Solid-phase denitrification in high salinity and low-temperature wastewater treatment

Area of Science:

• Environmental Science
• Microbiology
• Water Treatment Engineering

Background:

• Wastewater nitrogen removal is challenging under high salinity and low temperatures.
• Solid-phase denitrification (SPD) offers a potential solution by providing a stable carbon source.
• Existing methods struggle with efficiency in adverse environmental conditions.

Purpose of the Study:

• To establish and evaluate a solid-phase denitrification (SPD) biofilm reactor for treating high salinity and low-temperature wastewater.
• To investigate the impact of low temperature on microbial communities and their denitrification pathways.
• To assess the production of extracellular polysaccharides and soluble microbial products under stress conditions.

Main Methods:

• Established an SPD biofilm reactor using halophilic sludge and poly (butanediol succinate) (PBS) granules.
• Operated the reactor at low temperatures (15°C) and assessed total nitrogen removal efficiency (TNRE).
• Analyzed microbial community composition, gene expression (nirS, narG), and soluble microbial products (SMPs) using fluorescence spectroscopy and PARAFAC.

Main Results:

• Achieved over 96% TNRE at low temperatures, demonstrating the efficacy of SPD.
• Observed increased production of extracellular polysaccharides at low temperatures.
• Identified shifts in dominant denitrifying bacteria and highlighted the roles of nirS and narG genes in low-temperature denitrification. SMP analysis indicated increased protein content.

Conclusions:

• Solid-phase denitrification (SPD) is a viable and efficient technology for treating high salinity and low-temperature wastewater.
• Low temperatures induce specific microbial community shifts and influence denitrification gene expression.
• The study provides valuable insights for applying SPD in challenging wastewater treatment scenarios.