Phosphorus sorption characteristics of a light-weight aggregate.
A light-weight aggregate (LWA) made of expanded clay used as a filter media in wastewater treatment, was tested for sorption of phosphorus (P) in laboratory experiments. The objectives were to investigate the different P retention pools and how grain size, time, temperature and changed P concentration influenced the P binding mechanisms in this type of filter. Three different grain sizes (0-2 mm, 2-4 mm and 0-4 mm) were tested in a batch experiment. The isotherm for the P sorbed by the contact medium (including retention and fixation) was obtained under laboratory conditions. Fifty percent of the P sorption occurred in the first 4-8 hours. Temperature did not substantially influence P sorption for 0-2 mm grain size LWA. In the LWA suspension system, P desorption did not occur when the P content in the loading solution decreased. Fractionation analysis indicated that Ca-bound P, loosely-bound P, and Al-bound P were the predominant P retention pools. The loosely-bound P pool was determined primarily by the equilibrated P concentration in the system. Fe-bound P was negligible in the P sorption of LWA.
Zhu
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Norwegian Centre for Soil and Environmental Research, N-1432 As, Norway.
Maehlum
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Jenssen
P D
PD
Krogstad
T
T
D000327:Adsorption; D000538:Aluminum Silicates; D000077215:Clay; D005374:Filtration; D010316:Particle Size; D010758:Phosphorus / Q000737:chemistry / Q000302:isolation & purification*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
D000538:Aluminum Silicates; D010758:Phosphorus; D000077215:Clay