Environmental risk assessment of heavy metal extractability in a biosludge from the biological wastewater treatment plant of a pulp and paper mill

• Published in: Environmental monitoring and assessment Vol. 128; no. 1-3; pp. 153 - 164
• Main Authors: Pöykiö, R, Nurmesniemi, H, Keiski, R. L
• Format: Journal Article
• Language: English
• Published: Dordrect Dordrecht : Kluwer Academic Publishers 01.05.2007; Springer; Springer Nature B.V
• Subjects: Acetates; Acetic acid; Agricultural land; Agriculture; Ammonium; Ammonium acetate; Ammonium compounds; Applied sciences; Arable land; Bioavailability; Biological; Biological wastewater treatment; By products; Cadmium; Calcium; Chromium; Clarifiers; Copper; Digestion; Dry weight; Drying; El Nino; Environmental assessment; Environmental monitoring; Environmental protection; Environmental risk; Environmental science; Exact sciences and technology; Extraction; Extraction procedures; Heavy metals; Hydrogen; Hydrogen peroxide; Hydroxylamine; Hydroxylamines; Industrial Waste; Iron; Lead; Legislation; Liming; Manganese; Metal concentrations; Metals; Metals, Heavy - isolation & purification; Mills; Other industrial wastes. Sewage sludge; Paper mill; Paper mills; pH effects; Plant extracts; Plants (organisms); Pollution; Pulp & paper mills; pulp and paper mills; Risk Assessment; Sediments; Sequential extraction; Sewage; Sewage - chemistry; Sewage sludge; Sludge; Soil; Soil (material); Soil conditioners; Soil conditions; Soil improvement; Soils; Studies; Textile Industry; Wastes; Wastewater treatment; Wastewater treatment plants; Water Pollutants, Chemical - isolation & purification; Water treatment; Water treatment plants; Zinc; Europe; Finland; European Union; Fractionation; Paper mill; Sequential extraction; Sludge; Sewage sludge; Heavy metals; Biological purification; Paper industry; Heavy metal; Pulp mill; Industrial waste water; Risk assessment; Environment impact; Extraction; Waste water purification
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-006-9301-y

A five-stage sequential extraction procedure was used to fractionate heavy metals (Cd, Cu, Pb, Cr, Zn, Fe, Mn, Ni, Co, As, V and Ba) in a biosludge from the biological wastewater treatment plant of Stora Enso Oyj Veitsiluoto Mills at Kemi, Northern Finland, into the following fractions: (1) water-soluble fraction, (2) exchangeable fraction, (3) easily reduced fraction, (4) oxidizable fraction, and (5) residual fraction. The biosludge investigated in this study is a combination of sludge from the primary and secondary clarifiers at the biological wastewater treatment plant. Extraction stages (2)-(4) follow the protocol proposed by the Measurements and Testing Program (formerly BCR Programme) of the European Commission, which is based on acetic acid extraction (stage 2), hydroxylamine hydrochloride extraction (stage 3), and hydrogen peroxide digestion following the ammonium acetate extraction (stage 4). The residual fraction (stage 5) was based on digestion of the residue from stage 4 in a mixture of HF + HNO₃ + HCl. Although metals were extractable in all fractions, the highest concentrations of most of the metals occurred in the residual fraction. From the environmental point of view, it was notable that the total heavy metal concentrations in the biosludge did not exceed the maximal allowable heavy metal concentrations for sewage sludge used in agriculture, set on the basis of environmental protection of soil by European Union Directive 86/278/EEC, and by the Finnish legislation. The Ca (98.6 g kg-¹; dry weight) and Mg (2.2 g kg-¹; dry weight) concentrations in the biosludge were 62 and 11 times higher than the typical values of 1.6 and of 0.2 g kg-¹ (dry weight), respectively, in arable land in Central Finland. The biosludge had a slightly alkaline pH (~8.30), a high loss-on-ignition value (~78%) and a liming effect of 10.3% expressed as Ca equivalents (dry weight). This indicates its potential as a soil conditioner and improvement agent, as well as a pH buffer.