Toxicity identification of chlorinated humic acid at various pH and ionic strength

Ying Shih Ma*, Jih-Gaw Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


It been proven that humic acid is the precursor for the chlorinated by-products formed in the chlorination reaction. These by-products are hazardous to the human health and the natural environment. In this study, the dissolved organic carbon (DOC) removal, chlorine consumption, and by-products formation in the reaction between NaOCl and humic acid are investigated. To approach the toxicity of the chlorinated by-products, we extend the dilution method for the measurement of the biochemical oxygen demands BOD5. Initial pH value and the ionic strength are the parameters investigated in this paper. When the humic acid reacts with the NaOCl, we focus our attention on the effects of the varying reaction conditions on the changing toxicity based on the changing concentration of BOD5. The experimental results suggests that the pH value or the ionic strength would affect the extent of DOC removal, chlorine consumption, and by-products formation. It is concluded that the structure and nature of humic acid are changed with different reaction conditions. It is observed that a lower pH value or a higher ionic strength increased the biodegradability of the chlorinated humic acid. In addition, a greater extent of DOC removal is also obtained.

Original languageEnglish
Pages (from-to)239-246
Number of pages8
JournalWater Supply
Issue number3-4
StatePublished - 1 Jan 1999


  • Chlorinated humic acid
  • Toxicity identification
  • Various pH and ionic strength

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