Studies on mechanical and biodegradability properties of PVA/lignin blend films

The mechanical and biodegradation properties of polyvinyl alcohol/lignin blended films have been studied. The biodegradable composite films were developed by mechanical mixing followed by film casting method using poly (vinyl alcohol) (PVA), with lignin in different compositions. The progress of biodegradation was evidenced by means of the soil burial test. There was also an evaluation of the weight loss of the samples at the end of the biodegradation process. Blending the PVA with lignin improves tensile strength and the modulus of elasticity and causes a slight decrease in the elongation at break. The best tensile mechanical properties of a PVA/lignin blend were at ratio 2:30 where the tensile strength was 38 MPa, elastic modulus 83.22 MPa and elongation at break 213.9%. Blends of various PVA/lignin ratios have shown transparency, flexibility and good mechanical properties. Film composites also showed good biodegradability. The addition of lignin to the PVA matrix increases the degradation rate of the blends. The weight loss is affected by the composition of the blend, and by the nature of the microorganisms in the soil. PVA/lignin film may be potentially suitable as eco-friendly packaging materials.     

自固定化高效菌种强化处理焦化废水研究

以喹啉为唯一碳源驯化高铲菌种,将其一部分附着在陶粒载体上,比较了自化前后菌种活性的变化,然后在用活性污泥处理焦化废水时,以三种投加高效菌种的方式强化处理焦化废水：（１）只投加悬浮高效菌种,（２）投加悬浮高铲菌种和空白陶粒,（３）投加附着有效高效菌种的陶粒,研究了不同投加方式对保持菌种高效降解特性的作用。     

Biodegradation of petroleum hydrocarbons in an immobilized cell airlift bioreactor

An "immobilized cell airlift bioreactor", was used for the aerobic bioremediation of simulated diesel fuel contaminated groundwater and tested with p-xylene and naphthalene in batch and continuous regimes. The innovative design of the experiments consists of two stages. At the first stage "immobilized soil bioreactor" (ISBR) was used to develop an efficient microbial consortium from the indigenous microorganisms, which exist in diesel fuel contaminated soil. The concept of ISBR relies on the entrapment of the soil particles into the pores of a semi-permeable membrane, which divides the bioreactor into two aerated and non-aerated portions. The second stage involves inoculating the "immobilized cell air lift bioreactor" with the cultivated microbial consortia of the first stage. Immobilized cell airlift bioreactor has the same configuration as ISBR except that in this bioreactor instead of soil, microorganisms were immobilized on the fibers of the membrane. The performance of a 0.83 L immobilized cell airlift bioreactor was investigated at various retention time (0.5-6 h) and concentrations of p-xylene (15, 40 and 77 mg/L) and naphthalene (8, 15 and 22 mg/L) in the continuous operation. In the batch regime, 0.9L bioreactor was operated at various biodegradation times (15-135 min) and concentrations of p-xylene (13.6, 44.9 and 67.5 mg/L) and naphthalene (1.5 and 3.8 mg/L). Under the conditions of the complete biodegradation of p-xylene and naphthalene, the obtained volumetric biodegradation rates at biomass density of 720 mg/L were 15 and 16 mg/L h, respectively.     

Investigation of isolation and immobilization of a microbial consortium for decoloring of azo dye 4BS

Eight high-effective decolorization strains were isolated by enrichment using Direct Fast Scarlet 4BS as sole source of carbon and energy. The optimal microbial consortium consisting of fungus 8-4(*) and bacterium 1-10 was selected by optimizing combination decolorization experiments with these eight freely suspended strains, whose decolorization activity was higher than individual strains due to synergistic reaction with each other. The optimal microbial consortium was also immobilized using polyvinyl alcohol (PVA) as the carrier. This paper optimized the immobilization and operational conditions, investigated the effect of the environmental factors (temperature, pH and dissolved oxygen (DO)) and initial dye concentration on the rate of decolorization by immobilized microbial consortium. The results showed that the optimal decolorization activity was observed in pH range (5-8), temperature range (25-40 degrees C) under shaking culture of high DO level. Decolorization with the optimal microbial consortium gave a relatively high maximum decolorization activity (ca. 81.25 mgl(-1)h(-1)), which occurred at a dye concentration of 1000 mgl(-1), suggesting the applicability of the strains in remediation of wastewater containing high azo dye concentrations. The immobilized beads could be reused for more than 30 cycles, without losing any degradation capacity. The changes of UV-visible spectra and the change curve of COD of 4BS solution before and after decolorization cultivation and the proliferation and distribution of microbial consortium in gel beads were also microscopically observed, which could be used for conferring the decolorization mechanisms of dye 4BS.     

