Comparison of the Performance of Internal and External Loop Air-lift Reactors for Water Treatment by Activated Sludge
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Article Type:
Research/Original Article (دارای رتبه معتبر)
Abstract:
Background and Objective

In This study the impacts of operating conditions such as aeration rate, the downcomer-to-riser cross-sectional area ratio (Ad/Ar), and liquid phase properties on the hydrodynamics and volumetric mass transfer coefficient in three-phase airlift reactors was investigated.

Method

Experiments were conducted in external loop air-lift reactor with downcomer to riser cross-sectional area ratio (AD/AR=0.14) and internal air-lift reactors with downcomer to riser cross-sectional area ratios 0.36 and 1. Air and Water were used as gas and liquid phases, respectively and activated sludge is used as the solid phase.

Findings

The liquid circulation velocity, gas holdup and mass transfer coefficient increased with an increase in the superficial gas velocity, decrease the sludge concentration and decrease downcomer to riser cross-sectional area ratio. The maximum amount of gas hold up, 0.178 in external air-lift reactor with 1%(w/w) activated sludge in superficial gas velocity 0.24(m/s) was observed. A model to predict the effect of activated sludge concentration, the superficial gas velocity and the downcomer-to-riser cross-sectional area ratio on the mass transfer activated sludge airlift reactors provided which with the experimental results are in good agreement.

Discussion and Conclusion

 The evaluation of internal and external reactors performance at different concentration and superficial gas velocity show that the air-lift reactor with external loop has better performance in comparison with internal airlift reactors.

Language:
Persian
Published:
Journal of Environmental Sciences and Technology, Volume:21 Issue: 9, 2019
Pages:
82 to 93
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