STP976

    Distribution of Heavy Metals in Sewage Sludge: The Effect of Particle Size

    Published: Jan 1988


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    Abstract

    The particle size distribution in two anaerobically digested sludges from contrasting United Kingdom catchments has been estimated by a manual sieving technique. Seven particle size fractions were isolated: <20, 20 to 35, 35 to 45, 45 to 64, 64 to 85, 85 to 125, and > 125 µm. In both samples, the less than 20-µm fraction was the largest fraction, accounting for almost 50% of the total. Particles recovered in the coarsest (>125 µm) fraction were readily distinguished as plant remains and cellulose fibers. The distribution of eight metals, chromium, iron, manganese, nickel, copper, zinc, cadmium, and lead, were controlled by the particle size distribution with the finest fraction dominating. However, the distributions of chromium, copper, zinc, cadmium, and lead differed from those of iron, manganese, and nickel in that there was a much wider span of concentration (on a dry weight basis) between coarsest and finest particles. We attribute the wide concentration range of the former group to the repartitioning of these contaminants in sewage from predominantly solution phases to solids, by a sorption process, governed at least to an extent by surface area. On the other hand, iron, manganese, and nickel, if predominantly associated with solid phases in raw sewage, would be little influenced by alteration during treatment.

    Keywords:

    sewage sludge, particle size, sieving, iron, manganese, chromium, nickel, copper, zinc, cadmium, lead, sludge-seawater mixing


    Author Information:

    Campbell, JA
    Head of inorganic chemistry, chemist, and assistant chemist, WRc Environment, Environmental Chemistry and Instrumentation Group, Medmenham Laboratory, Marlow, Buckinghamshire

    Towner, JV
    Head of inorganic chemistry, chemist, and assistant chemist, WRc Environment, Environmental Chemistry and Instrumentation Group, Medmenham Laboratory, Marlow, Buckinghamshire

    Vallurupalli, R
    Head of inorganic chemistry, chemist, and assistant chemist, WRc Environment, Environmental Chemistry and Instrumentation Group, Medmenham Laboratory, Marlow, Buckinghamshire


    Paper ID: STP26701S

    Committee/Subcommittee: D19.05

    DOI: 10.1520/STP26701S


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