research article power generation enhancement by utilizing...

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2013 Article ID 172010 10 pageshttpdxdoiorg1011552013172010

Research ArticlePower Generation Enhancement by Utilizing PlantPhotosynthate in Microbial Fuel Cell Coupled ConstructedWetland System

Shentan Liu1 Hailiang Song1 Xianning Li1 and Fei Yang2

1 School of Energy and Environment Southeast University Nanjing 210096 China2 School of Public Health Southeast University Nanjing 210096 China

Correspondence should be addressed to Xianning Li lxnseueducn

Received 27 June 2013 Accepted 31 August 2013

Academic Editor Manickavachagam Muruganandham

Copyright copy 2013 Shentan Liu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In the present study a new technology that coupled constructed wetland (CW) with microbial fuel cell (MFC) (CW-MFC) wasdeveloped to convert solar energy into electricity on the principles of photosynthetic MFC by utilizing root exudates of Ipomoeaaquatica as part of fuelThemaximumpower density of 1242mWmminus2 produced from the CW-MFCplanted with Ipomoea aquaticawas 142 higher than that of 513mWmminus2 obtained from the unplanted CW-MFC The maximum power output for the plantedCW-MFC could be divided into two parts the maximum power yield fromCOD

119877

in the water body was 6605 KJ Kgminus1 COD119877

andthemaximumpower transformation from plant photosynthesis was 231 GJ haminus1 yearminus1The average COD removal efficiencies were921 and 948 in the unplanted CW-MFC and planted CW-MFC respectively the average TN removal efficiencies amounted to544 and 908 in the unplanted CW-MFC and planted CW-MFCThis research demonstrates that planting Ipomoea aquatica inthe CW-MFC achieved a higher power density and nutrient removal of nitrogen simultaneously

1 Introduction

A microbial fuel cell (MFC) is a bioelectrochemical systemmaking use of biocatalyst for converting chemical energy intoelectricity and it has been considered as one of the promis-ing and sustainable technologies for power generation aswell as waste management [1ndash3] especially in the pastdecade there has been a remarkable promotion of MFCperformance through a large variety of methods includingadvancement of fuel cell configuration [4 5] selection andmodification of electrode material [6ndash8] and adoption ofcheap proton exchange membrane with high conductivityefficiency [9 10] Besides novel technologies in generatingpower by integrating photosynthesis with microbial fuel cells(photosynthetic MFC) have been researched and significantprogress has been made [11ndash14] The photosynthetic MFCoperates to generate sufficient electric current from sunlightwith either electrocatalysts or heterotrophic bacteria on theanode to convert photosynthetic products indirectly [15] andthe photosynthesis could be carried out by plants algae or

some photosynthetic bacteria The photosynthetic MFC canproduce electricity without the external input of exogenousorganics or nutrients but it is often restricted by sunlight andits power density is still too low for practical applications

Wetland treatment of wastewater has been widely prac-ticed in several countries for many years due to its easymaintenance low cost and good self-purification capacitymoreover it provides great quantities of biomass productionby photosynthesis [16] A well-designed microbial fuel cellinside a constructed wetland systemmay combine the advan-tages of the photosynthesis of wetland plants and electricitygeneration of electroactive microorganisms to transformsolar energy into electricity The first lab-scale CW-MFC wasdesigned and operated to evaluate the effect of configurationon power production [17] and it also showed good wastew-ater treatment effect with simultaneous power generationAs the constructed wetland has the ability of degradationof refractory organic matter the CW-MFC system had greatadvantages in treating dye containing wastewater [18]

2 International Journal of Photoenergy

The concept of CW-MFC is based on constructedwetlandand plant MFC (one form of photosynthetic MFC) of whichall contain plants The role of plants is important in theCW-MFC system including their role in excreting oxygenand organic matter into the rhizosphere [19] supportinga wide range of microbes and providing a surface forbacterial attachment [20] These unique characteristics maymake the CW-MFC system an ideal approach to generateelectricity at sites and reduce globing warming as they candecrease methane emissions However the effect of plantphotosynthesis and plant rhizospheremicroorganisms on thepower enhancement for the CW-MFC has not been studiedfully yet

In this study we built a single-chamber membrane-free continuously feeding upflow microbial fuel cell coupledwith constructed wetland in which the cathode is locatedin overlying water to use oxygen from air for reductionreactions and the anode is submerged in a support matrixnear the rhizosphere to obtain organic substrates in theinfluent or deprived fromwetland plants root as fuelThe aimof this study was to evaluate whether or not the wetland plant(Ipomoea aquatica) can improve power generation in a CW-MFC system and to explore the bacterial population in theelectrode biofilm in response to MFC performance Mean-while investigations of the removal efficiencies of chemicaloxygen demand (COD) and total nitrogen (TN) were carriedout

2 Experimental

21 CW-MFC Construction As schematically shown inFigure 1 two CW-MFC reactors were constructed in thesame way using a polycarbonate plastic cylinder (30 cm indiameter and 50 cm inheight)Thebottom20 cmwas supportmatrix composed of gravel (gravel diameter 3ndash6mm) andthen upwards it consisted of anode support matrix (20 cmgravel) and cathode The anode was constructed from 10 cmthick granular activated carbon (GAC a diameter of 3ndash5mmthe specific area of 500ndash900m2 gminus1 and the filling densityof 045ndash055 g cmminus3) GAC was pretreated by soaking in 1MNaOH and 1M HCl to eliminate possible oil stain and metalion contamination respectively The cathode was made fromstainless steel mesh (a diameter of 25 cm thickness of 03 cm12 mesh) buried in 2 cm thick layer of activated carbonparticleThe electrode spacingwas 25 cm (center of the anodeto the face of the cathode) Electrodes were connected to acircuit using titanium wires across an external resistance of1000Ω and epoxy was used to seal metals exposed to thesolution Nine adult plants of Ipomoea aquatica were plantedthrough the upper layer of one CW-MFC device (plantingdensity about 32 plants mminus2) and the other CW-MFC wasa control with no plants The volume of the whole containerwas 353 L with a total liquid volume of 124 L

22 CW-MFC Operation The CW-MFCs were inoculatedwith the anaerobic sludge from a wastewater treatmentplant located in Jiangning Development Zone (NanjingChina) and operated by continuous feeding at a flow

GACcathode

GACanode

Gravel

Water distribution

Effluent

Influent

Load

Figure 1 Schematic of the CW-MFCs used in the experiment

rate of 431mLminminus1 corresponding to a hydraulic reten-tion time (HRT) of 2 d The feed solution consistedof 50mM phosphate buffer solution (PBS) with pH 74glucose (020 g Lminus1) NH

