Advanced treatment of digested restaurant wastewater using a combination of anaerobic/oxic unit, Fenton, and a biological aerated filter in pilot-scale treatment

Abstract Biological treatment is the most economical and practical wastewater treatment method; however, for highly concentrated organic wastewater, such as digested restaurant wastewater, a single biological treatment method does not meet the discharge requirements. An anaerobic/oxic-Fenton-biological aerated filter (A/O-Fenton-BAF) system was employed to treat digested restaurant wastewater with a high concentration of organic compounds in a pilot-scale experiment. The degradation process and mechanism of chemical oxygen demand (COD), total nitrogen (TN), NH4+-N, NO3−-N, and dissolved organic nitrogen (DON) in each stage of the process were analyzed. Gas chromatography-mass spectrometry and fluorescence spectrum characteristics were also studied. The average removal rate of both COD and NH4+-N in the entire process was 98%. The removal rates of COD, TN, NH4+-N, and DON reached 78.5%, 66.0%, 95.3%, and 51% using the A/O unit. Although Fenton was ineffective in the removal of nitrogenous organic and inorganic substances, the fluorescence spectra and GC-MS showed that the nitrogen-containing organic compounds of macromolecules were transformed into small molecules after the Fenton reaction and could be removed by the BAF unit. The removal rate of DON was up to 24.3% in the Fenton + BAF process, which reduced the TN concentration in the effluent. The dominant species in all biological processes were nitrifying and organic matter-decomposing bacteria. This study provides key data for the design of a full-scale system for treating digested restaurant wastewater.