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Ecological Engineering 49 (2012) 264– 269

Contents lists available at SciVerse ScienceDirect

Ecological Engineering

jo u r n al hom ep age: www.elsev ier .com/ locate /ec oleng

erformance of constructed wetlands in the treatment of aerated coffeerocessing wastewater: Removal of nutrients and phenolic compounds

aike Rossmanna, Antonio Teixeira de Matosa, Edgar Carneiro Abreua, Fabyano Fonseca e Silvab,lisson Carraro Borgesa,∗

Universidade Federal de Vic osa, Departamento de Engenharia Agrícola, Av. Peter Henry Rolfs, s/n, Campus Universitário, CEP 36570-000, Vic osa, Minas Gerais, BrazilUniversidade Federal de Vic osa, Departamento de Estatística, Av. Peter Henry Rolfs, s/n, Campus Universitário, CEP 36570-000, Vic osa, Minas Gerais, Brazil

r t i c l e i n f o

rticle history:eceived 1 April 2012eceived in revised form 4 July 2012ccepted 10 August 2012vailable online 27 September 2012

eywords:reatment wetlandorizontal flowgro-industrial effluentoffeeeration

a b s t r a c t

Given the scarcity of studies on the behavior of constructed wetlands (CWs) when operating with pre-viously aerated wastewater, the objective of the present study was to evaluate the influence of artificialaeration and vegetation on removal of nutrients and phenolic compounds from coffee processing waste-water (CPW) treated in CWs cultivated with ryegrass (Lolium multiflorum Lam.) For this reason, CWs wereconstructed measuring 0.6 m × 0.5 m × 2.0 m (H × L × W) and filled with pea gravel to a height of 0.55 m.The experiment was carried out considering a completely randomized design (CRD). Each variant of theexperiment was replicated 10 times for each one of two replicates, implying in a total of 20 replicates,and 4 CWs characterized as follows: (i) ryegrass cultivated systems operating with an aerated influent(aiCWc), (ii) non-cultivated systems operating with an aerated influent (aiCW*), (iii) ryegrass cultivatedsystem operating with a non-aerated influent (CWc), and (iv) non-cultivated systems operating with anon-aerated influent (CW*). For oxygenation of the CPW which would be supplied as aerated CPW in twotreatments, an aeration system was implanted in the storage tank, consisting of a submerged SarlobetterS520 pump with a flow of 0.52 m3 h−1, a gravel filter and tulle. The CPW was applied at an average flowrate of 0.020 m3 d−1, corresponding to a hydraulic retention time of 12 days. Efficiencies of 69, 72, 30and 72% were obtained for the removal of total nitrogen (NT), total phosphorus (PT), total potassium (KT)and total phenolic compounds (FT), respectively, in the aiCWc. Aeration resulted in improved efficiency

of pollutant removal such as N, P and phenolic compounds. The cultivated plant species (L. multiflorum)influenced the removal efficiencies of total-N, total-P and total-K in the systems, however, the best resultswere obtained by means of combination of vegetation with artificial aeration. Artificial aeration does nottotally compensate the absence of plants, suggesting that the role of plants goes beyond the addition ofoxygen to the medium, permitting the development of a more active and diverse microbial communitynear the root zone.

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. Introduction

Coffee is an agricultural product of great socioeconomic impor-ance which provides jobs both directly and indirectly, includinghe contracting of labor in rural areas and generating taxes. How-ver, the activity of washing and peeling/pulping of coffee (Coffea

anephora, Coffea arabica), needed to reduce the cost of drying andor improving the quality of the drink, generates large volumes ofolid and liquid residues rich in organic and inorganic material.

∗ Corresponding author. Tel.: +55 31 38911876.E-mail addresses: maike.rossmann@ufv.br (M. Rossmann), atmatos@ufv.br

A.T. de Matos), abreu@ufv.br (E.C. Abreu), fabyanofonseca@ufv.br (F.F. e Silva),orges@ufv.br (A.C. Borges).

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925-8574/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.ecoleng.2012.08.017

© 2012 Elsevier B.V. All rights reserved.

hen untreated this material can cause serious environmentalroblems (Matos et al., 2006).

