Nitrous oxide emission by denitrifying phosphorus removal culture using polyhydroxyalkanoates as carbon source

Area of Science:

• Environmental Microbiology
• Biogeochemical Cycles

Background:

• Nitrous oxide (N2O) is a potent greenhouse gas with emissions often linked to denitrification.
• Internal carbon sources, like polyhydroxyalkanoates (PHA), have shown varied effects on N2O production during denitrification.

Purpose of the Study:

• To compare N2O production using internal PHA versus external acetate as carbon sources in denitrifying phosphorus removal cultures.
• To investigate the impact of carbon source type and chemical oxygen demand-to-nitrogen (COD/N) ratios on N2O emissions.

Main Methods:

• Culturing denitrifying phosphorus removal organisms.
• Controlled experiments varying carbon sources (PHA vs. acetate) and COD/N ratios.
• Monitoring N2O production and reduction rates.

Main Results:

• At low COD/N ratios, external acetate led to higher N2O production than PHA.
• At high COD/N ratios, N2O reduction rates were similar across carbon sources.
• N2O reduction rates were generally higher with PHA.
• PHA consumption appeared to be the rate-limiting step for N2O reduction.

Conclusions:

• External carbon sources may be competitively utilized by different microbial pathways when insufficient for complete denitrification.
• PHA utilization is a potentially significant factor in controlling N2O emissions during denitrification by DPAOs.