Effect of Mussel Shells as a Permeable Reactive Barrier in Municipal Sewage Sludge Treatment by Electrokinetic Remediation

Abstract

IIn this work, it was evaluate the utilization of mussel shells (raw and calcinated) as a permeable reactive barrier (PRB) for the treatment of municipal sewage sludge (MSS) contaminated with heavy metals, creating a novel combined system, which integrates two technologies: electrokinetic remediation technology, and adsorption by the utilization of mussel shells adsorbents. Regarding the adsorption process into the mussel shells adsorbents, it was also aimed to study the influence of aragonite and calcite on the adsorption of lead (Pb), copper (Cu), chromium (Cr), and zinc (Zn). For the preparation of the PRB, it was used three adsorbents: MEXMT (raw mussel shells); MEXMT 600 (mussel shells calcinated at 600°C) and finally, a commercial calcium carbonate (CCCom). It was applied an electric current of 1 V cm-1 and it was used an adsorbent/sludge ratio of 30 g kg-1 of contaminated sludge for the preparation of the PRB. Results proved that this process is perfectly suited for the removal of the heavy metals understudy from the sludge, especially with MEXMT (raw mussel shells) adsorbent. With this adsorbent, at the end of the 92 hours of operation time, it was obtained high removal rates for each metal in study. Results demonstrate that higher removals rates were achieved in lead (92%), followed by zinc (82%), copper (76%), and finally chromium with 72%. Based on these results, it was proved the technical viability of the proposed technology (electrokinetic remediation with raw mussel shells as a permeable reactive barrier) to treat municipal sewage sludges.