Constructed wetlands (CWs) have been proposed and used forhe reduction of pollutants in wastewaters, including domesticKayranli et al., 2010; Konnerup et al., 2009; Villasenor et al.,011), dairy (Gottschall et al., 2007; Lee et al., 2010), swineDong and Reddy, 2010; Ro et al., 2010) and also those from therocessing of coffee fruits (Fia et al., 2010a,b,c). In general, thiseduction is due to physical, chemical and biological mechanismsncluding the processes of sedimentation, filtration, absorption,hemical precipitation and adsorption, microbial interactions,

olatilization, complexation and extraction by plants (Vymazal,009).

Nitrogen removal in the CWs occurs through plant absorp-ion and synthesis, and the action of microorganisms, where the

M. Rossmann et al. / Ecological Engineering 49 (2012) 264– 269 265

Table 1Mean values and standard-deviations of the main characteristics of the coffee processing wastewater (CPW) both crude and as applied to the systems during the experimentalperiod.

Variables ARC crudea CPW appliedb (aerated influent) CPW appliedb

(non-aerated influent)

pH 4.7 ± 0.5 7.2 ± 0.3 6.5 ± 0.2CODtotal (g m−3) 17,244 ± 3486 4141 ± 377 4594 ± 245BODtotal (g m−3) 8005 ± 1631 2214 ± 836 1909 ± 670NT (g m−3) 231.6 ± 47.4 89.6 ± 11.9 87.6 ± 14.6PT (g m−3) 23.0 ± 5.1 14.4 ± 3.2 14.8 ± 2.2KT (g m−3) 624.9 ± 177.4 287.8 ± 29.5 288.8 ± 30.0FT (g m−3) 133.4 ± 13.6 26.1 ± 5.7 31.6 ± 4.8

pH – potential hydrogen; COD – chemical oxygen demand; BOD – biochemical oxygen demand; NT – total nitrogen; PT – total phosphorus; KT – total potassium; FT – totalphenolic compounds.

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itrification and denitrification processes are responsible for mostf its removal (Reddy and D’Angelo, 1997). Due to the predom-nantly anaerobic conditions in CWs and the concentrations ofiochemical oxygen demand (BOD) frequently elevated in theastewater, the nitrification process is generally limited (Cronk,

996). The increase in nitrification activity has been obtained bynducing a more aerobic environment (Cottingham et al., 1999;amieson et al., 2003).

Phosphorus removal from wastewater is of great interest due tohe limited nutrient status, and its disposal in water bodies causesdverse effects such as eutrophication (O’Neill et al., 2011). Theundamental phosphorus removal mechanisms in CWs include: (i)dsorption to the support medium (substrate), method of remov-ng saturated material for reduced contribution in the long term,ii) formation of complexes with organic matter, (iii) precipitationeactions with aluminum (Al), iron (Fe), calcium (Ca) and mineralonstituents of the sediment, and (iv) absorption by plants andicroorganisms (Vymazal, 2007).Because there are no specified limits for disposal of potassium

n water bodies, and in the majority of industrial and domesticffluents it is present to small concentrations, little informations available with regards to the removal of this chemical element inrocessing systems (Bustamante et al., 2011). However, it is knownhat potassium is not found associated with organic matter and isne of the nutrients absorbed in large quantity by plants, wherehis is the primary form of removal in wetland systems (Brasil et al.,005).

Phenolic compounds are removed from wastewater whenreated in CWs, especially by means of the degradation/microbialccumulation mechanisms (Herouvim et al., 2011). Besides this,dsorption mechanisms including the particles of organic matterr clay particles present, also contribute to the removal of theseompounds (Tee et al., 2009).

Based on the removal methods presented, the value of biologicalrocesses for removal of nutrients and phenolic compounds in CWsan be observed. It is noteworthy that the presence of oxygen favorsptimal conditions for the development of key microorganisms inhe removal processes, such as nitrifying bacteria. Because of thismportance and the insufficient supply of oxygen promoted by theas exchange system of the system surface and the transfer of oxy-en mediated by the plants, several techniques have been appliedo complement the natural aeration processes (Li et al., 2009; Nivalat al., 2007; Tang et al., 2009; Wen et al., 2010; Wu et al., 2011a; Yend Li, 2009; Zhang et al., 2010).

