Characterization, Recovery Opportunities, and Valuation of Metals in Municipal Sludges from U.S. Wastewater Treatment Plants Nationwide

U.S. sewage sludges were analyzed for 58 regulated and nonregulated elements by ICP-MS and electron microscopy to explore opportunities for removal and recovery. Sludge/water distribution coefficients (K D, L/kg dry weight) spanned 5 orders of magnitude, indicating significant metal accumulation in biosolids. Rare-earth elements and minor metals (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) detected in sludges showed enrichment factors (EFs) near unity, suggesting dust or soils as likely dominant sources. In contrast, most platinum group elements (i.e., Ru, Rh, Pd, Pt) showed high EF and K D values, indicating anthropogenic sources. Numerous metallic and metal oxide colloids (