电渗析脱盐时威尔逊公式修正的新方法

本文列举了铝制品洗白碱性废水［１］、海水第二脱盐段①和人工配制ＮａＣｌ水溶液②三种水质，采用伏－安法测定权限电流密度后，用三步作图法，分别求出威尔逊修正式中的系数Ｋ，浓度指数ｍ和流速指数ｎ，建立了威尔逊修正公式的新模式：Ｉ_（ｌｉｍ_＝ＫＣ~ｍＣ~（ａ＋ｂｃ）本模式适用于组份复杂、浓度变化范围大的水溶液体系。用该模式计算的极限电流密度值与实验测定值之间的偏差在±１０％之内，具有很好的实用性。     

电渗析-厌氧膜生物反应器处理含甘油高盐废水

利用电渗析(ED)-厌氧膜生物反应器(AnMBR)处理含甘油高盐废水,电渗析过程脱盐率达99%以上,平均能耗为616kJ/L,电流效率91.4%。AnMBR处理含甘油废水过程中COD去除率达95%,膜在COD去除中发挥了重要作用,其COD截留率为41%~81%。期间发生膜污染现象,跨膜压差快速上升并最终稳定在0.040~0.043MPa。AnMBR沼气中甲烷比例为78.3%,甘油比产甲烷速率0.252LCH4/g甘油。甘油在厌氧条件下首先转变成丙酸,然后再被分解。研究证明,在厌氧处理甘油的过程中有机负荷不宜过大,否则会造成严重的挥发性脂肪酸(VFA)积累,尤其是丙酸的积累。此外,CaCl2浓度与甘油转化关系的实验结果表明:厌氧菌群受到4%以下盐度冲击时能在6d内恢复活性,受到6%以上盐度冲击将导致活性恢复缓慢。因此,厌氧反应器进水盐度需控制在4%以内。研究还发现VFA中丙酸所占比例随着盐度升高逐渐下降,说明高盐度会使厌氧菌活性受到抑制,影响甘油降解。     

Removal of Mercury(Hg(Ⅱ)) from Seaweed Extracts by Electrodialysis and Process Optimization Using Response Surface Methodology

In this work,response surface methodology(RSM)was employed to model and optimize electrodialysis process for mercury(Hg(II))removal from seaweed extracts.Box-Behnken design(BBD)was utilized to evaluate the effects and the interaction of influential variables such as operating voltage,influent flow rate,initial concentration of Hg(II)on the removal rate of Hg(II).The developed regression model for removal rate response was validated by analysis of variance,and presented a good agreement of the experimental data with the quadratic equation with high value coefficient of determination value(R2=0.9913,RAdj 2=0.9678).The optimum operating parameters were determined as 7.17V operating voltage,72.54L h−1 influent flow rate and 5.04mgL−1 initial concentration of mercury.Hg(II)removal rate of 76.45%was acquired under the optimum conditions,which showed good agreement with model-predicted(75.81%)result.The results revealed that electrodialysis can be considered as a promising strategy for removal of Hg(II)from seaweed extracts.     

A rapid and direct method for organic nitrogen analysis in environment

Organic nitrogen is omnipresent in nature. The variations of dissolved organic nitrogen （DON） concentration are usually a result of microbial activity, anthropogenic influence, and/or other physical-chemical processes （e.g. photo-mineralization）. Therefore, DON serves as an important indicator for aquatic life cycles and water qualities. However, current DON detection methods inevitably produce exaggerated standard deviation, due to their inherent subtraction processes, as shown in the below equation. Consequently, they are incapable of propelling further understandings of the DON occurrence, DON role in nutrient recycling, and DON potential human toxicity as well. SDON=（STN2＋SDIN^2）0.5, where： S=standard deviation in an effort to overcome the barricade, the primary goal of this study is to develop a membrane pretreatrnent unit using electro-dialysis （EDI） process. Similar to the well-known mechanism used in dissolved organic carbon （DOC） analysis, which employs acidification and following purging to eliminate the inorganic carbon species, this study believes that EDI could significantly （〉99%） remove the dissolved inorganic nitrogen （DIN） species （i.e., ammonia, nitrite and nitrate） and concurrently retain most of organic nitrogen materials. By grafting the pretreatment unit with a total nitrogen （TN） analyzer, the system then enables direct detection of DON. Meanwhile, EDI discriminates nitrogen not only on size differences, but also on electrostatic force that separates nitrogen species according to their charge, thus making it more advantageous than other membrane technologies. Results showed that this approach was successfully used to separate inorganic from organic nitrogen for the selected water samples, including model amino acids, natural organic water ＆ isolates （i.e., humic substance）, and wastewater plant effluents. The EDI process was able to reduce more than 99% of inorganic nitrogen species within 2 hours under a 40-voltage operation condition, ending up with negligible DIN. Meanwhile, it retained more than 90% of organic matter （in terms of DOC） for natural water samples and 80% for wastewater effluent samples, meaning that DON can be analyzed directly without sacrifising significant organics. In addition, the EDI unit deleted other inorganic anions such as bicarbonate, chloride, sulfate, and phosphate, too, implying that this unit might also be applied to other organic matter like organic chloride, sulfur, phosphorous, etc.