Effect of COD/N ratio and salinity on the performance of sequencing batch reactors

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Microbiology

Background:

• Wastewater treatment faces challenges with organic and nitrogen removal, especially in saline conditions.
• Sequencing Batch Reactors (SBRs) are versatile systems for treating various wastewater types.
• Understanding operational parameters is crucial for optimizing SBR performance.

Purpose of the Study:

• To investigate the impact of COD/N ratio and salt concentration on organic and nitrogen removal in SBRs.
• To evaluate SBR performance with both synthetic and real fish market wastewater.
• To determine the influence of solids retention time (SRT) and aeration time on treatment efficiency.

Main Methods:

• Utilized three bench-scale SBRs with synthetic wastewater and one with fish market wastewater.
• Varied chemical oxygen demand to nitrogen (COD/N) ratios (3-6) and salt concentrations (0.5-2%).
• Adjusted operating schedules, including solids retention time (SRT, 20-100 days) and aeration time (4-10 hours).

Main Results:

• Achieved over 95% chemical oxygen demand (COD) removal for synthetic wastewater across all tested conditions.
• Higher COD/N ratios (>90%) favored nitrogen removal, while increased salt concentration reduced nitrification efficiency.
• Real fish market wastewater showed significant COD (>80%) and nitrogen (>40%) removal, attributed to biomass acclimatization.

Conclusions:

• SBRs demonstrate high efficiency in removing COD from wastewater.
• Optimizing COD/N ratio is key for effective nitrogen removal, while salinity poses a challenge to nitrification.
• Biomass acclimatization is vital for successful treatment of complex, real-world saline wastewater in SBRs.