Groundwater arsenic removal by coagulation using ferric(Ⅲ)sulfate and polyferric sulfate: A comparative and mechanistic study

Elevated arsenic(As) in groundwater poses a great threat to human health. Coagulation using mono- and poly-Fe salts is becoming one of the most cost-effective processes for groundwater As removal. However, a limitation comes from insufficient understanding of the As removal mechanism from groundwater matrices in the coagulation process, which is critical for groundwater treatment and residual solid disposal. Here, we overcame this hurdle by utilizing microscopic techniques to explore molecular As surface complexes on the freshly formed Fe flocs and compared ferric(III) sulfate(FS) and polyferric sulfate(PFS)performance, and finally provided a practical solution in As-geogenic areas. FS and PFS exhibited a similar As removal efficiency in coagulation and coagulation/filtration in a two-bucket system using 5 mg/L Ca(ClO)_2. By using the two-bucket system combining coagulation and sand filtration, 500 L of As-safe water( 10 μg/L) was achieved during five treatment cycles by washing the sand layer after each cycle. Fe k-edge X-ray absorption near-edge structure(XANES) and As k-edge extended X-ray absorption fine structure(EXAFS) analysis of the solid residue indicated that As formed a bidentate binuclear complex on ferrihydrite, with no observation of scorodite or poorly-crystalline ferric arsenate. Such a stable surface complex is beneficial for As immobilization in the solid residue, as confirmed by the achievement of much lower leachate As(0.9 μg/L–0.487 mg/L)than the US EPA regulatory limit(5 mg/L). Finally, PFS is superior to FS because of its lower dose, much lower solid residue, and lower cost for As-safe drinking water.     

Groundwater arsenic removal by coagulation using ferric(III) sulfate and polyferric sulfate: A comparative and mechanistic study

Elevated arsenic (As) in groundwater poses a great threat to human health. Coagulation using mono-and poly-Fe salts is becoming one of the most cost-effective processes for groundwater As removal. However, a limitation comes from insufficient understanding of the As removal mechanism from groundwater matrices in the coagulation process, which is critical for groundwater treatment and residual solid disposal. Here, we overcame this hurdle by utilizing microscopic techniques to explore molecular As surface complexes on the freshly formed Fe flocs and compared ferric(III) sulfate (FS) and polyferric sulfate (PFS) performance, and finally provided a practical solution in As-geogenic areas. FS and PFS exhibited a similar As removal efficiency in coagulation and coagulation/filtration in a two-bucket system using 5 mg/L Ca(ClO)₂. By using the two-bucket system combining coagulation and sand filtration, 500 L of As-safe water (<10 μg/L) was achieved during five treatment cycles by washing the sand layer after each cycle. Fe k-edge X-ray absorption near-edge structure (XANES) and As k-edge extended X-ray absorption fine structure (EXAFS) analysis of the solid residue indicated that As formed a bidentate binuclear complex on ferrihydrite, with no observation of scorodite or poorly-crystalline ferric arsenate. Such a stable surface complex is beneficial for As immobilization in the solid residue, as confirmed by the achievement of much lower leachate As (0.9 μg/L-0.487 mg/L) than the US EPA regulatory limit (5 mg/L). Finally, PFS is superior to FS because of its lower dose, much lower solid residue, and lower cost for As-safe drinking water.     

深圳市光环境功能区监管模式研究

根据深圳市地区特点。首先,划分光环境功能区,针对每个光环境功能区,再分成子区域,并提出区域光环境质量标准制定模式;然后,根据光环境的区域划分,结合具体区域功能,对不同光污染源进行划分和规范。提出光污染防护标准制定模式。通过区域光环境质量标准和光污染防护标准的制定,建立相应光环境监管模式,以达到防治光污染,保护和改善光环境,保障人类健康以及生态平衡,保证光的有效利用,构建一个绿色和谐可持续发展的光环境。     

浅析应急救援队伍在抢险救援中的应急保障能力

通过对当前应急救援队伍的装备配置和维护保养情况进行调查,结合基层队伍的专项训练情况,分析现阶段应急救援队伍应急保障中存在的薄弱点,就如何提高应急救援队伍的救援能力提出建议。     