4

Cl (015 g Lminus1) KCl (013 g Lminus1)NaHCO

3

(313 g Lminus1) and 1mLLminus1 trace essential ele-ments solution (contained per liter 56 g (NH

4

)2

SO4

2 gMgSO

4

sdot7H2

O 200mg MnSO4

sdotH2

O 3mg H3

BO3

24mgCoCl2

sdot6H2

O 1mg CuCl2

sdot2H2

O 2mgNiCl2

sdot6H2

O 5mgZnCl2

10mg FeCl3

sdot6H2

O and 04mg Na2

MoO4

sdot2H2

O) Allexperiments were carried out in a 1212-h lightdark cycle at26 plusmn 2

∘C under greenhouse conditions The ambient lightwas provided by artificial illumination using (light-emittingdiode LED) Grow Lights (14W GC-ZW225S-P GechuangElectronics Co Ltd Shenzhen China) and the average lightintensity was 1000 lux during the light phase

23 Fluorescent In Situ Hybridization (FISH) FISH analysiswas applied to investigate the quantity of microorganismson the anode and cathode in our study Granular activatedcarbon with attached biofilm (wet weight of 05 g) was mul-tisampled (parallel samples) and suspended in 5mL steriledeionized water and microorganism cells were detachedfrom the GAC and uniformly dispersed in the solution withultra-sonic oscillations treatment About 05mL supernatant

International Journal of Photoenergy 3

Table 1 Probe name and probe sequence used for FISH analysis

Probe Target microflora Probe sequence ReferencesEUB338 Bacteria GCTGCCTCCCGTAGGAGT [21 22]GEO2 Geobacter sulfurreducens GAAGACAGGAGGCCCGAAA [23]HGEO2-1 Helper probes for GEO2 GTCCCCCCCTTTTCCCGCAAGA [23]HGEO2-2 Helper probes for GEO2 CTAATGGTACGCGGACTCATCC [23]BET42a Betaproteobacteria GCCTTCCCACTTCGTTT [24]

after ultrasonic oscillations was shifted and suspended inphosphate-buffered saline solution (PBS pH 74) consistingof 8 g Lminus1 NaCl 02 g Lminus1 KCl 144 g Lminus1 Na

2

HPO4

and024 g Lminus1 K

2

HPO4

in distilled water Then the samples werefixed with 4 paraformaldehyde (in PBS) at 4∘C for 24 hThefixed samples were washed twice with PBS and suspended ina solution of 50 PBS and 50 ethanol and stored at minus20∘CFor FISH 10 120583L of the fixed sample was applied on a glassslide dried for 2 h at 37∘C and subsequently dehydrated withethanol at 50 80 and 96 (vv in 10mM Tris-HCl pH 75)during 3min at each concentration To start hybridization24120583L of hybridization buffer and 1 120583L of fluorescently labeledprobe (50 ngmLminus1) were added The hybridization was con-ducted for 5 h at 46∘C in a humidified chamber Slides werethen washed in a buffer solution (60mM NaCl 20mM Tris-HCl pH 80 01 SDS) at 45∘C for 20min

In the FISH procedure target microflora and oligonu-cleotide probes used were shown in Table 1 Hereinto Geo-bacter sulfurreducens andBetaproteobacteriahave been evalu-ated for the potential for current productionMicroscopy wasperformed on an Olympus BX50 microscope equipped withfilters HQ-CY3 (Analysentechnik AG Tubingen Germany)The bacterial number on each image was counted andthen the bacterial density (119863

119887

) of each biofilm cathode wascalculated from the following equation

119863119887

=1000119873119878

1

1198721198782

(1)

where 1198781

1198782

and 119872 represent the coating area the imagearea and the sample weight (g) respectively and 119873 is theaverage bacterial number on each image (cells) All celldensity data shown in this paper were statistical averagevalues

24Measurement andAnalysis Thecell voltagewas recordedevery 30min by a data acquisition system (USB120816HytekAutomation Inc Shanghai China)The cell potentialswere measured against a saturated AgAgCl (S) electrodePolarization curves were obtained in the daytime (high peakvoltage) by varying the external resistor over a range from 5Ωto 105Ω (105 4000 3000 2000 1000 800 600 400 200 10075 50 25 10 and 5Ω) to monitor the output voltage Thecurrent (119894) was calculated from Ohmrsquos law as shown in (2)and the power density (119875 area power density) was calculatedas shown in (3) where 119864 is the voltage 119877 is the externalresistance and119860 is the anode areaThe ohmic resistance (119877

Ω

)of each system was determined using the current interrupttechnique [25] and 119877

Ω

was calculated as shown in (4)

119864119877

is a steep potential rise when the current is interruptedand 119864OCV is the open circuit voltage

119894 =119864

119877 (2)

119875 =1198642

119877119860 (3)

119877Ω

=119864119877

119894=(119864OCV minus 119864)119877

119864 (4)

Chemical oxygen demand (COD) ammonia nitrogen(NH4

+-N) nitrite nitrogen (NO2

minus-N) and nitrate nitrogen(NO3

minus-N) were performed in accordance with the StandardMethods of American Public Health Association (APHA1998) and all the samples for chemical analysis were filteredthrough a 045120583m pore diameter syringe filter to removeparticles Total nitrogen (TN) concentration was calculatedas the sum of NH

4

+-N NO2

minus-N and NO3

minus-N Dissolvedoxygen (DO) concentration was measured in situ by the DOprobe (ORION 3 STAR Thermo Co USA) All measure-ments were made at least three times and the average valueswith standard deviations are presented in the figures

Specific power yield (SPY) was obtained by dividingpower generated (119875

119881

volume power density) with the sub-strate (COD) removed as shown in (5) [26] where 119881 is thetotal liquid volumeof theCW-MFCCODin the influentCODand CODout the effluent COD The power yield (PY) wascalculated as shown in (6) and it implicates the power outputper kilogram of organic substrate (COD

119877

) in the water body

SPY =119875119881

COD119877

=1198642

(CODin minus CODout) 119877119881 (5)

PY = SPY timesHRT (6)

3 Results

31 Power Output The two CW-MFCs were operated formore than 1 month to obtain a stable performance beforethe determination of cell voltage Figure 2(a) shows voltageoutputs from the planted CW-MFC and unplanted CW-MFCelectricity-generating systems from May 3 to June 10 At theinitial stage (1ndash8 days) the trough voltages of the plantedCW-MFC (051ndash053V) were close to the mean voltage ofthe unplanted CW-MFC (050V) As Ipomoea aquatica wasadapted to the experimental environment the peak andtrough voltages of the planted CW-MFC increased gradually(8ndash26 days) and remained stable (26ndash40 days)


