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  • Title: Mesophilic and thermophilic biological post treatment of anaerobic pretreated paper process water in a closed cycle paper mill.
    Author: Vogelaar JC, Van Lier JB, Klapwijk B, De Vries MC, Lettinga G.
    Journal: Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet; 2001; 66(3a):119-27. PubMed ID: 15954571.
    Abstract:
    Thermophilic treatment systems are gaining more and more interest due to increasing system closure and higher process water temperatures. The use of activated sludge as a suitable post treatment system for anaerobically pretreated paper process was studied at 30 and 55 degrees C. Two lab-scale plug flow activated sludge reactors were run in parallel for 6 months at 30 and 55 degrees C. Both reactors were operated simultaneously at a 20, 15 and 10 days SRT. The effects of temperature and SRT on sludge settleability and COD removal efficiencies of different fractions were studied. Total COD removal percentages over the whole experimental period were 58 +/- 5% at 30 degrees C and 48 +/- 10% at 55 degrees C. The effect of the SRT on the total COD removal was negligible. Differences in total COD removal between both systems were due to a lesser removal of soluble and colloidal COD at 55 degrees C compared to the reference system. Two major characteristics of the thermophilic reactor were: 1. a lesser removal of soluble COD compared to the mesophilic reactor and 2. a turbid effluent compared to the mesophilic reactor. Thermophilic effluent turbidity was caused by a combination of influent colloidal particles that were not effectively retained in the sludge flocs and an erosion of thermophilic activated sludge itself, as shown by DGGE profiles. DGGE patterns of mesophilic sludge differed from the thermophilic sludge indicating that different microbial communities were present in both reactor systems.
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