Simultaneous removal of nitrogen and phosphorus using anoxic phosphorus uptake

Abstract

A number of BNR processes have been developed, in addition to various biochemical models proposed in the past decade (Comeau et al., 1986; Mino et al., 1995; Smolders et al., 1995; Wentzel et al., 1986; Jeon and Park, 2000). Nevertheless, the biological mechanism and effecting factors for nutrient removal at the anoxic stage are not completely understood. In this study, the interrelationship and the characteristics of microorganisms as the effecting factors of phosphorus release, such as organic matter and nitrate under anoxic state were investigated. In addition, effects of nitrate and organic matter on phosphorus uptake in the anoxic state were investigated; especially a possible role for denitrifying phosphorus removing bacteria (DPB). Next, the fraction of DPB in the anoxic stage was measured and the species of microorganisms in the anoxic stage were identified using the PCR-DGGE method. Finally, the Daewoo nutrient removal (DNR) process was modelled using ASM No. 2d. From the results of respirometric measurements, it could be concluded that fraction of readily biodegradable substrate, slowly biodegradable substrate, inert soluble substrate and inert particular substrate were about 10-16%, 32-50%, 1-8% and 2-47%, respectively. The biosorption efficiency of the influent sewage with previous composition was 70-85% within 30-min anaerobic contact. The first COD sequestration rate by the physico-chemical reaction before 5 minutes was 4.8 to 9.6 $sec^{-1}$, while the second reaction rate by the biological reaction after 5 minutes was in the range of 1.68 to 2.16 $sec^{-1}$. However, after 30min, SCOD in the batch reactor increased and it was supposed that desorption of a part of the colloidal organic matter pre-sorbed on the activated sludge flocs was evidenced. As the dissolved organic carbon (DOC) of classified molecular weight with contact time, DOC smaller than 1kDa, which is 80% of total DOC, decreased from 76.5 to 5.1 mg/l before 30 minute but, after 30 ...