Evaluation of metals in wastewater sludge

• Published in: Journal - Water Pollution Control Federation 1976-01, Vol.48 (9), p.2165-2175
• Main Authors: Stover, R.C, Sommers, L.E, Silviera, D.J
• Format: Article
• Language: English
• Subjects: Acid soils; Agricultural soils; Carbonates; environmental science; natural resource management; Oxalates; pollution; Reagents; Sedimentary soils; Sludge; Sludge treatment; Sulfides; Wastewater
• ISSN: 0043-1303; 2327-7467

A study was conducted to develop a procedure for determining the forms and amounts of Pb, Zn, Cu, and Ni in anaerobically digested wastewater sludges obtained from 12 municipal treatment plants. Preliminary investigations were conducted to evaluate a variety of metal extractants for their complete but selective removal of specific metal forms from sludge. Based on these results, a sequential extraction procedure was devised that involved treatment of sludges with 1 M ${\rm KNO}_{3}$, 0.5 M KF, 0.1 M ${\rm Na}_{4}{\rm P}_{2}{\rm O}_{7}$, 0.1 M EDTA (ethylene-diaminetetracetic acid), 1 M ${\rm HNO}_{3}$ to remove metals present in exchangeable, adsorbed, organic matter-bound, carbonate and sulfide forms, respectively. For comparative purposes, a procedure developed for fractionating soil Cu was used to evaluate the forms of metals in sludge. The results indicated that, for a given metal, the proportion of the total metal extracted by each reagent varied for different sludges, which suggests that the predominant form of a metal is not constant for different sludges. The amounts of water soluble and 0.5 M HCl extractable Pb, Zn, Cu, Cd, and Ni were also determined.