Biodegradation of nodularin and effects of the toxin on bacterial isolates from the Gulf of Gdańsk

Nodularin (NOD), a cyclic pentapeptide produced by the cyanobacterium Nodularia spumigena, is one of the most abundant natural metabolites occurring in the Baltic Sea. The present study investigated the role of this compound in the interactions between cyanobacteria and other bacteria. The toxin inhibited the growth of 15 out of 32 bacterial strains isolated from water and sediments of the Gulf of Gdańsk, southern Baltic Sea. Most of the bacteria sensitive to NOD belonged to the Proteobacteria phylum. Incubation of nodularin in the presence of the bacterial isolates did not reveal any NOD-degrading activity. However, natural microbial communities from sediment removed the toxin within 5-7 days. Analysis by liquid chromatography/hybrid quadrupole-time-of-flight mass spectrometry with turboion spray (QTOF-LC/MS/MS) revealed seven biodegradation products, including five novel ones. The results showed that not only freshwater microorganisms, but also those living in brackish waters, play an important role in cyanotoxin removal.     

固定化微生物强化生物滤池处理硝基苯和苯胺废水

利用复合微生物菌群BCP35,对自制的大孔功能化载体FPU进行微生物的固定化,并与厌氧生物滤池和好氧生物滤池联用处理含高浓度硝基苯和苯胺的废水,研究了固定化微生物强化生物滤池处理污染物的运行效果、硝基苯和苯胺的降解特征,比较了固定化微生物和游离态微生物的除污性能,同时分析了载体上微生物的状态和生物量.结果表明,固定化微生物强化生物滤池工艺对硝基苯、苯胺具有很好的去除效果,对硝基苯和苯胺的降解率可分别达到99.8%和99.9%;同时生物滤池还对污染物浓度变化具有较强的抗冲击负荷能力;与游离态微生物相比,固定化微生物在去除COD、硝基苯、苯胺等方面更具优势;生物滤池内的微生物浓度较高,可达到38g/L.     

Microcosm investigations of phthalate behaviour in sewage treatment biofilms

Discharge from sewage works has been shown to be an important source of phthalates into the environment which is of major concern because some are toxic, suspected endocrine disruptors and recalcitrant. Laboratory trickle filter microcosms (continuous and re-circulating flow) were constructed and operated to investigate the biodegradation and adsorption of phthalates and also to isolate phthalate degrading microorganisms. It was found that adsorption was critical for the removal of both DEP (77.5%) and DEHP (55.7%) in continuous flow microcosms. The proportion of phthalates removed by biodegradation in the continuous flow microcosms was estimated. Re-circulating flow microcosms improved the removal of DEHP compared to continuous flow microcosms. Microcosm biofilm used for an enrichment culture on phthalate media isolated a varied group of microbes including Gram negative and Gram positive bacteria, yeasts and fungi. Bacteria species with all the necessary enzymes to degrade phthalic acid were isolated.     

Comparison of the fuel oil biodegradation potential of hydrocarbon-assimilating microorganisms isolated from a temperate agricultural soil

Strains of hydrocarbon-degrading microorganisms (bacteria and fungi) were isolated from an agricultural soil in France. In a field, a portion was treated with oily cuttings resulting from the drilling of an onshore well. The cuttings which were spread at the rate of 600 g HC m-2 contained 10% of fuel oil hydrocarbons (HC). Another part of the field was left untreated. Three months after HC spreading, HC adapted bacteria and fungi were isolated at different soil depths in the two plots and identified. The biodegradation potential of the isolated strains was monitored by measuring the degradation rate of total HC, saturated hydrocarbons, aromatic hydrocarbons and resins of the fuel. Bacteria of the genera Pseudomonas, Brevundimonas Sphingomonas, Acinetobacter, Rhodococcus, Arthrobacter, Corynebacterium and fungi belonging to Aspergillus, Penicillium, Beauveria, Acremonium, Cladosporium, Fusarium, and Trichoderma were identified. The most active strains in the assimilation of saturates and aromatics were Arthrobacter sp., Sphingomonas spiritivorum, Acinetobacter baumanii, Beauveria alba and Penicillum simplicissimum. The biodegradation potential of the hydrocarbon utilizing microorganisms isolated from polluted or unpolluted soils were similar. In laboratory pure cultures, saturated HC were more degraded than aromatic HC, whereas resins were resistant to microbial attack. On an average, individual bacterial strains were more active than fungi in HC biodegradation.     

