Effect of alum addition on the performance of submerged membranes for wastewater treatment.

The effect of aluminum sulfate (alum) addition on membrane performance was investigated, with a particular focus on membrane fouling. During initial operation, alum was added and the performance monitored. After terminating alum addition, the transmembrane pressure (TMP), which is indicative of membrane resistance to flow or fouling, increased. Accompanying the increase in TMP was an increase in the organic nonsettleable fraction (colloidal + dissolved) content of the mixed liquor and deterioration of permeate quality and floc strength. Permeate polysaccharide concentrations increased significantly, suggesting a preferential binding of solution polysaccharides by alum. Upon reinitiating alum addition, the TMP only partially recovered, indicating some irreversible fouling, while mixed liquor nonsettleable organic material, permeate quality, and floc strength returned to initial levels. These results suggest that direct alum addition to membrane bioreactors can improve membrane performance by reducing the organic fouling material and improving floc structure and strength. It appears that bulk liquid polysaccharides may contribute to irreversible membrane fouling, and this fraction can be efficiently controlled through the alum addition.     

Ambient toxicity due to chlorpyrifos and diazinon in a central California coastal watershed

The Salinas River watershed along the central coast of California, U.S.A., supports rapidly growing urban areas and intensive agricultural operations. The river drains to an estuarine National Wildlife Refuge and a National Marine Sanctuary. The occurrence, spatial patterns, sources and causesof aquatic toxicity in the watershed were investigated by sampling four sites in the main river and four sites in representative tributaries during 15 surveys between September1998 and January 2000. In 96 hr toxicity tests, significant Ceriodaphnia dubia mortality was observed in 11% of the mainriver samples, 87% of the samples from a channel draining anurban/agricultural watershed, 13% of the samples fromchannels conveying agricultural tile drain runoff, and in 100% of the samples from a channel conveying agricultural surface furrow runoff. In six of nine toxicity identificationevaluations (TIEs), the organophosphate pesticides diazinon and/or chlorpyrifos were implicated as causes of observed toxicity, and these compounds were the most probable causes oftoxicity in two of the other three TIEs. Every sample collectedin the watershed that exhibited greater than 50% C. dubia mortality (n = 31) had sufficient diazinon and/or chlorpyrifos concentrations to account for the observed effects.Results are interpreted with respect to potential effects on other ecologically important species.     

论精神分析批评及其缺陷

精神分析批评作为一种文学批评方法,可以用于解释作者的创作动机和研究文学文本。简要梳理精神分析批评的理论渊源,分析其对文学研究的影响,指出其缺陷,旨在帮助文艺批评者更好、更有效地运用于文学批评。     

Campylobacter coli infection causing second trimester intrauterine growth restriction (IUGR): a case report and review of the literature

Campylobacter is a gram-negative, microaerophilic, curved rod and a normal resident of the gastrointestinal flora and may be the cause of disease in animals. Transmission to humans occurs by ingestion of contaminated food or by direct contact with infected animals. In the past few decades, an increasing number of reports have implicated the presence of this organism in human abortions as well. An infectious mechanism due to primary placental inflammatory damage followed by secondary damage to the fetus following placental insufficiency and ischemia was suggested. The most common species of Campylobacter are Campylobacter jejuni and Campylobacter coli, which are classically associated with enteritis in humans. We present a rare case of mid-gestation intrauterine growth restriction (IUGR) associated with maternal bacteremia caused by C. coli infection. Our literature review focuses on Campylobacter infections occurring in the second and third trimesters of pregnancy. In all cases, mild maternal symptoms consisting of fever and weakness were presented. However, associated adverse fetal outcome, including abortions, IUGR or preterm labor may occur more frequently than anticipated. Our report strengthens the importance of awareness to this finding and focuses the need to consume properly cooked meat during pregnancy. © 2015 John Wiley & Sons, Ltd.