Considering the limited knowledge on behavior of CWs to treatoffee processing wastewater (CPW) generated during processing,specially when first aerated, this study aimed to evaluate thenfluence of artificial aeration and plant removal of nutrients and

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henolic compounds present in CPW treated in CWs planted withyegrass (Lolium multiflorum Lam.)

. Materials and methods

.1. Experimental system

To conduct the experiment, horizontal subsurface flow CWs,uilt on a pilot scale, were maintained inside a greenhouse. TheWs were composed of fiber glass reservoirs (0.6 m × 0.5 m × 2.0 m,

× L × W), seated on the ground. The bed of the system was filledith pea gravel (diameter = 7.0 mm) to the height of 0.55 m, leaving

free space of 0.05 m. To homogenize the distribution of CPW inhis support material, the spaces 0.10 m from the inlet and outletections were filled with larger gravel (diameter of 19–25 mm). Theater level was maintained 0.05 m below the surface of the gravel

ed.The experiment was carried out considering a completely

andomized design (CRD). Each variant of the experiment waseplicated 10 times for each one of two replicates, implying in

total of 20 replicates, and 4 CWs characterized as follows: (i)ystems operating with the aerated influent and cultivated withyegrass (L. multiflorum Lam.) (aiCWc), (ii) non-cultivated systemsperating with the aerated influent, containing only the supportedium (pea gravel) (aiCW*), (iii) systems operating with the

on-aerated influent and planted with ryegrass (CWc), and (iv)on-cultivated systems operating with the non-aerated influentCW*). For oxygenation of the CPW which would be supplied aserated CPW in two treatments, in the storage tank an aerationystem was implanted, consisting of a submerged Sarlobetter S520ump, with a flow of 0.52 m3 h−1, a gravel filter and tulle, used torevent clogging and/or damage to the pump.

.2. Coffee processing wastewater (CPW)

The CPW used in the experiment was obtained from a farm onhe outskirts of the city of Vic osa, in southeastern Brazil. On thisarm, the average water consumption is approximately 2.5 m3 m−3

f coffee beans processed, since part of the process water is recir-ulated. The water from this processing unit presented an averageOD of 17,244 g m−3 (Table 1). This high value can be attributedo the recirculation process, and does not represent the averageuality CPW produced in the region, and therefore it was diluted topproximately 6000 g of COD m−3 prior to implementation. More-

ver, the CPW applied had its pH adjusted to approximately 7.0ith hydrated lime, and its relationship BOD:N:P ratio was cor-

ected to 100:5:1, using urea and single super phosphate (Fia et al.,007).

266 M. Rossmann et al. / Ecological Engineering 49 (2012) 264– 269

Table 2Mean operational characteristics of the constructed wetland systems and their respective standard-deviations, according to the different treatments utilized.

Treatments HRT (days) OSL (kg ha−1 d−1) LR-N (kg ha−1 d−1) LR-P (kg ha−1 d−1) LR-K (kg ha−1 d−1) LR-F (kg ha−1 d−1)

aiCWc 11.8 ± 1.1 828.3 ± 75.3 17.9 ± 2.4 2.9 ± 0.6 57.4 ± 8.1 5.2 ± 1.1aiCW* 11.9 ± 1.3 828.3 ± 75.3 17.9 ± 2.4 2.9 ± 0.6 57.4 ± 8.1 5.2 ± 1.1CWc 11.8 ± 1.4 964.7 ± 51.3 18.4 ± 3.1 3.1 ± 0.5 60.6 ± 6.3 6.6 ± 1.0CW* 11.8 ± 1.3 941.7 ± 50.1 17.5 ± 2.9 3.0 ± 0.4 57.8 ± 6.0 6.3 ± 1.0

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iCWc – cultivated system operating with the aerated influent; aiCW* – non-cultivaon-aerated influent; CW* – non-cultivated system operating with the non-aeratedf nitrogen; LR-P – loading rate of phosphorus; LR-K – loading rate of potassium; LR

.3. Performing the experiment

Planting of ryegrass was performed by seeding (30 kg ha−1)Wutke et al., 2007), where the seeds were applied directly to theravel bed. For germination of seeds the CWs were saturated withater from the Universidade Federal de Vic osa (UFV) water sup-ly system. After germination and before application of the CPW,he system was saturated with Hoagland solution 50% and was lefthis way for 15 days. Feeding of the CWs was performed using aolenoid metering pump ProMinent® CONCEPT.

