Performance of a fluidized‐bed bioreactor with hydrogel biomass carrier under extremely low‐nitrogen availability and effect of nitrogen amendments

Abstract

AbstractBACKGROUND: Because of the lower fluidization energy required and the protection against shock loading and starvation due to their sorption capacity, light adsorbents such as hydrogels could be used as biofilm carrier media in fluidized bed bioreactors for wastewater processing. This work explores the feasibility of a cyclodextrin hydrogel as biomass support to degrade phenol under extremely low‐nitrogen availability and under nitrogen amendments.RESULTS: Phenol removal capacity was low (mean 0.589 kg m−3 day−1) under extreme nitrogen‐limited conditions (mean C:N ratio 3830). A pulsed nitrogen amendment increased the elimination capacity (up to 1.97 kg m−3 day−1) controlling the biofilm thickness. An 8‐h nitrogen pulse had a highly efficient long‐term effect removing 93.5 mg‐C mg−1‐N in 300 h. The continuous nitrogen amendment enhanced the elimination capacity (up to 5.84 kg m−3 day−1) although rapidly increasing the biomass growth. The inhibiting phenol concentration was smaller during the nitrogen‐limited period (below 100 mg L−1) than in the nitrogen‐amendment periods (140 mg L−1). Low liquid velocities were needed to fluidize the bioparticles (less than 3.1 mm s−1) during the entire experimentation.CONCLUSION: This work shows that a fluidized‐bed bioreactor with mixed culture on cyclodextrin‐based particles can be operated for long periods at extreme nitrogen limitation, and that a limited nitrogen supply with periodic pulsed amendments would be adequate for controlling the biofilm thickness. Copyright © 2011 Society of Chemical Industry