Removal of Atrazine Contamination in Soil and Liquid Systems Using Bioaugmentation

Reported levels of atrazine in soils at pesticide mix-load sites can vary between 7·9×10^-5 mM and 1·9 mM . We report on a mixed microbial culture, capable of degrading concentrations of atrazine in excess of 1·9 mM . At initial concentrations of 0·046 M and 0·23 M , the mixed population degraded 78% and 21% of atrazine in soil (100 days), respectively. At the same initial concentrations in liquid cultures, 90% and 56% of the atrazine was degraded (80 days), respectively. Decreased degradation in soil samples may have resulted from atrazine sorption to soil surfaces or decreased contact between the population and the herbicide. In the 0·23 M system, we attribute incomplete degradation to phosphorous depletion. Data for carbon dioxide evolution was fitted to a three-half-order regression model, but we feel that there are limitations of the application of this model to atrazine degradation. The population uses the herbicide as a nitrogen source and little carbon is incorporated into biomass, as the energy status of carbons in the ring leads to their direct evolution as [¹⁴C]carbon dioxide. This situation contributes to an evolution pattern that, when fitted to the three-half-order model, results in underestimation of the biomass produced. Data from our study suggest that our mixed culture could be used for bioremediation of atrazine at concentrations up to and exceeding those currently reported for agrochemical mixing-loading facilities. © 1997 SCI.     

Design and Performance of a Horizontal,Axial-Flow Water Circulator

An axial-flow water circulator was developed for use in channel catfish, Ictalurus punctatus, culture ponds. The circulator design incorporated a series of 0.76-m diameter fan blades housed within a belled inlet duct 0.92 m in diameter and 1.22 m in length. Power was provided by a 2.24-kW gear motor. Power demand and discharge rates were established using all combinations of the following design variables: impeller type-three blades set at 30' angle or six blades set at 25' angle; impeller speed-90, 120, 144, and 180 rpm; number of impellers in series-1, 2, 3, or 4. The highest discharge rate of 63 m³/minute was established using four six-blade impellers operating at 144 rpm. A maximum discharge rate per unit of power input (efficiency) of 91.4 m³/minute-kW was obtained using two three-blade impellers operating at 90 rpm. Circulator efficiency decreased with increasing discharge rates as described by the model Y = 12888.8X^-1.68315, where Y = m³/minute-kW and X = m³/minute. Field tests conducted in 1.62-ha channel catfish production ponds demonstrated the ability of the circulator to increase water movement in all areas of the ponds and to reduce the frequency and total duration of required emergency aeration by 39.3% and 54.6%, respectively. Net production of channel catfish in ponds outfitted with the water circulator (6,683 kg/ha, n = 3) was not different (P > 0.05) than production in control ponds (6,205 kg/ha, n = 3).     

Rhizosphere effect of Galega orientalis in oil-contaminated soil

Randomized lysimeters in an oil-contaminated field contained the following treatments: (1) Galega orientalis seeds inoculated with Rhizobium galegae HAMBI 540, (2) bioaugmentation with Pseudomonas putida PaW85, and (3) R. galegae -inoculated G. orientalis seeds plus bioaugmentation with P. putida PaW85. The bacterial abundance and diversity were analysed in composite samples after one growing season. A total of 208 m-toluate tolerating bacteria were isolated and screened with m-toluate tolerance and utilization tests, and the catechol test. Seventy-nine isolates were characterized with (GTG)₅-PCR genomic fingerprinting and 16S rRNA gene PCR-RFLP ribotyping. Only 10% of the isolated strains were able to degrade m-toluate. Most of the m-toluate utilizing bacteria were catechol positive indicating the existence of a TOL plasmid. Rhizosphere effect of G. orientalis was manifested in oil-contaminated soil. G. orientalis and Pseudomonas bioaugmentation increased the amount of bacteria in oil-contaminated soil. G. orientalis especially together with Pseudomonas bioaugmentation increased the numbers of m-toluate utilizing and catechol positive bacteria in the soil samples indicating an increase in degradation potential. The rhizosphere of G. orientalis increased also the diversity of bacteria. More ribotypes were found in soils treated with G. orientalis and P. putida PaW85 compared to the untreated soil, but the diversity of the m-toluate utilizing bacteria did not significantly increase.     

优势降解菌群生物强化修复石油污染土壤

通过单菌株的石油降解实验及GC—MS分析以4株降解菌构建成优势降解菌群投加到石油污染土壤进行生物强化修复,并以土壤呼吸作为评价生物活性的指标。结果表明,在40d的修复过程中,生物强化效率比自然修复提高了15．59％。影响生物修复效果的环境因素有温度、氮磷浓度、通氧量等。温度越高降解率越大,生物生长越活跃,在40℃翻土条件下的土壤修复率达到68．82％．比15℃同条件下的修复率高了25．88％;投加氮磷营养物质,增加土壤的通氧量也有利于生物生长,促进降解。     