For formation of the biofilm and acclimatization of the plants toPW, for a period of 10 days the system received CPW with increas-

ng COD. After approximately 20 days of filling the CWs with CPW,he systems were evaluated for a period of 90 days, from the monthsf June to September 2010, during which ten samples were takenrom the wastewater being treated.

During the experimental period the application of a loadf approximately 890 kg ha−1 d−1 of COD was established, withydraulic retention time of 12 days, obtained with the influent flowf 0.02 m3 d−1 (Table 2).

For monitoring of the CWs, samples were taken of the influentnd effluent, from which the following variables were quantified:otential of hydrogen (pH), total nitrogen (NT) by the semimicrojeldahl method with the addition of salicylic acid, adapted fromiehl (Kiehl, 1985), total phosphorus (PT) by spectrophotometry,

otal potassium (KT) by flame photometry (APHA et al., 2005),nd total phenolic compounds (FT) (Folin and Ciocalteu, 1927). Tobtain the real removal value of the pollutants studied, the massifference of elements was used, i.e., the concentrations of the vari-bles analyzed were compensated according to the volume lost dueo evapotranspiration or evaporation in each CW.

.4. Statistical analysis

The variables were analyzed by means of Analysis of Vari-nce (ANOVA), and when detecting a significant effect of the CWsp < 0.05), the Tukey’s test (alpha = 0.05) was used to comparehe means. The analyses in question were performed using the

ROC GLM with the SAS® statistical software (SAS Institute, 2011).ssumptions of normality of the residues and homogeneity of theariances were found according to the Shapiro–Wilk and Hartleymax tests, respectively, both using the PROC UNIVARIATE of the

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able 3ean values of removal efficiency (%) and standard-deviation of total nitrogen (NT), total

uring the monitoring period.

Treatments NT PT

aiCWc 69.1 ± 4.6 A 72.1 ± 9.5 A

aiCW* 50.7 ± 5.5 C 63.5 ± 9.4 B

CWc 57.1 ± 4.7 B 66.0 ± 6.9 AB

CW* 45.3 ± 4.0 D 54.3 ± 4.1 C

iCWc – cultivated system operating with the aerated influent; aiCW* – non-cultivated syon-aerated influent; CW* – non-cultivated system operating with the non-aerated influeans followed by same letter in column do not differ significantly at 5% probability by T

stem operating with the aerated influent; CWc – cultivated system operating withnt; HRT – hydraulic retention time; OSL – organic surface load; LR-N – loading rateoading rate of phenolic compounds.

AS® (SAS Institute, 2011). Since the repetitions were dependentf time, the Durbin-Watson test was used in order to verify thessumption of independent residuals using PROC AUTOREG (SASnstitute, 2011), which showed this independence (alpha = 0.05) forll considered variables.

. Results and discussion

.1. Nitrogen removal

Regardless of the treatment, the average values of total- removal were considered significant (Table 3). According toymazal (2007), single-stage CWs cannot achieve high nitrogenemoval efficiencies due to their inability to provide aerobic andnaerobic conditions in the same environment. Fia et al. (2010b)onfirmed this when reporting nitrogen remove of only 7.9%hen applying 29.6 kg ha−1 d−1 of nitrogen in CWs treating CPW.

he lowest average nitrogen load applied in the present study17.9 kg ha−1 d−1), associated with a long retention time, certainlyontributed to the high average of NT removal efficiencies of CPWpplied to the systems.

Nitrogen removal in the non-aerated systems receiving CPWas significantly higher in the cultivated module (Table 3). Theositive role of the plants in nitrogen removal from the CWs, eithery direct absorption of NH4

+ and nitrate or by the conditions foricrobial growth provided by the rhizosphere, has been repeatedly

bserved for several plant species in a wide range of experimentalonditions (Maltais-Landry et al., 2009a,b; Tang et al., 2009; Wut al., 2011b; Zhang et al., 2010).

