The effect of selected acidic or alkaline chemical agents amendment on leachability of selected heavy metals from sewage sludge

The aim of the study was to evaluate the effect of acidic (Fenton's reagent, peracetic acid) or alkaline (CaO) chemical agents amendment on chemical forms of Pb, Ni, and Cd in sewage sludge. The dose of Fenton's reagent was as follows: Fe2+=1g.L-1, Fe2+/H2O2=1:100; stabilisation lasted for 2 h. The dose of CaO was equal to 1 g CaO center dot g d.m.(-1). The dose of CH3COOOH was 2.5 g.L-1. Total concentration of all metals in the digested sewage sludge was higher than in the soil and it did not meet Polish law requirements. Acidic chemical stabilisation of sludge did not significantly decrease total metal content in the sludge. Amendment of CaO decreased the content of Pb, Cd, and Ni in the sludge. Chemical fractions of heavy metals were identified in the sludge (exchangeable, carbonate bound, iron oxides bound, organic and residual). The results indicate that stabilisation of the sludge with Fenton's reagent and peracetic acid increased the exchangeable fraction of Pb, Cd, and Ni compared to the digested sludge, but it did not increase shares of mobile forms of metals considered as a total of I-st and II-nd fraction. Amendment of CaO increased percent share of examined metals in residual fraction. Not-mobile fractions of examined metals overweight the mobile ones in all sludge samples regardless of the treatment method. (C) 2018 Elsevier B.V. All rights reserved.