Recovery of phosphorus as struvite from sewage sludge ash

• Published in: Journal of environmental sciences (China) Vol. 24; no. 8; pp. 1533 - 1538
• Main Authors: Xu, Huacheng, He, Pinjing, Gu, Weimei, Wang, Guanzhao, Shao, Liming
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2012; State Key Laboratory of Pollution Control and Resource Reuse,College of Environmental Science and Engineering,Tongji University,Shanghai 200092,China
• Subjects: Ashes; bioavailability; cation exchange; Chemical Precipitation; fertilizers; heavy metal; Heavy metals; hydrochloric acid; Incineration; leaching; magnesium ammonium phosphate; Magnesium Compounds - isolation & purification; Phosphates - isolation & purification; Phosphorus; Phosphorus - chemistry; Phosphorus - isolation & purification; phosphorus recovery; Precipitation; Recovery; Reserves; Rock; rock phosphate; Sewage - chemistry; sewage sludge ash; Sludge; sludge ash; Struvite; X-ray diffraction; X-射线衍射分析; 污水; 污泥灰; 磷回收; 磷矿石; 重金属含量; 阳离子交换树脂; 鸟粪石; phosphorus recovery; X-ray diffraction; heavy metal; struvite; sewage sludge ash
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/S1001-0742(11)60969-8

Phosphorus (P) is an element vital for all living organisms, yet the world's reserves of phosphate rock are becoming depleted. This study investigated an effective P recovery method from sludge ash via struvite precipitation. Results showed that more than 95% of the total P content was extracted from sludge ash by applying 0.5 mol/L HCl at a liquid/solid ratio of 50 mL/g. Although heavy metal leaching also occurred during P extraction, cation exchange resin efficiently removed the heavy metals from the P-rich solution. Orthogonal tests showed that the optimal parameters for P precipitation as struvite would be a Mg:N:P molar ratio of 1.6:1.6:1 at pH 10.0. X-ray diffraction analysis validated the formation of struvite. Further investigations revealed that the harvested precipitate had a high struvite content (97%), high P bioavailability (94%), and low heavy metal content, which could be considered a high quality fertilizer.