As described for the systems receiving non-aerated CPW, in sys-ems receiving the aerated influent, the cultivated module alsohowed higher nitrogen removal. The rate of N-total removal inhe aiCWc was 18.4%, 12.1% and 3.8% higher than in the aiCW*,Wc and CW*, respectively. Additionally, there are indications thatrtificial aeration does not fully compensate the absence of plantsn constructed wetlands, with nitrogen removal efficiency in theWc 6.4% higher than in the aiCW*. These results suggest that the

ole of plants goes beyond the addition of oxygen to the medium,ermitting the development of a more active and diverse micro-ial community near the roots, resulting in better conditions foremoval of nitrogen contributed to the system.

phosphorus (PT), total potassium (KT) and total phenolic compounds (FT) obtained

KT FT

30.7 ± 7.6 A 72.2 ± 9.9 A21.3 ± 8.5 B 67.4 ± 9.4 A28.6 ± 9.0 A 65.9 ± 10.7 AB21.7 ± 6.6 B 58.4 ± 11.3 B

stem operating with the aerated influent; CWc – cultivated system operating withent.ukey’s test.

M. Rossmann et al. / Ecological Engineering 49 (2012) 264– 269 267

Table 4Mean values and standard-deviations for pH of the influent as well as concentrations of total nitrogen (NT), nitrogen in the form of ammonia (N-NH4

+), organic nitrogen(N-org) and nitrogen in the form of nitrate (N-NO3

−) obtained during monitoring of the systems.

Influent pH NT (g m−3) N-NH4+ (g m−3) N-org (g m−3) N-NO3

− (g m−3)

Aerated 7.2 ± 0.3 89.6 ± 11.9 A 54.6 ± 9.8 A 34.3 ± 10.3 B 0.6 ± 0.3 A

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Non-aerated 6.5 ± 0.2 87.6 ± 14.6 A

eans followed by same letter in column do not differ significantly at 5% probabilit

Greater nitrogen removal efficiencies were obtained by Zhangt al. (2010) when assessing the effect of limited artificial aerationn CWs for treatment of domestic wastewater. The greatest effi-iency observed in the systems presented by these authors, despitehe high rate applied by the authors of 58 kg ha−1 d−1 of nitrogen,s probably due to the fact that the aeration is inserted along theength of the CW and is also limited, with oxygen concentrationsanging from 0.2 to 0.6 g m−3. These two features allow for the var-ous forms of nitrogen transformation, such as nitrification, partialitrification and denitrification, and these occur simultaneously orequentially, increasing the number of ways in which nitrogen isemoved from the system.

In the storage tank and feed to the aerated CWs an elevatedmmonifying and nitrifying activity was verified (Table 4). Thisnding is resultant of lower concentrations of organic-N and higher

evels of ammonium and nitrate in the aerated influent. Changes inhe relationship between the forms of nitrogen, with higher con-entrations of ammonium and nitrate, permitted higher removalsf total N in the systems receiving the aerated influent, since theseorms are absorbed by plants and assimilated by microorganisms.

It is believed that the nitrogen losses by ammonia volatilizationave been small in magnitude, since the mean values of pH in theastewater remained below 8.0, a condition in which basically all

mmonia is in the form of NH4+, with no significant transformation

n NH3 (Reddy and Patrick, 1984).

.2. Phosphorus removal

Considerable reduction in the average concentration of total-Petween the crude CPW (23 g m−3) and that stored in the feed-

ng tanks of the CWs (about 14 g m−3) was observed (Table 1),espite the nutritional correction performed in the CPW with theddition of phosphate fertilizers. Part of this removal may haveesulted from increasing the pH of the CPW with the addition ofime, which caused the precipitation of phosphorus as calciumhosphate (Ca3(PO4)2). In the present study, no removal of total-Pas observed in the aerated storage tank and feed.

