Enzyme activities in a sandy soil amended with sewage sludge and coal fly ash

Ka Man LAI, D. Y. Ye, Jonathan W C WONG*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

65 Citations (Scopus)


Previous studies showed that coal fly ash could stabilize sewage sludge by reducing metal availability, but fly ash may cause an adverse effect on soil microbial activities. Therefore, an experiment was performed to evaluate the effects of amendment of soil with anaerobically digested dewatered sewage sludge, stabilised with alkaline coal fly ash, on soil enzyme activity and the implications for soil nutrient cycling. Sewage sludge was amended with 0, 5, 10, 35 and 50% w/w of fly ash, and then the ash-sludge mixtures were incubated with a sandy soil at 1:1 (v/v). Dehydrogenase activity decreased with an increase in fly ash amendment level and the time of incubation. Soil receiving 5% ash-sludge amendment had a higher dehydrogenase activity than other treatments. Soil receiving 10% ash-sludge mixture had the highest urease activity and in general, urease activity decreased with increasing incubation time. Phosphatase activity was the highest at 5% ash-sludge mixture amended soil and no general trend was observed with time. Water- soluble Zn, Mn and Cu contents were suppressed by the addition of fly ash. The present experiment indicated that addition of 10% ash-sludge mixture should have a positive benefit on the activity of soil microorganisms, N and P nutrient cycling, and reduce the availability of heavy metals.

Original languageEnglish
Pages (from-to)261-272
Number of pages12
JournalWater, Air, and Soil Pollution
Issue number1-4
Publication statusPublished - 1999

Scopus Subject Areas

  • Environmental Engineering
  • Environmental Chemistry
  • Ecological Modelling
  • Water Science and Technology
  • Pollution

User-Defined Keywords

  • Coal fly ash
  • Heavy metals
  • Nutrient cycling
  • Sewage sludge
  • Soil enzymes


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