Wastewater Reclamation at South Tahoe Public Utilities District

This article reports on a unique project in wastewater reclamation at South Lake Tahoe, California. In 1961, large‐scale pilot plant studies were conducted at South Tahoe on chemical coagulation, mixed‐media (or coarse‐ to‐fine) filtration with polyelectrolyte filter aid, and granular carbon adsorption. It was found that the process not only increased removal of BOD, COD, suspended solids, bacteria, and other substances, but also removed color, odor, colloids, viruses, phosphates, ABS, and other organic chemicals that are relatively unaffected by secondary treatment. In 1963, the South Tahoe Public Utilities District (PUD) commissioned a 2.5 mgd tertiary plant that incorporated these processes, including facilities for thermal regeneration of granular activated carbon for flows up to 10 mgd. In February 1964, further studies were begun on coagulant recovery and reuse, nitrogen removal, and data collection in connection with full‐scale carbon regeneration and reuse. In 1966, the capacity of the entire South Tahoe plant was expanded from 2.5 to 7.5 mgd, with an addition of facilities for coagulant recovery and reuse (with lime as the coagulant) and for the incineration of all sludge produced. In addition, a 7.5‐mgd ammonia stripping tower for nitrogen removal is in the design stage.