An evaluation of the performance and optimization of a new wastewater treatment technology: the air suction flow-biofilm reactor

Abstract

In this laboratory study, a novel wastewater treatment technology, the air suction flow-biofilm reactor (ASF-BR) – a sequencing batch biofilm reactor technology with a passive aeration mechanism – was investigated for its efficiency in removing organic carbon, nitrogen and phosphorus, from high-strength synthetic wastewaters. A laboratory-scale ASF-BR comprising 2 reactors, 350 mm in diameter and 450 mm in height, was investigated over 2 studies (Studies 1 and 2) for a total of 430 days. Study 1 lasted a total of 166 days and involved a 9-step sequence alternating between aeration, anoxic treatment and settlement. The cycle time was 12.1 h and the reactors were operated at a substrate loading rate of 3.60 g filtered chemical oxygen demand (COD_f)/m² media/d, 0.28 g filtered total nitrogen (TN_f)/m² media/d, 0.24 g ammonium-nitrogen (NH₄-N)/m² media/d and 0.07 g ortho-phosphate (PO₄-P)/m² media/d. The average removal rates achieved during Study 1 were 98% COD_f, 88% TN_f, 97% NH₄-N and 35% PO₄-P. During Study 2 (264 days), the unit was operated at a loading rate of 2.49 g COD_f/m² media/d, 0.24 g TN_f/m² media/d, 0.20 g NH₄-N/m² media/d and 0.06 PO₄-P/m² media/d. The energy requirement during this study was reduced by modifying the treatment cycle in include fewer pumping cycles. Removal rates in Study 2 averaged 97% COD_f, 86% TN_f, 99% NH₄-N and 76% PO₄-P. The excess sludge production of the system was evaluated and detailed analyses of the treatment cycles were carried out. Biomass yields were estimated at 0.09 g SS/g COD_{f, removed} and 0.21 g SS/g COD_{f, removed} for Studies 1 and 2, respectively. Gene analysis showed that the use of a partial vacuum did not affect the growth of ammonia-oxidizing bacteria. The results indicate that the ASF-BR and passive aeration technologies can offer efficient alternatives to existing technologies.

Keywords:

• biofilm
• low energy
• sequencing batch biofilm reactor
• high-strength synthetic wastewater
• biofilm analysis

Acknowledgements

The authors acknowledge the financial support provided by Enterprise Ireland who funded this research project (Grant No. CFTD-2008-315). The authors also thank M. Barrett and K. Kilroy for kindly providing bacterial and amoA plasmids for real-time PCR experiments. This publication has also emanated from research conducted with the financial support of the European Research Council (ERC Starting Grant No: 2613303 ‘C-BIOTECH’).

Disclosure statement

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