According to Vymazal (2007), total phosphorus removal in CWsaries between 40 and 60% among all CWs types, and similarlyo the behavior of nitrogen, is dependent on the loads appliednd the form of wastewater flow in the system. As a result, thefficiencies of total-P removal obtained in this study, 54.3–72.1%Table 3), under average loading rates of 3.0 kg ha−1 d−1 of phos-horus may be considered satisfactory since according to the sameuthor, phosphorus removal in all CWs is considered low, unlesssing special substrates with high adsorption capacity togetherith the support medium. Substrates rich in Ca and/or CaO andith pH above 7.0 are described for obtaining greater phosphorus

emoval in CWs (Lee et al., 2010; Vohla et al., 2011).Phosphorus removal efficiencies were statistically different

mong treatments (p < 0.0001), where the lowest average wasbtained in the non-cultivated system receiving the non-aerated

nfluent (CW*) and the greatest in the cultivated system operating

ith the aerated influent (aiCWc) (Table 3). Because of this behav-or, it is noted that aeration and vegetation positively contributed tohe removal of phosphorus from the CPW, the first by fostering the

dabT

40.7 ± 7.6 B 46.6 ± 11.7 A 0.4 ± 0.3 A

ukey’s test.

evelopment of microorganisms responsible for the immobiliza-ion of phosphorus, and the second by absorption and assimilationf soluble inorganic phosphate. The lack of reduced phosphorusoncentrations in the aerated influent, characterizing absence ofhe precipitation process in the storage tank and feed, contradictshe claims of Tang et al. (2009) and Zhang et al. (2010), who claimhat the increase of the mixture and dissolved oxygen concentra-ions led to chemical precipitation of phosphorus, therefore greateremovals of this element.

.3. Potassium removal

Efficiencies of potassium removal between 21.3 and 30.7% werebserved (Table 3) when applying an average loading rate of8 kg ha−1 d−1 of KT (Table 2). Reduced efficiencies of K removal areenerally attributed to application of excessive rates of this nutri-nt to the systems. Elevated concentrations of potassium in theoot zone result in a decrease in osmotic potential of the solutionnd in water flow in the soil–plant–atmosphere direction, with aeduction in plant transpiration (Rhoades and Loveday, 1990) andonsequently reduced absorption of nutrients.

As was expected, because the efficiency of potassium removaln the CWs is totally dependent on plant absorption, there was aignificant difference (p = 0.0003) between the average potassiumemovals of the cultivated and non-cultivated CWs. Among the CWsperating with the aerated and non-aerated influent, no significantifference was observed between the removals obtained.

.4. Removal of phenolic compounds

For phenolic compounds, significant reduction was observedetween the average concentration in crude CPW (133.4 g m−3)nd that applied to the CWs (26.1 g m−3 in the aerated influentnd 31.6 g m−3 in non-aerated influent) (Table 1). The addition ofime to increase the pH of the CPW may have caused sedimenta-ion of the particulate organic and subsequent removal of phenols.ontextualizing, Boukhoubza et al. (2009) achieved 63% removalf polyphenols when adding 2% lime (mass/volume) to wastewa-er resultant from manufacture of olive oil. Furthermore, Hsu et al.2007) observed that the presence of calcium ions, some interme-iates of phenols, including maleic acid, oxalic acid and productsf high molecular weight, may combine with these ions to formnsoluble compounds which precipitate.

The removal efficiency of phenolic compounds presented by theon-cultivated system receiving the non-aerated influent (CW*)iffered statistically from the other CWs, where this presentedhe lowest average among the treatments (Table 3). Although thenalyses showed no statistical differences between cultivated andon-cultivated CWs, there was a tendency for higher removalf phenolic compounds in cultivated CWs. This tendency can bettributed to the role played by plants to create micro-aerobic zonesear to the roots, which permits faster degradation and a higher

egree of mineralization of organic material, and also has a directction on absorption, metabolism and fixation of the products formiodegradation of phenols in their tissues (Herouvim et al., 2011;ee et al., 2009).

