[Effect of osmotic pressure on nitrification]
1Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, China. pzheng@zju.edu.cn
Summary
High osmotic pressure significantly impacts nitrification in bioreactors, with critical levels identified. Interestingly, osmotic stress can initially stimulate nitrifying activity, and potassium addition mitigates these effects.
Area of Science:
- Environmental microbiology
- Biochemical engineering
Context:
- Nitrification is a crucial process in wastewater treatment.
- Internal-loop air-lift bioreactors are commonly used for nitrification.
- Understanding the impact of environmental factors like osmotic pressure is vital for optimizing bioreactor performance.
Purpose:
- To investigate the effect of varying osmotic pressure on the efficiency of ammonia conversion during nitrification.
- To identify the critical osmotic pressure threshold that impairs nitrification.
- To analyze the morphological and structural changes in nitrifying bacteria under osmotic stress.
Summary:
- Nitrification efficiency remained high (93-100%) until osmotic pressure reached 18.8 x 10(5) Pa.
- A significant drop in ammonia conversion to 69.2% occurred at 19.2 x 10(5) Pa, indicating a critical threshold.
- Osmotic stress caused bacterial population simplification, reduced cell size, and altered cell structure, which were reversible upon stress removal.
- Potassium addition was found to alleviate the negative effects of osmotic pressure on nitrification.
- Specific ammonia conversion rates were initially stimulated by osmotic stress, increasing significantly.
Impact:
- Identifies a critical osmotic pressure range for air-lift nitrifying reactors, crucial for operational control.
- Reveals the reversible cellular mechanisms by which nitrifying bacteria respond to osmotic stress.
- Suggests potassium as a potential agent to enhance resilience and performance of nitrifying bioreactors under osmotic challenges.
- Provides insights into microbial adaptation strategies in high-salinity or high-solute wastewater environments.
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