High rate nitrogen removal by the CANON process at ambient temperature

Nitrogen removal from wastewater remains a significant challenge in environmental engineering. Traditional methods often require high energy input and chemical use. Recent studies have explored autotrophic processes that combine nitrification and denitrification in a single system. The CANON process, which integrates ammonium oxidation and anaerobic ammonium oxidation, has emerged as a promising alternative. However, maintaining stable performance under ambient conditions is still a challenge. Previous research has shown that controlling dissolved oxygen and providing inorganic carbon are essential for microbial activity. Yet, the long-term stability of CANON systems at room temperature is not well established. This gap motivated the investigation of CANON under ambient conditions. The study aimed to test whether stable nitrogen removal could be achieved without temperature control.

The goal was to evaluate the feasibility of the CANON process at ambient temperature. Researchers sought to determine if stable nitrogen removal could be maintained without temperature regulation. They focused on the role of microbial communities in forming functional granular sludge. The study aimed to assess how dissolved oxygen and inorganic carbon levels affect system performance. By operating the reactor for over 100 days, the team intended to observe long-term stability. The investigation also aimed to confirm the presence of ammonium-oxidizing and Anammox bacteria. Researchers wanted to verify if granular sludge formation supports efficient nitrogen removal. This work sought to provide evidence for the practical application of CANON in real-world settings.

The experiment used a reactor fed with synthetic inorganic wastewater containing ammonium. The system was operated for 106 days at ambient temperature. Dissolved oxygen levels were strictly controlled to favor specific bacterial activity. Inorganic carbon was added to the influent to support microbial metabolism. The reactor was monitored for nitrogen removal rates and microbial community changes. Morphological analysis of granular sludge was performed to assess structure. Bacterial community composition was analyzed using standard microbiological techniques. The study combined operational data with microbial analysis to evaluate system performance.

Nitrogen removal rates reached up to 1.4 kg N per cubic meter per day. These rates were maintained consistently over the 106-day period. The reactor operated successfully at ambient temperature without heating. Granular sludge with distinct aerobic and anaerobic zones formed in the reactor. Ammonium-oxidizing and Anammox bacteria were present in sufficient quantities. Inhibiting nitrite-oxidizing bacteria was confirmed through microbial analysis. The system achieved stable performance without temperature regulation. These findings suggest CANON can function effectively under normal environmental conditions.

The CANON process can achieve stable nitrogen removal at ambient temperature. The presence of ammonium-oxidizing and Anammox bacteria supports this process. Granular sludge formation enhances system efficiency and stability. Controlling dissolved oxygen and adding inorganic carbon are key operational factors. The study confirms that CANON can function without temperature regulation. This finding suggests potential for real-world applications in wastewater treatment. The results align with the authors' hypothesis about microbial cooperation in CANON systems. These findings may guide future efforts to optimize CANON under natural conditions.