Nitrification via microorganism‐immobilized media using polyvinyl alcohol (PVA)

This study was conducted to investigate the nitrification of wastewater using polyvinyl alcohol (PVA) media immobilized with nitrifying bacteria. The microorganism‐immobilized media used in this study was prepared by mixing 10% (v/v) PVA, 6% (v/v) polyethylene glycol (PEG) and nitrifying microorganism culture solution. Analysis revealed that the nitrification rate when using the microorganism‐immobilized media increased to 49.1, 80.0 and 83.9% as the filling rate increased to 5, 15 and 25%, respectively. The mass transfer rate of the prepared microorganism‐immobilized media was estimated to be 37.69 mg/L·h maximum. The respiration rate was measured in order to compare with the microorganism‐immobilized media and the conventional biological treatment process of anaerobic‐anoxic‐oxic (A₂O). Respiration time of sludge and the media were similar, but the respiration rate of the microorganism‐immobilized media (initial 20.8 mg O₂/(L·h)) was higher than that of the activated sludge (initial 12.4 mg O₂/(L·h)).     

Biodegradation of oxadiazon by a soil isolated Pseudomonas fluorescens strain CG5: Implementation in an herbicide removal reactor and modelling

An oxadiazon-degrading bacterial, Pseudomonas strain CG5, was isolated from an agricultural contaminated soil. This strain CG5 was able to grow on 10mg of oxadiazon per l, yielding 5.18+/-0.2 mg of protein biomass mol(-1). GC-MS analyses of the metabolites from oxadiazon catabolism revealed its dehalogenation and degradation to form non-toxic end-products, cells were then immobilized by adsorption on a ceramic support to be used as biocatalysts in herbicide removal biofilm-reactor processes. Seventy-two per cent of the oxadiazon was removed, and the maximum specific substrate uptake rate was 10.63+/-0.5 microg h(-1) mg(-1) prot. A new mathematical model was developed to interpret and predict the behaviour of the bacteria and pollutants in a biofilm-reactor system, to consider biofilm structural and morphological properties.     

混杂纤维增强应变硬化水泥基复合材料的弯曲性能预测

基于混凝土断裂力学与细观力学理论,同时考虑钢纤维(SF)/聚乙烯醇(PVA)混杂纤维对应变硬化水泥基复合材料(SHCC)弯曲性能的影响,提出了一种适用于SF/PVA纤维混杂SHCC(SF-PVA/SHCC)弯曲性能的预测方法.开展了SF-PVA/SHCC弯曲性能试验,分析了纤维种类和掺量对SHCC抗弯强度、极限弯曲挠度及弯曲荷载挠度曲线的影响.结果表明所提出的弯曲性能计算方法可以较好地预测SF-PVA/SHCC的抗弯强度和极限弯曲挠度.     

纺锤芽孢杆菌降解水中萘的特性研究

从处理石油废水的曝气池污泥中筛选、分离到一株能有效降解萘的菌株,经鉴定为纺锤芽孢杆菌(BFN),研究了其对水中萘的降解特性。结果表明:在温度为30℃、自然pH(6.68～6.76)、接种量为0.2%、(NH4)2SO4浓度为0.15g/L的最适降解条件下,BFN对萘(初始浓度为50mg/L)的降解率在96h内达到99.8%;BFN还具有较好的耐盐度,对高浓度的萘也有较好的耐受性。BFN对萘的降解过程符合一级反应动力学。通过检测不同底物水样的吸光度、pH和底物浓度的变化,发现BFN还能降解苯甲酸、水杨酸、邻苯二甲酸、甲苯、苯酚以及1-萘酚。     

BTEX biodegradation by bacteria from effluents of petroleum refinery

Groundwater contamination with benzene, toluene, ethylbenzene and xylene (BTEX) has been increasing, thus requiring an urgent development of methodologies that are able to remove or minimize the damages these compounds can cause to the environment. The biodegradation process using microorganisms has been regarded as an efficient technology to treat places contaminated with hydrocarbons, since they are able to biotransform and/or biodegrade target pollutants. To prove the efficiency of this process, besides chemical analysis, the use of biological assessments has been indicated. This work identified and selected BTEX-biodegrading microorganisms present in effluents from petroleum refinery, and evaluated the efficiency of microorganism biodegradation process for reducing genotoxic and mutagenic BTEX damage through two test-systems: Allium cepa and hepatoma tissue culture (HTC) cells. Five different non-biodegraded BTEX concentrations were evaluated in relation to biodegraded concentrations. The biodegradation process was performed in a BOD Trak Apparatus (HACH) for 20 days, using microorganisms pre-selected through enrichment. Although the biodegradation usually occurs by a consortium of different microorganisms, the consortium in this study was composed exclusively of five bacteria species and the bacteria Pseudomonas putida was held responsible for the BTEX biodegradation. The chemical analyses showed that BTEX was reduced in the biodegraded concentrations. The results obtained with genotoxicity assays, carried out with both A. cepa and HTC cells, showed that the biodegradation process was able to decrease the genotoxic damages of BTEX. By mutagenic tests, we observed a decrease in damage only to the A. cepa organism. Although no decrease in mutagenicity was observed for HTC cells, no increase of this effect after the biodegradation process was observed either. The application of pre-selected bacteria in biodegradation processes can represent a reliable and effective tool in the treatment of water contaminated with BTEX mixture. Therefore, the raw petroleum refinery effluent might be a source of hydrocarbon-biodegrading microorganisms.     