Cell

vol

tage

(V)

Time (days)

0807060504030201

00 4 8 12 16 20 24 28 32 36 40

PlantedUnplanted

(a)

Time (hours)

Cell

vol

tage

(V)

0807060504030201

00

12 24 36 48 60 72 84 96 108 120

PlantedUnplanted

(b)

Figure 2 Continuous records of voltage with a fixed external load of 1000Ω for the planted CW-MFC and unplanted CW-MFC (a) A dailyrecord of voltages at 000 (night through time) and 1200 (day peak time) fromMay 3 to June 10 (b) half-hourly records of voltages from June12 to June 16

As shown in Figure 2(b) the voltage for the planted CW-MFC was characterized by diurnal oscillations with clearfluctuations but no such circadian oscillation was observedfor the unplanted CW-MFC As temperatures were relativelystable throughout the experiments the observation impliedthat the cyclical fluctuation of voltage for the planted CW-MFCwas closely related to the sunlight From June 12 to June16 the electric output was stable and the average voltagesin the planted CW-MFC and unplanted CW-MFC were 064and 049V respectively Therefore it was calculated thatthe average power outputs for the planted CW-MFC andunplanted CW-MFC were 0129 and 0076GJ haminus1 yearminus1respectively Taking into account the consistency of theinfluent condition and the culture environment in the twoCW-MFCs the power output about 0053GJ haminus1 yearminus1 wasgenerated from plant photosynthetic products in the plantedCW-MFC

32 Fuel Cell Behavior The performance of the planted CW-MFC was depicted and compared with the unplanted CW-MFC in terms of power density curves and polarizationcurves It can be seen from Figure 3 that planting Ipomoeaaquatica in CW-MFC effectively enhanced the electricitygenerationTheopen circuit voltages of the plantedCW-MFCand unplanted CW-MFC were 074 and 062V respectivelyand the maximum power density of the planted CW-MFCwas 1242mWmminus2 2-folds more than that of the unplantedCW-MFC (513mWmminus2) Maximum power outputs of theplanted CW-MFC and unplanted CW-MFC were 392 and161 GJ haminus1 yearminus1 respectively According to (3) the internalresistances of the planted CW-MFC and unplanted CW-MFCwere 156 and 256Ω respectively

33 Relation of Electrode Potentials and Cell Density on theElectrode It was demonstrated that the catalytic activity ofthe electrode positively correlates with biomass [27] Toverify the hypothetical inference electrode potentials and celldensities in various GAC electrodes zone were determined(Figure 4) The average cathode potential (299mV) of theplanted CW-MFC was higher than that of the unplanted

Cell

vol

tage

(V)

09

08

07

06

05

04

03

02

01

0

18

16

14

12

10

8

6

4

2

00 1 2 3 4 5

Current (mA)

Pow

er d

ensit

y (m

W m

minus2)

V plantedV unplanted

P plantedP unplanted

Figure 3 Polarization curves of the planted CW-MFC andunplanted CW-MFC (solid symbols for the cell voltage and opensymbols for the power density)

CW-MFC (202mV) (Figure 4(a)) and the average anodepotential (minus341mV) of the planted CW-MFC was lower thanthat of the unplanted CW-MFC (minus288mV) (Figure 4(b))As shown in Figure 4(a) the average bacteria density incathodic biofilms of the planted CW-MFC (385 plusmn 061 times 107cells gminus1) was higher than that of the unplanted CW-MFC(243 plusmn 040 times 107 cells gminus1) From Figure 4(b) it was clearlyobserved that cell densities of bacteria G sulfurreducensand Betaproteobacteria in anodic biofilms of the plantedCW-MFC (866 plusmn 101 times 107 cells gminus1 122 plusmn 018 times 107cells gminus1 and 091 plusmn 013 times 107 cells gminus1) were also higherthan that of the unplanted CW-MFC (513 plusmn 086 times 107cells gminus1 067 plusmn 011 times 107 cells gminus1 and 048 plusmn 009 times 107cells gminus1) The results indicated that the cathode potentialshowed a positive correlation with the microbial amount


10

04

03

02

01

0

8

6

4

2

0CW-MFC Unplanted CW-MFC

Different reactors

Cathode potentialPo

tent

ial (

V)

Cel

l den

sity

(107

cell g

minus1)

Bacteria

(a)

10

8

6

4

2


Different reactors

Pote

ntia

l (V

)

0

minus01

minus02

minus03

minus04

120573-proteobacteriaAnode potential

Cel

l den

sity

(107

cell g

minus1)

G sulfurreducensBacteria

(b)

Figure 4 Electrode potential and cell density in electrodes zone for the planted CW-MFC and unplanted CW-MFC (a) cathode zone and(b) anode zone

but a negative correlation between the anode potential andmicrobial amount was observed

34 Waste Treatment Throughout the experimental stagethe influent chemical oxygen demand (COD) and totalnitrogen (TN) reached to the ranges of 193ndash205mg Lminus1 and31ndash39mg Lminus1 respectively More or less the same CODremoval efficiency (planted CW-MFC 948 unplantedCW-MFC 921) was noticed with both the CW-MFCs but SPY (planted CW-MFC 0178WKgminus1 COD

119877

unplanted CW-MFC 0107WKgminus1 COD

119877

) and PY (plantedCW-MFC 3067 KJKgminus1 COD

119877

unplanted CW-MFC1851 KJ Kgminus1 COD

119877

) showed that the CW-MFC plantedwith Ipomoea aquatica had higher power productivityefficiency Unlike the COD removal efficiency a greatdifference in the TN removal efficiency (planted CW-MFC908 unplanted CW-MFC 544) was observed

In order to ascertain the reason for the difference of TNremoval efficiencies between the CW-MFCs the concentra-tion of DO and various forms of nitrogen along the reactorheight were investigated in the day time DO had a ldquoVrdquotype change in both the planted CW-MFC and unplantedCW-MFC (Figure 5) The concentration of DO decreasedgradually with the increasement of reactor height till itreached 30 cm due to the consumption of O

2

and then itincreased with the increasement of reactor height becauseof the reoxygenation The lowest concentrations of DO werein the anode zone and they were 015ndash038mg Lminus1 and011ndash031mg Lminus1 for the planted CW-MFC and unplantedCW-MFC respectively The maximum differentiation of DOoccurred at height of 40 cm and the concentrations ofDO were 310mg Lminus1 and 137mg Lminus1 for the planted CW-MFC and unplanted CW-MFC respectivelyThe effluent had

