Does technology advancement reduce aggregate carbon dioxide emissions? Evidence from 66 countries with panel threshold regression model

Environmental Science and Pollution Research - The influence of technology advancement on carbon dioxide (CO2) emissions is complex and controversial, yet existing literature ignores the level of...     

H_2O_2与间歇进水方式对污泥膨胀控制研究

投加 1 0 0mg/L的H2 O2 ,可明显抑制丝状菌 ,使污泥膨胀得到控制 ,但不能根除。采用间歇进水方式 ,进水时间1h ,反应时间 4h ,可以控制污泥膨胀 ,但所需时间较长。在间歇进水的同时投加H2 O2 ,可快速使污泥膨胀得到控制。     

Simulation of urban expansion patterns by integrating auto-logistic regression,Markov chain and cellular automata models

This research analyses urban expansion patterns and their eco-risks in the Poyang Lake region in China. A hybrid model consisting of auto-logistic regression, Markov chain and cellular automata (CA) is designed to improve the performance of the standard logistic regression model. An eco-risk assessment (ERA) index by integrating landscape fragmentation index and area weighted eco-service value index is established to promote the effectiveness for dynamically evaluating the environment and eco-security in watersheds. Scenario predictions are introduced to better understand the relationship between urban dynamics and their eco-risks. Three urban development scenarios such as historical development trend (HDT), environment protection priority (EPP) and goal-oriented restriction (GOR) are designed and transplanted into the CA model through the parameter self-modification method. The quantitative analysis results showed that in the period of the past five years, the urban growth primarily concentrated in the metropolitans. The simulations show that under the HDT scenario the urban growth will mainly emerge in the metropolitans, while under the EPP and GOR scenarios the urban growth will expand along with the metropolitans or the road networks and highways, respectively. Moreover, the ERA demonstrated that the GOR scenario was more effective in meeting the goal of environment protection and urban sustainable development for the study area.     

Evaluation of removal efficiency for acute toxicity and genotoxicity on zebrafish in anoxic–oxic process from selected municipal wastewater treatment plants

The anoxic–oxic (A/O) process has been extensively applied for simultaneous removal of organic contaminants and nitrogen in wastewater treatment. However, very little is known about its ability to remove toxic materials. Municipal wastewater contains various kinds of pollutants, some of which have recalcitrant genotoxicity and may cause potential threat to environment, and even can lead to extinction of many species. In this study, we have selected three municipal wastewater treatment plants (WWTPs) employing anoxic–oxic (A/O) process to evaluate their ability to remove acute toxicity and genotoxicity of wastewater. Mortality rate of zebrafish (Danio rerio) was used to evaluate acute toxicity, while micronucleus (MN) and comet assays were used to detect genotoxicity. Results showed that in this process the acute toxicity was completely removed as the treatment proceeded along with decrease in chemical oxygen demand (COD) (<50 mg L^?1) in the effluent. However, in these treatment processes the genotoxicity was not significantly reduced, but an increase in genotoxicity was observed. Both MN and comet assays showed similar results. The eliminated effluent may pose genotoxic threaten although its COD level has met the Chinese Sewage Discharge Standard. This study suggests that further treatment of the wastewater is required after the A/O process to remove the genotoxicity and minimize the ecotoxicological risk.     

蠕虫捕食对污泥性质的影响

利用一种新型静态序批式蠕虫生物反应器处理剩余污泥,另设一个未加蠕虫的反应器作为对照。通过对比分析2个反应器中污泥的比减量速率、沉降性能、脱水性能和比好氧速率来研究蠕虫捕食对污泥性质的影响。实验结果表明,蠕虫具有良好的污泥减量效果,蠕虫加入后可使污泥比减量速率增加（0．15±0．02）mg／（mg·d）。蠕虫作用后污泥沉降性能明显改善,污泥容积指数（SVI）降低28．9％,胞外聚合物（EPS）含量减少和污泥絮体结构变得更加密实规则是污泥沉降性能得到改善的重要原因。蠕虫捕食后污泥脱水性能变差,污泥标准化毛细吸水时间和比阻分别增大2．45倍和1．16倍,推测主要是由污泥絮体平均粒径减小造成的。另外,蠕虫的存在会降低污泥的微生物活性,异养细菌、氨氧化细菌和亚硝酸盐氧化细菌的比好氧速率分别降低7．09％、7．84％和8．29％。     