A study of external mass transfer effect on biodegradation of phenol using low‐density polyethylene immobilized Bacillus flexus GS1 IIT (BHU) in a packed bed bioreactor

The impact of external mass transport on the biodegradation rate of phenol in a packed bed bioreactor (PBBR) was studied. A potential bacterial species, Bacillus flexus GS1 IIT (BHU), was isolated from the petroleum‐contaminated soil. Low‐density polyethylene (LDPE) immobilized with the B. flexus GS1 IIT (BHU) was used as packing material in the PBBR. The PBBR was operated by varying the inlet feed flow rate from 4 to 10 mL/min, and the corresponding degradation rate coefficients were found to be in the range of 0.119–0.157 L/g h. In addition, the highest removal rate of phenol was obtained to be 1.305 mg/g h at an inlet feed rate of 10 mL/min. The external mass transfer was studied using the model . A new empirical correlation for the biodegradation of phenol in the PBBR was developed after the evaluation at various values of K and n.     

混杂PVA-ECC配合比优化设计及力学性能试验研究

为了降低工程用水泥基复合材料(ECC,Engineered Cementitious Composites)制造成本,使ECC能够在实际工程中大规模应用,将中国产PVA纤维和日本产PVA纤维以一定的比例混合,配制混杂PVA-ECC。基于ECC的材料设计理论,兼顾抗压强度和受拉能力,对掺有硅粉的混杂PVA-ECC中的纤维体积含量进行了优化设计。通过四点弯曲试验和轴心抗压试验,研究了混杂PVA-ECC在不同龄期下的弯曲性能和抗压性能。试验结果表明,混杂PVA-ECC试件均表现出明显的应变硬化和多缝开裂的特征,此外,其抗压强度后期增长明显。基于UM法,提出一种改进的反分析方法,可利用四点弯曲试验结果推导ECC的极限拉伸应变,并与试验结果进行了比较,结果表明,通过建议的反分析方法得到的预测值与试验值吻合较好。     

Laboratory column study for remediation of MTBE-contaminated groundwater using a biological two-layer permeable barrier

In this study, an in situ biological two-layer permeable reactive barrier system consisting of an oxygen-releasing material layer followed by a biodegradation layer was designed to evaluate the remediation effectiveness of MTBE-contaminated groundwater. The first layer containing calcium peroxide (CaO(2)) and other inorganic salts is to provide oxygen and nutrients for the immobilized microbes in the second layer in order to keep them in aerobic condition and maintain their normal metabolism. Furthermore, inorganic salts such as potassium dihydrogen phosphate (KH(2)PO(4)) and ammonium sulphate ((NH(4))(2)SO(4)) can also decrease the high pH caused by the alkali salt degraded from CaO(2). The second layer using granular expanded perlite as microbial carrier is able to biodegrade MTBE entering the barrier system. Batch experiments were conducted to identify the appropriate components of oxygen-releasing materials and the optimum pH value for the biodegradation of MTBE. At pH=8.0, the biodegradation efficiency of MTBE is the maximum and approximately 48.9%. A laboratory-scale experiment using two continuous upflow stainless-steel columns was then performed to evaluate the feasibility of this designed system. The fist column was filled with oxygen-releasing materials at certain ratio by weight. The second column was filled with expanded perlite granules immobilizing MTBE-degrading microbial consortium. Simulated MTBE-contaminated groundwater, in which dissolved oxygen (DO) content was 0mg/L, was pumped into this system at a flow rate of 500mL/d. Samples from the second column were analyzed for MTBE and its major degradation byproduct. Results showed that MTBE could be removed, and its metabolic intermediate, tert-butyl alcohol (TBA), could also be further degraded in this passive system.     

