Persistency of bacterial indicators in biosolids stabilization with coal fly ash and lime

Jonathan W C WONG*, M. Fang, R. Jiang

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

23 Citations (Scopus)


Alkaline coal fly ash and lime were tested for their effectiveness in pathogen removal from biosolids at different time intervals and temperatures. Coal fly ash at 10 and 35% w/w was mixed with dewatered biosolids and then the ash-biosolids mixture was mixed separately with 0, 1.1, 2.2, 4.4, 8.5, 11, and 18% calcium oxide (w/w on a dry weight basis) with and without heating to 55°C. Total bacteria, salmonella, and total coliforms were monitored at various time intervals. Both ash-biosolids mixtures with or without lime amendment had a significantly lower total bacterial population than the biosolids control, but the residual indigenous bacterial flora in the ash and lime stabilized biosolids still maintained a population of greater than 104 g-1 dry biosolids. Alkaline-stabilized biosolids with a lime amendment rate greater than 8.5% could maintain pH greater than or equal to 12 for more than 2 hours, which effectively removed total coliforms and salmonella in the mixture. Heat treatment to 55°C and a storage time of 14 days provided an added advantage resulting in a further reduction in pathogens for all treatments. It is recommended that 10% ash-biosolids mixture should be amended with a minimum of 8.5% lime on a dry weight basis for at least 2 hours to achieve acceptable levels of salmonella and total coliforms to ensure no pathogenic risk following land pplication.

Original languageEnglish
Pages (from-to)607-611
Number of pages5
JournalWater Environment Research
Issue number5
Publication statusPublished - 2001

Scopus Subject Areas

  • Environmental Chemistry
  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

User-Defined Keywords

  • Biosolids
  • Coal fly ash
  • Lime
  • Pathogens
  • Salmonella
  • Stabilization
  • Total coliforms


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