10

7

6

5

4

3

2

1

00 20 30 40 50

Reactor height (cm)

Anode Rhizosphere

PlantedUnplanted

DO

(mg L

minus1)

Figure 5The change of DO in the planted CW-MFC and unplantedCW-MFC

the highest DO of 456mg Lminus1 and 379mg Lminus1 respectivelyfor the planted CW-MFC and unplanted CW-MFC Further-more diurnal variation ofDO in cathode zone for the plantedCW-MFC was higher (431 plusmn 018mgLminus1) in the day andlower (385 plusmn 014mgLminus1) at night

Figures 6 and 7 present the change curves of differentforms of nitrogen in the planted CW-MFC and unplantedCW-MFC respectively over a period of 13 days The con-centration of TN and NH

4

+-N declined continuously withwater flows in both the two CW-MFCs TN concentrations


100 20 30 40

40

35

30

25

20

15

10

5

050

Reactor height (cm)

Anode Rhizosphere

TNNH3-N

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NO2minus-N

Figure 6 The change of different forms of nitrogen in the plantedCW-MFC

Anode

100 20 30 40 50Reactor height (cm)

TN

40

35

30

25

20

15

10

5

0

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NH4+-N NO2

minus-N

Figure 7The change of different forms of nitrogen in the unplantedCW-MFC

decreased drastically from 3500mg Lminus1 to 322mg Lminus1 inthe planted CW-MFC but there was a less decrease from3500mg Lminus1 to 1596mg Lminus1 in the unplanted CW-MFCComparing the change curve of TN for the two CW-MFCsthere were similarities that TN removal was less in thebottom region (0ndash20 cm) andmore in the central region (20ndash30 cm) but there was a great difference in the top region(30ndash50 cm) that TN removal in the planted CW-MFC (from2250mg Lminus1 to 322mg Lminus1) was much higher than that inthe unplanted CW-MFC (from 2170mg Lminus1 to 1596mg Lminus1)The removal efficiencies of NH

4

+-N for the planted CW-MFC and unplanted CW-MFC were 9651 and 6486

respectively In the planted CW-MFC there were two sharpdescending regions for NH

4

+-N removal NH4

+-N decreasedfrom 3500mg Lminus1 to 2630mg Lminus1 at the bottom of 0ndash10 cmand from 1980mg Lminus1 to 430mg Lminus1 at the top of 30ndash40 cm However in the unplanted CW-MFC NH

4

+-N onlydecreased sharply from 3500mg Lminus1 to 2560mg Lminus1 at thebottom of 0ndash10 cm and then it began to descend smoothly

In the planted CW-MFC the accumulated NO2

minus-N con-centration gradually increased from 0mgLminus1 in the influentto themaximal 630mg Lminus1 at height of 10 cm but it decreasedslowly to 070mg Lminus1 in the effluent The same change rulesof NO

2

minus-N were observed in the unplanted CW-MFC butthe concentration of NO

2

minus-N in the effluent was slightlyhigher about 156mg Lminus1 The change of NO

3

minus-N can bedivided into four stages in the planted CW-MFC taking onthe trend of rising first dropping then rising and droppingnamely two inverse ldquoVrdquo type curves and the maximalNO3

minus-N concentrations were 35mg Lminus1 and 57mg Lminus1 atthe height of 20 cm and 40 cm respectively However only aflush of NO

3

minus-N concentration from 0mgLminus1 to 370mg Lminus1was observed in the bottom region in the unplanted CW-MFC and then the concentration gradually decreased to170mg Lminus1 at the height of 30 cm and it changed little in thetop region

Under aerobic conditions NH4

+-N could be oxidated toNO2

minus-N and NO3

minus-N by nitrococcus and nitrobacteria andthe increase in NO

119909

minus-N concentration (sum of NO2

minus-N andNO3

minus-N) and the decrease in the NH4

+-N concentrationwere significantly correlated with DO in the bottom regionboth in the two CW-MFCs (119875 lt 001) But the increasein NO

119909

minus-N concentration and the decrease in the NH4

+-Nconcentration at height of 30ndash40 cm in the planted CW-MFCwere generally correlated with DO (119875 lt 005)

4 Discussion

41 Comparison of Power Output of the Planted CW-MFC andUnplanted CW-MFC When Ipomoea aquatica was plantedin CW-MFC the bacteria density in anode and cathodeboth increased cathode potential became larger and anodepotential become more negative (Figure 4) thus generatingmore power Here the grown Ipomoea aquatica is generallyvery important feature because it can improve the catalyticactivity of anode and cathodemainly due to the enhancementof the microbial density activity and diversity in the plantrsquosrhizosphere [28] Furthermore root exudates that comprisecarbohydrates carboxylic acids and amino acids are highlydegradable to microorganisms and the most responsible forelectron donation [29] In addition the internal resistanceof the planted CW-MFC accounted for only 61 of theunplanted CW-MFC and the cause of such difference maylie in the quantity of current-producing bacteria (such asG sulfurreducens and Betaproteobacteria) which are able togenerate electrically conductive pili or nanowires that assistthe microorganism in reaching more distant electrodes Thepower densities in the two CW-MFCs were consistent withthe change of the internal resistances It is generally knownthat the maximum power output occurs when the internal


Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus

Figure 8The principal reactions for the overall process of the CW-MFC (1) Plant roots secrete O2

and (CH2

O)119899

(2) Electrons are producedat the anode from the anaerobic degradation of (CH

2

O)119899

and C6

H12

O6

(3) NH4

+ was converted to NO3

minus by Nitrifying bacterias in therhizosphere (4) O

2

and NO3

minus were electron acceptors at the cathode

resistance is equal to external resistance [25] thus thedecrease in internal resistance is one reason for the improve-ment in power generation performance for the planted CW-MFC The improvement in power generation for the plantedCW-MFC resulted from three different factors increasedbiomass in anode and cathode a decrease in the internalresistance and more available fuel secreted from plantroots

42 High Nitrogen Removal in the Planted CW-MFC Theremoval of nitrogen (including nitrate nitrite and ammonia)in MFC has been reported in recent years In a MFC nitrateand nitrite can be removed as electron acceptors in thecathode through electrochemical reduction or autotrophicdenitrification [30ndash32] A high level of ammonia removalfrom 198 plusmn 1 to 34 plusmn 1mgLminus1 (83 removal) was obtainedfrom swine wastewater in a single-chamber air cathode MFCsystem [33] However subsequent research demonstratedthat the removal of ammonia occurred primarily by physical-chemical mechanisms due to ammonia volatilization withconversion of ammonium ion to the more volatile ammoniaspecies as a result of an elevated pH near the cathode [34]In this study effective TN removal efficiency obtained in theplanted CW-MFC might be attributed to Ipomoea aquaticauptaking of NH

