Experimental and theoretical investigations of rotating algae biofilm reactors (RABRs): Areal productivity, nutrient recovery, and energy efficiency

Abstract

Microalgae biofilms have been demonstrated to recover nutrients from wastewater and serve as biomass feedstock for bioproducts. However, there is a need to develop a platform to quantitatively describe microalgae biofilm production, which can provide guidance and insights for improving biomass areal productivity and nutrient uptake efficiency. This paper proposes a unified experimental and theoretical framework to investigate algae biofilm growth on a rotating algae biofilm reactor (RABR). Experimental laboratory setups are used to conduct controlled experiments on testing environmental and operational factors for RABRs. We propose a differential–integral equation‐based mathematical model for microalgae biofilm cultivation guided by laboratory experimental findings. The predictive mathematical model development is coordinated with laboratory experiments of biofilm areal productivity associated with ammonia and inorganic phosphorus uptake by RABRs. The unified experimental and theoretical tool is used to investigate the effects of RABR rotating velocity, duty cycle (DC), and light intensity on algae biofilm growth, areal productivity, nutrient uptake efficiency, and energy efficiency in wastewater treatment. Our framework indicates that maintaining a reasonable light intensity range improves biomass areal productivity and nutrient uptake efficiency. Our framework also indicates that faster RABR rotation benefits biomass areal productivity. However, maximizing the nutrient uptake efficiency requires a reasonably low RABR rotating speed. Energy efficiency is strongly correlated with RABR rotating speed and DC.

Exploring the dynamics of astaxanthin production in Haematococcus pluvialis biofilms using a rotating biofilm‐based system

“…Integrating these tools as real‐time sensors, combined with research into the biofilm formation capability of other high value‐added producing microalgae (Levasseur et al, 2020), could fundamentally further improve this technology. Finally, it becomes evident that additional progress in mathematical models (Bara et al, 2019; Jones et al, 2023; Zhang et al, 2016) and optimization of control strategies will be crucial to ensure that the implementation of microalgae biofilm‐based technology is robust on an industrial scale.…”

“…Additionally, exploring the rotation dynamics to introduce additional stressors, such as a controlled drought of the biofilm, may be a cost-effective strategy to induce astaxanthin synthesis for industrial applications (Boussiba, 2000;Roach et al, 2022). Finally, it becomes evident that additional progress in mathematical models (Bara et al, 2019;Jones et al, 2023;Zhang et al, 2016) and optimization of control strategies will be crucial to ensure that the implementation of microalgae biofilm-based technology is robust on an industrial scale.…”