The Role of Biofilm Growth in Bacteria-Facilitated Contaminant Transport in Porous Media

Groundwater contaminants adhered to colloid surfaces may migrate to greater distances than predicted by using the conventional advective-dispersive transport equation. Introduction of exogenous bacteria in a bioremediation operation or mobilization of indigenous bacteria in groundwater aquifers can enhance the transport of contaminants in groundwater by reducing the retardation effects. Because of their colloidal size and favorable surface conditions, bacteria can be efficient contaminant carriers. In cases where contaminants have low mobility because of their high partition with aquifer solids, facilitated contaminant transport by mobile bacteria can create high contaminant fluxes. In this paper, we developed a methodology to describe the bacteria-facilitated contaminant transport in a subsurface environment using the biofilm theory. The model is based on mass balance equations for bacteria and contaminant. The contaminant is utilized as a substrate for bacterial growth. Bacteria are attached to solid surfaces as a biofilm. We investigate the role of the contaminant adsorption on both biofilm and mobile bacteria on groundwater contaminant transport. Also, the effect of bacterial injection on the contaminant transport is evaluated in the presence of indigenous bacteria in porous media. The model was solved numerically and validated by experimental data reported in the literature. Sensitivity analyses were conducted to deduce the effect of critical model parameters. Results show that biofilm grows rapidly near the top of the column where the bacteria and contaminant are injected, and is detached by increasing fluid shear stress and re-attach downstream. The adsorption of contaminant on bacterial surfaces reduces contaminant mobility remarkably in the presence of a biofilm. The contaminant concentration decreases significantly along the biofilm when contaminant partition into bacteria. Bacterial injection and migration in subsurface environments can be important in bioremediation operations regardless of the presence of indigenous bacteria.     

Bioremediation of Aged Petroleum Oil Contaminated Soil: From Laboratory Scale to Full Scale Application

Large quantity of aged petroleum oil contamination such as dehydrated oil sludge, generated in the disposal process of oil-containing sewage in Indonesia. This study aims to investigate the OSCS removal by mean of bioremediation technique. Results found that petrofilic consortia and biosurfactants addition increased the removal efficiency up to 46% and 85%, respectively. At full scale application, this technique succeed in removing of 46 g TPH per kg soil from 4 883 m³ of OSCS during 16 mo of treatment. These results suggest that petrofilic consortia and biosurfactants addition stimulate the biodegradation and overcome the limitation of OSCS degradation process.     

Cadmium recovery by a sulfate-reducing magnetotactic bacterium,Desulfovibrio magneticus RS-1, using magnetic separation

Cadmium recovery by a sulfate-reducing magnetotactic bacterium, Desulfovibrio magneticus strain RS-1, was investigated. D. magneticus precipitated >95% of cadmium at an initial concentration of 1.3 ppm in the growth medium. Electron microscopic analysis revealed that D. magneticus formed electron-dense particles on its surface when cultivated in the presence of cadmium ions (Cd²⁺). Sulfide was also found in the precipitate, and the composition ratio of sulfide/cadmium was 0.7. Sixty percent of viable RS-1 cells was recovered by a simple magnetic separation revealing the removal of 58% cadmium from the culture medium.     

2-D Numerical Modeling of Bioremediation in Heterogeneous Saturated Soils

This paper presents a numerical solution approach for an existing model for simulating transport and biodegradation in saturated porous media. The discrete approximation makes use of an appropriate blending of mixed-hybrid finite-element and shock-capturing finite-volume schemes. The model is applied for simulating enhanced-bioremediation of highly heterogeneous porous media contaminated by organic pollutants. Injection of water enriched in dissolved oxygen (DO) is considered for accelerating contaminant degradation and concentration of both organic pollutant (substrate) and DO. Heterogeneity is found to produce pools of contaminants which strongly affect DO delivery and, then, the degradation of the organic contaminant. A set of numerical results on representative situations illustrates the effectiveness and the robustness of the present approach. The computational efficiency of the present approach is also estimated in terms of CPU costs and memory requirements.     