4

+ or NO3

minus as their N source for growth andyield [35] In this experiment the influent N was sufficientand dominated by NH

4

+ Many researches indicate thataquatic plant roots can release oxygen (O

2

) in constructedwetland [36 37] thus the rhizosphere was aerated andthe nitrification process was promoted by microbial activityand the NH

4

+ was converted into NO3

minus via NO2

minus by

the ammonia oxidizing bacteria and nitrite oxidizing [38]whereas the produced NO

3

minus (1198641015840120579NO3

N2

= 074V) could beused as the final electron acceptor in the cathode (Figure 8)Although the electric production of MFC with nitrate aselectron acceptor is inferior to other types ofMFC (eg O

2

asthe electron acceptor) realizing the biological denitrificationin the cathode is crucial and significant for the total nitrogenremoval in the CW-MFC system

43 Comparison of the Planted CW-MFC with Similar Pub-lished MFCs Because of the alternating phases of light anddark the electric output generated from plant photosyntheticproducts may show diurnal oscillations with clear fluctu-ations between the trough and the peak values [39 40]Similarly in this study the voltage outputs of the plantedCW-MFC were cyclically fluctuant depended on the daynightcycle In the planted CW-MFC system the fuel sourceconsisted of glucose fed from waste water and a certainamount of organic compounds released by Ipomoea aquaticaroots (Figure 8) Generally the photosynthates producedduring the daymay have led to increased exudates productionavailability for the anode in the planted CW-MFC Whenoperated in the light the CW-MFC could use photosynthatesand glucose as fuel generating more electricity Moreoverroots of Ipomoea aquatica (20 plusmn 2 cm length but mostdistributed in the upper part) releasedmore oxygen in the dayand created more suitable aerobic conditions in the cathodezone which induced the improvement of electric output Sothe high peak voltages for the planted CW-MFC in the daywere attributed to sufficient fuel available in the anode andfavorable oxygen condition in the cathode


The CW-MFC system can utilize the organic substratein the influent and plant photosynthate as fuels so itspower output could be divided into two parts power yieldfrom COD

119877

in the water body and power transformationfrom plant photosynthesis In current study the maximumpower output for the planted CW-MFC was 392GJ haminus1yearminus1 (1242mWmminus2) the maximum power yield fromCOD119877

in the water body was 6605KJKgminus1 COD119877

and themaximum power transformation from plant photosynthe-sis was 231 GJ haminus1 yearminus1 A maximum power density of1573mWmminus2 for a CW-MFC system planted with cannaindica was achieved during the treatment of wastewatercontaining 1000mg Lminus1 methylene blue [18] and it was about26 higher than that generated in this study Our CW-MFCdevice is constructed with a large anodic geometric surfacearea about 70650 cm2 that is 17 times higher than the CW-MFC planted with canna indica (4093 cm2) moreover thesubstrate concentration (200mg Lminus1 glucose) in the influ-ent is relatively low in our CW-MFC so these differencesmay make the power density slightly less Besides manysimilar MFCs generated power from plant photosynthatehave been reported and the maximum power outputs varyin different systems such as 189GJ haminus1 yearminus1 of plant-MFC in a rice paddy field [39] 455GJ haminus1 yearminus1 of rice-paddy MFC [41] 041 GJ haminus1 yearminus1 of sediment MFC witha biocathode in the rice rhizosphere [19] 7001 GJ haminus1 yearminus1of plant MFC planted with Spartina anglica [42] 11983 plusmn599GJ haminus1 yearminus1 of Direct Photosynthetic Plant FuelCell by using Lemna minuta duckweed [43] and 098 plusmn006GJ haminus1 yearminus1 of vascular plant biophotovoltaics plantedwith Oryza sativa [40] Through comparison and analysisfor the previously reports the power outputs were mainlyaffected by plant species plant area (anode surface area) andinternal resistance As MFC tests have been demonstratedthat increasing the anode surface area resulted in a slightincrease in volumetric power density [4] there would be ahuge drop in area power density if the anode surface areawere too large Our device had relatively large anode surfacearea (70650 cm2) and high internal resistance (156Ω) so thepower output was much lower than some of the plant MFCs(for instance 11983 plusmn 599GJ haminus1 yearminus1 of Direct Photo-synthetic Plant Fuel Cell with anode area only 1575 cm2 andinterresistance 91Ω) The current power generated by CW-MFC is not competitive however the CW-MFC technologypossesses potential advantages in removing contaminants inwastewater and reducing greenhouse gas emissionwhichwillattract attention andmay worth applying in the future In thisstudy the CW-MFC system operatingwith cheapGAC anodeand cathode with no use of precious metals was low cos andhad large volume (35 L) so its application is more possible inthe future

5 Conclusions

Conversion of solar energy into electricity can be fulfilledby coupling wetland plant photosynthesis with the microbialconversion of organics to electricity in CW-MFC system

The CW-MFC planted with Ipomoea aquatica produced amuch higher power than that from unplanted CW-MFCbecause plant root can improve electrode activity and providemore organic compounds available for fuel Moreover theroot of aquatic plants could uptake ammonia nitrogen andpart of the pollutants to promote the degradation of con-taminants in the wastewater and reduce the greenhouse gasThese results show that developing CW-MFC could providesignificant prospects for wastewater treatment and bioenergyrecovery Further studies are necessary to investigate theimpact of CW-MFC on the rhizospheric environment andaquatic plant physiology as well as the microbial community

Acknowledgment

This work was financially supported by the National NaturalScience Foundation of China (Grant no 21277024)

References

[1] B E Logan and J M Regan ldquoElectricity-producing bacterialcommunities in microbial fuel cellsrdquo Trends in Microbiologyvol 14 no 12 pp 512ndash518 2006

[2] Z Du H Li and T Gu ldquoA state of the art review on microbialfuel cells a promising technology for wastewater treatment andbioenergyrdquo Biotechnology Advances vol 25 no 5 pp 464ndash4822007

[3] D R Lovley ldquoThe microbe electric conversion of organicmatter to electricityrdquo Current Opinion in Biotechnology vol 19no 6 pp 564ndash571 2008

[4] H Liu S Cheng L Huang and B E Logan ldquoScale-up ofmembrane-free single-chamber microbial fuel cellsrdquo Journal ofPower Sources vol 179 no 1 pp 274ndash279 2008

[5] J R Kim G C Premier F R Hawkes R M Dinsdale and AJ Guwy ldquoDevelopment of a tubular microbial fuel cell (MFC)employing a membrane electrode assembly cathoderdquo Journal ofPower Sources vol 187 no 2 pp 393ndash399 2009

