Evaluating algal growth performance and water use efficiency of pilot‐scale revolving algal biofilm (RAB) culture systems

Abstract

A Revolving Algal Biofilm (RAB) growth system in which algal cells are attached to a flexible material rotating between liquid and gas phases has been developed. In this work, different configurations of RAB systems were developed at pilot-scale by retrofitting the attachment materials to a raceway pond (2000-L with 8.5 m(2) footprint area) and a trough reservoir (150 L with 3.5 m(2) footprint area). The algal growth performance and chemical composition, as well as the water evaporative loss and specific water consumption were evaluated over a period of nine months in a greenhouse environment near Boone, Iowa USA. Additionally a raceway pond was run in parallel, which served as a control. On average the raceway-based RAB and the trough-based RAB outperformed the control pond by 309% and 697%, respectively. A maximum productivity of 46.8 g m(-2) day(-1) was achieved on the trough-based RAB system. The evaporative water loss of the RAB system was modeled based on an energy balance analysis and was experimentally validated. While the RAB system, particularly the trough-based RAB, had higher water evaporative loss, the specific water consumption per unit of biomass produced was only 26% (raceway-based RAB) and 7% (trough-based RAB) of that of the control pond. Collectively, this research shows that the RAB system is an efficient algal culture system and has great potential to commercially produce microalgae with high productivity and efficient water use.

Robust, high-productivity phototrophic carbon capture at high pH and alkalinity using natural microbial communities

“…Interestingly, their system was inoculated with municipal wastewater and the subsequent biofilm was dominated by the cyanobacterium Phormidium autumnale . The rotating algal biofilm cultivation system (RAB) inoculated with C. vulgaris has demonstrated productivities of 3.51 g m −2  day −1 (laboratory scale) [18] and 5.80 g m −2  day −1 (pilot scale) [40, 41]. Schnurr et al [42] cultivated Nitzschia palea and Scenedesmus obliquus biofilms on a flat plate parallel horizontal photobioreactor with areal productivities of 2.8 and 2.1 g m −2  day −1 .…”

Advanced nutrient removal from surface water by a consortium of attached microalgae and bacteria: A review

“…Natural substrate colonization and artificial inoculation are the two main mechanisms to obtain attached microalgae-bacteria consortium, with many substrate materials being tested for algalbacterial biofilm formation (Table 5) (Yu and Mohn, 2002;Adey et al, 2013;Kesaano and Sims, 2014;Gross et al, 2015b;Liu et al, 2016a). Natural colonization occurs spontaneously whenever a solid substrate is under proper climate and nutrient conditions in surface water (Mulbry et al, 2008;Liu et al, 2016b;Su et al, 2016).…”

Removal of total dissolved solids from wastewater using a revolving algal biofilm reactor

“…The detailed RAB system design has been described in our previous publications (Gross et al, , ; Gross & Wen, ). In brief, a flexible cotton duct canvas belt was stretched around drive shafts to form a vertical configuration.…”

“…To harvest algal cells from these systems, the cell suspension is usually concentrated through sedimentation followed with centrifugation, which usually results in 20%–25% of total operation costs (Davis, Aden, & Pienkos, ). To overcome the high biomass harvest cost, an attachment‐based algal culture system, revolving algal biofilm (RAB) reactor, has been developed (Gross, Henry, Michael, & Wen, ; Gross, Mascarenhas, & Wen, ; Gross & Wen, ; Gross, Zhao, Mascarenhas, & Wen, ). In the RAB system, algal cells grow in an attachment material (“belt”), which rotates through the liquid medium to absorb nutrients, then rotates out of the water to facilitate light exposure, and gas (CO 2 and O 2 ) exchanges.…”