Abstract
Cassava processing wastewater (CPW) is a highly polluting, liquid residue of cassava processing, usually discarded or treated anaerobically. However, it can serve as a low-cost culture medium for microalgae. After a preliminary evaluation of the growth of 10 microalgal strains in diluted CPW, the microalgae Haematococcus pluvialis SAG 34−1b and Neochloris (Ettlia) oleoabundans UTEX 1185 were selected for cultivation in CPW without a supply of additional nutrients and evaluated for their growth, lipid production, and nutrients removal. Maximal biomass concentrations of 1.79 g·L−1 for H. pluvialis and 3.18 g·L−1 for N. oleoabundans were achieved with 25% CPW medium on the 13th day of growth. The algae H. pluvialis and N. oleoabundans removed 60.80 and 69.16% of the chemical oxygen demand, 51.06 and 58.19% of total nitrate, and 54.68 and 69.84% of phosphate, respectively. On average, lipid productivities reached 0.018 and 0.041 g·L−1 day−1 for H. pluvialis and N. oleoabundans, respectively. Therefore, cultivating these microalgae in diluted CPW is a promising treatment for cassava wastewater with simultaneous valuable biomass production.
Highlights
Microalgal biomass can be used for many applications, from feed to biofuels [1,2,3], but its large-scale production requires large amounts of water and nutrients [4]
Microalgae cultivation on cassava processing wastewater could be economically valuable for the production of biomass rich in lipids
Despite the variations in its composition, cassava wastewater remains a viable alternative for use as a microalgae medium without any supplementation, including the cultivation of H. pluvialis and N
Summary
Microalgal biomass can be used for many applications, from feed to biofuels [1,2,3], but its large-scale production requires large amounts of water and nutrients [4]. The use of agro-industrial residues in bioprocesses provides many new possibilities of nutrient-rich substrates while reducing pollution problems [7]. Cassava (Manihot esculenta L.) is a root cultivated in more than 100 countries, with an annual production of around 300 million tons (2018–2019), making it the 5th most important staple crop in the world, ahead of barley, sweet potatoes, and apples [8,9]. The top 10 producer countries are in Africa, Asia, and South America, and cassava is used for direct human consumption and processed into starch products. Cassava processing wastewater (CPW) is a carbohydrate-rich residue generated in large amounts during cassava flour and starch production. It has been estimated that the volume of cassava wastewater generated by beneficiation of 1 ton of roots ranges from 300 to 3000 L [8,10,11] due to different dilutions during processing
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