Colloid deposition rates in porous media under unfavorable filtration conditions were compared for filter media cleaned by a variety of methods. The bed media consisted of soda-lime glass beads or ultrapure quartz sand, and the colloids were 0.245-/tm-diameter carboxyl latex spheres. Deposition rates, expressed as attachment efficiencies, a, were determined as a function of pH at constant ionic strength. The filter media were cleaned with strong acid (HC1) alone, strong acid in combination with concentrated chromic acid, heat (810 °C), acetone, or boiling 4 N HN03. Filter media treated with the two most aggressive oxidation methods, combustion and chromic acid, yielded attachment efficiencies that were significantly more sensitive to solution chemistry changes and the lowest a values, f potentials of the filter media, however, were independent of the treatment methods. Deposition rates were also compared for two bed media size fractionation methods, sieving and a wet-sedimentation technique. Sieving irreversibly enhanced particle deposition rates. Electrophoresis measurements indicate that soda-lime glass surfaces undergo relatively slow hydration, which complicates their characterization.

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In the United States, environmentally impaired rivers are subject to regulation under total maximum daily load (TMDL) regulations that specify watershed wide water quality standards. In California, the setting of TMDL standards is accompanied by the development of scientific and management plans directed at achieving specific water quality objectives. The San Joaquin River (SJR) in the Central Valley of California now has a TMDL for dissolved oxygen (DO). Low DO conditions in the SJR are caused in part by excessive phytoplankton growth (eutrophication) in the shallow, upstream portion of the river that create oxygen demand in the deeper estuary. This paper reports on scientific studies that were conducted to develop a mass balance on nutrients and phytoplankton in the SJR. A mass balance model was developed using WARMF, a model specifically designed for use in TMDL management applications. It was demonstrated that phytoplankton biomass accumulates rapidly in a 88 km reach where plankton from small, slow moving tributaries are diluted and combined with fresh nutrient inputs in faster moving water. The SJR-WARMF model was demonstrated to accurately predict phytoplankton growth in the SJR. Model results suggest that modest reductions in nutrients alone will not limit algal biomass accumulation, but that combined strategies of nutrient reduction and algal control in tributaries may have benefit. The SJR-WARMF model provides stakeholders a practical, scientific tool for setting remediation priorities on a watershed scale.