Abstract

Applying activated carbon (AC) to contaminated sediments is an in-situ approach to remediation with great potential. The bioavailability of persistent organic pollutants can be rapidly reduced and kept low over long periods of time. However, there are limitations to the method. The high buoyancy of AC particles makes their application difficult in the field, and AC retention on the amended site can be low in turbulent waters. Furthermore, the fine particles of powdered AC (PAC) can have adverse effects on organisms, but their remediation potential is superior to coarser, granular ACs (GAC). To tackle these shortcomings, a novel sorbent material was developed, consisting of PAC embedded into a stable, granular clay–matrix, significantly reducing buoyancy. These AC–clay granules (ACC-G) were tested for remediation potential (PCB-bioaccumulation reduction) and adverse effects on the benthic invertebrates Chironomus riparius and Lumbriculus variegatus. The novel ACC-G material was compared to GAC of the same particle size, the clay–matrix, and PAC. The findings show that ACC-G has a significantly higher remediation potential than GAC, allowing for reductions in PCB-bioaccumulation of up to 89%. Adverse effects could not be totally eliminated with ACC-G, but they were less severe than with PAC, likely due to the increased particle size.

Highlights

  • Using traditional methods for the remediation of contaminated sediments, such as dredging or capping with inert materials, can be highly laborious and expensive

  • The aim of this study was to find a solution for the abovementioned trade-off by developing a novel remediation material that would combine the low environmental impact of granular activated carbon (AC) (GAC) and high remediation potential of powdered ACs (PAC)

  • About 25−50% of the prepared AC−clay mixture was lost due to AC burnoff

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Summary

Introduction

Using traditional methods for the remediation of contaminated sediments, such as dredging or capping with inert materials, can be highly laborious and expensive. As a more cost-efficient alternative, the in-situ amendment of sorbents has been developed and tested For this approach to sediment remediation, the contaminant does not have to be physically removed or separated, but its mobility and bioavailability are significantly lowered by binding to the applied sorbent material.[1]. For the remediation of sediments contaminated with hydrophobic organic contaminants (HOCs), activated carbon has been identified as a highly effective sorbent Both the bioaccumulation and the release into the water phase of a wide variety of HOCs have been reduced by up to 98% with AC amendments.[2−6] The AC doses necessary to achieve results of this magnitude generally lie under 5% of sediment dry weight (dw) when the sorbents are mixed directly into the sediment.[7] When applied as a thin-layer cap, required AC amounts may be higher, as a gapless coverage of the treated site is desired. AC cap thicknesses of 2−5 mm have been found to be effective under both laboratory and field conditions.[6,8,9]

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