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 degrees C to 30 degrees C) 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 degrees C). 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. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

A novel integrated system was developed to enhance carbon and nitrogen removal for treating raw municipal wastewater, showing high removal efficiency for Total-N, COD, BOD, and TSS at all tested HRTs, with 5-hour HRT being optimal for low temperatures. Analysis of the immobilized biomass revealed the presence of various bacteria responsible for different nitrogen removal processes, indicating the system's capability to enhance pollutant removal efficiency, especially for carbon and nitrogen removal from wastewater.