Microsoft Word - 55castellanos.docx
CHEMICAL ENGINEERING TRANSACTIONS
VOL. 64, 2018
A publication of
The Italian Association
of Chemical Engineering
Online at www.aidic.it/cet
Guest Editors: Enrico Bardone, Antonio Marzocchella, Tajalli Keshavarz
Copyright © 2018, AIDIC Servizi S.r.l.
ISBN 978-88-95608- 56-3; ISSN 2283-9216
Biosurfactant Application as Alternative Collectors in
Dissolved Air Flotation System
Elias J. Silva a, Marcos J. Chaprão a, Ivison A. Silva a, Pedro P.F. Brasileiro c,
Darne G. Almeida b,c, Juliana M. de Luna b,c, Raquel D. Rufino b,c, Valdemir A.
Santos b,c, Leonie A. Sarubbo *a,b,c
a Northeast Biotechnology Network, Federal Rural University of Pernambuco –Recife – Pernambuco, Brazil
b Catholic University of Pernambuco, Rua do Príncipe, n. 526, Boa Vista, Cep: 50050-900, Recife-Pernambuco, Brazil
c Advanced Institute of Technology and Innovation (IATI), Rua Joaquim de Brito, n. 216, Boa Vista, CEP: 50070-280,
Recife, Pernambuco, Brazil
leonie@unicap.br
The effluent production of oily water type has generated many environmental problems for several industries.
The use of flotation as a separation process of oily waters has been described, although it has been
sometimes criticized due to the toxicity of collectors. The development and use of biodegradable surfactants
may enhance the further acceptance of this separation technology. In this sense, the dissolved air flotation
(DAF) process continues to be widely used in industries, both for water and wastewater supplies. The use of
collectors is essential to improve the efficiency of the process, due to its specific characteristics that facilitate
the adhesion of the particles and, consequently, the separation of the pollutants. These surface-active
molecules of biological origin also have several advantages over synthetic surfactants such as higher
biodegradability, higher foaming, less toxicity, better environmental compatibility, more tolerant to pH, salt, and
temperature variation, and higher selectivity for metals and organic compounds and can be synthesized from
renewable feedstocks. The aim of this study was to investigate a water-oil separation by DAF, with and
without the addition of biosurfactant produced by Pseudomonas cepacia CCT 669 in mineral medium and
formulated with 2.0% of corn steep and 3.0% of canola waste frying oil at 28°C for 60 h under 200 rpm. The
experiments used to compare the effects of the addition of biosurfactant followed an experimental planning
CCRD, where the response variable was the separation efficiency. Results indicated the biosurfactant added
a considerable value to the process, increasing from 41.0% to 98.0% the separation efficiency, presenting
potential of application as a collector of oily contaminants in the DAF process form.
1. Introduction
Petroleum industry and related industries unavoidably generates large volumes of oily wastewater which has
become an urgent challenge for most oilfield and petroleum company focusing attention toward efficient
treatment techniques. Effluent production of oily water type has generated many environmental problems for
several industries (Yu et al., 2013).
Separation technologies such as centrifugation, ultrafiltration, decantation, flotation, and flocculation are
examples of physical/chemical processes effectively used for the separation of oil-water mixtures
(Painmanakula et al., 2010). In this context, the flotation process has proven to be quite efficient, with the
capability of removing a larger amount of oil in comparison to other methods (Albuquerque et al. 2012).
Flotation is a bubbles adhesion based particle separation process. The oil particle-bubble union has less
density than the aqueous medium and floats to the surface of the flotation chamber, where the oil particles are
removed (Bahadori et al. 2013). Flotation was first used in mineral processing and has long been employed in
solid/liquid separation processes that involve the use of stable foams to recover mineral particles (Peng et al.
2009).
With the industrial sector development, the flotation process application was improved, leading to the
emergence of dissolved air flotation (DAF), which involves solute removal through adsorption, co-precipitation
DOI: 10.3303/CET1864092
Please cite this article as: Silva E., Chaprao M.J., Silva I., Brasileiro P., Almeida D., Luna J., Rufino R., Dos Santos V. A., Sarubbo L., 2018,
Biosurfactant application as alternative collectors in dissolved air flotation system, Chemical Engineering Transactions, 64, 547-552
DOI: 10.3303/CET1864092
547
or occlusion in a floc transporter and subsequent release by the addition of an adequate tensioactive agent
(Beneventi et al. 2009). With DAF, the water is saturated with pressurised air through a nozzle, forming
bubbles that reach the flotation chamber, which is at atmospheric pressure. The air becomes supersaturated
and precipitates from the solution in the form of small bubbles (Babaahmadi, 2010; Rocha e Silva et al. 2015).
