Plant availability of heavy metals and phosphorus in the agricultural reuse of biological sludges.

Concerns about the agricultural use of sludges are usually associated with heavy metals. In this study, plant-availabilities of heavy metals and phosphorus (P) in different P amendments were investigated. The dewatered sludge from Paşaköy Biological Nutrient (N, P) Removal (BNR) Plant in Istanbul, a chemical fertilizer (Triple Superphosphate), and a P-deficient, alkaline soil were used in pot experiments. Unstabilized sludge (S), lime-stabilized sludge (LS), and triple superphosphate (TSP) were applied to pots in a manner to supply 0, 100, 200, 300, 400 ppm P. Lollium Perenne was grown on these soils to compare P and heavy metal (Cu. Ni, Zn) availabilities in terms of plant uptake. The results of plant analyses showed that P-recycling through the agricultural use of biological nutrient removal (BNR) sludges was possible. Plant availability of heavy metals in sludge amended soil samples was comparable with those in control samples (soil only) and chemical fertilizer amended samples. Lime stabilization reduced the plant-availability of P and heavy metals. The choice of lime stabilization must depend on the specific soil to be amended.