The coupling use of advanced oxidation processes and sequencing batch reactor to reduce nitrification inhibition of industry wastewater: Characterization and optimization

The excess emission of ammonia nitrogen is a common issue encountered by many industry wastewater treatment plants, due to the elevated concentrations and toxicities of compounds released from a large number of industries which might inhibit the growth of nitrifying bacteria. In this work, we are aiming at addressing the above issue raised by an industry wastewater treatment plant and elucidating the nitrification inhibitory mechanisms. A straight-forward and reliable method i.e., respirometry, was developed for the characterisation of nitrification inhibition. The pretreatment methods of Fenton and ozone oxidations and iron carbon micro electrolysis have been attempted to reduce the nitrification inhibition and the former two turned out to be effective. The nitrification inhibition rate (NIR) of the wastewater after Fenton oxidation was reduced from 87% to 13.6% with the optimized condition (pH= 3.0, H2O2 dosage of 14.7 mM, Fe2+ dosage of 4.90 mM, and reaction time of 20 min). The optimal parameters for ozonation were: pH = similar to 8.2 (original pH of wastewater), reaction time of 25 min (equivalent to an ozone dosage of 381 mg/L), under which the NIR was declined to 12.7%. The nitrification inhibition might be attributed to the presence of compounds with hydrophobic properties, high molecular weight, and aromatic and unsaturated structures in industry wastewater. The coupling use of Fenton-SBR and ozone-SBR achieved NH3-N removal efficiency of 98% and 93%, respectively. The effluent NH3-N finally met with the Integrated Wastewater Discharge Standard (DB31/199-2009).