分置式膜-生物反应器处理生活污水的抗冲击负荷能力

分置式膜 -生物反应器处理生活污水的运行结果表明 ,在 3倍于正常水平的冲击负荷下 ,分置式膜 -生物反应器能够正常运行 ,膜过滤出水 COD维持在 1 0 mg/ L以下 ,生物反应器污泥上清液 COD和透膜压力 TMP比正常水平略微上升 ,但在冲击负荷消除后能够恢复正常水平 ,呈现出较强的抗冲击负荷能力 .分置式膜 -生物反应器与普通活性污泥法相比 ,在冲击负荷下 ,其有机物去除速率、污泥浓度都呈现较快增长 ,而污泥混合液 COD浓度上升幅度较小 ,并且在冲击负荷消除后迅速恢复稳态运行 .分析表明分置式膜 -生物反应器的强抗冲击负荷能力来自于膜对污泥的完全截流作用 .膜 -生物反应器的强抗冲击负荷能力意味着该技术出水水质的安全稳定性和操作简便性 .     

室外大型空气压缩机的噪声治理技术

某室外安装的大型空气压缩机对环境造成了严重噪声污染,离机器2m远处噪声高达114 5dB(A)。在不允许停机的情况下,充分利用现场条件,采取了为空气压缩机加隔声罩、进气口滤清器加消声百页和管道作隔声包扎等综合治理措施,相应测点噪声已降至88 7dB(A),厂界噪声降至机器安装前背景值。室外机器的噪声控制方法与室内机器有许多不同,分析了这些差异并重点介绍了所设计的隔声罩在声学、通风、耐气候性和结构等方面的设计要点。     

Catalytic ozonation of reactive red X-3B in aqueous solution under low pressure: decolorization and OH· generation

Catalytic ozonation of Reactive Red X-3B in aqueous solution had been carried out in an ozone oxidation reactor where Mn-Fe-ceramic honeycomb was used as the catalysts. The presence of Mn-Fe-ceramic honeycomb catalyst could obviously improve the decoloration efficiency of Reactive Red X-3B and the utilization efficiency of ozone compared to the results from non-catalytic ozonation. Adsorption of Reactive Red X-3B had no obviously influence on the degradation efficiency. Addition of tert-butanol significantly decreased the degradation efficiency, indicating that the degradation of Reactive Red X-3B followed the mechanism of hydroxyl radical (OH·) oxidation. The operating variables such as reaction pressure and ozone supply had a positive influence on the degradation efficiency, mainly attributing to facilitate the ozone decomposition and OH· formation.     

A pulsed switching peroxi-coagulation process to control hydroxyl radical production and to enhance 2,4-Dichlorophenoxyacetic acid degradation

• A new pulsed switching peroxi-coagulation (PSPC) system was developed. • The EC_T for 2,4-D removal in the PSPC was lower than that in the EF. • The iron consumption for 2,4-D removal in the PSPC was lower than that in the PC. The aim of this study was to develop a new pulsed switching peroxi-coagulation system to control hydroxyl radical (?OH) production and to enhance 2,4-Dichlorophenoxyacetic acid (2,4-D) degradation. The system was constructed with a sacrifice iron anode, a Pt anode, and a gas diffusion cathode. Production of H₂O₂ and Fe²⁺ was controlled separately by time delayers with different pulsed switching frequencies. Under current densities of 5.0 mA/cm² (H₂O₂) and 0.5 mA/cm² (Fe²⁺), the ?OH production was optimized with the pulsed switching frequency of 1.0 s (H₂O₂):0.3 s (Fe²⁺) and the ratio of H₂O₂ to Fe²⁺ molar concentrations of 6.6. Under the optimal condition, 2,4-D with an initial concentration of 500 mg/L was completely removed in the system within 240 min. The energy consumption for the 2,4-D removal in the system was much lower than that in the electro-Fenton process (68±6 vs. 136±10 kWh/kg TOC). The iron consumption in the system was ~20 times as low as that in the peroxi-coagulation process (196±20 vs. 3940±400 mg/L) within 240 min. The system should be a promising peroxi-coagulation method for organic pollutants removal in wastewater.