Cleaning of fouled ultrafiltration (UF) membrane by algae during reservoir water treatment

Ultrafiltration (UF) membrane fouling is often encountered in water treatment. Algae could be removed by UF membrane for its nominal pore size, and the algae cells deposited on the surface of UF membrane. The cells attach to the membrane, they start to release secretion and produce extracellular polymetric substances (EPS), which accumulate on the surface and cause the flux decline. This study examined the effects of hydraulic and chemical cleaning on fouled membrane by algae-rich reservoir water. Four kinds of hydraulic cleaning method were investigated, including forward flushing, backwashing, forward flushing followed by backwashing and backwashing followed by forward flushing. Backwashing followed by forward flushing was more effective for flux recovery, and 20 min duration were enough for the cleaning. To maximize flux recovery for the algae-fouled membrane, chemical cleaning was applied as enhanced cleaning strategies. NaOH, NaOCl, and citric acid were used for cleaning agents. The cleaning with the combination of NaOH (0.02 N) and NaOCl (100 mg/L) was effective than separate uses. And the cleaning duration was determined as 4 h.     

再谈异性纤维的在线检测清除

为了用好异性纤维检出设备,对提高异纤检出率的问题进行了分析,综合评定了异纤检出机的作用.认为异纤检出机的检出率一般应在80%左右,将开清棉工序异纤检出机和带异纤检出功能的电子清纱器结合使用,可有效提高异纤检出率,保证产品质量.     

金刚石膜电化学氧化液的制备及清洗技术研究

提出了一种采用电化学去除硅片表面有机物的新的清洗方法,用金刚石膜电极作为阳极,电化学氧化硫酸铵溶液生成稳定的强氧化溶液,电解液的氧化性通过间接碘量法测量。通过大量实验,优化初始电解液的浓度以及初始温度等因素,得到氧化强度最佳的电化学清洗液。用自制氧化液进行硅片表面有机物的清洗实验,并与传统的RCA清洗方法进行对比。通过XPS分析可知,采用新的电化学氧化溶液清洗后的硅片表面有机物去除效果明显优于对比实验样品。     

Do indoor chemicals promote development of airway allergy?

Allergic asthma has increased worldwide in the industrialized countries. This review evaluates whether the major groups of indoor chemical exposures possess allergy-promoting (adjuvant) effects; formaldehyde was excluded, because of the size of the literature. Volatile organic compounds (VOCs) are used as an example of gases and vapors. The precipitation of asthmatic symptoms by VOC exposures is probably because of VOC levels considerably above typical indoor levels, or VOCs may be a surrogate for exposure to allergens, combustion products or dampness. Indoor particles possessed adjuvant effects in animal studies and allergy-promoting effects in humans. Quaternary ammonium compounds may possess adjuvant effects in animal studies and promoted sensitization in humans in occupational settings. The use of cleaning agents, anionic and non-ionic surfactants are not considered to possess an important adjuvant effect in the general population. Regarding phthalate exposures, results from animal and epidemiological studies were found to be discordant. There is little evidence that the indoor chemicals evaluated possess important adjuvant effects. If buildings are kept clean, dry and free of combustion products, the important question may be would it be profitable to look for lifestyle factors and non-chemical indoor exposures in order to abate airway allergy? PRACTICAL IMPLICATIONS: Indoor chemicals (pollutants) have been accused to promote development of airway allergy by adjuvant effects. In this review, we evaluated the scientific literature and found little support for the supposition that indoor chemicals possess important adjuvant effects. This rises the question: would it be profitable for abatement of airway allergy to look for non-chemical indoor exposures, including lifestyle factors, and exposures to allergens, microorganisms, including vira, and their interactions?     

