Fate of metals in wastewater discharge to ocean

Abstract

Trace metals with sewage and sludge particulates from the City of Los Angeles Hyperion Treatment Plant are found to mobilize to a great extent from solids to seawater in the ocean environment. The fate of these metals and the amount of annual transport to the ocean are evaluated, based on: (1) Concentrations of trace metals in the wastewater particulates; (2) sediment metal concentrations in the proximity of sewer outfalls; (3) the degree of metal release from wastewater particulates upon mixing and dilution with seawater under laboratory conditions; and (4) the settling velocity of sewage and sludge particulates. More than 90 percent of trace metals, such as cadmium, copper, lead, nickel, and zinc in the sludge particulates are solubilized through biochemical reactions. A higher degree of solubilization from the mixture of primary and secondary effluents is observed.