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The combined fouling during ultrafiltration(UF) of surface water pretreated to different extents was investigated to disclose the roles of polysaccharides, proteins, and inorganic particles in UF membrane fouling. Both reversible and irreversible fouling decreased with enhanced pretreatment(biologically active carbon(BAC) treatment and sand filtration). The sand filter effluent fouled the membrane very slowly. The UF membrane removed turbidity to less than 0.1 nephelometric turbidity unit(NTU), reduced polysaccharides by 25.4%–29.9%, but rejected few proteins. Both polysaccharides and inorganic particles were detected on the fouled membranes, but inorganic particles could be effectively removed by backwashing. The increase of turbidity in the sand filter effluent to 3.05 NTU did not significantly increase the fouling rate, but an increase in the turbidity in the BAC effluent to6.11 NTU increased the fouling rate by more than 100%. The results demonstrated that the polysaccharide, not the protein, constituents of biopolymers were responsible for membrane fouling. Membrane fouling was closely associated with a small fraction of polysaccharides in the feed water. Inorganic particles exacerbated membrane fouling only when the concentration of fouling–inducing polysaccharides in the feed water was relatively high. The combined fouling was largely reversible, and polysaccharides were the predominant substances responsible for irreversible fouling. 相似文献
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Natascha Krepsky Maria das Graças S. Bispo Luiz F. Fontan Frederico S. da Silv João P.M. Torres Olaf Malm Cleverson G. Silv Mirian A.C. Crapez 《环境科学学报(英文版)》2019,31(12):175-186
A comprehensive understanding of the complex biogeochemical interactions between organic matter and persistent contaminants in the suspended matter is vital for ecoefficient estuary recovery. However, little is known regarding aeration effects in suspended particulate aggregates. Therefore, this study aimed to investigate the effects of aeration on the suspended matter from a Tropical and Eutrophic estuarine environment. Anoxic water with 60 g/L of suspended particulate matter(SPM) was collected from Guanabara Bay, Rio de Janeiro, Brazil, transferred to experimental boxes and aerated for 61 days. SPM aggregates monitoring included abiotic variables measurements and, determination of total organic matter(TOM), biopolymers composition, bacterial activity, trace metals, and polycyclic aromatic hydrocarbons(PAHs) concentrations. The aeration enhanced dissolved oxygen(DO) concentration and the redox potential(Eh). However, from days 0 to 61 the predominant bacterial activities were denitrification and fermentation. Electron transport system activity increased after day 10, and aerobic activity was detected after day 19. In summary, aeration increased aerobic bacterial activity, lipids(LIP) and trace metal concentrations, although diminished protein/carbohydrate ratio and PAH concentration.Trace metals concentration(Ni, Pb, Cu, Cr, Mn, and Fe) were the highest on day 19 when the p H was 5.9. Copper presented toxic values(Cu 20.0 μg/g). The p H showed a strong negative correlation with Eh(r =-0.94; p 0.001). Acidic environment(p H ≤ 5.9) in marine ecosystems with high loads of toxic trace metals is unsafe for biota. Therefore, managers must be aware of the environmental and biological risks of introducing the aeration technique into a eutrophic marine environment. 相似文献
3.
B. J. Wiley D. H. Ball S. M. Arcidiacono S. Sousa J. M. Mayer D. L. Kaplan 《Journal of Polymers and the Environment》1993,1(1):3-9
The influence of carbon, nitrogen, and phosphate source, along with concentration, was determined for effect on the weight average molecular weight, molecular weight distribution, and yield of pullulan produced byAureobasidium pullulans NRRL-Y 6220. Batch systems, scale-up batch, and continuous fermentations of 1 L and 10 L were also evaluated as were processing variables, including solvents, and extraction conditions. Products with weight average molecular weight from 1.0 × 105 to 4.0 × 106 were produced in 100-g quantities by varying fermentation conditions such as constituents of the culture medium, pH, and length of incubation. Three sets of culture conditions were defined for the formation of low (<5.0×105), medium (1.0–2.0×106), and high (>2.0×106) weight average molecular weight polymer. These defined molecular weight fractions of pullulan were used in further studies in producing films and fibers. 相似文献
4.
