Phosphorus Removal from Hoggery Sewage Using Natural Calcium Carbonate
For the treatment of hoggery sewage, an attempt was made to develop a phosphorus removal technique by using natural calcareous materials whose products can be restored to farmland as phosphate materials with minimal waste, at a low cost and with easy management. The results of tests on packed materials passing through a water column under the same conditions reveled that the efficiency of phosphorus removal characteristics was in the order of Sakhalin surf clam > oyster seashell, scallop seashell > coral sand > fossilized seashell > dolomite for twice the daily amount of passed water. In brief, young calcareous sources originating from marine Conchifera were superior as dephosphorization materials. The mechanism involved in phosphorus removal of natural calcareous materials was neither absorption to materials nor crystallization but a direct replacement reaction from carbonates to phosphates. Since the produced salts were CaHCO3 and Ca4H (PO4) 3 with low Ca/P and OH/P ratios, highly valuable phosphates for fertilizer were obtained. Since the pH of effluents was 8.5 at the maximum and lies within the legal standard range, the dissolution of carbonates and the production of phosphates prevent clogging and the total cost is low. If the TOC and TIC concentrations of influents are high, the TIP concentration in the effluents easily increases. However, it was demonstrated that 24 h aeration in the presence of sludge results in a decrease of the pH due to accelerated nitrification and that the release of supersaturated CO2 into the atmosphere can lower the TIC significantly.
|作成者||Makoto TAKEUCHI Michio KOMADA|