Comparison of membrane fouling in ultrafiltration of down-flow and up-flow biological activated carbon effluents

The UF membrane fouling by down- and up-flow BAC effluents were compared. Up-flow BAC effluent fouled the membrane faster than down-flow BAC effluent. The combined effects dominated irreversible fouling. The extent of fouling exacerbated by inorganic particles was higher. The TMP, permeate flux, and normalized membrane flux during 21 days of UF of DBAC and UBAC effluents. Fouling during ultrafiltration of down- and up-flow biological activated carbon effluents was investigated to determine the roles of polysaccharides, proteins, and inorganic particles in ultrafiltration membrane fouling. During ultrafiltration of down- flow biological activated carbon effluent, the trans-membrane pressure was≤26 kPa and the permeate flux was steady at 46.7 L?m⁻²?h⁻¹. However, during ultrafiltration of up-flow biological activated carbon effluent, the highest trans-membrane pressure was almost 40 kPa and the permeate flux continuously decreased to 30 L?m⁻²?h⁻¹. At the end of the filtration period, the normalized membrane fluxes were 0.88 and 0.62 for down- and up-flow biological activated carbon effluents, respectively. The membrane removed the turbidity and polysaccharides content by 47.4% and 30.2% in down- flow biological activated effluent and 82.5% and 22.4% in up-flow biological activated carbon effluent, respectively, but retained few proteins. The retention of polysaccharides was higher on the membrane that filtered the down- flow biological activated effluent compared with that on the membrane that filtered the up-flow biological activated carbon effluent. The polysaccharides on the membranes fouled by up-flow biological activated carbon and down- flow biological activated effluents were spread continuously and clustered, respectively. These demonstrated that the up-flow biological activated carbon effluent fouled the membrane faster. Membrane fouling was associated with a portion of the polysaccharides (not the proteins) and inorganic particles in the feed water. When there was little difference in the polysaccharide concentrations between the feed waters, the fouling extent was exacerbated more by inorganic particles than by polysaccharides.     

Multi-stakeholder collaboration in community post-disaster reconstruction: case study from the Longmen Shan Fault area in China

While multi-stakeholder collaboration is critical for effective community post-disaster reconstruction (CPDR), it is often very difficult in practice. The Longmen Shan Fault active seismic zone in China has experienced several recent earthquakes with the 2008 Wenchuan earthquake and 2013 Lushan earthquake, both of which caused extensive and widespread damage to many communities, presenting unprecedented challenges for post-disaster reconstruction. This paper develops a multi-cycle field research method that involves three interconnected cycles: internet research, field visits, and extensive surveys: to examine multi-stakeholder collaboration for the CPDR following the Wenchuan earthquake. It was found that there were 12 types of active stakeholders engaged across four main areas: infrastructure rebuilding, psychological recovery, socio-economic rehabilitation, and ecological restoration. Specifically, local community participation and effective collaboration between the community and the external stakeholders were found to be the most crucial elements for successful reconstruction. Multi-stage field research after the Lushan earthquake verified that CPDR was effective and that multi-stakeholder collaboration had improved from the lessons learnt from the Wenchuan earthquake reconstruction experience. Some advantages and limitations of this research are also given.     

Exploring the administrative mechanism of China's Paired Assistance to Disaster Affected Areas programme

The Paired Assistance to Disaster Affected Areas (PADAA) programme is a mutual aid initiative with Chinese characteristics, which speeded up the process of restoring and reconstructing regions affected by the Wenchuan earthquake on 12 May 2008. 1 The PADAA is an efficient instrument for catastrophe recovery, yet it remains a mysterious mechanism to many members of disaster management communities. This paper aims to lift the veil on it by assessing its origins and evolution. It draws on the multi‐level moderated competition model to explain how the PADAA functions within the Chinese administrative system. The country's top‐down political system allows the central authority to mandate provincial and local governments from more economically developed regions to assist devastated areas with post‐disaster reconstruction. The practices of local accountability complement vertical control by giving leaders from donor regions strong incentives to accomplish assigned reconstruction tasks, resulting in intense competition between them.     

三棱钻杆粉体负载扭矩计算模型研究

为了实现三棱钻杆转动过程的定量化计算,在分析了三棱钻杆排粉机理的基础上,提出了基本假设,建立了扭矩基本物理模型,并阐述了物理模型的求解过程,得到了基本参数的解析解。在此基础上,对相关参数的求取方法以及最小扭矩问题进行了分析讨论,求得了钻孔内煤粉密度ρ的解析解以及降低钻杆整体扭矩的方法,提出了实际应用环节测定临界转速w界的实验方法,并得到了提高钻孔长度的理论方法。     

我国干旱半干旱煤矿区环境问题及对策

近年来,伴随着东部地区煤炭资源的枯竭,我国煤炭开采的重心逐步由东部湿润地区转移到西部干旱半干旱地区。生态环境脆弱是干旱半干旱区自然本底特征,大规模的煤炭开采一定程度上改变了当地的环境现状,带来了诸多环境问题。基于"井工"和"露天"两种不同煤炭开采方式,文章分析了干旱半干旱区煤炭开采造成的主要环境问题,并基于生态累积效应理论,分析了采煤活动的生态累积评估方法。最后,针对存在的主要环境问题提出了相应的对策与策略。     