The use of flotation as a separation process of oily waters have been widely employed wastewater treatments,
of oil industries (Bahadori et al., 2013; Rocha e Silva et al. 2015). The dissolved air flotation may be
considered as a clean technology since it uses small quantities of coagulant and air to promote separation.
The size, speed, and bubbles, along with the velocity gradient are important parameters to control the
efficiency of the process and operating costs (Babaahmadi, 2010). On the other hand, this technique has been
sometimes criticized due to the toxicity of the synthetic surfactants used as collectors in this process
(Menezes et al., 2011). Surfactants are compounds composed of amphipathic molecules with a hydrophilic
portion and a hydrophobic portion that partition at the oil/water or air/water interface. The apolar portion is
often a hydrocarbon chain, whereas the polar portion may be ionic (cationic or anionic), non-ionic or
amphoteric. These characteristics enable surfactants to reduce surface and interfacial tension and form
microemulsions, in which hydrocarbons can be solubilised in water or vice versa (Almeida et al. 2016).
Currently, the development and use of biodegradable surfactants (biosurfactants) has helped to increase
acceptance of this separation technology (Rocha e Silva et al., 2015). Biosurfactants are amphipathic
molecules that reduce the surface and interfacial tensions of liquids. Such compounds have a predilection for
interfaces of dissimilar polarities (liquid–oil) and are soluble in both organic (non-polar) and aqueous (polar)
solvents (Silva et al., 2014). These surface-active molecules of biological origin also have several advantages
over synthetic surfactants such as higher biodegradability, higher foaming, less toxicity, better environmental
compatibility, more tolerant to pH, salt, and temperature variation, and higher selectivity for metals and organic
compounds and can be synthesized from renewable feedstocks (Menezes et al., 2011).
The aim of this study was to investigate a water-oil separation by DAF, with addition of biosurfactant, in a pilot-
scale DAF system. The experiments used to evaluate the effects of biosurfactant addition followed an
experimental planning CCRD, where the response variable was the oil removal efficiency.
2. Materials and Methods
2.1 Materials
All chemicals were of reagent grade. Growth media were purchased from Difco Laboratories, USA. Canola
waste frying oil was received from a local restaurant in Recife-PE, Brazil and was stored according to
supplier’s recommendations and used without any further processing. Corn steep liquor was obtained from the
Ingredion Brasil factory, Cabo de Santo Agostinho-PE, Brazil.
2.2 Bacterial strain and inoculum preparation
A strain of P. cepacia CCT6659 was provided from the culture collection of the Fundação André Tosello de
Pesquisa e Tecnologia, Campinas city, São Paulo, Brazil. The microorganism was maintained in nutrient agar
slants at 4°C. For pre-culture, the strain from a 24-h culture on nutrient agar was transferred into 50 ml nutrient
broth to prepare the seed culture. The cultivation condition for the seed culture was 28°C, 200 rpm, and 24h of
incubation time.
2.3 Biosurfactant production
The fermentation for the biosurfactant production was carried out in distilled water containing 2% of canola oil
residual, 3% of corn steep liquor, 0.2% NaNO3, 0.05% KH2PO4, 0.1% K2HPO4, 0.05% MgSO4 .7H2O, 0.01%
KCl and 0.001% FeSO4 .7H2O. After media preparation, the pH was adjusted to 7.0 and these were
autoclaved at 121°C for 20 minutes. The culture was incubated in a rotary Marconi MA832 shaker (Marconi
Laboratory equipment, SP, Brazil) for 60 h at 200 rpm (Silva et al., 2013).
2.4 Surface tension measurement
Surface tension was determined in the cell-free broth obtained by centrifuging the cultures at 10,000 × g for 15
min. Surface tension was determined with a Tensiometer (Sigma 700, KSV Instruments Ltd., Finland), using
the Du Nouy ring method at room temperature (Silva et al., 2014).
2.5 CCRD Experimental factorial design
In order to study biosurfactant potential as an alternative collector on the oil-water separation in a DAF pilot
scale system prototype (Figure 1), central composite rotational design (CCRD) application was performed.
