【作者】 隋红；

【导师】 李鑫钢；

【作者基本信息】 天津大学 ， 化学工程， 2004， 博士

【摘要】 生物通风(Bioventing, BV)是用于修复不饱和区土壤中可降解有机污染物的一种新兴技术。本文首先建立了BV的数学物理基础,对BV过程中复杂的运移、相间传质、生物降解和多组分污染物相互影响作用及共代谢作用进行了描述,得到基本控制方程。对来自天津大港油田土壤中的土著混合微生物进行了两个月左右的培养驯化,然后确定了微生物最佳生长条件,并对混合微生物进行了分离和筛选。用渗透仪获得了BV过程的气相相对渗透率,由吸附平衡实验确定了苯、甲苯、对二甲苯和三氯乙烯(TCE)的吸附常数。描述生物降解过程的Monod参数(基质最大利用速率和半饱和常数)及生物得率通过间歇实验并用非线性最小二乘拟合获得。采用土柱实验研究了单一污染物(甲苯)和多组分污染物(BTX)情况下的挥发运移及生物降解规律,对于多种污染物,用间歇实验探讨了基质之间的相互作用。以上研究分别在气-水-固和气-水-NAPL-固两种BV体系中进行,当没有NAPL存在时,生物降解占总去除污染物的40%左右,而当有NAPL存在时,生物降解贡献率减少到18%左右。在BV数学物理模型基础上,用动力学模型预测一维土柱实验修复效果,整个通风过程与实验结果比较吻合。系统地研究了不同实验条件下饱和体系的TCE共代谢降解影响因素,实验结果表明甲苯浓度过高或过低都不利于TCE生物降解; TCE浓度过高会对微生物有毒性作用; 低温会成为降解的限制因素。另外,用土柱实验研究了以甲烷为生长基质共代谢生物通风去除TCE的过程。微生物在消耗甲烷和溶解氧的同时,约有10~15%的TCE被生物降解。提出了一维共代谢生物通风模型,模拟结果与实验数据吻合较好。基于BV动量方程,提出了BV现场修复竖井非稳态流场的数学模型,采用有限元方法求解,得到不同操作时间下的流场计算结果。基于BV质量守恒方程,将流场模拟结果与传质方程耦合,采用OS(Operator Splitting)算法对污染物运移过程和生物降解过程进行二维模拟,系统研究了各种操作条件对BV修复效果的影响作用。模拟计算结果与现场测量数据吻合良好,说明本文所提出的数学模型能够对现场BV修复过程进行正确预测和理论指导。更多还原

【Abstract】 Bioventing is an innovatory remediation technique removes biodegradable organic contaminants from the unsaturated zone. Firstly, a conceptual model is presented for describing comprehensive transport, rate limited interphase mass transfer, biodegradation, substrate interactions and cometabolism present during bioventing. The microorganisms are initially obtained from Dagang Oil Field, Tianjin, China and acclimated for about two months. Growth conditions for microorganisms are determined by experiments. Mixed microorganisms are isolated and screen out the species for degrading contaminants faster. Permeability was measured by TST-70 soil penetrate apparatus, and adsorption partition coefficients on benzene, toluene and p-xylene are measured from batch experiment. Monod coefficients (the maximum specific substrate utilization rate and half-saturation coefficient) and the yield coefficient Y are measured from batch experiments and fitted by least-square method. The volatilization and biodegradation of single contaminant (toluene) and multi-contaminants (BTX) from unsaturated soil during bioventing is studied. The experiment is done in a stainless steel column. The interactions between the contaminants are also explored by batch experiment. In gas-aqueous-solid system, 40% of removed contaminant was due to biodegradation. However, only 18% of contaminant was removed by biodegradation in gas-aqueous-NAPL-solid system. Based on conceptual model, one-dimensional model was used to forecast the remediation process of soil column experiment, and simulation results fitted well with experimental data. The effect of concentrations of toluene and TCE and temperature on cometabolic biodegradation is discussed. Results show that no TCE degradation occurred in the absence of toluene. Higher concentration of TCE may be more toxic to microorganisms. Low temperature becomes the limiting factor and the thermally enhanced biodegradation will be required. Cometabolic bioventing for removal of TCE in unsaturated zone was studied in the soil column using methane as the growth substrate. Among the total removed TCE, about 14% and 10% of TCE were biodegraded when TCE was existed in aqueous phase and NAPL phase respectively. The model of cometabolic bioventing is presented and simulations are found to provide reasonable agreement with experimental data. A two-dimensional numerical model is developed for simulating the flow, transport and biodegradation of toluene during bioventing process in the unsaturated zone. The changes of fluid fields with time were obtained and results from simulation show that the required time to develop the steady fluid fields is both about 1 hour. Numerical solutions are obtained with a Galerkin finite element approach. In this approach, the flow, transport and biodegradation equations are solved separately using Operator Splitting method. Effect of different operating conditions on remediation efficiency is detailedly studied. Compared two-dimensional simulations with data measured at site, the model has proved accurate and can be applied to full-scale studies.更多还原