Flexural responses of hybrid steel–polyethylene fiber reinforced cement composites containing high volume fly ash

Strain hardening and multiple cracking behavior of hybrid fiber reinforced cement composites containing different hybrid combinations of steel and polyethylene (PE) fibers under four-point bending are reported. The total volume fraction of fibers was kept constant at 2.5% to maintain a workable mix. Effects of increase in fly ash content as partial replacement of cement beyond 50%, such as 60% and 70% on the flexural response of hybrid steel–PVA (polyvinyl alcohol) and steel–PE fiber composites are also evaluated here. Among composites with different volume ratios of steel and PE fibers, the composite with 1.0% steel and 1.5% PE was found to show the highest flexural strength and that with 0.5% steel and 2.0% PE exhibited highest deflection and highest flexural toughness. Generally, the steel–PE hybrid composites exhibited lower flexural strength but higher deflection capacity than steel–PVA hybrid composites. The rate of strength loss after peak load in steel–PE hybrid composites was found low compared to steel–PVA hybrid system. The 50% replacement of cement by fly ash is found to be an optimum fly ash content in hybrid fiber composites.     

Biodegradation of a cationic surfactant in activated sludge

The biodegradation of DTDMAC (ditallowdimethylammonium chloride, a fabric softening agent) was established in semi-batch activated sludge reactors. Three ¹⁴C-forms of DTDMAC were studied separately under the simulated organic loading rates of conventional and extended aeration activated sludge treatment. Primary biodegradation was shown by means of a specific analytical technique in combination with radiochemical procedures. Ultimate biodegradation for each carbon position in the DTDMAC molecule was established by the detection of ¹⁴CO₂. Intermediate metabolites were followed throughout the study by both radio thin-layer chromatography and radiochemical procedures. Each carbon position of the DTDMAC molecule was equally accessible to metabolism and ultimate degradation by acclimated microorganisms. Degradation occurred more rapidly under extended aeration conditions and was influenced by the strong tendency of DTDMAC to associate with the microbial population. The low levels of metabolites observed were not of a single classification or characteristic and they did not persist in the activated sludge. This study suggests that DTDMAC removal in an activated sludge plant is a result of both sorption/precipitation and biodegradation mechanisms.     

丙烯酸酯低皂乳液与有机硅杂化反应研究

采用种子乳液聚合,以聚乙烯醇、壬基酚聚氧乙烯醚作为低皂乳化剂,合成了苯乙烯/丙烯酸丁酯/乙酸乙烯酯/丙烯酸-2-乙基己酯四元共聚乳液,再与硅溶胶、正硅酸乙酯(TEOS)进行杂化反应,制得有机硅丙烯酸酯杂化乳液。用红外光谱对产物进行结构分析,证明PVA、硅溶胶均与TEOS发生水解缩聚反应,使得反应产物的性能有较大提高。实验还考察了PVA浓度、硅溶胶与TEOS配比对样品性能的影响。     

Evaluation of natural and enhanced PCP biodegradation at a former pesticide manufacturing plant

Pentachlorophenol (PCP) has been used in the past as a pesticide, herbicide, antifungal agent, bactericide, and wood preservative. Thus, PCP is among the most ubiquitous chlorinated compounds found in groundwater contamination. A former pesticide manufacturing plant located in southern Taiwan has been identified as a PCP spill site. In this study, groundwater samples collected from the PCP site were analyzed to assess the occurrence of natural PCP biodegradation. Microcosm experiments were conducted to (1) evaluate the feasibility of biodegrading PCP by indigenous microbial consortia under aerobic and cometabolic conditions, and (2) determine the potential of enhancing PCP biodegradation using cane molasses and biological sludge cake as the substitute primary substrates under cometabolic conditions. The inocula used in this microcosm study were aquifer sediments collected from the PCP site and activated sludges collected from the municipal and industrial wastewater treatment plants. Results from this field investigation indicate that the natural biodegradation of PCP is occurring and causing the decrease in PCP concentration. Microcosm results show that the indigenous microorganisms can biodegrade PCP under both aerobic and aerobic cometabolism conditions. A PCP-degrading bacterium was isolated from the collected aquifer sediments and identified as Pseudomonas mendocina NSYSU via some biochemical tests and further conformation of DNA sequencing. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy. The isolated bacterium, P. mendocina NSYSU, was capable of completely degrading PCP as indicated by the increase in biomass formation with the decrease in PCP concentrations occurred in the carbon-free medium simultaneously. Results indicate that the in situ or on-site aerobic bioremediation using indigenous microorganisms or inoculated bacteria would be a feasible technology to clean up the studied PCP-contaminated site. Results from this study will be useful in designing a scale-up in situ or on-site PCP bioremediation system (e.g., on-site bioreactor) for field application.