生物进行了识别和分析。研究结果表明:超滤膜面无机污染物主要为Fe(OH)3、Cu(OH)2、Al(OH)3和Si等胶体物和少量CaSO4;有机污染物主要为多菌霉素类化合物;微生物可能富含铁类化合物。同时污染膜的清洗液分析结果说明该超滤膜污染物主要为无机胶体和有机物。     

Preparation of Cationic Asphalt Emulsifier from Cyclohexanone Wastewater

以环己酮生产废水(以下简称废水)为溶剂,以木质素、三乙烯四胺及甲醛为原料,通过Mannich反应制备了阳离子沥青乳化剂木质素胺.实验结果表明,制备木质素胺的最佳工艺条件为:反应温度85℃,反应时间5h,n(甲醛)∶n(三乙烯四胺)=3.0.经FTIR表征,以废水为溶剂和以去离子水为溶剂所制备的木质素胺结构相同.以实验制备的木质素胺为乳化剂制成的乳化沥青的性能指标达到JTG E20-2011《公路工程沥青及沥青混合料试验规程》的指标.