1
Introduction
The landfill
leachate can be considered as a matrix of extreme complexity, composed by four
fractions: dissolved organic matter, represented by volatile fatty acids; humic
and fulvic compounds; xenobiotic organic compounds, represented by aromatic
hydrocarbons; inorganic macro-components such as calcium, magnesium, sodium,
potassium, ammonia, iron, etc. and potentially toxic metals. The conventional
processes used in leachate treatment are based on physical-chemical and
biological processes. The first, are usually based on
precipitation-flocculation processes which present high purification efficiency
only for suspended substances. In addition, the contaminants are not completely
degraded, which necessarily implies the generation of a solid phases (sludge)
(Tchoubanoglous & Kreith, 2002). Biological processes can be used to
leachate treatment. Unfortunately, characteristics such long detention times,
from days to weeks, and low efficiency in the recalcitrant compounds and
pigments removal, make their efficiency quite controversial (Tchoubanoglous
& Kreith, 2002).
To increase the
efficiency of the pollutant compounds removal in the leachate, the wetlands as
a low-cost alternative for this purpose. In the wetlands, physical (sedimentation,
filtration and adsorption), chemical (decomposition) and biological (microbial
metabolism, plant metabolism and natural decay) mechanisms of pollutant removal
are performed (Jordão and Pessoa, 2005). The wetlands can be classified as a
natural system of wastewater treatment, based on saturated areas by water or
groundwater, where several species of plants that depend directly on the
nutritional characteristic of the region where they found (Wood &
McAtamney, 1996). These systems were created to optimize the removal or
transformation of pollutants from wastewater, in addition to creating an
environment to the development of different types of vegetation. Vertical flow
baths operate with intermittent vertical flow of wastewater, are filled with
gravel and sand and the level of the applied liquid remains below the support
medium. (Kadlec, 1995).
The use of wetlands
provides greater operational control with regard to wastewater purification,
appearing as an environmentally more adequate alternative. They also have
advantages when compared to natural systems, emphasizing the need for a smaller
surface to treat the same load and the fact that they are more easily applied
to specific effluents. (Porchaska and Zouboulis, 2006). The good results of
wetlands in the leachate treatment are already known internationally. The
suspended solids present in the leachate can be rapidly removed by the process,
due to the conditions of tranquility of flow that determines the deposition of
these materials. Growth and microbial activity are responsible for the removal
of soluble organic matter. The removal of total nitrogen can reach 70%
efficiency, not only by the incorporation into the aquatic macrophytes fabric
but also by the nitrification and denitrification processes that take place
inside the wetland (Bidone, 2008).
Studies conducted
by Fleck (2003), treating leachate in wetlands, obtained removals of 42.5% of
organic matter, 36.7% of phosphorus, 77.5% for total suspended solids and
overall removal of 37.7% for all forms of nitrogen.
Beltrão (2006) also
used wetlands for leachate treatment, obtaining efficiencies above to 46% in
the removal of organic matter.
In the wetlands,
the plants and the support medium allow the accumulation and the fixation of
the active biomass in the system. As a result of their activity, the plants
introduce oxygen into the liquid medium forming an environment favorable to the
aerobic stabilization of the organic matter. Plants develop from the
consumption of nutrients, which were presents in the liquid to be treated and
can be assimilated by plants (Bidone, 2008).
Ruttens et al.
(2011) report a great tendency in the use of oil plants as phytoextractors of
heavy metals and biomass producers for transformation into biodiesel,
contributing to the decontamination of polluted areas and to the production of
energy that is less polluting to the environment. Good phytoextraction results
were obtained using species such as castor bean (Romeiro et al., 2006),
sunflower (Zeittouni et al., 2007) and maize (Pereira et al., 2007).
Oleaginous plants have
a large quantity of oil, both from their seeds (soybean, rape, sunflower) and
from their fruits (palm, coconut), and can be used for the production of vegetable
oil. Another important characteristic of some of these plants is the fact that
after the extraction of the oil, by-products can be used for different
applications. In Brazil, with the model adopted for the development of the
Biodiesel Program, the production chain of this biofuel uses oilseed species as
its main raw material. The diversity of agricultural crops (oilseeds) used
varies according to the characteristics of each Brazilian region or State
(Ministério do Meio Ambiente, 2006).
