Conditioning and dewatering of phosphorus-rich biological sludge

S. H. Chen, J. C. Liu*, G. H. Cheng, Wei Chin Chang

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

10 Scopus citations


The conditioning and dewatering of phosphorus-rich biological sludge, obtained from a pilot-scale biological phosphorus removal plant, was investigated. Dual conditioning utilizing a polyampholyte (AC4601) in combination with aluminum chloride (AlCl3), ferric chloride (FeCl3), and calcium chloride (CaCl3) was studied. Capillary suction time (CST) and specific resistance to filtration (SRF) were utilized to assess sludge dewaterability. The dewaterability and removal of dissolved phosphorus from the phosphorus-rich sludge were examined. Compared with conditioning with only AC 4601, dual conditioning by adding 49 kg/ton of AlCl3 prior to addition of AC4601 resulted in formation of large flocs, better dewaterability, and removal of 50% of soluble phosphorus. Better dewaterability, even larger flocs (> 1 cm), and 75% removal of soluble phosphorus were found when dosage of AlCl3 increased to 189.2 kg/ton. The use of alumina (Al2O3) in combination with AC4601 could achieve equivalent dewaterability. However, only insignificant removal of soluble phosphorus (ca. 10%) was found. Sludge conditioning utilizing FeCl3 and AC4601 was also very effective. A higher dosage of AC4601 was required and insignificant removal of soluble phosphorus was found when CaCl2 was used in combination with AC4601. The interactions between hydrolyzed species of trivalent metal ions and polyampholyte contributed to enhanced dewaterability. Precipitates acted as skeleton builder and assisted in dewaterability as well. In addition, the removal of phosphorus was due to its precipitation reactions with metal ions. This study demonstrated an alternative way to condition phosphorus-rich sludge that could control the release of phosphorus from sludge to aqueous phase under anaerobic environment and achieve enhanced dewaterability simultaneously.

Original languageEnglish
Pages (from-to)1217-1223
Number of pages7
JournalDrying Technology
Issue number10
StatePublished - 2006
Externally publishedYes


  • Aluminum chloride
  • Calcium chloride
  • Conditioning
  • Dewatering
  • Ferric chloride
  • Phosphorus
  • Polyampholyte
  • Sludge
  • Wastewater treatment


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