Mobilization of DNAPL lenses in heterogeneous aquifers using shear-thinning PEO polymers: Experimental and numerical study

IF 12.4 1区环境科学与生态学 Q1 ENGINEERING, ENVIRONMENTAL

Water Research Pub Date : 2024-12-12 DOI:10.1016/j.watres.2024.122952

Amir Alamooti , Adil Baigadilov , Idriss Sawadogo , Richard Martel , Dorian Davarzani , Azita Ahmadi-Sénichault , Stéfan Colombano

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Abstract

Polymer solution injection has emerged as a promising method for the remediation of NAPL (non-aqueous phase liquids)-contaminated aquifers. This technique enhances recovery efficiency by modifying viscous forces, stabilizing the displacement front, and minimizing channeling effects. However, there remains a significant gap in understanding the behavior of polymer solutions, particularly those with different molecular weights (MW), for mobilizing DNAPL (dense non-aqueous phase liquids) trapped in heterogeneous aquifers, especially within low-permeability layers. In this study, we address this gap by investigating the mobilization of DNAPL lenses confined by low-permeability layers through the injection of polyethylene oxide (PEO) polymers of varying MW. PEO solutions with MW of 5 M (million) and 8 Mg/mol displayed shear-thinning behavior for shear rates of 0.01 to 100 s^-1, while the 1 Mg/mol solution showed shear-thinning below 10 s^-1 and Newtonian behavior above. PEO solutions in porous media exhibit Newtonian behavior at low-to-moderate shear rates for all MWs, likely due to confinement-limited entanglement.

Adsorption studies found non-significant PEO adsorption on soil surfaces, likely due to its large molecular size. Post-flushing of PEO-saturated columns with water led to notable permeability reductions attributed to viscous fingering. Column tests indicated a decrease of the residual DNAPL saturation with the capillary number (Ca), more sharply in low permeability soils.

2D cell tests identified three stages of DNAPL mobilization: initial stabilization, sharp recovery increase upon PEO arrival, and a final stabilization at residual saturation. The duration of each transition was found to be influenced by concentration. Numerical simulations accurately mirrored these stages and provided additional insights into PEO viscosity distribution and DNAPL mobilization patterns in heterogeneous media. The results highlighted that higher injection rates promote mobilization from the two low permeability layers surrounding the DNAPL bank from both sides and the upper zone, while lower rates mainly drive mobilization from the upper side. Using numerical simulations the performance of PEO injection on displacement of DNAPL in multiple lenses and various position of recovery points was evaluated.

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利用剪切稀化 PEO 聚合物调动异质含水层中的 DNAPL 透镜：实验和数值研究

聚合物溶液注入已成为一种很有前途的修复非水相液体污染含水层的方法。该技术通过改变粘性力、稳定驱替前缘和最小化窜流效应来提高采收率。然而，对于聚合物溶液，特别是那些具有不同分子量（MW）的聚合物溶液，在非均质含水层中，特别是在低渗透层中，动员DNAPL（致密非水相液体）的行为的理解仍然存在很大的差距。在本研究中，我们通过注射不同分子量的聚氧聚乙烯（PEO）聚合物来研究受低渗透层限制的DNAPL透镜的动员，从而解决了这一差距。分子量为5 M（百万）和8 Mg/mol的PEO溶液在剪切速率为0.01 ~ 100 s-1时表现出剪切变薄的特性，而分子量为1 Mg/mol的PEO溶液在剪切速率小于10 s-1时表现出剪切变薄的特性，剪切速率大于10 s-1时表现出牛顿剪切变薄的特性。多孔介质中的PEO溶液在低至中等剪切速率下表现出牛顿力学行为，这可能是由于受限的缠结。吸附研究发现，PEO在土壤表面的吸附不显著，可能是由于其分子大小较大。对peo饱和柱注水后，由于粘指作用，渗透率显著降低。柱试验表明，残余DNAPL饱和度随毛细数（Ca）的增加而降低，在低渗透土壤中下降幅度更大。二维细胞测试确定了DNAPL动员的三个阶段：初始稳定，PEO到达时急剧恢复增加，以及剩余饱和度时的最终稳定。每次转变的持续时间都受到浓度的影响。数值模拟准确地反映了这些阶段，并为非均质介质中PEO粘度分布和DNAPL动员模式提供了更多的见解。结果表明，较高的注入速率促进了两侧和上部围绕DNAPL储层的两个低渗透层的运移，而较低的注入速率主要推动了上部的运移。通过数值模拟，评估了PEO注入对DNAPL在多个透镜和不同恢复点位置的位移的影响。

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来源期刊

Water Research 环境科学-工程：环境

CiteScore

20.80

自引率

9.40%

发文量

1307

审稿时长

38 days

期刊介绍： Water Research, along with its open access companion journal Water Research X, serves as a platform for publishing original research papers covering various aspects of the science and technology related to the anthropogenic water cycle, water quality, and its management worldwide. The audience targeted by the journal comprises biologists, chemical engineers, chemists, civil engineers, environmental engineers, limnologists, and microbiologists. The scope of the journal include: •Treatment processes for water and wastewaters (municipal, agricultural, industrial, and on-site treatment), including resource recovery and residuals management; •Urban hydrology including sewer systems, stormwater management, and green infrastructure; •Drinking water treatment and distribution; •Potable and non-potable water reuse; •Sanitation, public health, and risk assessment; •Anaerobic digestion, solid and hazardous waste management, including source characterization and the effects and control of leachates and gaseous emissions; •Contaminants (chemical, microbial, anthropogenic particles such as nanoparticles or microplastics) and related water quality sensing, monitoring, fate, and assessment; •Anthropogenic impacts on inland, tidal, coastal and urban waters, focusing on surface and ground waters, and point and non-point sources of pollution; •Environmental restoration, linked to surface water, groundwater and groundwater remediation; •Analysis of the interfaces between sediments and water, and between water and atmosphere, focusing specifically on anthropogenic impacts; •Mathematical modelling, systems analysis, machine learning, and beneficial use of big data related to the anthropogenic water cycle; •Socio-economic, policy, and regulations studies.