The development of
agroenergy production chains of different oilseeds needs to take into account
factors that involve the environment in order to indicate the best cultivars to
be explored. For the South Region the oil plants with the greatest potential
for cultivation are soya, rape, sunflower and cotton (Ministério do Meio Ambiente,
2006).
From an economic
point, the viability of biodiesel is related to the establishment of a
favorable equilibrium to the Brazilian trade balance, since diesel is the most
consumed petroleum derivative in Brazil, and that a growing fraction of this
product is being imported annually. Data from the National Petroleum Agency
(ANP) (2005) indicate that Brazil imports 9% of the total diesel oil it
consumes. However, this percentage rises to 15% when oil imports are taken into
account, since diesel accounts for approximately 35% of the total refined
volume. In environmental terms, the adoption of biodiesel, even if progressively,
from 2 to 5% additions in petroleum diesel, will result in a significant
reduction in particulates emissions, sulfur oxides and the greenhouse effect
(Mitellbach, 1990; Koverski and Hess, 2006).
In the present
study were evaluated the efficiency of wetlands used in the tertiary treatment
of leachate from the landfill of the city of Lages / SC and the cultivation of
oleaginous plants in these wetlands for the biodiesel production. These results
will serve as a basis for future projects in the environmental area, especially
as regards the improvement in the treatment of leachate, its reuse as a source
of nutrients for growing plants with energy potential. The lack of specific
research using soybean and sunflower, irrigated with treated slury, creates a perspective
for the study and application of this process of reutilization of treated
effluent for irrigation of energy crops.
2
Materials and Methods
Before the application
in the wetlands, the leachate was treated at the landfill wastewater treatment
plant, which included the steps: anaerobic lagoon, facultative lagoon, aerated
lagoon and physical-chemical treatment. Results of preliminary analyzes
indicated that the treated leachate had organic matter, nitrogen and phosphorus
suitable for the use in wetlands. The metals present in the treated leachate
were determinated and quantified using Plasma Optical Emission Spectrometry
(PerkinElmer Optima 8300).
The plants used in
wetlands were soybean and sunflower because they have great potential to
generate oil that can transformed into biodiesel.
It was constructed 9
wetlands with 8L each, were filled with a gravel number 3 (5cm of height) and
sand (15cm of height). To the removal of the leachate were used valves
installed in the lower part of the wetlands, and they were operated in batch
mode with hydraulic detention time (HRT) of 2 and 4 days. The concentrations of
effluent treated used were 10% and 25% (applied in 3 wetlands for each
concentration), both concentrations was determined by laboratory toxicity tests.
The liquid chemical fertilizer was applied in other 3 wetlands in concentration
of 5 mL / L, added every 20 days, the other irrigation was performed only with
water. Each wetland was received 3 liters of the treated effluent per
irrigation.
In HRT 2-day, twelve
samples were collected for each concentration, and were analised parameters
such as: Chemical Oxygen Demand (COD), Total Kjeldahl Nitrogen (NTK), ammonia
(NH3), nitrate (NO3-), nitrite(NO2-)
and total phosphorus (PT), according with APHA (2005).
In the tests
carried out with HRT of 4 days, eighteen samples were collected for each
concentration. Due to the small amount of sample at the end of each irrigation
cycle, only COD and NH3 were monitored in this condition, according
to the methodologies described in APHA (2005).
After 4 months, the
development of the plants was analyzed comparing the wetlands irrigated with
leachate and wetlands irrigated with chemical fertilizer.
3
Results and discussion
The table 1 presented the average concentrations of NO2-,
NO3-, NH3, COD, BOD and PT found in treated
leachate before to dilutions and applications in wetlands.