The independent variables were coded at five levels (-2.00, -1.00, 0.00, +1.00, +2.00) and the complete
design consisted of 28 experimental points including 4 replications of the central points. The coded levels of
548
the independent variables used in the experimental design are listed in Table 1. The response variable was
the oil removal efficiency of the pilot prototype. All determinations were performed at least three times.
ANOVA, regression coefficients and the construction of graphs were performed using the Statistica® program,
version 10.0 (Statsoft Inc, USA).
Table 1: Experimental range and levels of independent variables for oil removal efficiency in the pilot scale
DAF system with use of the biosurfactant
Levels Oily Water
Flow (X1)*
Microbubble
Flow (X2)*
Biosurfactant
Flow (X3)*
Biosurfactant
Concentration (X4)**
-2.00 2.50 5.00 0.50 0.05
-1.00 5.00 5.50 1.00 0.15
0.00 7.50 6.00 1.50 0.25
1.00 10.00 6.50 2.00 0.35
2.00 12.50 7.00 2.50 0.45
* (L/min); ** (g/L)
Figure 1: Three dimensional scheme of pilot scale DAF system. Oily water storage tank (1); Flotation chamber
(2); Second section where separation between treated water and oily foam formed (3); Oily foam collectors
(4); Chamber of treated water collection (5); Return pump for treated water (6); Microbubble production pump
(7); and oily water production pump and DAF chamber feed (8)
3. Results and Discussion
3.1 Biosurfactant production
The properties and integrity of the biosurfactant produced were verified prior to the tests for the study of its
potential as an alternative collector. The biosurfactant produced was able to reduce the surface tension of the
culture medium from 55.0 mN/m to 28.0 mN/m corroborating with the results obtained by Soares da Silva et al
(2017) under the same conditions evaluated.
3.2 Evaluation of water-oil separation efficiency using biosurfactant in the DAF system
The CCRD matrix and corresponding results are given in Table 2.
As a result, the effluent flow rate of 5.00 L/min, microbubble water flow of 5.50 L/min, biosurfactant flow rate of
1.00 L/min and biosurfactant concentration of 0.35 g/L were the more favorable parameters for the oil removal
process using this type of biosurfactant, reaching a percentage of removal of 98.25% (Run 2), compared with
41.20% of oil removal without the use of the biosurfactant as an alternative collector. The results were not
favorable for biosurfactant action of the in the DAF process occurred in the tests 10 and 11 (11.08 and
12.09%, respectively), which was probably due to the considerable increase of the effluent flow (oily water)
and low concentration of the biosurfactant which must have influenced negatively in the micelles formation
and compromised the collision between the microbubbles and the particles of the oil.
549
Table 2: Experimental design results matrix and values of observed factors on separation efficiency in the
pilot scale DAF system with use of biosurfactant
Runs Oily Water
Flow (X1)
Microbubble
Flow (X2)
Biosurfactant
Flow (X3)
Biosurfactant
Concentration(X4)
Removal
efficiency (%)(Y)
1 5.00 5.50 1.00 0.15 63.20
2 5.00 5.50 1.00 0.35 98.25
3 5.00 5.50 2.00 0.15 85.18
4 5.00 5.50 2.00 0.35 73.83
5 5.00 6.50 1.00 0.15 65.38
6 5.00 6.50 1.00 0.35 49.76
7 5.00 6.50 2.00 0.15 37.82
8 5.00 6.50 2.00 0.35 80.86
9 10.00 5.50 1.00 0.15 80.20
10 10.00 5.50 1.00 0.35 11.08
11 10.00 5.50 2.00 0.15 12.09
12 10.00 5.50 2.00 0.35 71.74
13 10.00 6.50 1.00 0.15 63.95
14 10.00 6.50 1.00 0.35 36.36
15 10.00 6.50 2.00 0.15 29.59
16 10.00 6.50 2.00 0.35 30.39
17 2.50 6.00 1.50 0.25 51.38
18 12.50 6.00 1.50 0.25 19.08
19 7.50 5.16 1.50 0.25 34.13
20 7.50 6.84 1.50 0.25 42.42
21 7.50 6.00 0.50 0.25 40.00
22 7.50 6.00 2.50 0.25 51.37
23 7.50 6.00 1.50 0.05 38.89
24 7.50 6.00 1.50 0.45 73.44
25 7.50 6.00 1.50 0.25 51.88
26 7.50 6.00 1.50 0.25 46.61
27 7.50 6.00 1.50 0.25 47.29
28 7.50 6.00 1.50 0.25 50.54
The Pareto diagram shown in Figure 2 shows the statistical significances of the studied variables at p-values
(< 0.05). As can be observed, the Oily Water Flow (X1) was the most significant variable for the process and
its increase causes a decrease in the efficiency of oil removal by the system. The Biosurfactant Flow did not
present statistical significance (X3), however, its concentration (Biosurfactant Concentration) was positively
correlated with the oil removal efficiency.
