연안어장 준설 퇴적물에 함유된 유기물 및 중금속의 친환경적 처리

Abstract

A study on the treatment of an dredged sediment from a coastal fisheries and it's reuse were performed. Sediment sample was taken from a coastal fisheries near Jinhae bay and the pollutants contained in the sediment were analyzed. For the stabilization of organic pollutants, a liquid stabilization technology was studied, and bioleaching process was adopted for removal of the heavy metals from the sediment. Adsorption characteristics for nutrients on the activated sediment was also studied to find out a proper reuse method.

The sediment was severely contaminated with organics, but the levels of nutrients including nitrogen and phosphorus were not serious. The organics contained in the sediment were consisted of about 2% of cellulose, 27% of hemicellulose, 3% of total sugar, and 13% of lipid. For the heavy metals, the levels of cadmium and chromium were much higher than the standards for soil contamination concern. The sediment was also contaminated with PAHs (Polyaromatic hydrocarbons), dioxin and PCB (Polychrolinated biphenyl).

For the stabilization of organic materials contained in the sediment, the easily biodegradable organics, indicating that the portion could be stabilized, was around 30-40% of the total organics. The biodegradability of the organics was affected by the inoculation of compost or sewage sludge, and could be enhanced by the increase of inoculation amount. The biodegradability of the organics was also affected by the incubation temperature, and was higher at 35℃ than that at 25℃. The biodegradability of the organic could be enhanced by the ultrasonic pretreatment. The organic materials diluted with water, around three times, was more easily stabilized, but the removal of ammonia nitrogen was slightly higher when the sediment was diluted six times with water.

For the removal of heavy metals from the sediment using bioleaching process, both elemental sulfur and ferrous sulfate were the effective the energy sources for bioleaching bacteria, and the proper amounts of energy sources for the effective acidification for the leaching of heavy metals were around 0.3% for both elemental sulfur and ferrous sulfate. However, pyrite was not suitable as the energy source for the bioleaching bacteria. The solubilization efficiency of heavy metals from the sediment was affected by kinds of heavy metals, as well as the energy source. Copper was rapidly solubilized, and final percentage of solubilization was amount to around 81-84%. The solubilization efficiency of cadmium was around 87-89%, but the efficiency for chromium was just 22.6-32%. Plumbum was slowly solubilized, and the final efficiency was not high because of low solubility of PbSO4. Overall, most of the heavy metals contained in the sediment could be cleaned satisfactorily and their remaining concentrations are unlikely to be toxic. However, the remaining concentrations of plumbum and chromium in sediment seem to be somewhat unsatisfactory.

For the study on the reuse of the cleaned sediment, the sediment was treated with various activation methods, and their adsorption characteristics for nutrients were also studied. The time for adsorption equilibrium and adsorption capacity for nitrate were affected by the activation methods, but were amount to about 17min and 2.2mg NO3-N/g, respectively. This indicates that the sediment from coastal fisheries could be reused as a material for the improvement of coastal water quality by a proper activation.