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The primary productivity of the Salton Sea, California is excessively high, leading to low-oxygen conditions, low clarity, and odors associated with algal decomposition. Treating the inflow water with aluminum sulfate (alum) to remove soluble phosphorus (P), the limiting nutrient, is being considered to improve water quality. The objective of this study was to evaluate the use of alum to remove dissolved phosphorus from New River water, and the potential for the Al-bound P to be released into the Salton Sea. The New River is dominated by agricultural wastewater and has a salinity somewhat higher than normally encountered for alum treatment (total dissolved solids = 2,300 mg l−1), thus, evaluation of alum’s effectiveness is needed. In addition, alum may be dosed directly into the New River and the floc allowed to flow into the Salton Sea if the precipitated P is stable in Salton Sea water. In this study, we evaluated the potential for floc-bound P to be desorbed in Salton Sea water, which has an unusually high salinity (46 g l−1). Aluminum at a 5-mg l−1 dose was effective in removing over 90% of the soluble phosphorus from the New River water. However, when the alum floc was added to Salton Sea water, up to 100% of the Al-bound P was released into the Sea water due to desorption, dissolution, and recrystallization of the alum floc. These results indicate that treatment of agricultural drainage water to reduce P-loading can be effective if the alum floc is settled and not allowed to enter the saline Salton Sea. In addition to alum costs, estimated at US$13 million year−1, settling basin construction and maintenance for floc removal would be required. [ABSTRACT FROM AUTHOR]

The Salton Sea is a hypereutrophic, saline lake in the desert of southern California. Like many lakes, the primary productivity of the Sea is limited by phosphorus. However, unlike most lakes, the release of P from the sediments is not controlled by the reductive dissolution of Fe(III)-oxide minerals. Most of the iron in the sediments of the Salton Sea is present as Fe(II)-sulfides and silicates. Rather, the sediments are dominated by calcite which is actively precipitating due to alkalinity production via sulfate reduction reactions. We hypothesized that calcite could be an important sink for phosphorus released from the decomposing organic matter. In this work we evaluated the potential for phosphate to coprecipitate with calcite formed in simulated Salton Sea sediment pore water. At calcite precipitation levels and P concentrations typical for the Salton Sea pore water, coprecipitation of P removed 82–100% of the dissolved phosphorus. The amount of P incorporated into the calcite was independent of temperature. The results of this work indicate that the internal loading of P within the Salton Sea is being controlled by calcite precipitation. Management of external P loading should have an immediate impact on reducing algae blooms in the Salton Sea. [ABSTRACT FROM AUTHOR]