Evaluation of Capping Materials for the Stabilization of Contaminated Sediments
With the development of economic status and living standard, eutrophication of lakes has become serious problem. Due to continuous inflow of external nutrients into lakes, phosphorus, a critical nutrient for lake production, has been accumulated in large amount in the sediment. Thus phosphorus rich sediment acts as an internal nutrient source and reduction of phosphorus release from the sediment is very important for restoring eutrophied lakes. Among the various strategies to restore lakes, in-situ capping is known as an attractive and cost-effective method for remediation of contaminated sediments. In this paper, lab-scale batch column test was conducted to evaluate the characteristics of capping materials on reduction of phosphorus release from the sediment. Three different types of capping materials including sand, zeolite, and natural gypsum (CaSO4·2H2O) were used. Each column was filled 7 cm with sediment and covered by 1 cm of sand, zeolite, and natural gypsum, respectively. The change of water quality in supernatant solution was monitored for 10 days in each column. From the results, addition of gypsum showed higher treatment efficiency than sand and zeolite. In case of the capping with gypsum, it was found that the phosphorous release from the sediment could be reduced by around 90% as compared with untreated column. On the contrary, phosphorus reduction efficiencies of sand and zeolite were 60% and 14%, respectively. Moreover, in case of the capping with sand and zeolite, sudden increase of phosphorus concentration was observed with the generation of CH4 gas from sediment. Methanobacterial ebullition is one of the important factors for transporting phosphorus from sediment into water column. It was reported that the addition of gypsum could reduce the progress of methanogensis by supplying sulfate into sediment, which enhances the activity of sulfate-reducing bacteria (SRB) and mineralization rate of organic matter.
Hyungsun Kim, Junichi Hojo and Soo Wohn Lee
S. L. Yun et al., "Evaluation of Capping Materials for the Stabilization of Contaminated Sediments", Materials Science Forum, Vols. 544-545, pp. 565-568, 2007