Assessment of Environmental Quality of Soil Fertilized Grapefruit Trees with Municipal Sewage Sludge

To reuse municipal sewage sludge safely, experiment was carried out on grapefruit trees fertilized with composted sludge from Shiweitou Sewage Treatment Plant in Xiamen City of China, and a method was introduced of how to assess the environmental quality of grapefruit trees soil fertilized with sludge by Set Pair Analysis (SPA) model. The results showed that the soil in the surface layer (0-15cm) and the deeper layer (15-30cm) was less clean, and the environment of soil was not polluted. Thus it was feasible to use sludge as fruit fertilizer. The maximum service life of sludge for continuous land application was estimated by taking Cd as the limiting factor, which would provide scientific guide and technical support for safe land application of sludge.