Optimization to maximize nitrogen removal and microbial diversity in PVA-gel based process for treatment of municipal wastewater

In this study, a novel integrated system (MBBR, anoxic and oxic) was developed to enhance carbon and nitrogen removal for treating raw municipal wastewater. Poly Vinyl Alcohol (PVA) gel beads were used as a biomass carrier in MBBR. The system was operated for more than a year at seasonally varied temperatures (10 ºC to 30 ºC) at HRT of 6, 5 and 4.4 h, respectively with an average of 9 days SRT. High efficiency of the system was recorded for removal of Total-N (> 90%), COD (> 90%), BOD (> 95%) and TSS (> 96%) at all three HRTs, but 5 h HRT was found optimum at low temperature range (≤10 ºC). 16S rRNA analysis of the immobilized biomass revealed the presence of ammonia oxidizers (21 %), sulfate reducing bacteria (14 %), nitrite reducers (7 %), and denitrifiers (7 %). Organic compounds degrader (Alpha proteobacteria), includes the species of ammonia oxidizer (Nitrosomonas, Nitrosococcus), while the species of Pseudomonas Flavobacterium and Beta proteobacteria class were responsible for the denitrification process. A significant amount of extracellular polymeric substance (EPS) content was extracted; 171.2 mg and 150 mg from 1 g of volatile solids of attached biomass on PVA-gel beads and suspended biomass, respectively. The results demonstrated that the PVA-gel media based integrated system was capable of enhancing the pollutant removal efficiency, especially for the carbon and nitrogen removal from the wastewater.