Annual production of microalgae in wastewater using pilot-scale thin-layer cascade photobioreactors

Abstract

Microalgae based wastewater treatment has been suggested as an alternative to polluting and energy-consuming conventional processes. The main advantage of this strategy is the dual role of microalgae: they recover nutrients from waste and simultaneously produce biomass with varied industrial applications. In the current study, biomass of Scenedesmus sp. was produced using primary wastewater in two pilot-scale thin-layer cascade photobioreactors (63 and 126 m 2 ). The wastewater used for microalgal growth was not subjected to any conventional treatment process, besides removal of solids, and contained a variable N-NH4 + content of 83.0-210.6 mg•L -1 . Biomass productivity values were comparable to those obtained when operating using freshwater and commercial chemicals as nutrient sources. When operating at a dilution rate of 0.3 day -1 , the average annual productivity was 24.8 g•m -2 •day -1 (82.0 t•ha -2 •year 1 ) with a maximum of 32.8 g•m -2 •day -1 in summer. Inorganic nitrogen and phosphorus removal rates varied between 695.4-2383.4 and 70.4-111.8 mg•m -2 •day -1 respectively. Production of Scenedesmus sp. using wastewater would allow not only to process large volumes of water that could be reused for agricultural irrigation or safely disposed into water streams, but also reduce production costs by 0.44 €•kg -1 , based on a preliminary economic analysis. Overall, results demonstrate that thin-layer cascade reactors can be used to effectively remove nutrients from wastewater while simultaneously produce valuable biomass with potential applications in agriculture or animal feed production.

Year-long evaluation of microalgae production in wastewater using pilot-scale raceway photobioreactors: Assessment of biomass productivity and nutrient recovery capacity

“…It is likely that the lower biomass productivity of the 1500 L raceway reactor used in that study (4.2 g•m -2 •day -1 ) was the reason for the lower nitrogen removal. Indeed, thin-layer cascade reactors that are highly productive allow higher areal nitrogen removal rates but allow to process less wastewater per surface area [20]. Higher removal efficiencies (85-14 98%) were observed when processing domestic wastewater using the microalga Chlorella variabilis TH03 and 3.7 m 2 raceway reactors [40].…”

“…A limited number of studies demonstrated the robustness of Scenedesmus strains outdoors in pilot-scale reactors. This strains was recently produced using wastewater at pilot-scale using thin-layer cascade bioreactors [4,20]. Thin-layer cascade bioreactors are highly productive in terms of biomass production [21].…”

Production of Scenedesmus almeriensis Using Pilot-Scale Raceway Reactors Located inside a Greenhouse

“…This microalga also showed potential for use as a feed ingredient promoting the gut functionality of fish [8] and as a biostimulant in agriculture [9]. In addition, S. almeriensis is a robust strain that can be produced using wastewater and different reactor designs [14,15] which has been suggested as key to reduce production costs [16].…”

Potential of the cyanobacteria Anabaena sp. and Dolichospermum sp. for being produced using wastewater or pig slurry: Validation using pilot-scale raceway reactors

“… Medium D, medium formulated using commercial-grade chemicals (commercial fertilisers): 1.00 g•L -1 NaNO3, 0.25 g•L -1 MgSO4, 0.30 g•L -1 KH2PO4, 30.0 g•L -1 NaCl, and 0.02 g•L -1 Karentol ® . This medium was used to produce microalgae using large photobioreactors in previous reports [10,11].…”

“…When produced outdoors using open raceway bioreactors, biomass productivity is highly influenced by environmental conditions, namely solar radiation and temperature [11]. Figure 3 [24] and Dolichospermum sp.…”