Greenhouse and laboratory study for the land application of water treatment residual

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Virginia Tech


The disposal of water treatment residual has received little attention due to a lack of regulation, funding, and concern about their environmental impacts. Many treatment plants discharge alum residual directly into nearby water courses or dewater them for landfilling. If suitable land is available, land application of residual is cost effective and has the potential for negligible effects on the environment and may prove to be a long-term solution to the disposal problem. This research project investigated the effects of land application of alum residual on crops or vegetation grown on fine loamy Slagle soil (siliceous, thermic aquic hapludults). Prior research identified the reduction in plant available P as a potential concern. During summer months. many water treatment plants also add powdered activated carbon (PAC) during the treatment process to prevent taste and odor problems. The PAC ultimately ends up in the residual and alters its chemical characteristics. The effects of land-applied PAC residual on plant growth was also investigated.

Fescue (festuca arundinacae) yields decreased with increased residual addition. Lime addition did not Significantly effect fescue yield. Reductions in plant yield were attributed to a reduction in plant available phosphorus (P) in soils receiving higher residual loadings. Supplemental fertilization was able to overcome the P availability problem. The presence of manganese in the residual did not adversely affect plant yields. Likewise, incorporation of spent PAC into the residual did not reduce yields.