High nitrite buildup during nitrification in a rotating disk reactor

Area of Science:

• Environmental Microbiology
• Water Treatment Engineering

Background:

• Incomplete nitrification, characterized by high nitrite accumulation, presents practical advantages in wastewater treatment.
• These advantages include reduced oxygen demand for nitrification, lower organic substrate requirements for subsequent denitrification, and decreased sludge production during denitrification.

Purpose of the Study:

• To experimentally investigate incomplete nitrification and high nitrite formation in a continuous single rotating disk reactor (RDR).
• To compare the performance of the RDR with a modeled continuous completely stirred tank reactor (CSTR) for nitrite accumulation.

Main Methods:

• Experimental study of nitrification in a continuous rotating disk reactor (RDR).
• Modeling of nitrification in a continuous completely stirred tank reactor (CSTR) under various conditions.
• Comparison of nitrite accumulation percentages between RDR and CSTR systems.

Main Results:

• CSTR models predicted high nitrite accumulation (>50%) required pH > 8.5-9.0 at high oxygen levels (>3.5 mg O2/L).
• CSTR models predicted low nitrite accumulation (<5%) at pH 7 and 1 mg O2/L.
• A partially submerged RDR achieved high nitrite accumulation (>75%) at pH 7 and 1.3 mg O2/L, with pH having minimal impact.
• Nitrification occurred under oxygen transport limitation in a totally submerged RDR.

Conclusions:

• Rotating disk reactors (RDRs) are more effective than CSTRs for achieving high nitrite accumulation under typical wastewater treatment conditions.
• Mass transfer limitations in RDRs significantly influence nitrification pathways, promoting nitrite accumulation.
• Incomplete nitrification via high nitrite formation is a viable strategy for optimizing wastewater treatment processes.