Institute Of Recerca Of Lenergia Of Catalonia Irec

Tarragona, Spain

Institute Of Recerca Of Lenergia Of Catalonia Irec

Tarragona, Spain

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Sirin S.,Rovira i Virgili University | Trobajo R.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Ibanez C.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Salvado J.,Rovira i Virgili University | Salvado J.,Institute Of Recerca Of Lenergia Of Catalonia Irec
Journal of Applied Phycology | Year: 2012

The purpose of this study was to explore efficient methods of harvesting the microalga Phaeodactylum tricornutum. Natural sedimentation experiments, performed at different light and temperature conditions, did not yield significant improvements in efficiency even after 1 week. When alkalinity-induced flocculation was performed, both the flocculation efficiency and the concentration factor dramatically improved at pH = 9. 75 (0. 5-0. 7 units over the original pH of the culture) after 10 min settling time. Sedimentation rates are documented at pH ranging between pH 9. 75 and 11. 0. The results of the application of two conventional flocculants used in wastewater treatment, polyaluminium chloride and aluminium sulphate, are also presented. Chitosan was also used as a natural flocculating agent to improve possible contamination problems in the downstream process. pH was adjusted in order to determine optimum flocculation efficiency of chitosan in combination with a high concentration factor. Satisfactory results were found with chitosan at an adjusted pH of 9. 9 using concentrations as low as 20 mg L -1, after testing a flocculant range of 5-200 mg L -1. © 2011 Springer Science+Business Media B.V.


Sirin S.,Rovira i Virgili University | Clavero E.,Institute Of Recerca Of Lenergia Of Catalonia Irec | Salvado J.,Rovira i Virgili University | Salvado J.,Institute Of Recerca Of Lenergia Of Catalonia Irec
Bioresource Technology | Year: 2013

We compared potential pre-concentration techniques for Nannochloropsis gaditana (Nng) by testing natural sedimentation; flocculation with aluminium sulphate, polyaluminium chloride and chitosan; and induced pH. Promising flocculation efficiencies and concentration factors were obtained in a short time with alkalinity-induced flocculation at an adjusted pH of 9.7 and with chitosan at an adjusted pH of 9.9 using a concentration of 30mgL-1. The sedimentation rates of alkalinity-induced flocculation were also evaluated. Additionally, viscosity, particle size distribution and Ca/Mg ions were analysed for pre-concentrated samples of N. gaditana (Nng) and the previously studied Phaeodactylum tricornutum (Pht) which were obtained by various different harvesting methods under optimal conditions. The rheological properties of the concentrated algae suspensions of two microalgal species showed Newtonian behaviour. The mean diameters of the flocs were between 39 and 48μm. The Ca/Mg analysis showed that Mg+2 is the triggering ion for alkalinity-induced flocculation in the conditions studied. © 2013 Elsevier Ltd.


Sirin S.,Rovira i Virgili University | Clavero E.,Institute Of Recerca Of Lenergia Of Catalonia Irec | Salvado J.,Rovira i Virgili University | Salvado J.,Institute Of Recerca Of Lenergia Of Catalonia Irec
Environmental Technology (United Kingdom) | Year: 2015

Harvesting is one of the key challenges to determine the feasibility of producing biodiesel from algae. This paper presents experimental results for a cost-effective system to harvest Chaetoceros calcitrans, using natural sedimentation, flocculation, and inducing pH. No efficient sedimentation of microalgal cells was observed only by gravity. By alkalinity-induced flocculation, at a pH value of 9.51, 86% recovery of the cells was achieved with a sedimentation rate of 125 cm/h and a concentration factor (CF) of 4 (volume/volume (v/v)) in 10 min. The maximum photochemical quantum yield of photosystem II (Fv/Fm) of concentrated cells was almost the same as fresh culture (0.621). Commercial flocculants, aluminium sulphate and poly-aluminium chloride (PAC), were also successful in harvesting the studied algal cells. Optimum concentration of aluminium sulphate (AS) could be concluded as 10 ppm with 87.6% recovery and 7.10 CF (v/v) in 30 min for cost-efficient harvesting, whereas for PAC it was 20 ppm with 74% recovery and 6.6 CF (v/v). Fv/Fm yields of concentrated cells with AS and PAC showed a 1% reduction compared to fresh culture. Mg+2 was the triggering ion for alkalinity-induced flocculation in the conditions studied. The rheology behaviour of the concentrated cells was Newtonian with values between 2.2 × 10-3 and 2.3 × 10-3 Pa s at 30°C. © 2015 Taylor & Francis.

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