Efficiency of Heavy Metals Removal in Municipal Sewage Treatment Plants

Abstract From January to July, 1972, six municipal sewage treatment plants were routinely monitored for the efficiency of heavy metals removal. The municipalities served ranged from a small agricultural community to an industrial city. Four basic plant types were studied: 1) Primary with sludge digestion; 2) Primary with sludge filtration; 3) Trickling-filter secondary with sludge digestion; and 4) Activated-sludge secondary with sludge digestion. Composite samples from the influent, effluent, and sludge were homogenized, acid-digested, and analyzed by atomic absorption spectrophotometry for Cd, Cr, Cu, Zn, and Pb. The efficiency of heavy metals removal and the relationship between heavy metals removal and suspended solids removal are discussed.