In this Study, Polyhydroxyalkanoate (PHA) was used as the Carbon Resource in. post-treatment process (Phase 2). PHA, a kind of intracellular polyester, is synthesized by bacteria as carbon and energy storage. source, which can be completely biodegraded into carbon dioxide. and water without any secondary pollution. Nitrogen and phosphorus components can also be consumed when PHA is used for. bacterial growth. Comprehensively, the nitrate and phosphate in. the surface water could be assimilated as the microbial components during this process. Thus, organic matters, nitrogen and. phosphorus would be degraded to achieve the purification of. surface water.