Comparison of the Recovery of Phosphorus from Wastewater into Magnesium Ammonium Phosphate by Sedimentation Tank and Up-flow Fluidized Crystallization Bed [以沉澱槽及上流式流體化結晶床回收廢水中的磷成磷酸銨鎂的比較]
Journal
Taiwanese Journal of Agricultural Chemistry and Food Science
Journal Volume
59
Journal Issue
2
Pages
54-63
Date Issued
2021
Author(s)
Abstract
High contents of phosphorus in discharged wastewater can cause eutrophication of rivers and lakes. Therefore, how to reduce phosphorus content effectively is important in wastewater treatment. Magnesium ammonium phosphate (MAP), also known as struvite, is a slow-release phosphate fertilizer. MAP does not dissolve well like chemical fertilizers, so it is friendly to the environment. In this research, we conducted a field study to test the recovery of phosphorus from wastewater as MAP. Anaerobic digestion effluent was used for the mass production test of struvite using a traditional sedimentation tank, and an up-flow type MAP fluidized crystallization bed. By using a traditional precipitation tank, 80-90% of the phosphorus could be recovered. However, the product contained only about 50% struvite and the others were mostly calcium and magnesium carbonate (dolomite) precipitates. MAP recovery rate can be improved when the up-flow MAP fluidized crystallization bed was used. When a decalcification tank was added, calcium ions, but not the magnesium ions, could be selectively precipitated by addition of oxalic acid. Consequently, 80-90% of the phosphorus could be recovered as MAP after pH adjustment of the decalcified fermentation broth. Therefore, after the decalcification treatment, the up-flow MAP fluidized crystallization bed can effectively recover the dissolved phosphorus from wastewaters in the form of MAP with higher purity and yield. © 2021 Chinese Agricultural Chemical Society. All rights reserved.
Subjects
Magnesium ammonium phosphate; Pig manure wastewater; Sedimentation tank; Upflow fluidized crystallization bed
Type
journal article