Comparative evaluation of drying methods for struvite produced from electrocoagulated source-separated urine: Implications for quality, energy and cost-effectiveness

• Published in: Journal of environmental management 2024-04, Vol.356, p.120665-120665, Article 120665
• Main Authors: Zaffar, Alisha, Jayaraman, Sivaraman, Sutar, Parag Prakash, Balasubramanian, Paramasivan
• Format: Article
• Language: English
• Subjects: Cost-Benefit Analysis; Cost-effective; Desiccation - methods; Drying kinetics; Electrocoagulation; Energy; Source-separated urine; Struvite; Temperature; X-Ray Diffraction
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2024.120665

Struvite precipitation from source-separated urine is crucial for waste utilization and sustainability. However, after precipitation, the high moisture content of struvite necessitates an additional drying process that can be costly and inefficient. In the present study, the performance of different drying methods—open sun drying, air drying, conventional drying (20–100 °C), and microwave drying (180–720 W) on the quality of struvite obtained from source-separated urine through electrocoagulation using Mg–Mg electrodes were evaluated. It was found that higher temperatures and power in the convective oven and microwave resulted in higher diffusivity (10−9-10−7 m2s−1), leading to reduced drying times. Different models were employed to comprehend the drying mechanism, and the one with the highest correlation coefficient (R2 = 0.99) and the lowest statistical values was selected. The key findings indicated that higher power and temperature levels were more cost-effective. However, characterization of the dried struvite using X-ray diffraction and Fourier-transformed infrared spectroscopy, disintegration of struvite crystals at temperatures above 60 °C in the conventional oven and 180 W in the microwave oven was observed. Based on the results, we conclude that sun drying is a cost-effective and environmentally friendly alternative for drying struvite without compromising its quality. •Struvite was precipitated through electrocoagulation method from source separated urine.•Different drying methods on struvite quality and its energy requirement were evaluated.•Foremost study reporting the mathematical modelling of drying kinetics of struvite.•Higher temperatures and microwave power showed higher effective diffusivity, resulting in reduced drying time.•XRD and FTIR revealed the impact of temperature on the disintegration of struvite crystals.