The technique that employs flash freezing and environmental scanning electron microscopy (ESEM) was utilised for detailed investigation of the fouling materials in a membrane bioreactor (MBR). The method involves the flash freezing of a wet sample in liquid nitrogen for 10 s to preserve its structure for direct ESEM observation with a high image resolution. ESEM images show that the sludge cake formed by simple filtration of the MBR bulk sludge has a highly porous, sponge-like structure with a fairly low resistance. However, the fouling layer attached to the membrane surface contains a thin gel layer under the main body of the sponge-like sludge cake, which is similar to that formed by filtration of a dispersion of biopolymer clusters (BPCs). It is apparent that BPCs tend to accumulate on the membrane surface, and the gel layer is largely responsible for the high filtration resistance of the cake layer on the fouled membranes. 相似文献
5.
A comparative study of biopolymers and alum in the separation and recovery of pulp fibres from paper mill effluent by flocculation 总被引:1,自引:0,他引:1
Sumona Mukherjee Soumyadeep Mukhopadhyay Agamuthu Pariatamby Mohd. Ali Hashim Jaya Narayan Sahu Bhaskar Sen Gupta 《环境科学学报(英文版)》2014,26(9):1851-1860
Recovery of cellulose fibres from paper mill effluent has been studied using common polysacchatides or biopolymers such as Guar gum, Xanthan gum and Locust bean gum as flocculent. Guar gum is commonly used in sizing paper and routinely used in paper making. The results have been compared with the performance of alum, which is a common coagulant and a key ingredient of the paper industry. Guar gum recovered about 3.86 mg/L of fibre and was most effective among the biopolyrners. Settling velocity distribution curves demonstrated that Guar gum was able to settle the fibres faster than the other biopolymers; however, alum displayed the highest particle removal rate than all the biopolymers at any of the settling velocities. Alum, Guar gum, Xanthan gum and Locust bean gum removed 97.46%, 94.68%, 92.39% and 92.46% turbidity of raw effluent at a settling velocity of 0.5 cm/min, respectively. The conditions for obtaining the lowest sludge volume index such as pH, dose and mixing speed were optimised for guar gum which was the most effective among the biopolymers. Response surface methodology was used to design all experiments, and an optimum operational setting was proposed. The test results indicate similar performance of alum and Guar gum in terms of fioc settling velocities and sludge volume index. Since Guar gum is a plant derived natural substance, it is environmentally benign and offers a green treatment option to the paper mills for pulp recycling. 相似文献
6.
Hwan-Man Park Amar K. Mohanty Lawrence T. Drzal Ellen Lee Deborah F. Mielewski Manjusri Misra 《Journal of Polymers and the Environment》2006,14(1):27-35
Injection molded nanocomposites have been successfully fabricated from cellulose acetate (CA), eco-friendly triethyl citrate
(TEC) plasticizer, and organically modified clay with and without maleic anhydride grafted cellulose acetate butyrate (CAB-g-MA)
as a compatibilizer. The effects of processing conditions such as mixing methods, pre-plasticizing times, extruder retention
times (RT) and addition of compatibilizer on the performance of these nanocomposites have been evaluated. The cellulosic plastic
with CA/TEC (80/20 wt%) was used as the polymer matrix for nanocomposite fabrication. The morphologies of these nanocomposites
were evaluated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. The mechanical properties
of the nanocomposites were measured and have been correlated with the XRD and TEM observations. From all of the sequential
mixing methods used, powder–powder mixing leads to the most transparent nanocomposites. Cellulosic plastic-based nanocomposites
obtained using increased pre-plasticizing times and RT showed better exfoliated structures. In the system containing compatibilizer,
the minimum retention time required for obtaining almost completely exfoliated hybrid nanocomposites was shorter than in the
system without compatibilizer. 相似文献
7.
Zeou Dou Maria Vitoria Bini Farias Wensi Chen Dongjing He Yuhang Hu Xing Xie 《Frontiers of Environmental Science & Engineering》2023,17(5):53
8.
