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J Environ Sci (China). 2014 Apr 1;26(4):765-74. doi: 10.1016/S1001-0742(13)60469-6.

Enhanced struvite recovery from wastewater using a novel cone-inserted fluidized bed reactor.

Author information

1
UNEP-Tongji Institute of Environment for Sustainable Development, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: awokeguadie@gmail.com.
2
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: siqingxia@gmail.com.
3
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
4
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: zhiqiang@tongji.edu.cn.
5
Department of Civil and Environmental Engineering, University of California, Berkeley, 629 Davis Hall #1710, Berkeley, CA 94720-1710, USA.

Abstract

The feasibility of struvite recovery at low (12.5 mg/L) and high (120 mg/L) phosphorus concentrations was studied by constructing a novel fluidized bed reactor with cones (FBRwc) and without cones (FBRwoc). The crystallization process was continuously operated for 133 days under different hydraulic retention times (HRT = 1-10 hr), pH (7.5-10), and molar ratios of Mg/P (0.75-1.75), N/P (1-10) and Ca/Mg (0-2). The optimum operating conditions of HRT, pH, Mg/P and N/P molar ratios were found to be 2 hr, 9, 1.25, and 7.5, respectively. Under these optimum conditions, the phosphorus precipitation efficiencies of FBRwc were 93% for low and 98% for high phosphorus influent; however, the efficiencies were 78% and 81% for FBRwoc, respectively. Due to crystal losses at each junction (17%-31%), the crystal recovery efficiency of FBRwoc was relatively low (47%-65%) for both influent concentrations. However, the losses were minimal in FBRwc, which showed 75% and 92% crystal recovery for low and high phosphorus concentrations, respectively. At low calcium concentration, crystal chemical analysis showed the product to be pure struvite (> 99%). The scanning electron microscope and X-ray diffraction results further confirmed that the crystal recovered from FBRwc contained pure struvite, which could be considered a high quality fertilizer. Except HRT, all parameters (pH, Mg/P, N/P and Ca/Mg) were found to be influencing factors for FBRwc performance. Overall, inserting cones in each part of the reactor played a significant role in enhancing struvite recovery from a wide range of phosphorus-containing wastewater.

KEYWORDS:

fluidized bed reactor; phosphorus; recovery; struvite; wastewater

PMID:
25079406
DOI:
10.1016/S1001-0742(13)60469-6
[Indexed for MEDLINE]

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