A study on phosphate recovery from a biofilter blowdown in a poultry farm

• Main Authors: Ming-jhong Hu, 胡明中
• Other Authors: none
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/69185801406168304325

碩士 === 國立臺灣科技大學 === 化學工程系 === 97 === The poultry or large livestock farms always produce odor in composting of fecal matters. Biofilters are usually used for controlling odorous gases, such as ammonia, methylamine, sulfide and volatile organic compound. Overdue milk and phosphate are usually added to the biofilter and provide the nutrient for biofilm growth. In the present study, recovery of nutrients was assessed from the blowdown of a biofilter from a large chicken farm in Tainan containing 20,000 mg/L of phosphate, 8,000 mg/L of ammonium and 835.8 mg/L of nitrate. Both calcium and magnesium salts were used as precipitants, respectively. Effects of pH and molar ratio of metal to phosphate were examined, and the experimental results were compared with modeling data as predicted by PHREEQC. Results revealed that maximum removal efficiencies of phosphate were 98% and 99% when using MgCl2 and CaCl2, respectively. The precipitates are mostly bobierrite (Mg3(PO4)2•8H2O) and hydroxyapatite (Ca5(PO4)3OH, HAP). Solution pH is also a significant parameter in the process. In general, removal efficiency of phosphate increases with increasing pH value. The favorable pH for magnesium and calcium salts are approximately at pH 9 and 10, respectively. Excess magnesium and ammonium concentrations seem to induce the formation of struvite (MAP) at pH 8.5.