Mechanisms of ultraviolet disinfection and chlorination of Escherichia coli: Culturability, membrane permeability, metabolism, and genetic damage

Traditional culture methods may underestimate the tolerance of microorganisms to disinfectants because of the existence of viable but nonculturable or sublethally injured cells after disinfection.The selection of a strict method is crucial for the evaluation of disinfection performance.The actions of 2 typical disinfectants–ultraviolet(UV)and chlorine–on the fecal indicator Escherichia coli were investigated by the detection of culturability,membrane permeability,metabolic activity,deoxyribonucleic acid(DNA),and messenger ribonucleic acid(m RNA).During UV disinfection,the irreversible damages in the cell membrane and cellular adenosine triphosphate(ATP)were negligible at low UV doses(80 m J/cm~2).However,membrane permeability was damaged at low doses of chlorine(5 mg/L),leading to leakage of cellular ATP.Our study showed that a slight lesion in DNA was detected even at high doses of UV(400 m J/cm~2)and chlorine(5 mg/L)treatments.The decay of m RNA was more rapid than that of DNA.The degradation level of m RNA depended on the choice of target genes.After exposure to 50 m J/cm~2UV dose or 5 mg/L chlorine for30 min,the DNA damage repair function(Rec A m RNA)was inhibited.The m RNA involved in the DNA damage repair function can be a potential indicator of bacterial viability.     

Towards a better hydraulic cleaning strategy for ultrafiltration membrane fouling by humic acid: Effect of backwash water composition

As a routine measurement to alleviate membrane fouling, hydraulic cleaning is of great significance for the steady operation of ultrafiltration (UF) systems in water treatment processes. In this work, a comparative study was performed to investigate the effects of the composition of backwash water on the hydraulic cleaning performance of UF membranes fouled by humic acid (HA). Various types of backwash water, including UF permeate, Milli-Q water, NaCl solution, CaCl₂ solution and HA solution, were compared in terms of hydraulically irreversible fouling index, total surface tension and residual HA. The results indicated that Milli-Q water backwash was superior to UF permeate backwash in cleaning HA-fouled membranes, and the backwash water containing Na⁺ or HA outperformed Milli-Q water in alleviating HA fouling. On the contrary, the presence of Ca^2 + in backwash water significantly decreased the backwash efficiency. Moreover, Ca^2 + played an important role in foulant removal, and the residual HA content closely related to the residual Ca^2 + content. Mechanism analysis suggested that the backwash process may involve fouling layer swelling, ion exchange, electric double layer release and competitive complexation. Ion exchange and competitive complexation played significant roles in the efficient hydraulic cleaning associated with Na⁺ and HA, respectively.     

Preparation of high concentration polyaluminum chloride with high content of Alb or Alc

A novel membrane distillation concentration method was used to prepare high concentration polyaluminum chloride (PACl) with high content of Al_b or Al_c. 2.52 mol/L PACl₁ with 88% Al_b and 2.38 mol/L PACl₂ with 61% Al_c were successfully prepared. Three coagulants, AlCl₃, PACl₁ and PACl₂ were investigated on their hydrolysis behavior and speciation under different conditions. The effects of pH and dilution ratio on Al species distribution were investigated by ferron assay. Experimental result showed that pH had a significant effect on Al species distribution for the three coagulants. Dilution ratio had little effects on Al_b and Al_c distribution in whole dilution process except the beginning for PACl₁ and PACl₂. The results indicated that transformation of Al depends largely on their original composition. AlCl₃ was the most unstable coagulant among these three coagulants during hydrolysis process. PACl₁ and PACl₂ with significant amounts of highly charged and stable polynuclear aluminum hydrolysis products were less affected by the hydrolysis conditions and could maintain high speciation stability under various conditions.     

开发膜生物反应器的经济技术因素探讨

经济因素是制约膜生物反应器废水处理工艺发展的关键，影响经济性的直接原因是能耗，间接原因是膜受污染失效。ＭＢＲ中降解有机物的主要手段仍是生物反应器，膜分离对生物反应器起到了独特的强化作用，但必须考虑适当的运行条件，否则会带来负面效应。     

优化精馏操作 实现清洁生产

简述了低污染甲醇精馏优化操作控制技术，在江氨公司的应用及取得的效果。     

减压蒸馏法处理化工厂二硝基重氮酚(DDNP)废水

简要概述了化工厂DDNP废水来源及水质，详细阐述了减压蒸馏法处理DDNP废水实现水闭路循环的机理，工艺流程。与目前常用几种DDNP废水处理法相比较，论述了减压蒸馏法处理DDNP废水的特点。     

Prenatal diagnosis of severe combined immunodeficiency with defective synthesis of HLA molecules

The immunodeficiency associated with a defective expression of HLA molecules is an autosomal recessive disorder leading to death during childhood. We have performed prenatal diagnosis for six fetuses at risk for this disease by membrane immunofluorescence on blood lymphocytes and monocytes, using specific monoclonal antibodies for HLA class I and II molecules. Two pregnancies have been found to be affected. The diagnosis has been confirmed on each abortus by the study of the membrane expression of HLA class I and II molecules on blood lymphocytes and monocytes, and on thymic and splenic cells. The four other cases were found to be normal both during pregnancy and after birth. The detection of the defect as early as the 20th week of gestation allows selective termination.     

超滤法处理清洗乳化液废水的应用研究

采用自制超滤膜设备对上海拖拉机内燃机公司油嘴油泵 清洗乳化废水进行了实验室试验，和近一年的生产性应用，结果表明，清洗乳化液废水经超滤处理，ＣＯＤｃｒ去除率为８５％－９１％，油的去除率为９９．４％－９９．９％，出水添加适量新清洗剂后可以回用于生产。     

化工生产中的清洁工艺

简述了清洁生产产生的背景及其重要意义，从改进工艺（聚乙烯醇生产工艺改革），改变生产原料（以乙烯取代乙炔作为合成有机中间体的原料），应用生物技术（两步发酵法生产维生素Ｃ）和改变反应设备（离子膜法生产氢氧化钠）等４个方面说明清洁工艺在化工生产领域取得的实际成效。     

膜分离稀土废水预处理中钙镁去除的研究进展

稀土废水成分复杂,硬度高,利用膜法处理时,进膜之前必须进行预处理.介绍了降低稀土废水硬度传统的和新型的方法.经过分析得出,根据具体水质情况,选择适当的互补处理方法,稀土废水完全可达到膜分离装置进水水质要求.