Abstract: In order to meet the requirements of Discharge Standard of Water Pollutants in the Yellow River Basin of Henan Province (DB41/2087-2021), the sewage treatment plant of Luoyang Branch needs to be upgraded. It is especially difficult to carry out biochemical treatment of wastewater discharged from the first and second catalytic cracking units during the flue gas desulfurization and denitrification processes?? and neutralized water from the desalting station and so on due to the high salt content, high nitrogen and chlorine content in such kind of wastewater. ?Achieving stable compliance with the new standard for wastewater poses significant challenges?. In this paper, aiming at the characteristics of water quality and quantity of difficult-to-treat high-salt nitrogen wastewater such as the aforementioned wastewater, a series of optimization and upgrading measures were implemented in 2022 based on the original process flow, achieving a successful first-time startup of the revamped facilities and ensuring stable compliance of effluent discharge with the new local standards.

Key words: biological methods, high-salt wastewater, denitrification