Bacterial re-contamination of surfaces of food processing lines during cleaning in place procedures

The possible contamination of surfaces of food processing lines during cleaning in place (CIP) procedures was investigated. Experiments were focused on surface contamination of straight pipes and a two-way valve, chosen as an example of complex pieces of equipment. Pipes and a two-way valve were inserted into a CIP rig, at the same time as a series of pipes highly contaminated with spores of three Bacillus cereus strains, with various surfaces properties. Following a CIP procedure, performed in conditions close to those encountered in food industries, the contamination level of the various items was estimated. A significant surface contamination occurring during CIP was evidenced, depending on the spore surface properties. Similarly to previously reported observations, when spores were suspended in optimal adhesion conditions (suspension in water at 20 °C), the re-adhesion phenomenon was controlled by the flow pattern and contamination levels inside the valve were significantly higher than in tubes. Cleaning strategies should therefore take into account the re-adhesion phenomenon to limit the risk of contamination by the process line.     

A review of current and emergent biofilm control strategies

Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin).The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry.     

CO2 dry cleaning: Acoustic cavitation and other mechanisms to induce mechanical action

High pressure carbon dioxide (CO₂) is a potential solvent for textile dry cleaning. However, the particulate soil (e.g. clay, sand) removal in CO₂ is generally insufficient. Since cavitation has been proven to be beneficial in other CO₂ cleaning applications, this study aims to investigate the possibility of improving the performance of CO₂ textile dry cleaning by using ultrasound or other mechanisms to induce the mechanical action such as bubble spray and jet spray. In the experiments, several types of textiles soiled with a mixture of motor oil and soot were cleaned using 1 L and 90 L CO₂ dry cleaning set-ups. Using either ultrasound, stirring, liquid spray or bubble spray does not give a significant improvement on particulate soil removal from textile. It was also found that the additional use of ClipCOO detergent does not give a significant improvement on particulate soil removal either. The cleaning performance of CO₂ is 50% lower than that of PER and thus another method to increase the particulate soil removal in CO₂ textile dry cleaning still needs to be developed.     

Model based approach to synthesize spare-supported cleaning schedules for existing heat exchanger networks

Almost every modern chemical process is equipped with a heat-exchanger network (HEN) for optimal energy recovery. However, as time goes on after startup, fouling on the heat-transfer surface in an industrial environment is unavoidable. If the heat exchangers in an operating plant are not cleaned regularly, the targeted thermal efficiency of HEN can only be sustained for a short period of time. To address this practical issue, several mathematical programming models have already been developed to synthesize online cleaning schedules. Although the total utility cost of a HEN could be effectively reduced accordingly, any defouling operation still results in unnecessary energy loss due to the obvious need to temporarily take the unit to be cleaned out of service. The objective of the present study is thus to modify the available model so as to appropriately assign spares to replace them. Specifically, two binary variables are adopted to respectively represent distinct decisions concerning each online exchanger in a particular time interval, i.e., whether it should be cleaned and, if so, whether it should be substituted with a spare. The optimal solution thus includes not only the cleaning schedule but also the total number of spares, their capacities and the substitution schedule. Finally, the optimization results of a series of case studies are also presented to verify the feasibility of the proposed approach.     

焦油管式炉结焦的预防及处理

阐述了管式加热炉炉管结焦的机理及危害,分析了焦油管式炉结焦的原因,通过改进机械化焦油氨水澄清槽、提高二次蒸发器过热蒸汽量、降低管式炉辐射段出口温度和燃烧法清理结焦炉管等措施,解决了炉管频繁结焦问题。     

MODELING AND OPTIMIZATION OF MEMBRANE CHEMICAL CLEANING BY ARTIFICIAL NEURAL NETWORK,FUZZY LOGIC,AND GENETIC ALGORITHM

Robust artificial neural network (ANN) and fuzzy logic (FL) models were derived for chemical cleaning of microfiltration membranes fouled by milk under a wide range of operating conditions. The accuracies of the models were compared with multiple linear regressions (MLR). The developed models are useful tools for predicting the performance of chemical cleaning. The effects of different operating conditions on cleaning performance were elucidated using the ANN developed model. Moreover, optimum cleaning condition was determined by genetic algorithm and ANN model. The current research demonstrated that fuzzy logic and an artificial neural network can quantitatively capture cumulative effects of a range of operating conditions on flux recovery and resistance removal during a cleaning process.