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

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, 350mm in diameter and 450mm 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 12.1h and the reactors were operated at a substrate loading rate of 3.60g filtered chemical oxygen demand (COD_f)/m² media/d, 0.28g filtered total nitrogen (TN_f)/m² media/d, 0.24g ammonium-nitrogen (NH₄-N)/m² media/d and 0.07g 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 2.49g COD_f/m² media/d, 0.24g TN_f/m² media/d, 0.20g 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 0.09g SS/g CODf, removed and 0.21g SS/g CODf, 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.