以pH和ORP作为脉冲SBR工艺的实时控制参数

为了实现脉冲SBR深度脱氮的实时控制,以某污水处理厂市政污水为处理对象,考察了脉冲SBR在深度脱氮过程中pH及ORP的变化规律.试验结果表明,pH及ORP的变化规律与脉冲SBR有机物去除、硝化与反硝化过程存在较好的相关关系.可以根据pH和ORP变化曲线上的特征点对脉冲SBR进行实时控制.并考察了污水C/N(COD/NH4 -N)对pH及ORP的变化规律的影响.在硝化过程中,C/N对pH及ORP曲线变化点的出现没有影响;在反硝化过程中,应结合pH值"硝酸盐峰"和ORP"硝酸盐膝"来判断低C/N污水反硝化的终点.在该试验中,出水TN低于2 mg/L,TN去除率可达到96%以上.     

农药“增效双效灵”的致突变试验

本文报导了“增效双效灵(HDE”的 Ames 试验结果。结果表明,HDE 有抑菌能力,其最大无抑菌浓度为1.225%(W/V)。在本试验条件下未发现其有致突变活性。     

变压吸附技术在环境工程中的应用

变压吸附技术具有能耗低、投资少、流程简单、操作方便、可靠性好和自动化程度高等优点,在环境工程领域得到了广泛的应用。介绍了变压吸附技术在废水处理、废气处理、固体废弃物处理等领域的研究进展和应用成果,探讨了在环境工程中应用变压吸附技术的发展方向。     

复合生物反应器工艺对化纤废水的处理研究

在普通活性污泥系统的曝气池中投加一定量的填料构成复合生物反应器 ,可以增加曝气池中的生物体量至 6g/L左右 ,在HRT为 8h ,泥龄为 5d时 ,CODCr、氨氮的去除率分别提高了 2 0 %和9.6% ,容积负荷对复合生物反应器的脱氮能力影响较小。该工艺对污泥膨胀有较好的控制     

2,3,7,8,-四氯苯噁英对NIH小鼠早期妊娠和生殖激素的影响

用不同剂量的2,3,7,8 四氯苯二英(2,3,7,8 tetrachlorodibenzopdioxin,TCDD)对小鼠胚胎附植数量和生长发育情况进行剂量反应评估,分析TCDD对假孕小鼠子宫蜕膜生长状况的影响以及比较胚胎种植前后染毒效果.所有样本采集血液,测定母体血清雌二醇和孕酮的浓度变化.结果表明,50和100ng·(kg·d)-1TCDD处理的孕鼠,胚胎附植数量明显减少(P<0 05),着床后胚胎出现发育迟缓,质量减轻(P<0 05);同等剂量TCDD处理的假孕小鼠,子宫蜕膜生长受到了极显著的抑制(P<0 01);种植前后染毒效果比较发现种植前期染毒的小鼠胚胎对TCDD更为敏感.母体血清雌二醇浓度随剂量和染毒时段有不同程度的升高,而孕酮浓度则极显著下降(P<0 01).由此表明低剂量TCDD可能通过对生殖激素的干扰,强烈影响NIH小鼠妊娠早期生殖生理状态和着床后胚胎的发育.实验同时证明小鼠也可作为早期妊娠毒物研究的供试动物,用以筛选动物和人类早期妊娠的有害化合物.     

服务业循环经济发展研究综述

近年来,服务业循环经济研究引起越来越多学者的重视。梳理国内外研究文献,主要得出以下结论:内涵主要从整个服务周期、服务业与其他产业相联系这两个角度界定;发展模式主要体现在企业、行业、社会3个层面;综合评价主要从经济、资源、环境、废物排放等方面构建指标体系,选用特尔斐法与层次分析法或主成分分析法进行评价;保障体系集中在行政、法律、经济、社会4个方面。目前,研究还没有形成系统的理论体系,部分研究成果与实践脱节,未来需要完善发展模式、增加定量研究、独立保障体系研究。