Abstract
A greenhouse experiment was conducted to compare (1) application effect on the growth of oats between two kinds of conditioning for sewage sludge with different dewatering methods and those ashes and (2) uptake of heavy metals by oats. 1) Application effect of nitrogen contained in the cakes was large in the sludge cake conditioned with chemical precipitation method (lime and ferric chloride) while it was nil in the sludge cake conditioned with heat precipitation method. 2) Application effect of phosphorus contained in the ashes was larger than that contained in the sludge cakes. Utilization percentage of phosphorus contained in the ashes was two times larger than that in the cakes. There was no difference in the utilization percentage of phosphorus between two kinds of ashes and between two kinds of ashes and between two kinds of conditioning for the sewage sludge cakes with different methods. 3) Application effect of potassium contained in the sludge cakes and in the ashes was indistinct because amounts of potassium uptake by oats were more than amounts of potassium by application of the materials. 4) Content of Mn, Zn, Pb, and Cd in oat plant was decreased and Cu was not different by ashes application compared with sludge cakes application. It was considered that heavy metals contained in the sewage sludge were transformed into insoluble form by incineration treatment.
