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Land application of water treatment residue (WTR) the by-product from the production of potable water, is becoming the preferred method of disposal, as there are environmental concerns and increasingly high costs associated with other disposal options. However, before WTR can be applied to land, consideration needs to be given to their chemical and physical characteristics to determine potential impacts. Six WTR samples were obtained from five South African water treatment facilities (Faure Water Treatment Plant (two samples), Rand Water, Umgeni Water, Amatola Water and Midvaal Water Company). The Rand Water WTR was a CaO, FeCl 3 , long-chain organic polymer (LCP) residue with activated silica and CO 2 being added. The Umgeni and Amatola Water WTRs were lime and LCP residues. The Midvaal Water WTR was an Al 2 (SO 4 ) 3 .nH 2 0, FeCl 3 , lime and LCP residue and the Faure WTRs were Fe 2 (SO 4 ) 3 , activated charcoal, lime and LCP residues. These WTR samples were analysed for some physical (particle size distribution, particle density and plant available water) and chemical attributes (pH, electrical conductivity, cation exchange capacity, calcium carbonate equivalence, exchangeable acidity, extractable bases and metal cations, total and plant available nutrients, total elemental analysis and metal fractionation) and mineralogical properties, and their potential for application to land considered. The WTRs tended to be neutral to alkaline in pH, with low electrical conductivity. Generally, amounts of N, P and K were low, but some of the WTRs showed potential to supply other plant nutrients (Ca, Mg, S, Zn, Cu and Fe). Their physical characteristics were variable, showing a wide range in particle size distribution as well as plant available water. Heavy metal concentrations tended to be low, but Mn was elevated in some WTRs, especially in the Faure WTRs, which may lead to plant growth problems. Land application of these WTRs appears to be a feasible disposal option, but currently they are regulated by the 'minimum requirements for disposal of hazardous waste'. Delisting would firstly be required for land application and if then permitted by legislation, the application rates would need to be based on existing soil conditions, the characteristics of a particular WTR, and the proposed land use.

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Water treatment residue (WTR), a waste by-product of the 'drinking' water treatment industry, consists mainly of clay and fine silt flocculated out of suspension by chemicals such as polyelectrolytes and aluminium sulfate. This residue was disposed of almost exclusively in landfill, but land treatment is increasingly being seen as a possible alternative for this form of waste. A key concern, however, is that should the WTR decompose to its constituent fractions, this could cause blockage of pores and decrease the hydraulic properties of soil. To test this hypothesis, 2 field experiments were established on physically contrasting soils in KwaZulu-Natal, South Africa. Application rates from 0 to 1280 Mg/ha of WTR were compared with amendments of lime, gypsum, and polyacrylamide to determine their effects on water retention and hydraulic conductivity. Although after 3 years at one experiment and 2 years at the second differences between the WTR treatments were measurable, only the 1280�Mg/ha application rate was significantly different from the control. The chemical amendments that were applied purely as comparative treatments had no significant influence on either water retention or hydraulic conductivity. Neither soil showed any difference in readily available water content. The experiments showed that, in both soil types, the WTR increased water retention and hydraulic conductivity but that improvement in both of these properties was only significant at the 1280 Mg/ha application rate. Thus, very high amounts of WTR must be added to affect these physical properties of soils.