Table 1 – Characteristics of the treated
leachate collected in the landfill
|
Parameter
|
Average concentration (mg/L)
|
|
NO3-
|
11,5
|
|
NO2-
|
1,41
|
|
NH3
|
21,3
|
|
DQO
|
803,88
|
|
DBO
|
11,00
|
|
PT
TKN
|
13,07
504,00
|
The characterization of the treated leachate showed that
it had potential to be used in the irrigation of the wetlands, because it has
high concentrations of phosphorus and COD remaining, which could be used as
nutrients in the growth of crops for energetic purposes, would promote a post
treatment to leachate improving your final characteristics.
The metals concentrations presents in the leachate
collected at the end of the landfill treatment plant are presented in Table 2.
Table 2 – Metals concentrations in leachate
landfill and respective standards according to CONAMA 430/11 resolution
|
Metals
|
Concentration
(mg/L)
|
CONAMA
430/2011 (mg/L)
|
|
Al
|
1,45
|
10
|
|
Ba
|
nd
|
5
|
|
Cd
|
nd
|
0,2
|
|
Co
|
0,017
|
0,05
|
|
Cr
|
0,031
|
1
|
|
Cu
|
nd
|
1
|
|
Fe
|
0,050
|
15
|
|
Mn
|
0,618
|
1
|
|
Ni
|
0,045
|
2
|
|
Pb
|
0,013
|
0,5
|
|
Zn
|
nd
|
5
|
|
B
|
0,581
|
5
|
|
Li
|
0,053
|
2,5
|
The metals analyzed in the treated leachate were in
concentrations below the limit established by the CONAMA 430/2011 resolution,
making it possible to reuse them for the cultivation of energetic plants.
Furthermore, the dilutions used in this work greatly reduce the risk of soil
contamination where will be applied.
In
the experiments with soybean, in both HRT tested, the seeds did not develop in
the wetlands. According to Aguiar (1978), Wetzel (1978) and Souza (1996),
soybean seeds have membrane more permeable,
facilitating its liquid saturation and causing the rupture of the seed. In
addition, soybean seed needs to absorb at least 50% of its weight in water to
ensure good germination. At this stage, the soil water content should not exceed
85% of the maximum available water and should not be less than 50% (Lantmann,
2014). In the wetlands studied the amount of liquid exceeded 85% since there
was excess of liquid in the surface, being able to be the cause of the
non-development of the soybean seeds.
The mean results, and respective standard deviations in
parentheses, of the parameters analyzed in the wetlands operated with HRT of 2
days and cultivated with sunflower was show in Table 3.
Table 3 - Initial and final average concentrations of the
analysed parameters in the wetlands cultivated with sunflower and operated with
HRT of 2 days, their removal percentage and standard deviations
|
Leachate concentration (%)
|
Parameter
|
Initial concentration (mg/L)
|
Final concentration (mg/L)
|
Remotion (%)
|
|
25
|
COD
|
238,71
(±90,8)
|
180,55
(±45,2)
|
24,4
|
|
NH3
|
2,27(±0,23)
|
0,27(±0,81)
|
88,1
|
|
NO3-
|
8,39(±1,12)
|
23,54
(±8,1)
|
-180,5
|
|
NO2-
|
0,02(±0,01)
|
0,01(±0,01)
|
50
|
|
PT
|
0,08(±0,005)
|
0,04(±0)
|
50
|
|
TKN
|
146,0(±1,0)
|
131,4
(±1,2)
|
10
|
|
10
|
COD
|
184,52(±20,02)
|
79,61
(±35,19)
|
56,9
|
|
NH3
|
1,94(±0,06)
|
0,46(±0,69)
|
76,3
|
|
NO3-
|
5,79(±0,91)
|
22,69
(±8,55)
|
-291,9
|
|
NO2-
|
0,037(±0,03)
|
0,03(±0)
|
18,9
|
|
PT
|
0,05(±0,005)
|
0,03(±0)
|
40
|
|
TKN
|
102,48(±0,4)
|
100,5(±0,0007)
|
1,9
|
|
|
|
|
|
|
Removal of phosphorus, ammonia, nitrite and TKN was higher
when the wetlands were irrigated with treated leachate at 25%. The plants consume
phosphorus, mainly in the time of the flowering,
being necessary the vegetation removal, because the phosphorus can return to
the system later, due to the decay of the plant. Phosphorus adsorption by the
wetland is limited, so when this limit is reached, phosphorus elimination is
reduced (Soares, 2012).