成渝经济区河流表层沉积物中多溴联苯醚的分布特征

在成渝经济区内采集了19个表层沉积物样品,采用GC/MS方法对其中的PBDEs(Polybrominated Diphenyl Ethers,多溴联苯醚)进行了检测. 结果表明,沉积物中w(ΣPBDEs)(ΣPBDEs包括BDE-1,BDE-15,BDE-17,BDE-28,BDE-47,BDE-66,BDE-71,BDE-85,BDE-99,BDE-100,BDE-126,BDE-138,BDE-153,BDE-154,BDE-166,BDE-181,BDE-183和BDE-190)为0.20～6.45 ng/g,w(BDE-209)为0.44～6.29 ng/g. 与其他地区相比,成渝经济区内PBDEs的污染水平相对较低, 大部分样品中的PBDEs以BDE-209为主,说明成渝经济区河流沉积物中的PBDEs主要来自十溴联苯醚; 但PBDEs的组成特征显示,彭山岷江大桥沉积物中的PBDEs主要来自五溴联苯醚,而官渡沉积物中的PBDEs主要来自八溴联苯醚. 此外,一些以往工作较少关注的PBDEs单体,如BDE-1,BDE-15,BDE-181和BDE-190等,不但在沉积物中的检出率较高(均高于70%),而且有的含量也相对较高.      

三峡水库香溪河库湾氮磷分布状况及沉积物污染评价

为了解三峡大坝蓄水完成之后香溪河库湾水体及沉积物中氮、磷的分布状况以及沉积物污染水平,2013年4月对三峡水库香溪河库湾进行调查采样,测定表层水及沉积物中氮磷含量和形态组成。结果表明,香溪河库湾表层水总磷(TP)含量范围为0.20~0.51 mg·L~(-1),总氮(TN)含量范围为0.54~2.25 mg·L~(-1),TP主要由磷酸盐(PO_4~(3-))组成,TN主要由硝酸盐(NO_3~-)以及氨氮(NH_4~+)组成,TP在空间上呈现从河口向库尾逐渐升高的分布格局,TN分布从河口向库尾逐渐降低。香溪河库湾沉积物中TP含量变化范围为642~1 189 mg·kg~(-1),TN含量变化范围为867~1 718 mg·kg~(-1),沉积物TP含量分布呈现上游高下游低,沉积物TN分布趋势呈现中间高,两头低。沉积物中TP主要由无机磷(IP)组成,有机磷(OP)所占比例较小,其中IP由钙磷(Ca-P)、铁铝磷(Fe/Al-P)组成,三者含量:Ca-POPFe/Al-P,且沉积物TP含量空间变化受到三者影响(P0.05)。采用单一因子标准指数法对香溪河库湾沉积物中TN、TP污染水平进行评价,结果表明,表层沉积物中TN、TP最低级别污染指数平均值为2.0和1.6,表层沉积物中TN、TP污染指数均超过最低污染水平,且TP的严重级别污染指数达到0.5以上。三峡水库三期蓄水完成以后,香溪河库湾表层水体中氮磷含量较初期蓄水有所升高,各样点沉积物中氮磷含量表现出相同的趋势,沉积物中不稳定磷释放对水体富营养化具有影响,香溪河库湾的表层沉积物已经受到一定的污染,磷污染水平较高。     

O3查算表的建立及其在区域空气质量模式中的应用

利用光化学机制RADM2、CBM-Z建立箱模式,分析了影响O3生成的主要物理、化学因子,将这些因子进行分档计算,建立了能够描述光化学反应中O3及其前体物(挥发性有机物VOC、氮氧化物NOx)浓度变化的查算表,并在区域空气质量模式CALGRID中加以应用.通过对2006年1、4、7、10月珠江三角洲的模拟计算和比较分析表明,查表法显著提高了计算效率,运算时间减少45%~48%,并且与光化学机制直接耦合计算结果符合较好,其中基于RADM2的查算表对O3模拟效果较好,而基于CBM-Z的查算表对NOx模拟更佳.     

污泥龄对高浓度含氮废水亚硝化稳定性的影响研究

为考察污泥龄与高浓度含氮废水亚硝化稳定性之间的关系,采用连续进水、间歇排水SBR工艺,当水力停留时间为0.75 d,污泥停留时间为3 d时,系统亚硝化率约为75%和氨氮降解率约为60%。试验结果证明SRT控制在一定范围内能实现对硝酸菌的"洗出",使亚硝酸菌占据系统中的优势地位,从而保证了系统较高的亚硝化率。     

长江流域重要保护物种分布格局与优先区评价

开展大尺度重要物种的保护优先区研究对于提高生物多样性保护效率十分重要. 选取1 020个物种(包括植物568种、哺乳动物142种、鸟类168种、两栖动物57种、爬行动物85种)为长江流域重要保护物种. 在分析重要保护物种类群分布格局的基础上,利用系统保护规划与专家参与的方法,提出了长江流域物种保护的27个保护优先区.保护优先区总面积占流域面积的41.8%,涵盖了重要保护物种973种,占全部重要保护物种数目的95.4%.建议以保护优先区为基本单元,开展有关生物多样性保护研究及保护区群的建设.