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Published on: June 15, 2014
Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater
J L Campos1, M Sánchez, A Mosquera-Corral
1Department of Chemical Engineering, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
Water Research
|July 2, 2003
Summary
This study optimized wastewater treatment using a coupled biofilm airlift suspension (BAS) and anoxic upflow sludge blanket (USB) reactor system. The optimal carbon-to-nitrogen ratio effectively removed nitrogen while managing formaldehyde and urea contaminants.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Bioreactor Systems
Background:
- Wastewater often contains formaldehyde and urea, requiring effective treatment methods.
- Conventional treatment systems may struggle with simultaneous nitrification, denitrification, and hydrolysis of these compounds.
- Coupled bioreactor systems offer potential for enhanced pollutant removal.
Purpose of the Study:
- To investigate the efficacy of a coupled biofilm airlift suspension (BAS) and anoxic upflow sludge blanket (USB) reactor system for treating wastewater containing formaldehyde and urea.
- To determine the impact of formaldehyde and urea on nitrifying and denitrifying biomass.
- To optimize the coupled system's performance by evaluating different recycling ratios and carbon-to-nitrogen (C/N) ratios.
Main Methods:
- Individual experiments assessed the effects of formaldehyde and urea on nitrifying (in BAS reactor) and denitrifying (in USB reactor) biomass.
- The coupled BAS-USB system was operated at varying recycling ratios (R=3 and 9) and C/N ratios (0.58, 1.0, and 1.5 g C-formaldehyde/g N-NH4+).
- Nitrogen removal efficiency, nitrification, denitrification, and urea hydrolysis rates were monitored.
Main Results:
- Formaldehyde inhibited nitrification and denitrification at higher concentrations (40-120 mg C-formaldehyde/L).
- The coupled system achieved maximum nitrogen removal percentages at a C/N ratio of 1.0 g C-formaldehyde/g N-NH4+ for both recycling ratios.
- A C/N ratio of 1.5 g C-formaldehyde/g N-NH4+ reduced system efficiency due to formaldehyde inhibition of nitrification.
- Formaldehyde was completely removed in the BAS reactor, with a heterotrophic layer forming around the nitrifying biofilm.
Conclusions:
- The coupled BAS-USB system is effective for simultaneous nitrification, denitrification, and urea hydrolysis in wastewater.
- Optimizing the C/N ratio is crucial for maximizing nitrogen removal efficiency and minimizing formaldehyde inhibition.
- The formation of a heterotrophic layer in the BAS reactor aids in formaldehyde removal.
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