The scarcity of land in Hong Kong makes landfilling an unattractive me
ans for the disposal of sewage sludge and coal fly ash. Therefore, reu
tilisation of these solid wastes might ease the disposal problems. A g
lasshouse pot leaching study was performed to evaluate the feasibility
of using alkaline fly ash as a stabilisation agent for sewage sludge
and the final product being used as a potting medium. Sludge was amend
ed with ash at 0, 5, 10, 35 and 50% (w/w). Each mixture was then mixed
with a loamy soil (1:1 v/v) and leached with 600 mL of deionized wate
r prior to plant growth experiment using Agropyron elongatum (Tall whe
at grass). Soil pH and electrical conductivity following leaching incr
eased consistently with an increase in ash amendment, from 6.3 to 8.2
and 1.6 to 2.3 dS m(-1) respectively. Pots amended with 35% ash showed
a significant reduction in Zn, Cu and Cd availability but an increase
in B contents. The total dry weight yields of ash amended pots were s
ignificantly increased as compared to the control without ash amendmen
t. Addition of ash also significantly reduced the uptake of Zn, Cu and
Mn but increased shoot B contents. However, the high tissue B content
s had no adverse effect on plant growth. The experimental results affi
rm that alkaline ash is effective in reducing the metal availability o
f sludge, and acts as a good stabilisation agent for sewage sludge.