G. G. D. Silva P. J. A. Sobral R. A. Carvalho P. V. A. Bergo O. Mendieta-Taboada A. M. Q. B. Habitante 《Journal of Polymers and the Environment》2008,16(4):276-285
The aim of this work was to develop biodegradable films based on blends of gelatin and poly (vinyl alcohol) (PVA), without a plasticizer. Firstly, the effect of five types of PVA with different degree of hydrolysis (DH) on the physical properties of films elaborated with blends containing 23.1% PVA was studied. One PVA type was then chosen for the study of the effect of the PVA concentration on the mechanical properties, color, opacity, gloss, and water solubility of the films. The five types of PVA studied allowed for films with different characteristics, but with no direct relationship with the DH of the PVA. Therefore, the PVA Celvol®418 with a DH = 91.8% was chosen for the second part, because they produced films with greater tensile strength. The PVA concentration affected all studied properties of films. These results could be explained by the results of the DSC and FTIR analyses, which showed that some interactions between the gelatin and the PVA occurred depending on the PVA concentration, affecting the crystallinity of the films. 相似文献
9.
Six strains of Pseudomonas were tested for their abilities to synthesize poly(hydroxyalkanoate) (PHA) polymers from crude Pollock oil, a large volume
byproduct of the Alaskan fishing industry. All six strains were found to produce PHA polymers from hydrolyzed Pollock oil
with productivities (P; the percent of the cell mass that is polymer) ranging from 6 to 53% of the cell dry weight (CDW).
Two strains, P. oleovorans NRRL B-778 (P = 27%) and P. oleovorans NRRL B-14682 (P = 6%), synthesized poly(3-hydroxybutyrate) (PHB) with number average molecular weights (Mn) of 206,000 g/mol and 195,000 g/mol, respectively. Four strains, P. oleovorans NRRL B-14683 (P = 52%), P. resinovorans NRRL B-2649 (P = 53%), P. corrugata 388 (P = 43%), and P. putida KT2442 (P = 39%), synthesized medium-chain-length PHA (mcl-PHA) polymers with Mn values ranging from 84,000 g/mol to 153,000 g/mol. All mcl-PHA polymers were primarily composed of 3-hydroxyoctanoic acid (C8:0) and 3-hydroxydecanoic acid (C10:0) amounting to at least 75% of the total monomers present. Unsaturated monomers were also present in the mcl-PHA polymers at concentrations between 13% and 16%, providing loci for polymer derivatization and/or crosslinking.
Mention of trade names or commercial products in this article is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the U.S. Department of Agriculture. 相似文献
10.
This study focused on using scale inhibitors for calcium sulfate that are not only highly effective, but also comply with
present restrictive environmental control legislations. In this respect, some biodegradable compounds-based biopolymers, such
as carboxymethyl starch (CMS), carboxymethyl cellulose (CMC), and chitosan (Ch), were evaluated at temperatures 90–95 and
130°C. The results obtained were compared with the performance of polyaspartic acid (PAA), which is well known in this application,
as well as other chelating synthetic polymers (polyacrylamide and amphoteric polyacrylamide). The role of the degree of substitution
(DS) of carboxymethylated biopolymer and the charge density of polyacrylamide (AmPAM-30 and AmPAM-50) on inhibition performance
of scale were also examined. The synergistic effect of PAA with investigated inhibitors was studied for economic and environmental
purposes. The results revealed that both the degree of substitution of carboxymethylated biopolymers and charge density of
polyacrylamide have a profound effect on improving the performance of the investigated scale inhibitors. The efficiency values
were correlated to the thermal degradation behavior (TGA) of biopolymers. PAA had the highest synergistic effect of all investigated
inhibitors, where the inhibition efficiency was found to range from 98% to 100%, at a temperature of 130°C, with low doses
of both PAA (2 ppm) together with biopolymers. This efficiency is observed using 20–40 ppm of PAA. The synergistic effect
of PAA (2 ppm) also showed enhancement of the performance of low doses of polyacrylamides (5 ppm) in maintaining soluble Ca2+ in solutions, increasing the efficiency from ∼57% to ∼100%, as well as its ecotoxicological property. 相似文献
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