Paper details

Title:

Treatment of Olive Mill Wastewater, CO₂ Removal and Biofuel Production Using the Microalgae Scenedesmus Quadricauda and Chlorella Pyrenoidosa

Author(s):

Maaitah, M., Hodaifa, G., Órpez, R., Sánchez, S.

Document(s):

Abstract:

It is important to highlight the fact that one of the most important problems in the olive oil industry is the wastewater that is generated. These wastewaters are characterized by a high organic and inorganic load, which includes sugars, phenolic compounds, polyalcohol’s, pectin’s, lipids, mineral salts ... On the other hand, this effluent can provide nutrients to produce a high added value algal biomass. Microalgae can treat this wastewater by removing its nutrients and have the potential to reduce the effects of greenhouse gases (GHG) and recycle industrial CO2 emissions. This is a very important fact because the growth of algae depends not only on nutrients but also on carbon dioxide in order to carry out the photosynthetic process extensively. The main benefit of using algae-based biofuels, compared to other biofuels, is that algae do not compete with limited resources such as natural freshwaters. Chlorella pyrenoidosa and Scenedesmus quadricauda are green unicellular algae that can produce a substantial amount of lipids [1]. In a previous selection using these two microalgae has been observed that C. pyrenoidosa is more suitable than S. quadricauda for the production of biofuels. These cultures previous were carried in a shaker system. Later, once the microalgae has been selected, experiments have been carried out in a batch culture facility using photobioreactors of 0.5 dm3 useful capacity [2], with dilutions of oil mill wastewater (olive washing); culture media have been formed with 50% (v/v) olive wash dilutions. Temperature was 25°C, pH 8, an air flow of 1 v/v/min was supplied, with different concentrations of CO2 (1.0, 2.0, 5.0, 10.0 and 15.0 %) and under a light-dark cycle of 12 h illumination per day. In all cultures, a concentration of 2 mg dm-3 of chloramphenicol was added, allowing minimizing the bacterial contamination. Fundamentally, this study tries to evaluate the growth kinetics (maximum specific growth rate, µm, and volumetric biomass productivity, Pb) as well as the formation of lipids in the biomass formed. At lab level, a concentration 50% waters from washing of fruit with 10.0% of CO2 permits to reach the highest values of µm and Pb, 0.032 h-1 and 3.35 10-3 g dm-3h-1, respectively. In relation to the lipids composition, a high concentration of total lipids (47.4%), were obtained in cultures that used a concentration of 10.0% CO2 in the air flow that enters the photobioreactor. Oil samples collected from C. pyrenoidosa were converted into fatty acid methyl ester (FAME) through a transesterification process. The fatty acid profiles obtained are suitable for biofuel production. High removal percentages were achieved after treatment in chemical oxygen demand (82.9%), total phenolic compounds (66.1%), total nitrogen (97.0%) and total phosphorus (69.2%). Final treated water could be used to irrigate the olive grove or in other operating units of the oil mill.

Keywords:

biofuel, microalgae, olive-mill wastewater, bioprocess, nutrients removal

Topic:

Sustainable Resources for Decarbonising the Economy

Subtopic:

Algae and Aquatic Biomass Production Systems

Event:

29th European Biomass Conference and Exhibition

Session:

1BV.1.13

Pages:

146 - 151

ISBN:

978-88-89407-21-9

Paper DOI:

10.5071/29thEUBCE2021-1BV.1.13

Price:

FREE