Rotating Algae Biofilm Reactor for Management and Valorization of Produced Wastewater

Abstract

Production and enhancement of high value phycocyanin pigment from microalgae biofilms cultured on oilfield and natural gas produced wastewater were investigated. Cyanobacteria isolated from Logan City, Utah, wastewater treatment Lagoons (LLC2) was cultured in produced water using rotating algal biofilm reactors (RABRs). The RABRs were operated under “low” and “high” light conditions and biomass and phycocyanin content were compared. Phycocyanin content was enhanced by growth under low light conditions to a maximum yield of 31.7 mg/g ash-free dry weight (AFDW) biomass for an 87.6% increase in phycocyanin yield. Phycocyanin productivity was equivalent for both the low and high light treatments (327 ± 81 and 305 ± 39 mg/m2/day, respectively), due to the significantly lower AFDW biomass productivity of the low light treatment (2.7 ± 0.4 g/m2-day). An indoor laboratory evaluation of 14 substrata for biofilm growth showed that cotton rope and cotton belt material provided the highest biomass yields. Further evaluation in a pilot-scale outdoor produced wastewater pond showed that the biomass characteristics from the two substrata differed. The corrugated surface area of the cotton rope cultured a biofilm with a large community of non-photosynthetic organisms with an autotrophic index of 507 and a low phycocyanin yield of 3.4 mg/g AFDW. However, the cotton belt substratum cultured a healthy photosynthetic biofilm with an autotrophic index of 127 and a phycocyanin yield of 47.0 mg/g AFDW. These results demonstrate the cultivation of microalgae biomass and valorization of oilfield and natural gas produced wastewater through the design and management of algal-based biofilm photobioreactors.

Improving biomass and carbohydrate production of microalgae in the rotating cultivation system on natural carriers

“…Currently, the design of algal biofilm bioreactors is mostly focused on different geometrical configurations and different support or attachment materials. Some examples of contemporary biofilm systems in microalgae cultivation for diverse purposes include flat rotating disks (Blanken et al 2014 ), cylindrical rotating drums (Christenson and Sims 2012 ), and conveyor rotating belts (Gross et al, 2013 ; Wood et al 2022 ). As compared to conventional harvesting methods including membrane filtration, centrifugation, and sedimentation, algal biofilm harvesting can overcome the high cost and energy consumption associated with it.…”

“…The effectiveness of various materials, such as natural and synthetic substrates, in the creation of algal biofilms, has been the subject of much research (Christenson and Sims 2012 ; Genin et al 2014 ; Venable and Podbielski 2019 ). It has been demonstrated that cotton (Wood et al 2022 ; Christenson and Sims 2012 ; Gross and Wen 2014b ), nylon mesh (Lee et al 2014 ), and polystyrene foam (Johnson and Wen 2010 ) have been proven best performers in terms of cell binding, durability and cost of the support material.…”

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

“…Rotating algae biofilm reactors (RABRs) have been used to combine nutrient recovery from wastewater through uptake by attached‐growth microalgal biofilms with harvesting by physical scraping from a growth surface. RABR biofilms cultivated on municipal and industrial wastewaters have been demonstrated to serve as feedstocks for microbial and chemical transformations to value bioproducts that include biofuels, biofertilizers, bioplastics, and chemicals for improved animal gut health and plant growth (Chew et al, 2017; Wood et al, 2022). Engineering challenges related to algae‐based biofilm reactors for these dual applications have been reviewed and addressed (Arora et al, 2021; Christenson & Sims, 2012; Kesaano & Sims, 2014).…”

Modeling the Production of Microalgal Biomass in Large Water Resource Recovery Facilities and Its Processing into Various Commodity Bioproducts

“…Unlike common tertiary treatments (e.g., flocculation, tertiary filters, or chlorine disinfection), algae sequester nitrates and phosphates from wastewater without producing carcinogenic byproducts [11,12]. The rotating algal biofilm (RAB) reactor system is exclusively developed to grow algae and can be used in multiple areas [13]. RAB-integrated WRRFs can be utilized to treat wastewater in the form of secondary or tertiary treatments via nutrient removal, industrial pretreatment, and side stream treatment such as anaerobic digestion effluents, as well as producing algal biomass, as shown in Figure 1B.…”