The feasibility of planting on stabilized sludge-amended soil

The feasibility of growing plants on stabilized anaerobically-digested slud ge from a local secondary sewage treatment plant (STP) and stabilized chemi cally-modified sludge from a pilot chemically-assisted primary treatment pl ant were studied. Apropyron elongatum (tall wheat grass) was used in this r esearch study. A sandy soil obtained locally was amended by the addition of the lime/pulverized fuel ash (PFA) stabilized sewage sludge at the rates o f 0, 25, 50, 100, and 200 g/kg. The total shoot yield of the grass harveste d from the amended soil was significantly higher than that of the natural s oil (except chemically-modified sludge 200 g/kg). The optimum application r ates that achieved the highest yield for digested sludge and chemically-mod ified sludge-amended soils were 50 g/kg and 25 g/kg, respectively. Applying the stabilized digested sludge to the soil reduced Zn, Cr, and P but incre ased Cu, Cd, N, and K concentrations in the root tissues of the grass. The Ni, Cr, B, and K concentrations in the shoot were increased with the additi on of stabilized digested sludge-amended soil. For the chemically-modified sludge samples, the concentrations of the metal contaminants as well as the nutrient levels of the crops (both in the shoot and root tissues) grown in the stabilized amended soil were increased as compared to the control. How ever, all the trace metal concentrations in the crop were below stipulated toxicity levels. The experimental results indicate that it is feasible to p lant on a mixture of natural soil and stabilized sewage sludge provided the dosage applied is carefully controlled. (C) 1999 Elsevier Science Ltd.