Mircobial Sediment Solidification

Abstract

In recent years, the reservoir sediments have been a disturbance to Taiwan government, and are getting worse due to the climate change. Consequently, it becomes an urgent issue for the authority to dredge and dispose reservoir sludge effectively. Material researchers in civil engineering and environmental engineering, cooperating with microbiologists and geochemists, have recently attempted the solidification of sludge granules into sandstone-like materials employing microorganisms. The aim of this study is to investigate the approach to solidify sludge or soil particle rapidly to attain strength through the growth of bacteria and apply the technique in practical. In this research, we used Bacillus pasteurii in the solidification of reservoir sludge. The sludge used in the experiment has a moisture content of 40%. The change of bacteria broth culture concentration (0%, 25%, 50%, 75%, and 100%) and CaCl2 ratio in the culturing Urea-CaCl2 medium (10%, 30% and 70%) were used as the experimental variables. The culture broth was mixed directly with reservoir sludge to form a cubic specimen (50 mm x 50 mm x 50 mm), which was then used in compressive strength, XRD and SEM test. The test results showed that being cultured in 70%-CaCl2 medium, the specimen blended with 100% bacteria broth had the highest compressive strength. Compared with the blank samples (0% bacteria broth), the compressive strength was enhanced by approximately 13.48%. Also, it was suggested that the solidification by bacteria can indeed enhance the compressive strength of the cube. The sludge solidified with bacteria cultured in 70%-CaCl2 medium has the highest compressive strength. The result also showed that the higher the content of CaCl2 used in the culturing medium is, the more CaCO3 deposit is induced by the bacteria.