Abstract
The interaction between digestion conditions and the sludge physical characteristics and behaviour was investigated for anaerobically digested primary sludge in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain sludge retention times (SRTs) of 10, 15, 20 and 30 days and temperatures of 25 and 35 degrees C. The change of the floe size as a result of digestion was examined using wet sieve analysis (0.100, 0.125, 0.200, 0.500 and 1.000 mm). The results reveal a substantial reduction in all floc sizes with improving digestion conditions. Digestion leads to the transfer of bigger flocs into smaller ones, which has a remarkable effect on the sludge physical behaviour. The majority of the raw and digested floes are smaller than 0.100 mm. The dewatering results showed the existence of an optimal SRT for dewaterability at 20 and 15 days for the reactors operated at 25 and 35 degrees C, respectively. The dewaterability of sludge digested at less favourable conditions, viz. 10 days at 25 degrees C deteriorates due to increase of small floes generated from destruction of larger flocs. The digested sludge settling results showed a slight worsening but insignificant trend with increasing the SRT.
Original language | English |
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Pages (from-to) | 196-200 |
Journal | Biochemical Engineering Journal |
Volume | 28 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2006 |
Keywords
- activated-sludge
- extracellular polymer
- de-waterability
- retention time
- particle-size
- dewaterability
- biopolymers
- sewage