Return sludge from two Swedish and two Danish wastewater treatment plants were hydrolysed in laboratory reactors. Treatment plants with/without pre-sedimentation and with/without nitrification were represented. Soluble organic matter was produced from all types of sludge, but the yield was to a large extent dependent on what type of sludge was hydrolysed. Activated sludge from wastewater treatment plants without pre-treatment returned more soluble carbon after hydrolysis than sludge from treatment plants with pre-sedimentation. In addition, more soluble carbon was formed from non-nitrifying activated sludge than from nitrifying sludge. Moreover, the maximum yield of soluble COD at 10 °C was less than the yield at 20 °C. The initial hydrolysis rate was found to be between 0.35 and 1.8 mg soluble COD/(g VS × h). With the exception of one case, between 15 and 50% of the produced soluble COD was shown to be volatile fatty acids, a suitable carbon source for biological phosphorus removal. Nitrification rate measurements indicated that the viability of the activated sludge was not affected by the hydrolysis.
Hydrolysis of return sludge for production of easily biodegradable carbon: effect of pre-treatment, sludge age and temperature
K. Jönsson, J. la C. Jansen; Hydrolysis of return sludge for production of easily biodegradable carbon: effect of pre-treatment, sludge age and temperature. Water Sci Technol 1 June 2006; 53 (12): 47–54. doi: https://doi.org/10.2166/wst.2006.405
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