Full-scale demonstration of a floating seal for enhanced biological nutrient removal in a sequencing batch reactor establishing chemical-free environment in wastewater treatment at low carbon source availability

ABSTRACT

Due to the cyclical nature and changing water levels in the sequencing batch reactor (SBR), oxygen diffusion and utilization can be difficult to control particularly in light of the need to conserve the limited quantity of carbon source required to optimize biological nutrient removal. During the fill period, oxygen penetration may be undesirable since heterotrophic and autotrophic organisms cause a reduction in the readily biodegradable carbon source (rbCOD). This carbon source is essential and often limited in the anaerobic and anoxic periods. As a consequence, unwanted oxygen penetration can hinder efficient biological phosphorus and nitrogen removal. The purpose of the present research was to verify the advantage of a floating seal on the continuously moving surface of an SBR reactor to minimize undesirable oxygen penetration. In the floating seal-covered SBR both nitrification and denitrification efficiency proved to be higher due to insulation, and even during wintertime biological phosphorus removal met target removals without chemical dosing. The SVI values in the two SBR trains proved to be close to each other, despite the high difference in chemical dosing. Having experienced the higher efficiency of the seal-covered train, microbiome compositions of the two differently operated systems were investigated to determine potential differences via 16S rRNA gene amplicon sequencing experiments. In the samples taken from the seal-covered system, higher ratios of fermentative bacteria and phosphate accumulating organisms (PAOs) as well as glycogen accumulating organisms (GAOs) could be observed as compared to the samples deriving from the uncovered system.

Highlights

• Seal-covering the periodically decreasing open water surface increased SBR efficiency

• Seal-covering the open water surface increased nitrification efficiency by insulation

• No chemical dosing was necessary for phosphorous removal in the Test system

• Metagenome investigations provided almost doubled amount of fermentative bacteria

• Production of GAOs indicated nutrient deficiency due to phosphorous removal.

GRAPHICAL ABSTRACT

KEYWORDS:

• SBR reactor
• floating seal
• nutrient removal
• microbiome compositions
• chemical savings

Acknowledgements

The project was supported by the grants from National Research, Development and Innovation Office of Hungary (K119493, K135231, VEKOP-2.3.2-16-2017-00013, NKP-2018-1.2.1-NKP-2018-00005), and by the BME-Biotechnology FIKP grant of EMMI (BME FIKP-BIO) to BGV. The contribution of Budapest University of Technology and Economics and UTB Environtec Ltd. as well as cooperation of Karsai Holding Ltd. in establishing the floating seal and technical support of József Simon are highly acknowledged. The contribution of Professor Timothy Ellis (Iowa State University, Department of Civil, Construction and Environmental Engineering) through advising appropriate formulation for better understanding of differences is highly acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Additional information

Funding

This work was supported by grants from National Research, Development and Innovation Office of Hungary: [Grant Number K119493,K135231,NKP-2018-1.2.1-NKP-2018-00005,VEKOP-2.3.2-16-2017-00013]; BME-Biotechnology FIKP grant of EMMI: [Grant Number BME FIKP-BIO].