Development of a membrane-based vapor-phase bioreactor

A vapor-phase bioreactor has been developed utilizing porous metal membranes in a cylindrical design employing radial flow as opposed to traditional axial flow for the vapor stream. The system was evaluated for the biodegradation ofp-xylene (p-xylene) from a water-saturated air stream byPseudomonas putida ATCC 23973 immobilized onto sand. The biocatalyst was placed in the annular space between two cylindrical, porous stainless-steel membranes. Details of the reactor system are presented along with biological data verifying system performance. The feed flow rate andp-xylene concentration were varied between 60 and 130 cm³/min and 15–150 ppm, respectively. Continuous reactor operation was maintained for 80–200 h with removal efficiencies (based onp-xylene disappearance) between 80 and 95%. The effluent concentration histories were compared to determine the operating range of the bioreactor.     

复合微生物菌剂处理城市污染河流的静态模拟

实验对高效复合微生物菌剂对城市污水的生态修复进行了静态模拟研究．复合微生物的加入对水质因子具有一定的影响,水体中CODcr,NH3-N,PO4-P的浓度均有不同程度的先上升后下降趋势,而NO3-N有逐渐下降的趋势．当复合微生物菌剂添加浓度为0．8g／L时,对CODcr,NH3-N,NO3-N的去除率最大分别为69．2％,81．06％,54．32％,当复合微生物菌剂的添加浓度为0．4g／L时,对PO4^3--P的去除率最大达到25．52％．     

电动生物修复底泥中电场对微生物活性的影响

采用电动生物复合技术修复底泥,探讨了电场对底泥污染物中微生物的生长活性、营养物质的迁移等的影响.实验发现,强电场(3V.cm-1)会降低细菌的活性,而弱电场(1V.cm-1)可激活微生物的活性.相应地,弱电场下的底泥中脱氢酶活性高于强电场下的底泥;电场作用下阳极附近的异养菌生长会受到抑制;较高频率的电极正负极交替有助于消除电场作用对阳极附近异养菌总数的影响.用电动方法向底泥中注入营养物质,发现含氮化合物能在底泥中电动迁移,其中硝酸根的迁移性强于铵盐,而阴极室中磷含量下降,但磷酸根在底泥中未发生迁移.     

细菌修复加固石质历史建筑遗产研究

为了避免历史建筑遗产保护过程中造成不可逆损伤,通过细菌诱导碳酸钙在大理石试样表面矿化沉积形成薄层达到保护目的。采用XRD、SEM、MIP及超声波研究分析了矿化晶体晶相、矿化层生长、沉积晶体对试样孔隙影响以及矿化层粘结与保护效果。实验结果表明：矿化晶体为方解石和球霰石,细菌在晶体矿化沉积过程中充当成核位点,且晶体均匀生长在试样的表面,沉积致使试样孔隙率减小22.2％,但对孔隙分布无显著影响,矿化层与底层可以形成有效粘结。细菌诱导矿化修复保护新颖、生态,可以作为石质历史建筑遗产保护方法的有效选择。     

蔬果类浸出液在景观水体原位生物修复中的应用研究

研究了玉米、土豆和番薯等蔬果类浸出液在景观水体原位生物修复中的作用。其作用机理是蔬果类浸出液能促进水体中微生物生长,加快微生物对有机污染物的降解。添加10 m g/L的玉米浸出液,模拟废水中的COD最终去除率增加了12.37%,并且混合浸出液对微生物生长的促进作用强于单一组分。在景观水体的原位生物修复中,投加玉米-土豆混合浸出液,COD、NH3-N和浊度的去除率分别增加了6.01%、8.05%和20.59%,取得了一定的生物修复效果。     

假单胞菌AD1菌株对阿特拉津污染土壤的生物修复

向每克土壤含1mg阿特拉津的模拟污染土壤中接种假单胞菌AD1菌株,补加适量碳源和磷源,30℃培养4周以后,96％的阿特拉津被去除。