ABSTRACT
Eutrophication or the overenrichment of global water bodies has grown from a rising concern to a major water-quality-impairment parameter over the past few decades. This phenomenon is mainly attributable to the inux of nitrogen (N) and phosphorus (P) into the water bodies from a variety of sources ranging from detergents to
7.1 Introduction .................................................................................................. 175 7.2 Anion Exchanger Development .................................................................... 177 7.3 Methodology ................................................................................................. 180
7.3.1 Batch Equilibrium Tests ................................................................... 180 7.3.2 Batch Kinetic Tests ........................................................................... 180 7.3.3 Fixed-Bed Column Runs .................................................................. 180 7.3.4 Regeneration, Recycling of Spent Regenerant, and Recovery
of Phosphate ...................................................................................... 181 7.3.5 Analytical Procedure ........................................................................ 181
7.4 Results ........................................................................................................... 181 7.4.1 Fixed-Bed Column Run: Exhaustion ................................................ 181 7.4.2 Fixed-Bed Column Run: Regeneration, Recovery, and Recycling .... 185
7.5 Discussion ..................................................................................................... 187 7.5.1 Phosphorous Recovery...................................................................... 187 7.5.2 Quantifying the Relative Contribution of Different Mechanisms
in Phosphate Sorption ....................................................................... 187 7.5.3 Kinetic Modeling of Sorption ........................................................... 188
7.5.3.1 Determination of Intraparticle Diffusivity ........................ 189 7.6 Conclusions ................................................................................................... 190 Abbreviations ......................................................................................................... 192 References .............................................................................................................. 192
fertilizers to atmospheric deposition. Eutrophication is a key driver in a number of environmental problems including reduced light penetration resulting in sea-grass mortality, increases in harmful algal blooms, and hypoxic and anoxic conditions. It is generally agreed upon that P is the rate-limiting nutrient in freshwater ecosystems, that is, the level of P in freshwater bodies governs the growth of aquatic organisms. Many streams and lakes in the United States have very little capacity to assimilate P loading during the “critical” warm and dry summer period without signicant water quality degradation. Large diurnal swings in pH and dissolved oxygen may occur as excessive amounts of nutrients are metabolized by aquatic plants and algae. The range of these swings is often measured to exceed the state water quality criteria established to protect sh and other aquatic organisms in their various life stages. Therefore, the amount of phosphorus currently entering these waters exceeds the seasonal loading capacity and must be reduced if these water quality problems are to be resolved (Goldman et al. 1973, Rhyther and Dunstan 1971, Valiela 1995).
