Premium
Releasing Phosphorus from Calcium for Struvite Fertilizer Production from Anaerobically Digested Dairy Effluent
Author(s) -
Zhang Tianxi,
Bowers Keith E.,
Harrison Joseph H.,
Chen Shulin
Publication year - 2010
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143009x425924
Subject(s) - struvite , phosphorus , effluent , chemistry , fertilizer , calcium , phosphate , enhanced biological phosphorus removal , wastewater , environmental chemistry , environmental engineering , environmental science , biochemistry , activated sludge , organic chemistry
Being a non‐renewable resource and a source of potential water pollution, phosphorus could be recovered from animal manure in the form of struvite (MgNH 4 PO 4 ·6H 2 O) to be used as a slow‐release fertilizer. It was found recently that the majority of phosphorus in anaerobically digested dairy effluent is tied up in a fine suspended calcium‐phosphate solid, thus becoming unavailable for struvite formation. Acidification and use of a chelating agent were investigated for converting the calcium‐associated phosphorus in the digested effluent to dissolved phosphate ions, so that struvite can be produced. The results demonstrated that the phosphorus in the effluent was released into the solution by lowering the pH. In addition, the phosphorus concentration in the solution increased significantly with increased ethylenediaminetetraacetic acid (EDTA) concentration, as EDTA has a high stability constant with calcium. Most of the phosphorus (91%) was released into the solution after adding EDTA. Further, the freed phosphorus ion precipitated out as struvite provided that sufficient magnesium ions (Mg 2+ ) were present in the solution. Furthermore, the phase structure of the solid precipitate obtained from the EDTA treatment matched well with standard struvite, based on the data from X‐ray diffraction analysis. These results provide methods for altering the forms of phosphorus for the design and application of phosphorus‐removal technologies for dairy wastewater management.