Reclaiming the Ecosystem: Eutrophication Control with Calcium Carbonate Filters and Denitrification in Fresh Water Lakes

Overview

Objectives/Goals Eutrophication, the process by which a lake becomes rich in dissolved nutrients due to point and non-point pollutant sources, is a major cause of the loss of natural lake ecosystems throughout the world. Especially in Madrona Marsh, one of the last remaining vernal marshes in the Greater Los Angeles Area, cultural eutrophication has become a major problem. Methods/Materials This experiment involved the testing of calcium carbonate as a phosphate binder in the laboratory and in the real ecosystem. A calcium carbonate lacing procedure was first carried out in order to determine its efficacy in Madrona Marsh. This was followed by an ammonia study. Ammonia interferes with the solubility of calcium carbonate and therefore hinders the reduction of phosphate. Various approaches for reduction of ammonia were tested including aeration, use of bacteria growth medium, and plants, mainly in an attempt to increase population of Nitrobacter and Nitrosomonas. In addition soil sampling, sediment analysis, microscopic plant analysis, microorganism and macroinvertibrate identification, and rate law formulations were conducted. This was followed by the construction of various phosphate binding calcium carbonate filters, which utilized the ion exchange principle, including a spring loading filter, PVC pipe filter, a galvanized filter, and an agitator clarifier system. All were tested with the aid of Stoke's Law. Results Calcium carbonate was found to be an excellent phosphate binder, reducing up to 70% of the phosphates in the lacing procedure, and the ammonia control phase also worked successfully, reducing ammonia, on average, by 0.2 ppm. The auxiiary phases were successful in determining the safety of the calcium carbonate, and the filters were built on that basis. The filters worked well, reducing phophates significantly and producing high flow rates and clarity overall. Conclusions/Discussion The experiment was extremely successful in designing a working phosphate binding and ammonia reducing filter, and a large scale filter is currently being constructed in Madrona Marsh; this filter will reduce phosphate and ammonia levels substantially in the following years.

Awards (1)

• Category Award

Competition history

• CSEF 2002 Environmental Engineering · Entry S0811

Resources

• CSEF project summary ↗

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