Phosphorus Recovery from Synthetic Municipal Wastewater through Lignin-induced Struvite Precipitation
Date
2020-01-08
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Abstract
Phosphorus recovery from wastewaters is essential to resolve the problems of the fast depletion of phosphate rocks due to the increasing demand for phosphorus fertilizer, and eutrophication due to excessive phosphorus discharging from wastewater. In this study, the feasibility of adding alkaline lignin as seed materials to promote phosphorus recovery through fertilizer struvite (NH4MgPO4ยท6H2O) crystallization from synthetic municipal wastewater was evaluated via batch experiments. Influencing factors tested included lignin dosage, Mg/P molar ratio, and pH. Lignin addition enhanced phosphorus recovery by 44.6% at a relatively low pH of 7.9 with Mg/P molar ratio of 1.5 and lignin dosage of 6 g/L, resulting in the reduced potential of co-precipitation and the cost-saving on alkali addition. As pH increases, however, this effect becomes less noticeable because of the higher solubility of lignin in wastewater. The characterizations by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and zeta potential analysis, combined with precipitation modeling by a thermodynamic model software (Visual MINTEQ) were done to understand the process. Struvite-lignin clusters were identified, likely due to the in-situ-pH-favorable nucleation sites on lignin enhanced struvite crystallization. As for the application in wastewater with different characteristics, the effect of lignin on enhancing phosphorus recovery efficiency is still significant under different PO4-P and NH4-N concentrations, indicating the effect-stability and availability of lignin in promoting struvite crystallization. As for the total suspended solids (TSS), the results show that the effect of TSS on phosphorus recovery efficiency is not significant (p > 0.05). Moreover, lignin is more efficient in increasing phosphorus recovery under relatively lower alkalinity while could reduce the co-precipitates potential under higher alkalinity. Overall, this study provides a new possibility of the use of lignin from paper mill black liquor as seed material to enhance phosphorus recovery from wastewater, making the struvite production more efficient and cost-effective.
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Li, M. (2020). Phosphorus Recovery from Synthetic Municipal Wastewater through Lignin-induced Struvite Precipitation (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.