大型浮顶储罐浮盘密封圈雷击起火事故分析

通过对近年来连续发生的大型浮顶储罐浮盘密封圈雷击起火原因分析,找出了浮顶储罐浮盘密封存在的安全问题,探讨了浮盘密封形式与储罐雷击起火事故的关系,并提出对策措施.     

改革开放以来广州市番禺区景观格局变化研究

番禺区作为广州市新的发展方向,处于中国经济和社会发展的前沿。研究番禺区20年来的景观格局变化,对于其经济社会的可持续、健康发展有一定的指导意义。利用番禺区1979年、1990年、2000年的MSS、TM、ETM^＋影像,在GIS的支持下,结合景观生态学的理论分析了番禺区三个时期的景观格局及其动态变化。结果表明,20年来,番禺区的景观格局变化迅速,斑块数量和空间格局变化较大;各景观类型之间的转移明显,耕地、林地快速向建设用地、养殖水域等转变。人文因素是景观格局变化的直接驱动力,人口增长、经济发展是导致景观系列变化最根本的原因。     

施工现场临时用电管理

据统计,全国施工现场临时用电发生触电死亡事故占事故总数8%左右,仅上海市2003年施工现场临时用电发生触电死亡事故就占事故总数的15.4%,触电事故已是建设工程发生事故的主要因素之一.……     

重大危险源辨识标准修订的探讨

20世纪 70年代以来 ,重大工业事故不断发生,给人们正常的生产、生活造成巨大的威胁和伤害,从而引起国际社会的广泛重视 ,预防重大工业事故成为各国社会、经济和技术发展的重点研究对象之一.     

甘肃省农村环境安全现况分析

通过分析影响甘肃省农村环境安全的主要因素,提出了改善甘肃省农村环境安全状况的措施和建议。采用"压力-状态-响应"模型,构建了甘肃省农村环境安全评价指标体系。运用层次分析法及环境安全综合评价指数对2003-2008年甘肃省农村环境安全状况进行评价。评价结果显示甘肃省环境安全状态处于第Ⅱ级,属中警状态(风险状态)。趋势分析结果表明近几年甘肃省农村环境安全总体上呈现缓慢好转,但安全形势依然相当严峻。     

Strategies to improve aerobic granular sludge stability and nitrogen removal based on feeding mode and substrate

A systemic strategy was proposed to improve aerobic granular sludge(AGS)stability and nitrogen(N)removal efficiency by optimizing feeding mode and substrate aiming at complicated wastewater characteristics.Key functional groups at the genus level identified by high-throughput sequencing were evaluated as well.The results showed that anaerobic feeding mode and acetate promoted the compact AGS formation with excellent total nitrogen(TN)removal efficiency(averaging 91.7%±4.1%)at various dissolved oxygen conditions.While the aerobic feeding mode led to a loose AGS structure with a vulnerable anaerobic core and poor TN removal efficiency(averaging58.8%±7.4%).Simultaneous nitrification and denitrification process played the dominant role in N removal in compact AGS over the alternating nitrification and denitrification process.High-concentration glucose undermined feast-famine condition with filamentous bacteria growth out of granule and decreased TN removal efficiency to 67.3%±15.2%.Lower food to microorganism ratio may result in a lower N removal rate attributed to the sharply increased biomass concentration fed by glucose.Ammonia-oxidizing bacteria,nitrite-oxidizing bacteria,denitrifying bacteria,and denitrifying phosphorus accumulation organisms enriched during AGS granulation also contributed to the efficient N removal.The proposed strategy provided insights into the relationship between various factors and stable AGS formation,and systemic operation methods for various complicated wastewater treatment.     