Figure 3 displays the fitted response surface plots for oil removal efficiency shown by Pareto diagram of the
statistically significant interactions. The combination of greater oily water flow and greater microbubble flow led
to maximum oil removal efficiency (Fig. 3A) and the elliptic curve found in the graph indicates a high degree of
interaction of these variables. Figure 3B shows that high oil removal efficiency was also achieved when both
oily water flow and biosurfactant concentration were maintained at their maximum levels. Better oil removal
efficiency was found when the biosurfactant flow and biosurfactant concentration was maintained at its
maximum level (Fig. 3C), however, these interactions were weak and did not produce well-defined regions in
the graphs.
550
Figure 2: Pareto’s Chart of the Central Composed Rotate Design.
In another study conducted by Rocha e Silva et al (2015), a biosurfactant obtained from Candida sphaerica
UCP 0995 also promotes an improvement of the oil removal in the DAF system. The authors reported
increasing separation efficiency from 80.0 to 98.0% in the presence of biosurfactants. The results demonstrate
a better performance of the bench scale system using the biosurfactant as a coadjuvant in the DAF process,
compared to the action of the microbubbles only without the use of this alternative collector. This confirms the
potential of these microbial biomolecules as an aid in the removal of hydrophobic compounds in Dissolved Air
Flotation. In addition, it is important to highlight that the biosurfactant from P. cepacia CCT 669 was produced
in a culture medium prepared only with industrial waste products, which further reduces the process costs,
since substrates used in the production of biosurfactants account for 20 to 30% of the production cost (Hazra
et al., 2012; Santos et al., 2016). The low cost of the proposed DAF process is evident by the small amount of
biosurfactant (350 ppm) required to achieve maximum efficiency (run number 2 in Table 2). As many
industries generate huge amounts of oily waters that require adequate treatment before being discarded or
reused, the benefits of treating oily waters with the system developed herein demonstrates its considerable
market potential. Therefore, biosurfactants are promising coagulants and/or dispersants capable of increasing
the efficiency of this technique.
Figure 3: Response surface plots and contour plots for maximum removal efficiency for the 28 experimental
runs carried out under conditions established by CCRD; removal efficiency as function of (A) oily water flow
and microbubble flow; (B) oily water flow and biosurfactant concentration; (C) biosurfactant flow and
biosurfactant concentration.
4. Conclusions
The present study demonstrated the effectiveness of using a central composite rotational design to identify the
optimum parameters for increase oil removal efficiency in DAF system. The above results confirm the great
potential of the biosurfactant to be used as an alternative collector, since these microbial surfactants act as
551
true "molecular glues", interacting with the oil and the air bubbles, facilitating the oil transportation during the
process flotation, as evidenced by the results presented.
Acknowledgments
This study was funded by the Research and Development Program from National Agency of Electrical Energy
(ANEEL) the Candeias Energy Company (CEC) from Global Group, through the Project code PD-06961-
0005/2016, the Foundation for the Support of Science and Technology of the State of Pernambuco
(FACEPE), the National Council for Scientific and Technological Development (CNPq), and the Coordination
for the Improvement of Higher Level Education Personnel (CAPES).The authors are grateful to the Centre of
Sciences and Technology of the Universidade Católica de Pernambuco and to the Advanced Institute of
Technology and Innovation (IATI), Brazil.
Reference
Albuquerque CF., Luna-Finkler CL., Rufino RD., Luna JM., Menezes CTB., Santos VA., 2012, Evaluation of
Biosurfactants for Removal of Heavy Metal Ions from Aqueous Effluent Using Flotation Techniques,
International Review of Chemical Engineering, 4, 156–161.