[6] B Logan S Cheng V Watson and G Estadt ldquoGraphite fiberbrush anodes for increased power production in air-cathodemicrobial fuel cellsrdquo Environmental Science and Technology vol41 no 9 pp 3341ndash3346 2007

[7] E Martin B Tartakovsky andO Savadogo ldquoCathodematerialsevaluation in microbial fuel cells a comparison of carbonMn2

O3

Fe2

O3

and platinum materialsrdquo Electrochimica Actavol 58 no 1 pp 58ndash66 2011

[8] S Ci Z Wen J Chen and Z He ldquoDecorating anode withbamboo-like nitrogen-doped carbon nanotubes for microbialfuel cellsrdquo Electrochemistry Communications vol 14 no 1 pp71ndash74 2012

[9] P S Jana M Behera and M M Ghangrekar ldquoPerformancecomparison of up-flowmicrobial fuel cells fabricated using pro-ton exchange membrane and earthen cylinderrdquo InternationalJournal of Hydrogen Energy vol 35 no 11 pp 5681ndash5686 2010

[10] M Rahimnejad M Ghasemi G D Najafpour et al ldquoSyn-thesis characterization and application studies of self-madeFe3

O4

PES nanocomposite membranes in microbial fuel cellrdquoElectrochimica Acta vol 85 pp 700ndash706 2012

[11] Z He J Kan F Mansfeld L T Angenent and K H NealsonldquoSelf-sustained phototrophic microbial fuel cells based on


the synergistic cooperation between photosynthetic microor-ganisms and heterotrophic bacteriardquoEnvironmental Science andTechnology vol 43 no 5 pp 1648ndash1654 2009

[12] K Nishio K Hashimoto and K Watanabe ldquoLightelectricityconversion by a self-organized photosynthetic biofilm in asingle-chamber reactorrdquo Applied Microbiology and Biotechnol-ogy vol 86 no 3 pp 957ndash964 2010

[13] RA TimmersD P B T B StrikHVMHamelers andC JNBuisman ldquoLong-term performance of a plantmicrobial fuel cellwith Spartina anglicardquo Applied Microbiology and Biotechnologyvol 86 no 3 pp 973ndash981 2010

[14] L Xiao E B Young J A Berges and Z He ldquoIntegratedphoto-bioelectrochemical system for contaminants removaland bioenergy productionrdquo Environmental Science and Technol-ogy vol 46 no 20 pp 11459ndash11466 2012

[15] M Rosenbaum Z He and L T Angenent ldquoLight energyto bioelectricity photosynthetic microbial fuel cellsrdquo CurrentOpinion in Biotechnology vol 21 no 3 pp 259ndash264 2010

[16] M P Ciria M L Solano and P Soriano ldquoRole of macro-phyte Typha latifolia in a constructed wetland for wastewatertreatment and assessment of its potential as a biomass fuelrdquoBiosystems Engineering vol 92 no 4 pp 535ndash544 2005

[17] X Li H Song W Xiang and L Wu ldquoElectricity generationduring wastewater treatment by a microbial fuel cell coupledwith constructed wetlandrdquo Journal of Southeast University vol28 no 2 pp 175ndash178 2012

[18] A K Yadav P Dash A Mohanty R Abbassi and B K MishraldquoPerformance assessment of innovative constructed wetland-microbial fuel cell for electricity production and dye removalrdquoEcological Engineering vol 47 no 0 pp 126ndash131 2012

[19] Z Chen Y Huang J Liang F Zhao and Y Zhu ldquoA novelsediment microbial fuel cell with a biocathode in the ricerhizosphererdquo Bioresource Technology vol 108 pp 55ndash59 2012

[20] RWang V Baldy C Perissol andN Korboulewsky ldquoInfluenceof plants on microbial activity in a vertical-downflow wetlandsystem treating waste activated sludge with high organic matterconcentrationsrdquo Journal of Environmental Management vol 95supplement pp S158ndashS164 2012

[21] G Zhang Q Zhao Y Jiao et al ldquoImproved performance ofmicrobial fuel cell using combination biocathode of graphitefiber brush and graphite granulesrdquo Journal of Power Sources vol196 no 15 pp 6036ndash6041 2011

[22] G Zhang K Wang Q Zhao Y Jiao and D Lee ldquoEffect ofcathode types on long-term performance and anode bacterialcommunities in microbial fuel cellsrdquo Bioresource Technologyvol 118 pp 249ndash256 2012

[23] H Richter M Lanthier K P Nevin and D R Lovley ldquoLack ofelectricity production by Pelobacter carbinolicus indicates thatthe capacity for Fe(III) oxide reduction does not necessarilyconfer electron transfer ability to fuel cell anodesrdquo Applied andEnvironmentalMicrobiology vol 73 no 16 pp 5347ndash5353 2007

[24] W Manz R Amann W Ludwig M Wagner and K SchleiferldquoPhylogenetic oligodeoxynucleotide probes for the major sub-classes of proteobacteria problems and solutionsrdquo Systematicand Applied Microbiology vol 15 no 4 pp 593ndash600 1992

[25] B E Logan B Hamelers R Rozendal et al ldquoMicrobial fuelcells methodology and technologyrdquo Environmental Science andTechnology vol 40 no 17 pp 5181ndash5192 2006

[26] S V Raghavulu S V Mohan R K Goud and P N SarmaldquoEffect of anodic pH microenvironment on microbial fuelcell (MFC) performance in concurrence with aerated and

ferricyanide catholytesrdquo Electrochemistry Communications vol11 no 2 pp 371ndash375 2009

[27] J C Wei P Liang X X Cao and X Huang ldquoA new insightinto potential regulation on growth and power generation ofGeobacter sulfurreducens inmicrobial fuel cells based on energyviewpointrdquo Environmental Science and Technology vol 44 no8 pp 3187ndash3191 2010

[28] R A Timmers M Rothballer D P B T B Strik et alldquoMicrobial community structure elucidates performance ofGlyceriamaxima plantmicrobial fuel cellrdquoAppliedMicrobiologyand Biotechnology vol 94 no 2 pp 537ndash548 2012

[29] H Deng Z Chen and F Zhao ldquoEnergy from plants andmicroorganisms progress in plant-microbial fuel cellsrdquo Chem-SusChem vol 5 no 6 pp 1006ndash1011 2012

[30] C Fang B Min and I Angelidaki ldquoNitrate as an oxidant inthe cathode chamber of a microbial fuel cell for both powergeneration and nutrient removal purposesrdquo Applied Biochem-istry and Biotechnology vol 164 no 4 pp 464ndash474 2011