微生物强化对石油污染土壤的修复特性研究

通过实验室模拟修复研究了接种量为10³~10⁸ cfu·g^-1的降解菌群在土壤中生长的湿度条件和存活状况、对土著菌群的影响作用以及对石油烃的去除效果。结果表明,从石油污染土壤中筛选出的石油烃降解菌群主要由变形菌门（Proteobacteria,99.75%）-γ-变形菌纲（Gamma-proteobacteria,99.49%）-假单胞菌目（Pseudomonadales,99.36%）-莫拉氏菌科（Moraxellaceae,87.33%）-不动杆菌属（Acinetobacter,87.32%）和假单胞菌科（Pseudomonadaceae,12.04%）-假单胞菌属（Pseudomonas,12.00%）组成。利用筛选的降解菌群在土壤湿度为5.4%、接种量为10⁸ cfu·g^-1土的条件下对污染土壤修复60 d,石油烃去除率为10.61%;在土壤湿度为15.0%、接种量为10⁷ cfu·g^-1土时对石油烃去除率为18.67%。在5.4%和15.0%湿度下接种7 d,土壤中变形菌门相对丰度由28.22%增加至57.98%~66.35%,不动杆菌属相对丰度由0.04%增加至25.86%~30.25%,假单胞菌属由初始时的0.26%增加至5.03%~30.87%,说明在不同湿度条件下,接种的降解菌均能迅速生长为土壤中的优势菌;接种60 d时,其仍保持存活状态。研究表明,降解菌群的接种改变了土壤菌群结构,使土壤菌群的alpha多样性明显降低。土壤污染物的去除不仅依靠某种优势菌的特定降解功能,还需要土壤菌群的协同代谢作用。     

不同添加剂改善甜高粱青贮质量及其降解性能比较

为提高青贮甜高粱的生物降解特性,克服木质纤维抗降解屏障,该研究比较了纤维素酶(CT组)、木聚糖酶(XT组)、瘤胃液(RT组)和沼液(BT组)4种添加剂对其青贮质量和生物降解性能的动态影响,结合扫描电镜、傅里叶红外光谱和X-衍射等表征方法评估不同添加剂在青贮过程中的强化作用效果.结果表明,整个青贮发酵期间,4种添加剂均能...     

In situ bioremediation of organochlorine‐pesticide‐contaminated microcosm soil and evaluation by gene probe

BACKGROUND: Pesticide‐formulating industries are contaminating the environment through various activities. Bioremediation is the best method for decontamination, as chemical and physical methods are not only costly but also not very effective in open field systems. In the present study, in situ bioremediation of organochlorine‐contaminated soil was demonstrated by combined biostimulation and bioaugmentation strategies, followed by evaluation using a molecular method. RESULTS: Three parameters were monitored: microbial biomass (colony‐forming units (CFU) g^?1 soil), residual pesticides after treatment and catabolic genes from microcosm soil. Both the biostimulation and the bioaugmentation treatments showed an initial lag phase of 80 days towards colony‐forming units. Gas chromatography of soil samples showed that concentrations of residual pesticides in the soil declined by up to 85–90% after 80 days, indicating their utilisation with time. On dot‐blot hybridisation of the total DNA from the same soil samples, it was observed that catabolic genes tfdC (catechol 1,2‐dioxygenase) and cm genes (chlorophenol monoxygenase) were predominant, whereas other catabolic genes such as catechol 2,3‐dioxygenase (xylE) were negligible. CONCLUSION: The strategy of in situ bioremediation and its evaluation by gene probe and also by conventional methods was demonstrated for organochlorine‐pesticide‐contaminated soil in open microcosms. It showed that bioaugmentation along with biostimulation was effective, although initial acclimatisation for a period of almost 2–3 months was required in the open field systems. Copyright © 2009 Society of Chemical Industry     

石油污染土壤降解细菌的分离、鉴定及生长条件优化

为研究石油污染土壤的微生物修复效果,从大庆油田受石油污染的土壤中分离得到特征明显的3株石油降解细菌（编号18、H、21）,这些菌株能以石油为唯一碳源生长,试验通过形态学鉴定以及分子生物学鉴定方法明确了这3株细菌的种属,分别为氧化微杆菌,节细菌和芽孢杆菌。采用单因素试验设计对试验菌株在无机盐培养基中的生长条件进行初步探讨,研究pH值、盐浓度、氮源、磷源等因素对菌株生长的影响。结果表明：H菌株的最适生长条件：pH=7,盐浓度为3%;18菌株的最适生长条件：pH=8,盐浓度为3%;21菌株最适生长条件：pH=7,盐浓度为1%。H、18、21菌株的最适氮源分别为KNO3、NH4NO3、NH4Cl。H菌株的最适磷源K2HPO4：KH2PO4为1:2（双磷源）,18菌株的最适磷源是K2HPO4,21菌株的最适磷源为K2HPO4。     

生物强化移动床生物膜反应器处理水产养殖循环水初步研究

利用自制的硝化细菌菌剂促进移动床生物膜反应器(Moving bed biofilm reactor,MBBR)的挂膜启动,分析不同载体氨氮负荷、碳氮比条件下反应器运行状况,并进一步进行了实验室模拟循环水养殖草金鱼实验。结果显示,利用自制硝化菌剂能够完成整个移动床反应器的启动过程,在接种15 d后使循环出水氨氮稳定在1 mg/L以下。单位体积载体氨氮负荷实验表明,MBBR能够在100 mg TAN/(L填料·d)条件下,使出水满足一般水产养殖水质要求(氨氮0.5 mg/L,亚硝氮0.1 mg/L)。进水碳氮比在1以内时MBBR能够稳定高效运行。在实验室模拟循环水养殖过程中,经菌剂强化的MBBR能维持循环出水氨氮低于0.5 mg/L,亚硝氮低于0.05 mg/L。