In the wetlands, the nitrogen removal occurs from the
sequential processes of nitrification and denitrification in aerobic/anoxic environments.
After these reactions, the ammoniacal nitrogen is converted into molecular
nitrogen, which is released into the atmosphere as gas (Haandel et al., 2009).
Nitrogen conversion occurs in three processes: ammonification (or assimilation
of ammonia); nitrification and denitrification (Haandel et al., 2009). It was observed
an increase in the nitrate concentration in the wetlands percolated, the
occurrence of this phenomenon is due that the nitrate is not adsorbed by the
substrate where the oleaginous plants were cultivated, due to its negative
charge. A portion of this nitrate have been used by the plants for its
development and the excess was eliminated with the effluent. Studies conducted
by Dutra et al. (2012) evaluating the influence of irrigation on sunflower
cultivation showed that this condition of moisture saturation leads to a lack
of oxygen to the roots. This condition causes the death of the root tissues,
favoring the lactic fermentation
and acidosis in the cells, the reduction in nutrient absorption, water and
influence the final size of the plant. The HRT may have influenced in the
removal efficiency of the analyzed parameters, since
the constant watering made the wetlands remain with high humidity. Excess water
contributed to the low removal of organic matter from the 25% concentration as
compared to the 10% concentration tested, because it may be in the form of
recalcitrant compounds and require a higher HRT for the reduction of its
concentration. The mean results, and respective standard deviations in
parentheses, of the parameters analyzed in the wetlands operated with HRT of 4
days and cultivated with sunflower was show in Table 4.
Table 4 - Initial and final average concentrations of the
analysed parameters in the wetlands cultivated with sunflower and operated with
HRT of 4 days, their removal percentage and standard deviations
|
Leachate concentration (%)
|
Parameter
|
Initial
concentration (mg/L)
|
Final
concentration (mg/L)
|
Remotion
(%)
|
|
25
|
COD
|
252,7 (±29,7)
|
84,1
(±22,2)
|
66,6
|
|
NH3
|
22,5 (± 1,4)
|
0,22
(±0,09)
|
99,0
|
|
10
|
COD
|
101,1 (±11,8)
|
38,1
(±3,2)
|
62,2
|
|
NH3
|
9,1 (± 1,0)
|
0,15
(±0,08)
|
98,3
|
|
|
|
|
|
|
High
HRT caused water and nutritional shortages, favoring high ammonia and COD
removal in studied concentrations, being higher when the applied leachate concentration
was 25%.
The
Table 5 presents the sunflower plants development.
Table
5 - Height of sunflower plants
|
HRT
(d)
|
Leachate concentration (%)
|
Plant height (cm)
|
|
2
|
10
|
20
|
|
25
|
17
|
|
|
Chemical fertilizer
|
33
|
|
4
|
10
|
73
|
|
25
|
54
|
|
|
Chemical fertilizer
|
55
|
It
was observed that the low concentration of leachate (10%), combined with the
high HRT (4d), resulted in larger plants, confirming the negative influence of
the excess of recalcitrant organic matter and excess
moisture in the plant growth.
4
Conclusions
The application of treated leachate at 10% concentration
and with HRT of 4 days favored the treatment of the effluent and the growth of
the sunflower plants.
The HRT of 2 days maintained the wetlands with excess
humidity, damaging its efficiency and the growth of cultivated plants.
The treated leachate presented an improvement in its
quality after passing through the wetlands, indicating the possibility of this
reuse for the sunflower seed cultivation that can be used to obtain biofuels.
Acknowledgements
Thanks to the reviewers and the Santa
Catarina State University.
References
APHA;
AWWA; WPCF. Standard Methods for the Examination of Water & Wastewater.
21 ed. Washington, 2005.
CHRISTENSEN,
T.R.; JOABSSON, A. Methane emissions from wetlands and their relationship with
vascular plants: an Arctic example. Global Change Biology, v. 7, p.
919-932, 2001.
Dutra, C. C.; Prado, E. A. F.; Paim, L. R.; Scalon, S. P.Q.