[31] S Puig M Serra A Vilar-Sanz et al ldquoAutotrophic nitriteremoval in the cathode of microbial fuel cellsrdquo BioresourceTechnology vol 102 no 6 pp 4462ndash4467 2011

[32] Y Zhang and I Angelidaki ldquoBioelectrode-based approach forenhancing nitrate and nitrite removal and electricity generationfrom eutrophic lakesrdquoWater Research vol 46 no 19 pp 6445ndash6453 2012

[33] B Min J Kim S Oh J M Regan and B E Logan ldquoElectricitygeneration from swine wastewater using microbial fuel cellsrdquoWater Research vol 39 no 20 pp 4961ndash4968 2005

[34] J R Kim Y Zuo J M Regan and B E Logan ldquoAnalysisof ammonia loss mechanisms in microbial fuel cells treatinganimal wastewaterrdquo Biotechnology and Bioengineering vol 99no 5 pp 1120ndash1127 2008

[35] X Zhou G Wang and F Yang ldquoCharacteristics of growthnutrient uptake purification effect of Ipomoea aquatica Loliummultiflorum and Sorghum sudanense grown under differentnitrogen levelsrdquo Desalination vol 273 no 2-3 pp 366ndash3742011

[36] F Yao G Shen X Li H Li H Hu and W Ni ldquoA comparativestudy on the potential of oxygen release by roots of selectedwetland plantsrdquo Physics and Chemistry of the Earth vol 36 no9ndash11 pp 475ndash478 2011

[37] C DongW Zhu Y Q Zhao andM Gao ldquoDiurnal fluctuationsin root oxygen release rate and dissolved oxygen budget inwetlandmesocosmrdquoDesalination vol 272 no 1ndash3 pp 254ndash2582011

[38] J Wu J Zhang W Jia et al ldquoImpact of CODN ratio onnitrous oxide emission frommicrocosmwetlands and their per-formance in removing nitrogen from wastewaterrdquo BioresourceTechnology vol 100 no 12 pp 2910ndash2917 2009

[39] N Kaku N Yonezawa Y Kodama and K WatanabeldquoPlantmicrobe cooperation for electricity generation in a ricepaddyfieldrdquoAppliedMicrobiology andBiotechnology vol 79 no1 pp 43ndash49 2008

[40] P Bombelli D Iyer S Covshoff et al ldquoComparison of poweroutput by rice (Oryza sativa) and an associated weed (Echi-nochloa glabrescens) in vascular plant bio-photovoltaic (VP-BPV) systemsrdquo Applied Microbiology and Biotechnology vol 97no 1 pp 429ndash438 2013

[41] K Takanezawa K Nishio S Kato K Hashimoto and KWatanabe ldquoFactors affecting electric output from rice-paddymicrobial fuel cellsrdquoBioscience Biotechnology and Biochemistryvol 74 no 6 pp 1271ndash1273 2010


[42] M Helder D P B T B Strik H V M Hamelers A J KuhnC Blok and C J N Buisman ldquoConcurrent bio-electricity andbiomass production in three plant-microbial fuel cells usingSpartina anglica Arundinella anomala and Arundo donaxrdquoBioresource Technology vol 101 no 10 pp 3541ndash3547 2010

[43] Y Hubenova and M Mitov ldquoConversion of solar energy intoelectricity by using duckweed in direct photosynthetic plant fuelcellrdquo Bioelectrochemistry vol 87 pp 185ndash191 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


The concept of CW-MFC is based on constructedwetlandand plant MFC (one form of photosynthetic MFC) of whichall contain plants The role of plants is important in theCW-MFC system including their role in excreting oxygenand organic matter into the rhizosphere [19] supportinga wide range of microbes and providing a surface forbacterial attachment [20] These unique characteristics maymake the CW-MFC system an ideal approach to generateelectricity at sites and reduce globing warming as they candecrease methane emissions However the effect of plantphotosynthesis and plant rhizospheremicroorganisms on thepower enhancement for the CW-MFC has not been studiedfully yet

In this study we built a single-chamber membrane-free continuously feeding upflow microbial fuel cell coupledwith constructed wetland in which the cathode is locatedin overlying water to use oxygen from air for reductionreactions and the anode is submerged in a support matrixnear the rhizosphere to obtain organic substrates in theinfluent or deprived fromwetland plants root as fuelThe aimof this study was to evaluate whether or not the wetland plant(Ipomoea aquatica) can improve power generation in a CW-MFC system and to explore the bacterial population in theelectrode biofilm in response to MFC performance Mean-while investigations of the removal efficiencies of chemicaloxygen demand (COD) and total nitrogen (TN) were carriedout

2 Experimental

21 CW-MFC Construction As schematically shown inFigure 1 two CW-MFC reactors were constructed in thesame way using a polycarbonate plastic cylinder (30 cm indiameter and 50 cm inheight)Thebottom20 cmwas supportmatrix composed of gravel (gravel diameter 3ndash6mm) andthen upwards it consisted of anode support matrix (20 cmgravel) and cathode The anode was constructed from 10 cmthick granular activated carbon (GAC a diameter of 3ndash5mmthe specific area of 500ndash900m2 gminus1 and the filling densityof 045ndash055 g cmminus3) GAC was pretreated by soaking in 1MNaOH and 1M HCl to eliminate possible oil stain and metalion contamination respectively The cathode was made fromstainless steel mesh (a diameter of 25 cm thickness of 03 cm12 mesh) buried in 2 cm thick layer of activated carbonparticleThe electrode spacingwas 25 cm (center of the anodeto the face of the cathode) Electrodes were connected to acircuit using titanium wires across an external resistance of1000Ω and epoxy was used to seal metals exposed to thesolution Nine adult plants of Ipomoea aquatica were plantedthrough the upper layer of one CW-MFC device (plantingdensity about 32 plants mminus2) and the other CW-MFC wasa control with no plants The volume of the whole containerwas 353 L with a total liquid volume of 124 L

22 CW-MFC Operation The CW-MFCs were inoculatedwith the anaerobic sludge from a wastewater treatmentplant located in Jiangning Development Zone (NanjingChina) and operated by continuous feeding at a flow

GACcathode

GACanode

Gravel

Water distribution

Effluent

Influent

Load

Figure 1 Schematic of the CW-MFCs used in the experiment

rate of 431mLminminus1 corresponding to a hydraulic reten-tion time (HRT) of 2 d The feed solution consistedof 50mM phosphate buffer solution (PBS) with pH 74glucose (020 g Lminus1) NH

