The Enhancement of Sludge Degradation Rates in Aerobic Thermophilic Sludge Digestion Process
Abstract:Thermophilic aerobic bacteria were applied to the degradation of industrial waste activated sludge (WAS) through batch thermophilic aerobic digestion experiments in laboratory scale. The six strains of thermophilic bacteria, three strains of Bacillus stearothermophilus and three strains of Thermus species, were used to enhance the performance of digestion process. The WAS was collected from the thickening tank of the wastewater treatment plant at oil refinery factory in Korea. The performance of WAS digestion experiments was estimated by the measurement of total suspended solids (TSS), dissolved organic carbon (DOC), and total organic carbon (TOC) concentration.
In the viewpoint of the overall reduction of TSS, DOC and TOC, Bacillus species represented the superior degradation efficiency than Thermus species. Especially, B. stearothermophilus ATCC 31197 represented the best overall performance for the WAS degradation. In the batch control experiment (without thermophilic aerobic bacteria addition), the reduction of TSS and TOC were respectively achieved only 22.7% and 27.2% of initial amounts, and DOC was not significantly decreased until 100 hours of batch experiment. In the batch experiment with ATCC 31197 addition, the TSS and TOC were decreased 41.6% and 35.1% of initial amounts, respectively. And the DOC was markedly decreased 65.5% of maximum amounts until 100 hours. Industrial WAS degradation could be successfully enhanced with the addition of ATCC 31197.
The stability of the continuous digestion operation with ATCC 31197 was successfully verified by semi-continuous (fill-and-draw) digestion experiment. In this operation mode, the bioreactor was operated with one-third volumetric fraction replacement every 48 hours during 20 days continuous experiment. Until about 80 hours, TSS and TOC concentrations were rapidly decreased 49.3% and 50.6%, respectively and then maintained. DOC concentration was decreased 79.9% and then maintained. From the results of this experiment, the degradation of industrial WAS produced from oil refinery plant was successfully achieved by the semicontinuous thermophilic aerobic digestion with B. stearothermophilus ATCC 31197.
Document Type: Research Article
Publication date: 2000-01-01
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