Contents lists available at ScienceDirect Algal Research journal homepage: www.elsevier.com/locate/algal Evaluation of the performance of different materials to support the attached growth of algal biomass Letícia Rodrigues de Assis a, ⁎ , Maria Lúcia Calijuri a , Paula Peixoto Assemany a , Elisa Couto Berg a , Laís Veloso Febroni a , Tereza Angélica Bartolomeu b a Universidade Federal de Viçosa, Advanced Environmental Research Group – nPA, Department of Civil Engineering, Av. PH Rolfs, s/n, 36570-900, Brazil b Universidade Federal de Viçosa, Department of Domestic Economy, Av. PH Rolfs, s/n, 36570-900, Brazil ARTICLE INFO Keywords: Biomass adherence Wastewater Algal biofilm Materials durability Microalgae Biofilm reactors ABSTRACT The attached microalgal biomass production in wastewater is promising for the development of biofilm reactors aimed at the economic separation and harvesting of biomass. However, the current impasse in the attached algal biomass production relies on the ability of materials to support such adherence. This study evaluated the effects of different support materials on the production and composition of algal biomass cultivated in domestic sewage. Durability and adherence of algal biomass to the threads of the support material were the most important criteria for choosing the material with the best performance. Three support materials were evaluated: cotton, nylon, and polyester. Polyester presented the best results in terms of durability; its resistance to friction tests was the highest, and even increased after its use in the experiment; this was associated with the high biomass production, mostly after the biomass inoculum (50.1 g∙m −2 ). This support also demonstrated greater development of ni- trifying bacteria, which are essential for biofilm formation due to the presence of filaments in their cells. As for biomass characterization, it was observed that the different support materials did not interfere in the compo- sition of the cells present in the attached biomass. 1. Introduction The search for technologies that are less damaging to the environ- ment, associated with the need to generate energy to supply the po- pulation demand, has stimulated research aimed at using renewable energy sources. The production of microalgae is within this context as a promising source of renewable energy. Among the applications of algal biomass, the following biofuels can be highlighted: the production of ethanol through sugar fermentation; bio-oil from thermal–chemical processing; and methane through anaerobic digestion. Other applica- tions include the production of fertilizers, and aquaculture [1]. Despite the great versatility of microalgae biomass use, it has not yet been commercialized due to its high production cost. Currently, its main production process is through high rate ponds, where the ex- traction of algal biomass is expensive. Grimma et al. [2] estimated that the costs of harvesting and separating biomass represent nearly 20 to 30% of the costs for producing microalgae biofuels. In order to harvest algal biomass from a diluted sample, the algal cells in solution are usually concentrated through sedimentation, flotation, flocculation or centrifugation [3]. These processes, if used on large scale, have a time- consuming operation and are not considered as economically feasible [4]. Newer technologies are available for algal biomass separation and for the production of high density biomass, such as membrane bior- eactors. These bioreactors act efficiently in these requirements and also in the removal of nutrients when used for wastewater treatment [5]. In this context, the recent search for innovative strategies to opti- mize the production and separation of algal biomass can be highlighted. Nowadays, the method of the algal biofilm growth system has been widespread, in which the cells are fixed to the surface of a solid support material [6]. The advantages of this new way of production are the low water demand and the ease of biomass harvesting, due to its greater concentration [6]. Consequently, these systems have a low cost of biomass harvesting and separation when compared to the suspended growth system. Adhered growth systems when used in wastewater treatment allow the formation of a consortium of microorganisms including microalgae and bacteria [7]. The interaction of these microorganisms and the as- sociation of several parameters interfere in the formation and structure of the formed biofilm [8]. However, there is not much information about the formation of biofilms in these adhered growth systems, making the studies to deepen the optimization of the various para- meters that involve flow velocity, support material, light availability, https://doi.org/10.1016/j.algal.2019.101440 Received 18 September 2018; Received in revised form 14 January 2019; Accepted 13 February 2019 ⁎ Corresponding author. E-mail address: leticia.assis@ufv.br (L.R. de Assis). Algal Research 39 (2019) 101440 2211-9264/ © 2019 Elsevier B.V. All rights reserved. T