Phosphorus adsorption characteristics of oyster shells and alum sludge and their application for nutrient control in constructed wetland system
Titel:
Phosphorus adsorption characteristics of oyster shells and alum sludge and their application for nutrient control in constructed wetland system
Auteur:
Park, W. H. Polprasert, C.
Verschenen in:
Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering
Paginering:
Jaargang 43 (2008) nr. 5 pagina's 511-517
Jaar:
2008-04
Inhoud:
This research aimed to evaluate the feasibility of employing some locally available oyster shells (OS) and alum sludge (AS) as the P adsorption media of constructed wetland beds. The batch and column tests were conducted with different sizes of OS and AS to observe the P adsorption characteristics and breakthrough, while P adsorption rates were determined from jar test. From the batch test, the ability to adsorb the amount of added P was different considerably between OS and AS media and sizes. At the same size, the P adsorption capacities of OS were higher than those of alum sludge. The P adsorption capacities of AS with 0.3-0.6 mm and > 0.6 mm sizes were similar, but those of 0.3-0.6 mm OS was higher than > 0.6 mm OS. Jar test results revealed the first-order P removal rates (k) to be 11.4, 4.5, 1.7 and 1.0 d- 1 for the 0.3-0.6 mm AS, > 0.6 mm AS, 0.3-0.6 mm OS, and > 0.6 mm OS, respectively. From the column tests, the adsorption capacities were found to be more than 26 and 24.5 g/kg for the OS media sizes of 0.3-0.6 and > 0.6 mm, respectively, and 12 g/kg for the AS media. The column tests revealed that AS was able to adsorb P faster than the oyster shells, but due to its low adsorption capacity, the periods of P breakthrough in the effluent of the alum sludge columns were shorter than those of the oyster shell columns. Experiments with a pilot-scale vertical-flow subsurface constructed wetland unit packed with > 0.6 mm OS media demonstrated the high P removal efficiencies of more than 96.2% during the 210 days of operation.
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