Optimization of the real-time control strategy in petroleum-refining catalyst production wastewater treatment with shortcut nitrification

Abstract

The characteristics of petroleum-refining catalyst production wastewater are high salinity, high ammonia concentration, and very low C/N ratio. When wastewater is treated with shortcut nitrification in a sequencing batch reactor, only nine cycles are required to reach a nitrite accumulation ratio (NAR) of 85.1%. A high NH₄⁺–N removal efficiency and steady NAR are achieved in the subsequent stable operation stage. However, the DO and pH break points do not always represent the end of ammonia oxidization. In this study, experiments were conducted to determine why break points appear on DO and pH curves. Results show that second break points appear and that pH is a more credible control parameter than DO is. From the start-up and steady running period, a pH controlled at 8.0 to 8.3 is found to be most conducive for nitrite accumulation, and the effluent quality is better than that involving treatment in a low pH condition.