Continuous Fill Lagoons

For a continuous-fill lagoon, a side water depth of 8 to 13 ft with a 3- to 5-yr capacity is recommended (Montgomery 1985; Faber et al. 1969). Multiple cells equipped with decanting devices are also preferred (Faber et al. 1969). In these lagoons, the sludge is applied in layers, and the su-

Sludge Produced (Ib/mg water treated)

FIG. 7.51.1 Relationship between water volume treated, solids concentration, and required lagoon storage volume. (Reprinted, with permission, from L. Streicher et al., 1972, Disposal of water treatment plant wastes, Jour. AWWA [December].)

Sludge Produced (Ib/mg water treated)

FIG. 7.51.1 Relationship between water volume treated, solids concentration, and required lagoon storage volume. (Reprinted, with permission, from L. Streicher et al., 1972, Disposal of water treatment plant wastes, Jour. AWWA [December].)

pernatant is removed periodically for air drying. This process is repeated until the lagoon is filled with solids. The lagoon is then covered, and the land is reclaimed. The type of disposed sludge dictates any future use of the land.

Lime sludge can reach 40% solids when settled through ponded water. Solids concentrations as low as 20 to 30% are also reported. If the supernatant is allowed to flow off the site or is removed with decanting equipment, up to 50% solids can be achieved (Faber et al. 1969).

Alum and iron coagulant sludge can reach 10 to 15% solids, with iron sludge dewatering faster than alum sludge. Neither is suitable for landfill at this dry-solids content. After 2 to 3 years, 30 to 40% solids can be reached (Masschelein 1992). The percent solids values are overall averages. The percent dry solids concentration varies with depth, being greater near the bottom of the lagoon.

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