Optimization and qualitative comparison of two vinasse pre-treatments aiming at microalgae cultivation

Candido, Camila; Bernardo, André; Lombardi, Ana Teresa

doi:10.1590/S1413-415220190306

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Technical Article • Eng. Sanit. Ambient. 26 (2) • Mar-Apr 2021 • https://doi.org/10.1590/S1413-415220190306 copy

Optimization and qualitative comparison of two vinasse pre-treatments aiming at microalgae cultivation

Otimização e comparação qualitativa de dois pré-tratamentos da vinhaça visando ao cultivo de microalgas

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The cultivation of microalgae is a possible destination for vinasse, a residue from the sugar and alcohol industry. This use can help reduce the costs of microalgae production and remediate this residue rich in nutrients. However, the physicochemical characteristics of vinasse limit its use for microalgae growth at low concentrations, except when the residue is pretreated. This work aimed at optimizing the vinasse pretreatments of centrifugation and adsorption by smectite clay and activated charcoal on laboratory scale in terms of amounts of materials used and time spent, making them more viable on larger scales. The optimized processes were then compared in productive, economic, and environmental terms. The dilution of treated vinasse with distilled water resulted in similar growth of Chlorella vulgaris to those obtained with the dilution in BG11 medium, indicating that the addition of nutrients in culture media is not necessary. Although microalgae growth occurs in higher concentrations of vinasse treated by adsorption, the results show that centrifugation required less processing time, has cheaper processing costs, and generated much less residue. Centrifugation treatment has greater economic and environmental viabilities and was more sustainable than the adsorption, even though the algae did not grow in the centrifuged residue in concentrations as high as it did after the adsorption treatment. Therefore, this article brings a new view about the economic and environmental aspects on the use of pretreated vinasse for microalgal growth, giving a lucrative destination for a highly polluting waste.

Keywords:
waste use; physicochemical treatments; sustainable production; algae biomass

Parameter	Methods
COD	SMEWW 22ᵃ Ed 2012 Method 5220 D - POPDAM029 vs.22:2014
BOD	SMEWW 22ᵃ Ed 2012 Method 5210 B - POPDAM009 vs.22:2015
Total suspended solids	SMEWW 22ᵃ Ed 2012 Method 2540 D - POPDAM024 vs.17:2014
Calculated hardness	MEWW 22º Ed 2012 Method 2340 B - POPDAM011 vs.16:2014
Electrolytic conductivity	SMEWW 22ᵃ Ed 2012 Method 2510 B - POPDAM006 vs.14:2014
Anions	USEPA300.1 rev 1:1997- POPDAM054 vs. 08:2013
Ammoniacal nitrogen	SMEWW 22ᵃ Ed 2012 Method 4500-NH3D - POPDAM016 vs.14:2013
Kjeldahl nitrogen	SMEWW 22ᵃ Ed 2012 Method 4500-Norg B - POPDAM107 vs.06:2013
Total metals	SMEWW 22ᵃ Ed 2012 - Method 3030E USEPA 6010 C - rev.03:2007 POPDAM060
Malic and trans-aconitic acids	High performance liquid chromatography (HPLC)
Organic, inorganic and total carbon and total nitrogen	Auto Sampler Shimadzu model ASI–L (Japan)

Parameters evaluated	Vinasse samples
Parameters evaluated	Rv	Cent.	Sc	Sc Ac
pH (-log[H⁺])	4.58	0	0	+61.1
Absorbance 570 nm (UA)	3.650	−81.3	−83.8	−89.3
Absorbance 455 nm (UA)	5.653	−67	−73.9	−88.5
COD (mg O₂ L⁻¹)	51,817	−13.4	−26.8	−37.2
BOD (mg L⁻¹)	24,207	−29.7	−30.3	−47.3
Total suspended solids (mg L⁻¹)	45,900	−97.3	−95.5	−98.2
Calculated hardness (mg CaCO₃ L⁻¹)	3,034	−48.1	−36.5	−44.8
Electrolytic conductivity (μS cm⁻²)	19,852	−41.5	−45	−31.4
Total carbon (mg L⁻¹)	17,416	−7.2	−13.5	−40.1
Total organic carbon (mg L⁻¹)	17,388	−7.2	−13.6	−40.4
Total inorganic carbon (mg L⁻¹)	28.16	−24.2	+20.8	+167.6
Total nitrogen (mg L⁻¹)	764	−17.2	−28.4	−58.6
Nitric N (mg L⁻¹)	< 11.400	ND	ND	ND
Nitrous N (mg L⁻¹)	< 0.300	ND	ND	ND
Ammoniacal N (mg L⁻¹)	134.7	−74.8	−78.5	−81.6
Kjendahl N (mg L⁻¹)	492	−30.8	−43.8	−59.5
Na (mg L⁻¹)	36.6	−71.6	−62.3	−65.6
Ca (mg L⁻¹)	735	−11.8	+5	+5.7
K (mg L⁻¹)	4,340	−1.4	−12	−11.8
Mg (mg L⁻¹)	498	0	−2.8	−5
Sulfate (mg L⁻¹)	1,327	−0.8	+39.8	+60.5
Fosfate (mg L⁻¹)	< 2,000	ND	ND	ND
K₂O (kg K₂O m⁻³)	5.21	−0.9	−12.1	−11.9
Malic acid	1,630,61	−19.4	−38.4	−36.4
Trans-acotinic acid	626,88	−19.6	−51.6	−62.5

Treatments	Centrifuged vinasse at 20%	Adsorbed vinasse at 60%
Dilution with distilled water	1.477 (0.062)	1.089 (0.056)
Dilution with BG11 medium	0.408 (0.020)	1.055 (0.043)

Parameter	Centrifugation	Smectite clay and actived charcoal
Treated vinasse^a a Percent (v/v) of the final treated vinasse in relation to vinasse at the beginning of the process	97%	40%
Materials for treatment	NaOH for pH correction	Smectite clay, activated charcoal, HCl for pH correction
Waste generated in treatments^b b smectite clay and activated carbon could be possibly reutilized if an elution step is considered, which would result in less material used, but more water consumption and effluent generation. This possibility was not tested in this study	0.02 kg of centrifugation cake L⁻¹ vinasse	0.10 kg of clay, 0.06 kg of charcoal and ∼ 0.60 kg of adsorbed materials L⁻¹ of vinasse and a porous membrane
Equipment used in treatment	Centrifuge	Mechanical mixer, decantation tank and filtration system
Stages of treatment	Centrifugation and supernatant collection	Mixing vinasse with smectite clay, decantation, supernatant collection, charcoal filtration
Processing time	0.2 h using 2,510 g	∼ 8 h
Treated vinasse in cultures	20%	60%
Algal growth	1.477 day⁻¹	1.089 day⁻¹
Algal cell yield in 96 h^c c according to the tests with treated vinasse diluted with distilled water to C. vulgaris.	2.0 10¹² cells m⁻³	1.1 10¹² cells m⁻³

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[1] * Corresponding author: cacandido90@gmail.com