Effects of air flowrate distribution and benzene removal in heterogeneous porous media during air sparging remediation

Meng Yao; Jing Bai; Yuehua Chang; Chuanyu Qin; Fengyu Li; Xinru Yang; Yongsheng Zhao

doi:10.1016/j.jhazmat.2020.122866

Effects of air flowrate distribution and benzene removal in heterogeneous porous media during air sparging remediation

J Hazard Mater. 2020 Nov 5:398:122866. doi: 10.1016/j.jhazmat.2020.122866. Epub 2020 May 15.

Authors

Meng Yao¹, Jing Bai², Yuehua Chang², Chuanyu Qin², Fengyu Li³, Xinru Yang², Yongsheng Zhao⁴

Affiliations

¹ National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun,130021, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun,130021, China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, China. Electronic address: ymmengyao@163.com.
² National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun,130021, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun,130021, China.
³ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun,130021, China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, China.
⁴ National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun,130021, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun,130021, China. Electronic address: zhaoyongsheng@jlu.edu.cn.

PMID: 32464561
DOI: 10.1016/j.jhazmat.2020.122866

Abstract

The decrease of remediation effect during air sparging (AS) remediation in heterogeneous porous media has attracted increasing attention. In this study, an improved light transmission visualization method was used to investigate the air accumulation, migration and flowrate distribution in benzene-contaminated heterogeneous porous media during AS. Experimental results indicated that the benzene removal rate in the porous media was mainly controlled by air flowrate distribution which could be used as a major factor to evaluate the remediation effect. Visualization of air migration showed that air accumulation occurred below the geologic heterogeneous interface when ΔPe > 0 kPa (ΔPe: the air entry pressure difference of the media above and below the interface), and the accumulation thickness and length presented exponential decay increases with increasing ΔPe and air injection rates. Air flowrate was monitored by gas flow sensors, and the flowrate distributions were found as Gaussian distribution when ΔPe ≤ 0 kPa, trapezoidal distribution when 0 <ΔPe< 0.3 kPa and fingered distribution when ΔPe ≥ 0.3 kPa. Fingered distribution of air flowrate resulted in extremely nonuniform benzene removal above the interface and reduced the overall benzene removal rate. These findings reveal the reasons for the poor performance of AS remediation in heterogeneous porous media, leading to a better understanding of the remediation mechanisms in heterogeneous aquifer.

Keywords: Air flowrate distribution; Air sparging; Benzene removal rate; Heterogeneous porous media; Visualization.

Publication types

Research Support, Non-U.S. Gov't