Desenvolvimento de plantas de girassol sob diferentes condições de fornecimento
de água. Semina: Ciências Agrárias, Londrina, v. 33, suplemento 1, p.
2657-2668, 2012.
FERRARI,
R.A.; OLIVEIRA, V.S.; SCABIO, A. Oxidative stability of biodiesel from soybean
oil fatty acid ethyl esters. Quim. Nova, v. 28, n.1, p.20, 2005.
JORDÃO,
E. P.; PESSÔA, C. A. 2005. Tratamento de esgotos domésticos. Associação
Brasileira de Engenharia Sanitária e Ambiental. 4. ed. Rio de
Janeiro, 2005
KADLEC,
R. H. Overview: surface flow constructed wetlands. Wat. Sci. and Tech.
v. 32, n. 3, 1995.
KERN,
J.; IDLER, C. Treatment of domestic and agricultural wastewater by reed bed
systems. Ecological
Engineering,
v. 12, 1999.
KOZERSKI,
R.G.; HESS, C.S. Estimativa dos poluentes emitidos pelos ônibus e microônibus
de Campo Grande/MS, empregando como combustível diesel, biodiesel ou gás natural.
Eng. Sanit. Ambient., v. 11, n. 2, p.113-117, 2006.
LUTZ,
I. A. Métodos Químicos e Físicos para Análise de Alimentos, São Paulo,
2ª ed. 1976.
MINISTÉRIO
DO MEIO AMBIENTE – MMA. Caracterização de Diferentes Oleaginosas para a
Produção de Biodiesel. Disponível on line:
(http://www.mma.gov.br/estruturas/sqa_pnla/_arquivos/item_5.pdf. Acesso: 18/09/2017,
2006.
MITTELBACH,
M. Lipase catalyzed alcoholysis of sunflower oil. J. of American Oil Chem.
Soc., v. 67, p.168-170, 1990.
Pereira,
B. F. F.; Abreu, C. A.; Romeiro, S.; Paz-González, A. Pb
phytoextraction by maize in a Pb treated Oxisol. Scientia Agricola,
v.64, p.52-60, 2007.
PROCHASKA,
C.A.; ZOUBOULIS, A. I. Removal of phosphates by pilot vertical-flow constructed
wetlands using a mixture of sand and dolomite as substrate. Ecological
Engineering, v. 26, 2006.
Romeiro,
S.; Lagôa, A. M. M. A.; Furlani, P. R.; Abreu, C. A.; Abreu, M. F.
Lead uptake and tolerance of Ricinus communis L. Brazilian Journal of
Plant Physiology, v.18, p.1-5. 2005.
Ruttens,
A.; Boulet, J.; Weyens, N.; Smeets, K.; Adriaensen, K.; Meers, E.; Slycken, S.
van.; Tack, F.; Meiresonne, L.; Thewys, T.; Witters, N.; Carleer, R.; Dupae,
R.; Vangronsveld, J. Short rotation coppice culture of willows and
poplars as energy crops on metal contaminated agricultural soils. International
Journal of Phytoremediation, v.13, p.194-207, 2011.
SUN,
G.; GRAY, K.R.; BIDDLESTONE, A. J.; COOPER, D.J. Treatment of agricultural
wastewater in a combined tidal flow-downflow reed bed system. Water Science
and Technology, v. 40, n. 1, 1999.
TCHOUBANOGLOUS,
G.; KREITH, F. Handbook of Solid Waste Management. 2 Ed. Nova Iorque.
McGraw-Hill, 2002.
WOOD,
R. B. & McATAMNEY, C. F. Constructed wetlands for wastewater treatment: the
use of laterite in the bed medium in phosphurus and heavy metal removal. Hidrobiology, v. 340, 1996.
Zeitouni, C. F.; Berton, R. S.; Abreu, C. A fitoextração de
cádmio e zinco de um latossolo vermelho-amarelo contaminado com metais pesados.
Bragantia, v.66,
p.649-657, 2007.
ZHAO,
Y. Q.; SUN, G.; ALLEN, S. J. Anti-sized reed bed system for animal wastewater
treatment: a comparative study. Water Research, v. 38, 2004.