268 M. Rossmann et al. / Ecological Engineering 49 (2012) 264– 269

Period of monit oring (da ys)

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20

30

40

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60

70

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ig. 1. Efficiency of phenolic compound removal (%) and pH values in the aiCWc – che aerated influent; CWc – cultivated system receiving the non-aerated influent; C

CWs operating with the aerated influent presented greater aver-ge phenolic compound removal efficiencies (Table 3). This resultay have been derived from the lower load applied to these

ystems (5.2 kg ha−1 d−1) as a result of degradation occurring inhe storage tank and feed in the CPW subjected to aeration. Theeduction in concentration of phenolic compounds in the influentubjected to aeration was 17.6% when compared to the non-aeratednfluent. The tendency for reducing the removal of phenolic com-ounds with the increase in applied load was also reported by Fiat al. (2010b,c).

Efficiencies of phenolic compound removal continued toncrease throughout the monitoring period (Fig. 1). The growingvailability of ions during the microbial decomposition processf organic matter may have caused the precipitation of phenolicroups, as discussed when adding lime, leading to the increasedemoval presented. This process may be proven with the resultingncrease in pH observed (Fig. 1), which possibly results from decar-oxylation of organic anions to CO2 and water, consuming H+ ionsRitchie and Dolling, 1985; Rukshana et al., 2012). This associationetween the removal of phenolic compounds and the increase inH of the effluent deserves further investigation.

Based on these results, it is believed that among the CWs eval-ated, the cultivated aiCWc system operating with the aerated

nfluent provided the best results, with higher removals of nitrogen,hosphorus, potassium and phenolic compounds.

Further studies are needed to better understand the effectsf artificial aeration on removing pollutants from CPW in CWs.onsidering the additional cost required for artificial aeration ofastewater, it is important to evaluate and identify the most appro-riate location for its installation within the CW, which may be innly a single portion of the entire system. Additionally, an evalua-ion of the best aeration system management should be performed,onsidering if aeration should be constant or intermittent, and ifntermittent the operation time that should be considered for theystem. Thus, economic feasibility studies are also needed to con-ider the increased efficiency provided by aeration and increasedosts for implementing such systems, since according to Austinnd Nivala (2009), the addition of energy inputs to the CWs canvercome the limited oxygen transfer in order to meet treatmenttandards.

Alternatively, implementation of cascade aeration may replacertificial aeration. Cascade aeration units are typically locatedownstream of wastewater treatment plants, utilized for increas-

ng the concentration of dissolved oxygen before it is released tohe water body (von Sperling, 2002; Magalhães et al., 2003). This

ay be a recommended practice, especially for topographic con-itions (mountainous) of regions where coffee fruits are produced

B

ed system receiving the aerated influent; aiCW* – non-cultivated system receivingnon-cultivated system receiving the non-aerated influent.

nd processed. Utilizing the differences in ground level duringonstruction of aeration cascades may substitute the introductionf artificial aeration in the system, consequently maintaining theow cost of implementation and maintenance, as well as ease ofperation of constructed wetlands.

. Conclusions

The highest average removal efficiencies of NT, PT, KT and FTere obtained by the cultivated CW operating with the aerated

nfluent (aiCWc).Aeration resulted in an improvement in the removal efficiency

f nutrients such as nitrogen, phosphorus and phenolic com-ounds.

The cultivated plant species (L. multiflorum) influenced theemoval efficiencies of total-N, total-P and total-K in the systems,owever, the best results were obtained by combining the plantsith artificial aeration. Average removal of NT in the cultivated sys-

em operating with the aerated influent (aiCWc) was 18, 12 and 24%igher than those obtained, respectively, from the non-cultivatedystem operating with the aerated influent (aiCW*), cultivated sys-em operating with non-aerated influent (CWC) and non-cultivatedystem operating with the non-aerated influent (CW*). In the casef PT it was 9, 6, and 18% higher, for KT was 9, 2 and 9% higher andith respect to phenolic compounds was 5, 6 and 14% higher.

Artificial aeration did not fully compensate for the absence oflants, suggesting that the role of plants goes beyond the additionf oxygen to the medium, permitting the development of a morective and diverse microbial community near the root zone, andesulting in better conditions for removal of nitrogen, phosphorusnd potassium from the system.

cknowledgement

The authors thank the “Conselho Nacional de Desenvolvimentoientífico e Tecnológico” (CNPq) for the financial support.

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