Landfill leachate was collected in March and July, 1984, at the Gin Drinkers' Bay Landfill Site, and the properties of the two leachates were examined. The leachate collected in March contained higher contents of total solid, ammonia, and metals than that collected in July. The leachates were treated with EDTA (10⁻³ M) and Al₂(SO₄)₃ (2 and 4 g/liter), alone and in combination. Addition of alum (2 g/liter) removed more than 60% of the phosphate content of the two leachates, and about 20 and 68% of total solid from leachates collected in March and July, respectively. Different concentrations of the leachates (untreated and alum-treated) were used to test the survival of tilapia, Sarotherodon mossambicus. The 96-hr LC₅₀ for untreated leachates of March and July were 1.4 and 12%, respectively. The alum-treated leachates raised the 96-hr LC₅₀ to 2.2 and 31.4%, accordingly. Copyright © 1989 Published by Elsevier Inc.