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Effect of influent carbohydrates with different molecule-size on sludge settleability |
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Abstract It’s still unclear whether the sludge settleability would be affected by the molecule-sizes of carbohydrates. In order to reveal this correlations, long term effects of influent carbohydrates with different molecule-size on sludge settleability were investigated in this study. Three lab-scale sequencing batch reactors were operated by using particulate starch, soluble starch and glucose as the solo carbon source, respectively. The smaller the carbohydrate molecule-size was, the more sensitive the activated sludge was with the environment changing. Therefore, the system would be more easily to suffer with bulking problems when feeding with micro-molecule carbohydrate. The adsorbed particulate carbohydrate would highly increase the sludge settleability in the polymeric carbohydrate-fed system. The SVI was kept lower than 150mL/g in the glucose-fed system although the PHA production was only about 0.6mmol C/L. The carbohydrate to protein (C/P) ratio of the extracellular polymeric substances showed positive correlation with SVI. The C/P value increased from 0.248to 1.201while the SVI increased from 100to 600mL/g. The dominant filamentous bacteria of the particulate starch-, soluble starch- and glucose-fed system were Type 0041、M. parvicella and S. natans, respectively. Finally, the phosphorous removal efficiency could reach to 80% with glucose as the sole carbon source.
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Received: 26 April 2014
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