The Midmar Water Treatment Works of Umgeni Water (the third largest supplier of potable water in South Africa), at Howick near Pietermaritzburg, KwaZulu-Natal, has a problem of disposal of the residue after the raw water is treated to be potable. The residue, consisting mainly of fine silt and clay particles flocculated by the addition of a cationic organic polymer and lime, is currently classified as a hazardous waste and has to be disposed of to a dedicated landfill. This work combined a laboratory incubation experiment using eleven contrasting soils from KwaZulu-Natal, and two field trials to investigate the possibility of land disposal of this Water Treatment Residue (WTR). In the incubation experiment, the WTR was applied to 2.5 kg samples of all eleven soils, the highest rate being equivalent to 1280 Mg/ha. The soils were incubated at ambient temperature and field capacity for 140 days. Analysis on completion of the incubation period established that there was an increase in pH, extractable Ca and Mg, and soluble nitrate in all soils. In two of the strongly acid soils, there was a decrease in extractable acidity and an increase in cation exchange capacity. The increase in pH and decrease in extractable acidity were attributed to the liming effect of the WTR. The increase in Ca and Mg came directly from the WTR, and the increase in nitrate was mostly from mineralization of organic matter in the WTR. The increase in cation exchange capacity could have been from the liming effect and/or a contribution from the negative charge of the WTR. The two field experiments were established at Brookdale Farm on a well drained red soil (Typic Haplustult), and at Ukulinga Research Farm of the University of KwaZulu-Natal on a poorly drained soil (Typic Plinthaquept). At both sites the highest rate of application of the WTR was 1280 Mg/ha. At the Brookdale trial, the WTR was both applied as a mulch and incorporated in the upper 200 mm of the soil. Dovey tall fescue (Festuca arundinaceae) followed perennial ryegrass (Lolium perenne) at Brookdale Farm, whereas at Ukulinga Farm only Dovey tall fescue was planted. Where dry matter yield was determined (mainly at Ukulinga due to logistical problems at the Brookdale site), no decline in yield was recorded over the 5 years of the field experiment. In fact there tended to be a general, if mostly non-significant, increase in yield with increase in the application rate of the WTR. From analysis of the grass, there was an occasional increase in Ca, K and N with increase in application of the WTR, and a decrease in Mn. Other elements analyzed, both major and trace, mostly indicated that there were no negative effects of the WTR with respect to plant growth as indicated by dry matter yields. Tissue concentrations of the heavy metals were well below those that could cause either phytotoxicity or zootoxicity. Land disposal of WTR has implications not only for the industry concerned in terms of economics but also for both agriculture and the environment, and the results are discussed to address these aspects.