Microalgae biomass production using wastewater: Treatment and costs Scale-up considerations Luísa Gouveia a , Sofia Graça a , Catarina Sousa a , Lucas Ambrosano b , Belina Ribeiro a , Elberis P. Botrel b , Pedro Castro Neto b , Ana F. Ferreira c, ⁎, Carla M. Silva d a LNEG — Laboratório Nacional de Energia e Geologia, I.P./Bioenergy Unit, Estrada do Paço do Lumiar 22, 1649-038 Lisboa, Portugal b Universidade Federal de Lavras, Laboratório de Pesquisa em Óleos, Gorduras e Biodiesel, Lavras, Brazil c IDMEC, Instituto superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal d IDL — Instituto Dom Luiz, Departamento de Engenharia Geográfica, Geofísica e Energia, Faculdade de Ciências, Universidade de Lisboa, Portugal abstract article info Article history: Received 30 November 2015 Received in revised form 25 February 2016 Accepted 5 March 2016 Available online xxxx This work is part of a LIFE project to treat urban wastewater from Águas da Figueira (AdF, Figueira da Foz, PT) using a vertical tubular photobioreactor (PBR) prototype (150 L), to be scaled up and integrated in a waste water treatment plant (WWTP). The PBR was inoculated with three different microalgae: Chlorella vulgaris (Cv), Scenedesmus obliquus (Sc) and Consortium C (ConsC), isolated from the effluent. The study intends to find the best microalga in terms of wastewater remediation, biomass productivity and quality, for further uses, such as biofuel, biofertilizer and bioplastic production. The experiments achieved volumetric productivities of 0.1 g/L·d (Cv), 0.4 g/L·d (Sc) and 0.9 g/L·d (ConsC). The maximum removals attained by Cv, Sc and ConsC were: 84, 95 and 98% for total nitrogen; 95, 92 and 100% for phosphorus; and 36, 63 and 64% for COD, respectively. The treated water had values that are in accordance with environmental legislation (Directive 98/15/CE). Electrocoagulation was tested and resulted in an energy saving of 89%, compared with centrifugation alone. For drying the biomass, a solar dryer was used. Costs of overall processes versus conventional technologies are discussed and compared with other facilities and target values. © 2016 Elsevier B.V. All rights reserved. Keywords: Bubble column photobioreactor Wastewater treatment Electrocoagulation Solar drying Scale-up 1. Introduction The global water crisis is mainly due to population growth in areas with low freshwater resources, pollution of both surface and ground- water, and long-term changes in the hydrological cycle due to climate change [1]. Wastewater recovery is crucial for the better management of water resources and can help the mitigation of regional or seasonal water scarcity [1]. Presently, the treatment of the wastewater treatment plants (WWTP) required a large amount of chemicals, and the operation and maintenance of the technologies used are energy demanding processes [2]. Both drawbacks reduced the environmental and energy sustainabil- ity of the WWTPs. In order to reduce the carbon footprint of these plants, other poten- tial uses for wastewater included: (1) residential irrigation with reused water [3,4], (2) land fertilization using the digested sludge [5,6] and (3) possible production onsite of combined heat and power systems (CHPs) [7]. The use of algae for wastewater treatment guaranteed remarkable advantages, such as: (1) the oxygen needed for the bacteria is provided through microalgae photosynthesis, avoiding aeration thus, reducing energy demand [8], (2) reduction in hazardous solid sludge formation (e.g., heavy metals andpathogens) [9] (3) reduction of GHG emissions, (4) reduced costs [9], and (5) the production of useful algal biomass—energy rich recycling of the nutrients present in the wastewa- ter. Fortier and Sturm [10] also claimed that a promising solution to re- duce the freshwater and fertilizer demand of algal biomass production is to utilize municipal wastewater effluent, which contains nitrogen, phosphorus, and other necessary nutrients. Nevertheless, as the microalgae are too small, cultures are much dilut- ed, it is necessary to spend a lot of energy to recover the biomass, which corresponds to a high percentage of the total production costs (30%) [11]. Although centrifugation is an effective harvesting method, it pre- sents high investment and operational costs. The electrocoagulation method, a non-conventional technique for harvesting microalgae, was studied in detail for Nannochloropsis sp. by the authors [12]. They obtained the best recovery (N 97%) using a current density of 8.3 mA·cm -2 for 10 min without significant changes in the quality of the biomass both in terms of fatty acid and pigment profiles. Algal Research 16 (2016) 167–176 ⁎ Corresponding author. E-mail address: filipa.ferreira@tecnico.ulisboa.pt (A.F. Ferreira). http://dx.doi.org/10.1016/j.algal.2016.03.010 2211-9264/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Algal Research journal homepage: www.elsevier.com/locate/algal