PERFORMANCE OF CONE-SHAPED FLUIDIZED BED STRUVITE CRYSTALLIZERS IN REMOVING PHOSPHORUS FROM WASTEWATER

Abstract

A struvite crystallizer design consisting of a continuously operating, cone-shaped fluidized bed was tested for itsability to remove phosphorus from swine lagoon liquid. A laboratory-scale apparatus was first tested, operating at 41 and57 L h-1 of lagoon liquid, and then a field-scale apparatus was tested, operating at 341 and 568 L h-1. Tests were arrangedin a randomized complete block design, with the two cited lagoon liquid flow rates and three levels each of magnesium (Mg)supplementation and pH increase as independent variables. Levels of Mg supplementation were 0, 30, and 60 ppm. Ammoniawas used to increase pH, and in the laboratory-scale tests, levels of this variable were set at 0, 100, and 200 ppm as nitrogen(N) of ammonia. In the field-scale tests, pH was controlled directly, and increased by 0, 0.5, and 1.0 pH units. In thelaboratory-scale tests, orthophosphate phosphorus (OP) removal ranged from 1% to 80%, and total phosphorus (TP) removalranged from -5% to 56%. In the field-scale tests, OP removal was 13% to 82%, and TP removal was 0% to 80%. Thelaboratory-scale apparatus exhibited greater removal with increasing Mg supplementation and pH augmentation, but flowrate showed no significant effect. The effects of the independent variables were similar in the field-scale apparatus, exceptthat decreasing flow rate was associated with greater removal.