Start-up of a microalgae-based treatment system within the biorefinery concept: from wastewater to bioproducts

Abstract

Within the European project INCOVER, an experimental microalgae-based treatment system has been built for wastewater reuse and added-value products generation. This article describes this new experimental plant and the start-up stage, starting from the new design of three semi-closed horizontal photobioreactors with low energy requirements for microalgae cultivation (30 m total), using agricultural runoff and urban wastewater as feedstock. The inflow nutrients concentration is adjusted to select cyanobacteria, microalgae able to accumulate polyhydroxybutyrates, which can be used for bioplastics production. Part of the harvested biomass is used as substrate for anaerobic co-digestion (AcoD) with secondary sludge to obtain biogas. This biogas is then cleaned in an absorption column to reach methane concentration up to 99%. The digestate from the AcoD is further processed in sludge wetlands for stabilization and biofertilizer production. On the other hand, treated water undergoes ultrafiltration and disinfection through a solar-driven process, then it is pumped through absorption materials to recover nutrients, and eventually applied in an agricultural field to grow energy crops by means of a smart irrigation system. This plant presents a sustainable approach for wastewater management, which can be seen as a resource recovery process more than a waste treatment.

Nutrient removal from agricultural run-off in demonstrative full scale tubular photobioreactors for microalgae growth

“…Group of the UPC in collaboration with the company Disoltech S.L after several previous investigations Solimeno et al, 2017;Uggetti et al, 2018). Each PBR is equipped with online sensors of pH (Hatch Lange SL., Spain), dissolved oxygen (DO) (Neurtek, Spain) and temperature (Campbell Scientific Inc., USA) in one of the two open tanks.…”

Natural Pigments and Biogas Recovery from Microalgae Grown in Wastewater

“…The digestate was obtained from the anaerobic digester (working volume 400 L, HRT 20 days) of a demo scale plant using photobioreactors to treat agricultural runoff. 26 The digestate was centrifuged (4200 rpm, 10 min) and the supernatant (centrate) was mixed with the secondary effluent from the HRAP to feed the photobioreactors. Physicochemical characteristics of the secondary effluent, centrate, and digestate used in this experiment are presented in the Supporting Information ( Table S1 ).…”

Current advances in microalgae-based treatment of high-strength wastewaters: challenges and opportunities to enhance wastewater treatment performance

“…Hybrid photobioreactors may incorporate the advantages of different conventional alternatives, combining suspended and attached growth, open and closed vessels or sunlight and artificial light. Semi-closed photobioreactors, coupled to biogasupgrading are a promising alternative for high-strength wastewater reuse and added-value product generation based on their higher photosynthetic efficiencies at lower operating costs (Uggetti et al 2018). Similarly, flat-panels photobioreactors have been successfully tested at pilot scales with relatively high treatment efficiencies for carbon and nitrogen (80-90% and 70-85%, respectively) (Choudhary et al 2017;Romero-Villegas et al 2018;Naaz et al 2019;Sun et al 2019).…”