Chemical treatment of sludge: in-depth study on toxic metal removal efficiency, dewatering ability and fertilizing property preservation.
The presence of toxic metals in municipal sewage sludge restricts the application of this biomass in agricultural area. A chemical leaching process using a combination of inorganic acid and two oxidants has been developed for sludge decontamination. The present study investigated the effects of the concentrations of sulphuric acid (H2SO4), hydrogen peroxide and ferric chloride on metal solubilization from sewage sludge, as well as preservation of fertilizing properties (nutrient content) and dewatering ability of the treated sludge. The analysis of the results from batch leaching tests has allowed to define the optimal conditions for the reagent concentrations, which are 56 kg Fe3+ tonne(-1) of dry sludge solids (tds), 8 kg H2O2 tds(-1), and enough H2SO4 to reach a pH between 2.0 and 2.5 but less than 142 kg H2SO4 tds(-1). Finally, under these conditions, oxidoreduction potential values are found to be between 450 and 475 mV.
Beauchesne
Isabel
I
Institut national de la recherche scientifique (Centre Eau, Terre et Environnement), Université du Québec, 490 rue de la Couronne, Québec, Que., Canada G1 K 9A9. Beauchesne@ete.inrs.ca
Cheikh
Ridha Ben
RB
Mercier
Guy
G
Blais
Jean-François
JF
Ouarda
Taha
T
D002712:Chlorides; D005290:Ferric Compounds / Q000737:chemistry; D005308:Fertilizers; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000302:isolation & purification* / Q000633:toxicity; D012722:Sewage / Q000737:chemistry*; D012995:Solubility; D013464:Sulfuric Acids / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*
D002712:Chlorides; D005290:Ferric Compounds; D005308:Fertilizers; D019216:Metals, Heavy; D012722:Sewage; D013464:Sulfuric Acids; D006861:Hydrogen Peroxide; C033158:sulfuric acid; C024555:ferric chloride