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Nitrite oxidation inhibition by hydroxylamine: experimental and model evaluation.
P Lek Noophan1, L A Figueroa, J Munakata-Marr
1Department of Environmental Science, Faculty of Science, Silpakorn University, Nakhon-pathom Province, Thailand 73000. pongsak@su.ac.th
Summary
This study introduces a cost-effective biological nitrogen removal method by inhibiting nitrite oxidation using hydroxylamine (HM). Low HM concentrations effectively stop nitrite oxidation without harming other key bacteria, reducing biomass and carbon needs.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
- Biogeochemical cycles
Background:
- Biological nitrogen removal is crucial for wastewater treatment.
- Current methods face challenges with high costs due to biomass production and carbon requirements.
- Inhibiting nitrite oxidation offers a potential strategy to optimize nitrogen removal efficiency and reduce operational expenses.
Purpose of the Study:
- To investigate the efficacy of hydroxylamine (HM) in inhibiting nitrite oxidation during biological nitrogen removal.
- To determine the optimal HM dosages and conditions for selectively inhibiting nitrite oxidizers.
- To model the impact of HM on microbial communities involved in nitrogen cycling.
Main Methods:
- Batch experiments were conducted to assess the effects of HM on nitrite oxidizers, ammonia oxidizers, and nitrite reducers.
- Experiments varied initial pH, nitrogen concentration, biomass concentration, and HM dosage.
- Kinetic modeling was employed to describe nitrite oxidation rates and the inhibitory effects of HM.
Main Results:
- Hydroxylamine (HM) completely inhibited nitrite oxidizer activity at specific dosages (7.0 and 8.9 mg/L at pH 8.4 and 7.6, respectively).
- Low HM concentrations (0.35-5.5 mg/L) selectively inhibited nitrite oxidation without significantly impacting ammonia oxidizers or nitrite reducers.
- Developed models accurately described the effect of pH on nitrite oxidation and HM inhibition (R2 values of 0.89 and 0.80, respectively).
Conclusions:
- Hydroxylamine is an effective inhibitor for nitrite oxidation in biological nitrogen removal processes.
- This approach offers a cost-effective strategy by reducing biomass production and carbon demands.
- Selective inhibition of nitrite oxidation using HM presents a promising advancement in wastewater treatment.