Evaluation of strategies to minimize ecotoxic side-effects of sorbent-based sediment remediation

Abstract

BACKGROUND In situ sorbent amendment for persistent organic pollutant sequestration in sediment has over the past 15 years steadily progressed from bench-scale trials to full-scale remediation applications. Hindering a wider technology uptake are, however, concerns about ecotoxic side-effects of the most commonly used sorbent, activated carbon, on sensitive, sediment dwelling organisms like Lumbriculus variegatus. Using River Tyne sediment polluted with polycyclic aromatic hydrocarbons (PAHs) and L. variegatus as a case study, sorbent alternatives and magnetic sorbent-recovery were investigated as potential engineering strategies to mitigate such ecotoxic side-effects. The potential benefits of contacting the treated sediment with fresh River Tyne water, as would naturally occur over time in the intended applications, were studied.

RESULTS Magnetic biochar was identified as an effective PAH sorbent with less ecotoxic side-effects than magnetic activated carbon. After 85.1–100% magnetic recovery of this biochar, no ecotoxic side-effects on L. variegatus were measurable in the treated sediment. Results show that ecotoxic effects of magnetic activated carbon can be alleviated through sorbent recovery. In contrast, contacting treated sediment repeatedly with River Tyne water had no measurable benefits.

CONCLUSIONS Magnetic biochar is a promising sorbent material for the remediation of PAH polluted sediment.