Assessing The Effect of Different Drying Conditions On Struvite Quality and Kinetic Modelling for Easier and Cost-Effective Downstream Processing

Abstract

Increasing agricultural demand and depletion of phosphorus rocks has made transition in research from contamination removal to nutrient recovery from wastewater. Precipitation of struvite or magnesium ammonium phosphate is an effective way of sustainable management and recycling of nutrients (N&P) from wastewater. However, conventional drying of struvite in hot air oven makes the process time consuming and cost ineffective. Our study focuses on evaluation of performance of conventional (20-100°C), microwave (180-720 W), sun and room temperature drying on the quality of struvite produced from source separated urine by electrocoagulation using Mg-Mg electrodes. The effective diffusivity is reported to be 1.01402e-08- 2.15936e-07; 2.30599e-07- 1.74507e-06; 5.43852e-08; 8.64472e-09 for conventional oven, microwave, sun and room temperature drying respectively. The falling rate period was observed to fit on Page, Newton and Handerson-Pabis model for most of the conditions with the correlation co-efficient value of >95%. The dried struvite was subjected to XRD analysis to determine the effect on the quality revealed the disintegration of struvite crystals with the increase of temperature above 60°C in conventional oven and 180 W in microwave oven into other forms. The sun drying is concluded to be a cheaper alternative which is less time consuming and retains struvite quality.