Evaluation of the performance of different materials to support the attached growth of algal biomass

The use of a natural substrate for immobilization of microalgae cultivated in wastewater

“…Pine bark in the PBRs formed a packed bed with thickness approximately 0.4 m. It was decided to use bark from pine trees because of the large range of this species in Europe and ease of acquisition. High porosity and roughness of the substrates are also important in the development of biofilm 3,7 and lignocellulose materials have additionally hydrophilic properties 23 . In addition, preliminary studies using artificial (PET bottles and mats with polymer fibers) 9 and natural materials (bark of pine, birch, oak, beech, ash, wood chips and charcoal) have shown the presence of a clear biofilm (visible to the naked eye) containing microalgae only on the surface of the pine bark.…”

“…Compared to the production of terrestrial plants biomass (€0.20 kg −1 for soybeans and €0.35 kg −1 for wheat and corn 2 ), these are significant amounts. Such large financial outlays in microalgae production in PBRs are generated mainly by the preparation of cultivation medium, irradiation, harvesting of biomass, CO 2 supplementation and mixing [5][6][7] . Among these factors, the costs of harvesting and separation of biomass may constitute up to 20-30% of the total production costs 7 .…”

“…Such large financial outlays in microalgae production in PBRs are generated mainly by the preparation of cultivation medium, irradiation, harvesting of biomass, CO 2 supplementation and mixing [5][6][7] . Among these factors, the costs of harvesting and separation of biomass may constitute up to 20-30% of the total production costs 7 . Therefore, the selection of a suitable method of separation of biomass is crucial in the economic aspect of cultivation 1 .…”

“…This system significantly reduces the costs of cultivation in comparison with conventional methods of separation (flocculation, membrane filtration, centrifugation etc.) and facilitates the harvesting of biomass 3,6,7 . Biofilm in PBRs constitutes a structure composed mainly of colonies of bacteria and microalgae.…”

“…The main producer of these substances are bacteria, and the more EPSs are extracted, the structure of biofilm will be more durable 11,12 . Among the most popular materials used as a substrate for the microalgae cultivation are artificially manufactured substrates from polyester, cotton or nylon fibers, as well as concrete and polystyrene 7,13,14 . However, natural substrates, which can be cheaper and easier to gain and even constitute waste materials, are not commonly used.…”