Microbiology and biochemistry of the enhanced biological phosphate removal process

This paper reviews microbiological and biochemical aspects of the enhanced biological phosphate removal (EBPR) process. The discussion includes: microorganisms responsible for EBPR, isolation of polyphosphate accumulating organisms (PAOs), microbial diversity of the EBPR sludge, biochemical metabolisms of PAOs, energy budget in PAOs metabolism, denitrification by PAOs, glycogen accumulating non-poly-P organisms (GAOs), etc. Since pure cultures which possess complete characteristics of PAOs have not been isolated yet, the biochemical mechanism cannot be definitively described. The criteria to obtain a pure culture isolate are proposed. Based on the review, essential characteristics of PAOs are summarized in a table and directions for future research are identified.