Soluble microbial products (SMPs), as secondary pollutants, comprise a dominant percentage of residual COD in effluents from biological wastewater treatment processes. They can also be regarded as substitute electron sources if the in-situ utilization of SMPs could be achieved. In this study, the fate of SMPs in a sequencing batch reactor (SBR) treating artificial municipal sewage was investigated. Based on the regular SBR operation mode, a 3 h extension of anoxic phase was provided to promote SMP degradation. Meanwhile, the denitrification efficiencies achieved by adopting SMPs and influent organic substrates (IOSs) were compared to reveal the significant contribution of the in-situ utilization of SMP for nitrogen removal. Approximately 21.1 mg N/L of total nitrogen (TN) was removed over a single cyclic reaction, in which only 13.2 mg N/L was removed via IOS-dependent denitrification. The remaining 7.9 mg N/L of TN was realized via SMP-dependent denitrification, including 3.9 mg N/L by utilization-associated products and 4.0 mg N/L by biomass-associated products, which significantly contributed 37.4% of TN removal. The aromatic proteins, tryptophan-like proteins, polysaccharides and fulvic acids contained in SMP were the potential precursors of electron donors to support SMP-dependent denitrification process.
Keywords: Aerobic-anoxic SBR; In-situ utilization; Nitrogen removal; SMP-dependent denitrification; Soluble microbial products.
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