Effects of humus soil on chemical speciation of heavy metals in activated sludge

Abstract:

A batch tests study was performed to evaluate the changes of heavy metal chemical speciation in sewage sludge with humus soil. Sewage sludge with humus soil (0, 0.5, 1, 2, 3, 5g) mix 20d in polyethylene flasks. The five stages of the Tessier sequential extraction method was employed to investigate changes in heavy metal fractions of Zn, Cu, Ni and Pb in sewage sludge with humus soil. The results showed that humus soil effected chemical speciation of heavy metals in sewage sludge significantly. Zinc: ion-exchange (F1) zinc, carbonate-bound (F2) zinc and iron-manganese oxide bound (F3) contents and HS dosage had significant negative correlation (0.9266, 0.9310, 0.9144, p<0.01), sulfides and organic-bound (F4) and HS dosage had a significant positive correlation (0.9304, p<0.01). Copper: F2 and HS dosage had a negative correlation (0.7145, p<0.05). Nickel: F1 and F2 nickel and HS dosage had significant negative correlation (0.9027, 0.9724, p<0.01), F4 nickel and residual (F5) and HS dosage had a significant positive correlation (0.9188, 0.9123, p<0.01). Lead: F3 and F4 lead and HS dosage had negative correlation (0.7027, 0.7635, p<0.05), F5 lead and HS dosage had a positive correlation (0.7668, , p<0.05). Adding humus significantly reduced the potential availability of zinc, copper, nickel, and lead in activated sludge.