Using Mixed Active Capping to Remediate Multiple Potential Toxic Metal Contaminated Sediment for Reducing Environmental Risk

Meng-Yuan Ou,Chi Chen,Yung-Hua Cheng,Tien-Chin Chang,Yu Ting,Hsing-Cheng Hsi,Boon-Lek Ch’Ng

doi:10.3390/w12071886

Abstract

In this study, kaolinite, carbon black (CB), iron sulfide (FeS), hydroxyapatite (HAP), and oyster shell powder (OSP) were selected as potentially ideal amendments to immobilize metals in sediment, including Ni, Cr, Cu, Zn, and Hg. In aqueous batch experiments, the five adsorbents were tested for capturing the five potential toxic metals individually at various concentrations. HAP and OSP showed the largest removal efficiencies towards Ni (OSP: 76.47%), Cr (OSP: 100.00%), Cu (HAP: 98.39%), and Zn (HAP: 64.56%), with CB taking the third place. In contrast, FeS and CB played a more significant role in Hg removal (FeS: 100.00%; CB: 86.40%). In the modified six-column microcosm experiments, five mixing ratios based on various considerations using the five adsorbent materials were tested; the water samples were collected and analyzed every week for 135 days. Results showed that caps including CB could immobilize the release of Hg and methylmercury (MeHg) better than those with FeS. More economical caps, namely, with a higher portion of OSP in the mixed capping, could not reach comparable effects to those with more HAP for immobilizing Ni, but performed almost the same for the other four metals. All columns with active caps showed greater metal immobilization as compared to the controlled column without caps.

Highlights

IntroductionWastewater containing potential toxic metals originating from anthropogenic activities discharged to river streams is a widespread environmental issue nowadays, processing significant toxicity to aquatic organisms and accumulating by food chain, causing various diseases and disorders [1]
Wastewater containing potential toxic metals originating from anthropogenic activities discharged to river streams is a widespread environmental issue nowadays, processing significant toxicity to aquatic organisms and accumulating by food chain, causing various diseases and disorders [1].Natural processes are frequently inadequate to deal with the elevated metal loading, there is an urgent need for remediation measures [2]
The present study aims to find mixed amendments with the best comprehensive benefits for immobilizing potential toxic metals in contaminated sediment

Summary

Introduction

Wastewater containing potential toxic metals originating from anthropogenic activities discharged to river streams is a widespread environmental issue nowadays, processing significant toxicity to aquatic organisms and accumulating by food chain, causing various diseases and disorders [1]. Natural processes are frequently inadequate to deal with the elevated metal loading, there is an urgent need for remediation measures [2]. Thin-layer capping has been applied as an economically-feasible in-situ method for sediment remediation, reducing contaminants release from sediment to overlying water, subsequently reducing ecological and human health risk [3]. Sediment can be seen as an important sink of various organic and inorganic compounds, resulting in the simultaneous existence of several different contaminants [4,5,6]. To cope with highly complex conditions in sediment, mixed capping with multiple materials was proposed. Using cheap and effective alternatives for the removal of potential toxic metals could reduce operating costs, reduce the prices of products, improve competitiveness, and benefit the environment [7]

Methods

Results

Discussion

Conclusion