Simultaneous removal of ammonia, P and COD from anaerobically digested piggery wastewater using an integrated process of chemical precipitation and air stripping

摘要

The paper presented an efficient integrated physicochemical process, which consists of chemical precipitation and air stripping, for the simultaneous removal of NH_3-N, total P and COD from anaerobically digested piggery wastewater. In the integrated process, Ca(OH)_2 was used as the precipitant for NH_4~+, PO_4~(3-) and organic phosphorous compounds, and as the pH adjuster for the air stripping of residual ammonia. The possibility of the suggested process and the related mechanisms were first investigated through a series of equilibrium tests. Laboratory scale tests were carried out to validate the application possibility of the integrated process using a new-patented water sparged aerocyclone reactor (WSA). The WSA could be effectively used for the simultaneous removal of NH_3-N, total P and COD. 3 g/L of Ca(OH)_2 is a proper dosage for the simultaneous removal. The simultaneous removal of NH_3-N, total P and COD in the WSA reactor could be easily optimized by selecting a proper air inlet velocity and a proper jet velocity of the liquid phase. In all the cases, the removal efficiencies of the NH_3-N, total P and COD were over 91%, 99.2% and 52% for NH_3-N, total P and COD, respectively. The formed precipitates in the process could be easily settled down from the suspension system. Therefore, the integrated process provided an efficient alternative for the simultaneous removal of NH_3-N, total P and COD from the wastewater.