Effects of Al-coagulant sludge characteristics on the efficiency of coagulants recovery by acidification

Yi Jui Chen, Wen May Wang, Ming Jun Wei, Jiann Long Chen, Ju Liang He, Kung Yuh Chiang, Chih Chao Wua

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21 Scopus citations


This study evaluated the effects of Al-coagulant sludge characteristics on the efficiency of coagulant recovery by acidification with H2SO 4. Two sludge characteristics were studied: types of coagulant and textures of the suspended solid in raw water. The coagulant types are aluminium sulphate and polyaluminium chloride (PACl); the textures of the suspended solid are sand-based and clay-based. Efficiency of aluminium recovery at a pH of 2 was compared for different sludges obtained from water treatment plants in Taiwan. The results showed that efficiency of aluminium recovery from sludge containing clayey particles was higher than that from sludge containing sandy particles. As for the effect of coagulant types, the aluminium recovery efficiency for sludge using PACl ranged between 77% and 100%, whereas it ranged between 65% and 72% for sludge using aluminium sulphate as the coagulant. This means using PACl as the coagulant could result in higher recovery efficiency of coagulant and be beneficial for water treatment plants where renewable materials and waste reduction as the factors for making decisions regarding plant operations. However, other metals, such as manganese, could be released with aluminium during the acidification process and limit the use of the recovered coagulants. It is suggested that the recovered coagulants be used in wastewater treatment processes.

Original languageEnglish
Pages (from-to)2525-2530
Number of pages6
JournalEnvironmental Technology (United Kingdom)
Issue number22
StatePublished - 2012


  • Acidification
  • Alum sludge
  • Coagulant recovery
  • Polyaluminium chloride
  • Waste reduction


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