Coagulation of phosphorus: effects of Al(III) species (Al-a, Al-b, and Al-c)

摘要

Phosphorus removal from a secondary sewage effluent using aluminum salt coagulants, such as alum and prehydrolyzed metal salts (PACls with different basicity values), was investigated in this study. It was observed that ortho phosphate was easier to remove by coagulation than other P fractions. The optimum pH for P removal was in the range of 5.0-6.6 using alum and in of 4.5-5.5 using PACl. Applying Ferron assay test, Al species in the coagulants were classified as Al-a (monomeric Al), Al-b (polymeric Al), and Al-c (colloidal and precipitated Al). The results obtained by performing jar tests indicated that phosphorus removal was correlated well with the distribution of Al species in the coagulants. The higher the Al-a content in PACl, the higher the P removal efficiency would be. Positive effects of Al-a for the removal of P might be due to high ability of Al monomer in forming the Al(OH)(x)(