Evaluation of hydraulic characteristics of a pilot-scale air-lift internal-loop bioreactor

Abstract

Using sodium fluoride as tracer, residence time distribution technique was employed to evaluate the hydraulic characteristics of a pilot-scale Internal-Loop Airlift Bio-particle (ILAB) bioreactor that was a novel system for ammonia removal from wastewater. The results showed that the flow pattern of ILAB reactor was close to completely mixed reactor under all the tested air flow rates and liquid flow rates (with average N of 1.88). The total dead zone (TDZ) was 32.43% with biological dead zone (BDZ) of 20.66% and hydraulic dead zone (HDZ) of 8.95%. At higher air flow rates, the flow pattern of reactor approached that of completely mixed reactor (N from 2.72 to 1.54), and the increase of air flow rate gave rise to the decrease of TDZ in the reactor (from 36.24% to 23.00%). Whereas at higher liquid flow rates, the flow pattern of ILAB reactor got away from that of completely mixed reactor (N from 1.51 to 1.72), and the increase of liquid flow rate yielded a rise of TDZ in the reactor (from 28.48% to 36.84%). The study highlighted that the effect of air flow rate on flow pattern and TDZ of the reactor was greater than that of liquid flow rate.

Keywords:

• Air flow effect
• dead zone
• flow pattern
• hydrodynamics
• liquid flow effect
• residence time distribution
• tracer test

Funding

The study was supported by National Key Technology R&D Program of China (No. 2013BAD21B04), Natural Science Foundation of China (No. 51278457), Zhejiang Provincial Foundation for Creative Team (2013TDXX) and Higher Education Commission (HEC) of Pakistan.