Effect of COD/N and COD/P ratios on the PHA transformation and dynamics of microbial community structure in a denitrifying phosphorus removal process

Abstract

BACKGROUND: A lab-scale anaerobic-anoxic/nitrification (A 2 N) two-sludge sequencing batch reactor (SBR) system was operated to assess the relationship among intracellular polymer conversions, bacterial population dynamics and nutrient removal performance in response to the varying influent COD/N/P. RESULTS: Complete nutrient removal was achieved in the A 2 N-SBR in Run 3 where the COD/P and COD/N were 20.6 and 6.9, respectively. This coincides well with the highest P release/HAc uptake ratio occurring in Run 3, confirming high abundance of denitrifying phosphorus accumulating organisms (DPAOs) in the biomass. Under the stress of N or P limitation, more poly-β-hydroxyalkanoates (PHA) was synthesized, with the increasing proportion of poly-hydroxyvalerate (PHV) in PHA. The population biodiversity decreased with increasing carbon loading when P loads were maintained at constant levels, and recovered to the initial level after P loading decreased. CONCLUSIONS: Increasing COD/P promoted anaerobically synthesized PHA amount and favored P removal. Also, PHB seems to be the crucial internal carbon source relating to P release and uptake, whereas high nitrogen and P removal efficiencies always relate to a high proportion of PHV in PHA. Increasing carbon loading led to a decreased biodiversity of the community structure but favored higher PAO enrichments, if only P loading is not limited.

Anoxic–aerobic SBR system for nitrate, phosphate and COD removal from high-strength wastewater and diversity study of microbial communities

“…Total DNA was isolated from MLSS (during steady state) with Fast DNA Spin Kit, MP Biomedicals [28]. Lysing Matrix and chaotropic buffer available in the kit were used for the optimal homogenization of the sludge sample.…”

Modeling sequential ammonia oxidation kinetics in enriched nitrifying microbial culture

“…The concept of enriched culture should not be interpreted literally; it was tailored for the specific objectives of this study, meaning a microbial population with higher nitrifier fractions than the conventional nitrifying biomass sustained with the conventional characteristics of domestic sewage, i.e. more explicitly, creating a growth environment with a reduced COD/N ratio of around 2, compared with the COD/N ratio of 8–10 in domestic sewage …”

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

“…Throughout the observation period, the processes of denitrification and SND were exhibited successfully for nitrogen removal, and both denitrifying phosphorus removal and oxic phosphorus uptake were noticeable. Wang et al (2013) achieved complete phosphorus removal in the anaerobic-anoxic/nitrification (A2N) two-sludge SBR, where the C/P ratio was 20.6. Park et al (2011b) considered that ozonolysate of excess sludge as a carbon source could be enhanced for phosphorus removal with a C/P ratio of 42-57 using a modified intermittently decanted extended aeration process.…”