Process analysis of PM2.5 pollution events in a coastal city of China using CMAQ

US EPA's Community Multiscale Air Quality modeling system(CMAQ) with Process Analysis tool was used to simulate and quantify the contribution of individual atmospheric processes to PM_(2.5) concentration in Qingdao during three representative PM_(2.5) pollution events in the winter of 2015 and 2016. Compared with the observed surface PM_(2.5) concentrations, CMAQ could reasonably reproduce the temporal and spatial variations of PM_(2.5) during these three events. Process analysis results show that primary emissions accounted for 72.7%–93.2% of the accumulation of surface PM_(2.5) before and after the events.When the events occurred, primary emissions were still the major contributor to the increase of PM_(2.5) in Qingdao, however the contribution percentage reduced significantly,which only account for 51.4%–71.8%. Net contribution from horizontal and vertical transport to the accumulation of PM_(2.5) was also positive and its percentage increased when events occurred. Only 1.1%–4.6% of aerosol accumulation was due to PM processes and aqueous chemical processes before and after events. When the events occurred,contribution from PM processes and aqueous chemistry increased to 6.0%–11.8%. Loss of PM_(2.5) was mainly through horizontal transport, vertical transport and dry deposition, no matter during or outside the events. Wet deposition would become the main removal pathway of PM_(2.5), when precipitation occurred.     

基于EFDC城市景观湖泊水动力模拟研究

城市景观湖泊是生态城市建设的重要组成部分,其水流缓慢,水动力交换和自净能力较弱,水质易受城市排污、径流、人为活动等因素影响。本文应用EFDC(environment fluid dynamic code)三维模型研究分析了典型城市景观湖泊-天印湖的水动力特征,模拟了2011年9月至2013年12月水龄变化过程和时空分布,分析降雨径流和风力驱动对水龄的影响力。结果表明:天印湖的水动力主要驱动力为降雨径流,风力对水龄的影响很小。研究结论有助于理解城市景观水体的水动力特性以及进一步研究水动力对水质变化的影响,并为城市水环境建设和保护提供一定的方案支持。     

Membrane fouling controlled by coagulation/adsorption during direct sewage membrane filtration (DSMF) for organic matter concentration

Unlike the role of the membrane in a membrane bioreactor, which is designed to replace a sediment tank, direct sewage membrane filtration(DSMF), with the goal of concentrating organic matters, is proposed as a pretreatment process in a novel sewage treatment concept. The concept of membrane-based pretreatment is proposed to divide raw sewage into a concentrated part retaining most organics and a filtered part with less pollutant remaining, so that energy recovery and water reuse, respectively, could be realized by post-treatment. A pilot-scale experiment was carried out to verify the feasibility of coagulant/adsorbent addition for membrane fouling control, which has been the main issue during this DSMF process. The results showed that continuous coagulant addition successfully slowed down the increase in filtration resistance, with the resistance maintained below 1.0 × 1013m~(-1) in the first 70 hr before a jump occurred. Furthermore,the adsorbent addition contributed to retarding the occurrence of the filtration resistance jump, achieving simultaneous fouling control and chemical oxygen demand(COD)concentration improvement. The final concentrated COD amounted to 7500 mg/L after 6 days of operation.     

Membrane fouling controlled by coagulation/adsorption during direct sewage membrane filtration (DSMF) for organic matter concentration

Unlike the role of the membrane in a membrane bioreactor, which is designed to replace a sediment tank, direct sewage membrane filtration (DSMF), with the goal of concentrating organic matters, is proposed as a pretreatment process in a novel sewage treatment concept. The concept of membrane-based pretreatment is proposed to divide raw sewage into a concentrated part retaining most organics and a filtered part with less pollutant remaining, so that energy recovery and water reuse, respectively, could be realized by post-treatment. A pilot-scale experiment was carried out to verify the feasibility of coagulant/adsorbent addition for membrane fouling control, which has been the main issue during this DSMF process. The results showed that continuous coagulant addition successfully slowed down the increase in filtration resistance, with the resistance maintained below 1.0 × 10¹³ m^− 1 in the first 70 hr before a jump occurred. Furthermore, the adsorbent addition contributed to retarding the occurrence of the filtration resistance jump, achieving simultaneous fouling control and chemical oxygen demand (COD) concentration improvement. The final concentrated COD amounted to 7500 mg/L after 6 days of operation.