Almeida, D.G., Soares da Silva, R.C.F., Luna, J.M., Rufino, R.D., Santos, V.A., Banat, I.M., Sarubbo, L.A.,
2016, Biosurfactants: Promising Molecules for Petroleum Biotechnology Advances, Frontiers in
Microbiology, 7, 1718, DOI: 10.3389/fmicb.2016.01718
Babaahmadi A., 2010, Dissolved Air Flotation: Numerical investigation of the contact zone on geometry,
multiphase flow and needle valves, Master’s thesis, Dept. Civil and Environm. Eng., Chalmers University
of Technology, Göteborg, Sweden.
Bahadori A., Clark M., Boyd B., 2013, Essentials of Water Systems Design in the Oil, Gas, and Chemical
Processing Industries; Springer: New York.
Beneventi D., Allix J., Zeno E., Nortier P., Carré B., 2009, Simulation of surfactant contribution to ink removal
selectivity in flotation deinking lines, Separation and Purification Technology, 64, 357–367, DOI:
10.1016/j.seppur.2008.10.033
Hazra C., Kundu. D., Chaudhari. A, 2012, Biosurfactant Assisted bioaugmentation in bioremediation. In:
Microorganisms in Environmental Management: Microbes and Environment. Eds.: Satyanarayana. T.;
Johri B.N.; Prakash. A. Springer. New York. pp. 631-664
Menezes C.T.B., Banos E.C., Rufino R.D., Luna J.M., Sarubbo L.A., 2011, Replacing synthetic with microbial
surfactants as collectors in the treatment of aqueous effluent produced by acid mine drainage, using the
dissolved air flotation technique, Applied Biochemistry and Biotechnology, 163, 540–546
Painmanakul P., Sastaravet P., Lersjintanakarn S., Khaodhiar S., 2010, Effect of bubble hydrodynamic and
chemical dosage on treatment of oily wastewater by Induced Air Flotation (IAF) process, Chemical
Engineering Research and Design, 88, 693–702, DOI: 10.1016/j.cherd.2009.10.009
Peng J.F., Song Y.H., Yuan P., Cui X.Y., Qiu, G.L., 2009, The remediation of heavy metals contaminated
sediment, Journal of Hazardous Materials, 161, 633–640, DOI: 10.1016/j.jhazmat.2008.04.061
Rocha e Silva F.C.P., Rocha e Silva N.M.P., Moura A.E., Galdino R.A., Luna J.M., Rufino R.D., Santos V.A.,
Sarubbo L.A., 2015, Effect of Biosurfactant Addition in a Pilot Scale Dissolved Air Flotation System,
Separation Science and Technology, 50, 618–625, DOI: 10.1080/01496395.2014.957319
Santos, D.K.F., Rufino, R.D., Luna, J.M., Santos, V.A., Sarubbo, L.A., 2016, Biosurfactants: multifunctional
biomolecules of the 21st century, International Journal of Molecular Sciences, 17, 401, DOI:
10.3390/ijms17030401
Silva R.C.F., Almeida D.G., Rufino R.D., Luna J.M., Santos V.A., Sarubbo L.A., 2014, Applications of
biosurfactants in the petroleum industry and the remediation of oil spills., International Journal of Molecular
Sciences, 15, 12523–42. DOI:10.3390/ijms150712523
Silva, R.C.F.S., Rufino, R.D., Luna, J.M., Farias, C.B.B., Filho, H.J.B., Santos, V.A., Sarubbo, L.A., 2013,
Enhancement of biosurfactant production from Pseudomonas cepacia CCT6659 through optimisation of
nutritional parameters using response surface methodology, Tenside Surfactants Detergents, 2, 137-142,
DOI: 10.3139/113.110241
Soares da Silva R.C.F., Almeida D.G., Meira H.M., Silva E.J., Farias B.B., Rufino R.D., Luna J.M., Sarubbo
L.A., 2017, Production and characterization of a new biosurfactant from Pseudomonas cepacia grown in
low-cost fermentative medium and its application in the oil industry, Biocatalysis and Agricultural
Biotechnology, DOI:10.1016/J.BCAB.2017.09.004
Yu L., Han M., 2013, A review of treating oily wastewater, Arabian Journal of Chemistry, 10, S1913-S1922,
DOI:10.1016/j.arabjc.2013.07.020
552