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Shujuan Meng Rui Wang Kaijing Zhang Xianghao Meng Wenchao Xue Hongju Liu Dawei Liang Qian Zhao Yu Liu 《Frontiers of Environmental Science & Engineering》2021,15(4):64
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Membrane bioreactor biofouling is usually described as an extracellular matrix in which biopolymers, inorganic salts and active microbes co-exist. For that reason, biomineralization (BM) models can be useful to describe the spatial organization and environmental constraints within the referred scenario. BM arguments were utilized as background in order to (1) evaluate CaCO3 influence on flux decline; pore blocking and cake layer properties (resistance, permeability and compressibility) in a wide range of Chitosan/Bovine serum albumin (BSA) mixtures during step-pressure runs and, (2) perform membrane autopsies in order to explore the genesis of mineralized extracellular building blocks (MEBB) during cake layer build up. Using low molecular weight chitosan (LC) and BSA, 2 L of 5 LC/BSA mixtures (0.25-1.85 ratio) were pumped to an external ultra filtration (UF) membrane (23.5 cm2, hydrophobic, piezoelectric, 100 kDa as molecular weight cut-off). Eight different pressure steps (40 ± 7 to 540 ± 21 kPa) were applied. Each pressure step was held for 900 s. CaCO3 was added to LC/BSA mixtures at 0.5, 1.5 and 3 mM in order to create MEBB during the filtration tests. Membrane autopsies were performed after the filtration tests using thermo gravimetric, scanning microscopy and specific membrane mass (mg cm−2) analyses. Biopolymer-CaCO3 step-pressure filtration created compressible cake layers (with inner voids). The formation of an internal skeleton of MEBB may contribute to irreversible fouling consolidation. A hypothesis for MEBB genesis and development was set forth. 相似文献
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Hosny K. Khordagui 《Environmental management》1992,16(3):309-316
It is estimated that some 17 metric tons of residual oxidants (chlorine) are discharged into the enclosed coastal seawater
of Kuwait on a daily basis from power-desalination plants alone. Alarmed by the unlimited number of reported cases of damage
to marine aquatic systems due to chlorine discharge around the world, several alternatives were proposed to control such a
massive discharge of residual oxidant into seawaters. Most of the proposed alternatives lacked the basic criteria necessary
for their evaluation, justification, and then selection.
The objective of this article is to provide a conceptual approach that can be used to select a control measure for residual
oxidant discharge in Kuwait coastal seawaters. This approach is based on state-of-the-art knowledge and the unique operational
and environmental factors involved. A matrix system was designed whereby the cost of residual chlorine control alternative,
its effectiveness, and environmental and public health impact, performance, and reliability in Kuwait can be compared and
evaluated. The selection approach considered currently operating power plants in terms of their engineering design and material
(cast iron or steel condensers), current operational conditions, operator's perception, acceptability, and projected problems
associated with the environmental management of proposed modifications.
The proposed approach revealed that in Kuwait, conventinal chlorination was marginally superseded only by chlorination/dechlorination
using SO2 and operation alteration using process optimization. The overall cost-effective assessment matrix classified other alternatives
as worse than chlorination by various degrees.
Ozone and UV were found to be the worst and the least desirable alternatives for biofouling control of seawater in Kuwait.
In light of the available information on the consequences of the Gulf War on the marine environment, and the potential formation
of additional halogenated organic compounds through the reaction of residual chlorine with the released petroleum hydrocarbons,
it is essential to control residual chlorine discharged into the nearshore environment of Kuwait. 相似文献
4.
Cooling towers have the potential to develop infectious concentrations of Legionella pneumophila. Legionella counts increases where biofilm and warm water temperatures are present. In this study, biofilm associated L. pneumophila and heterotrophic bacteria were compared in terms of material dependence. Model cooling tower system was experimentally infected
by L. pneumophila standard strain and monthly monitored. Different materials were tested for a period of 180 days. The lowest L. pneumophila and heterotrophic plate counts were measured on plastic polymers, whereas L. pneumophila and heterotrophic bacteria were accumulated rapidly on galvanized steel surfaces. It can be concluded that selection of plastic
polymers, as a manufacturing material, are suitable for recirculating water systems. 相似文献
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Jinxue Luo Jinsong Zhang Xiaohui Tan Diane McDougal Guoqiang Zhuang Anthony G. Fane Staffan Kjelleberg Yehuda Cohen Scott A. Rice 《环境科学学报(英文版)》2015
Biofilmformation, one of the primary causes of biofouling, results in reducedmembrane flux or increased transmembrane pressure and thus represents a major impediment to the wider implementation of membrane bioreactor (MBR) technologies for water purification. Most studies have focused on the role of bacteria in membrane fouling as they are the most dominant and best studied organisms present in the MBR. In contrast, there is limited information on the role of the archaeal community in biofilm formation in MBRs. This study investigated the composition of the archaeal community during the process of biofouling in an MBR. The archaeal community was observed to have lower richness and diversity in the biofilmthan the sludge during the establishment of biofilms at low transmembrane pressure (TMP). Clustering of the communities based on the Bray-Curtis similarity matrix indicated that a subset of the sludge archaeal community formed the initial biofilms. The archaeal community in the biofilm was mainly composed of Thermoprotei, Thermoplasmata, Thermococci, Methanopyri, Methanomicrobia and Halobacteria. Among them, the Thermoprotei and Thermoplasmata were present at higher relative proportions in the biofilms than they were in the sludge. Additionally, the Thermoprotei, Thermoplasmata and Thermococci were the dominant organisms detected in the initial biofilms at low TMP, while as the TMP increased, the Methanopyri, Methanomicrobia, Aciduliprofundum and Halobacteria were present at higher abundances in the biofilms at high TMP. 相似文献
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Yuqin Lu Xiao Bian Hailong Wang Xinhua Wang Yueping Ren Xiufen Li 《Frontiers of Environmental Science & Engineering》2018,12(4):5
Since the concept of the osmotic microbial fuel cell (OsMFC) was introduced in 2011, it has attracted growing interests for its potential applications in wastewater treatment and energy recovery. However, forward osmosis (FO) membrane fouling resulting in a severe water flux decline remains a main obstacle. Until now, the fouling mechanisms of FO membrane especially the development of biofouling layer in the OsMFC are not yet clear. Here, the fouling behavior of FO membrane in OsMFCs was systematically investigated. The results indicated that a thick fouling layer including biofouling and inorganic fouling was existed on the FO membrane surface. Compared to the inorganic fouling, the biofouling played a more important role in the development of the fouling layer. Further analyses by the confocal laser scanning microscopy (CLSM) implied that the growth of biofouling layer on the FO membrane surface in the OsMFC could be divided into three stages. Initially, microorganisms associated with ß-D-glucopyranose polysaccharides were deposited on the FO membrane surface. After that, the microorganisms grew into a biofilm caused a quick decrease of water flux. Subsequently, some of microorganisms were dead due to lack of nutrient source, in the meantime, polysaccharide and proteins in the biofouling layer were decomposed as nutrient source, thus leading to a slow development of the biofouling layer. Moreover, the microorganisms played a significant role in the formation and development of the biofouling layer, and further studies are needed to mitigate the deposition of microorganisms on FO membrane surfaces in OsMFCs.
相似文献
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Hao Wang Defang Ma Weiye Shi Zhiyu Yang Yun Cai Baoyu Gao 《Frontiers of Environmental Science & Engineering》2021,15(5):102
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