4

Cl (015 g Lminus1) KCl (013 g Lminus1)NaHCO

3

(313 g Lminus1) and 1mLLminus1 trace essential ele-ments solution (contained per liter 56 g (NH

4

)2

SO4

2 gMgSO

4

sdot7H2

O 200mg MnSO4

sdotH2

O 3mg H3

BO3

24mgCoCl2

sdot6H2

O 1mg CuCl2

sdot2H2

O 2mgNiCl2

sdot6H2

O 5mgZnCl2

10mg FeCl3

sdot6H2

O and 04mg Na2

MoO4

sdot2H2

O) Allexperiments were carried out in a 1212-h lightdark cycle at26 plusmn 2

∘C under greenhouse conditions The ambient lightwas provided by artificial illumination using (light-emittingdiode LED) Grow Lights (14W GC-ZW225S-P GechuangElectronics Co Ltd Shenzhen China) and the average lightintensity was 1000 lux during the light phase

23 Fluorescent In Situ Hybridization (FISH) FISH analysiswas applied to investigate the quantity of microorganismson the anode and cathode in our study Granular activatedcarbon with attached biofilm (wet weight of 05 g) was mul-tisampled (parallel samples) and suspended in 5mL steriledeionized water and microorganism cells were detachedfrom the GAC and uniformly dispersed in the solution withultra-sonic oscillations treatment About 05mL supernatant





2

HPO4

and024 g Lminus1 K

2

HPO4



119887


119863119887

=1000119873119878

1

1198721198782

(1)

where 1198781

1198782



Ω


Ω


119864119877


119894 =119864

119877 (2)

119875 =1198642

119877119860 (3)

119877Ω

=119864119877

119894=(119864OCV minus 119864)119877

119864 (4)





4

+-N NO2

minus-N and NO3



119881


119877

) in the water body

SPY =119875119881

COD119877

=1198642



3 Results



Cell

vol

tage

(V)

Time (days)

0807060504030201

00 4 8 12 16 20 24 28 32 36 40

PlantedUnplanted

(a)

Time (hours)

Cell

vol

tage

(V)

0807060504030201

00

12 24 36 48 60 72 84 96 108 120

PlantedUnplanted

(b)





Cell

vol

tage

(V)

09

08

07

06

05

04

03

02

01

0

18

16

14

12

10

8

6

4

2

00 1 2 3 4 5

Current (mA)

Pow

er d

ensit

y (m

W m

minus2)






10

04

03

02

01

0

8

6

4

2


Different reactors

Cathode potentialPo

tent

ial (

V)

Cel

l den

sity

(107

cell g

minus1)

Bacteria

(a)

10

8

6

4

2


Different reactors

Pote

ntia

l (V

)

0

minus01

minus02

minus03

minus04


Cel

l den

sity

(107

cell g

minus1)


(b)




119877


119877


119877


119877



2


10

7

6

5

4

3

2

1

00 20 30 40 50

Reactor height (cm)

Anode Rhizosphere

PlantedUnplanted

DO

(mg L

minus1)




4



100 20 30 40

40

35

30

25

20

15

10

5

050

Reactor height (cm)

Anode Rhizosphere

TNNH3-N

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NO2minus-N


Anode


TN

40

35

30

25

20

15

10

5

0

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NH4+-N NO2

minus-N



4



4

+-N removal NH4


4




2


2


3



3




minus-N and NO3


119909


minus-N andNO3



119909



4 Discussion



Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus


and (CH2

O)119899


2

O)119899

and C6

H12

O6

(3) NH4



2

and NO3




4

+ or NO3


4


2


4


minus via NO2

minus by


3

minus (1198641015840120579NO3

N2


2





119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





2

HPO4

and024 g Lminus1 K

2

HPO4



119887


119863119887

=1000119873119878

1

1198721198782

(1)

where 1198781

1198782



Ω


Ω


119864119877


119894 =119864

119877 (2)

119875 =1198642

119877119860 (3)

119877Ω

=119864119877

119894=(119864OCV minus 119864)119877

119864 (4)





4

+-N NO2

minus-N and NO3



119881


119877

) in the water body

SPY =119875119881

COD119877

=1198642



3 Results



Cell

vol

tage

(V)

Time (days)

0807060504030201

00 4 8 12 16 20 24 28 32 36 40

PlantedUnplanted

(a)

Time (hours)

Cell

vol

tage

(V)

0807060504030201

00

12 24 36 48 60 72 84 96 108 120

PlantedUnplanted

(b)





Cell

vol

tage

(V)

09

08

07

06

05

04

03

02

01

0

18

16

14

12

10

8

6

4

2

00 1 2 3 4 5

Current (mA)

Pow

er d

ensit

y (m

W m

minus2)






10

04

03

02

01

0

8

6

4

2


Different reactors

Cathode potentialPo

tent

ial (

V)

Cel

l den

sity

(107

cell g

minus1)

Bacteria

(a)

10

8

6

4

2


Different reactors

Pote

ntia

l (V

)

0

minus01

minus02

minus03

minus04


Cel

l den

sity

(107

cell g

minus1)


(b)




119877


119877


119877


119877



2


10

7

6

5

4

3

2

1

00 20 30 40 50

Reactor height (cm)

Anode Rhizosphere

PlantedUnplanted

DO

(mg L

minus1)




4



100 20 30 40

40

35

30

25

20

15

10

5

050

Reactor height (cm)

Anode Rhizosphere

TNNH3-N

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NO2minus-N


Anode


TN

40

35

30

25

20

15

10

5

0

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NH4+-N NO2

minus-N



4



4

+-N removal NH4


4




2


2


3



3




minus-N and NO3


119909


minus-N andNO3



119909



4 Discussion



Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus


and (CH2

O)119899


2

O)119899

and C6

H12

O6

(3) NH4



2

and NO3




4

+ or NO3


4


2


4


minus via NO2

minus by


3

minus (1198641015840120579NO3

N2


2





119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Cell

vol

tage

(V)

Time (days)

0807060504030201

00 4 8 12 16 20 24 28 32 36 40

PlantedUnplanted

(a)

Time (hours)

Cell

vol

tage

(V)

0807060504030201

00

12 24 36 48 60 72 84 96 108 120

PlantedUnplanted

(b)





Cell

vol

tage

(V)

09

08

07

06

05

04

03

02

01

0

18

16

14

12

10

8

6

4

2

00 1 2 3 4 5

Current (mA)

Pow

er d

ensit

y (m

W m

minus2)






10

04

03

02

01

0

8

6

4

2


Different reactors

Cathode potentialPo

tent

ial (

V)

Cel

l den

sity

(107

cell g

minus1)

Bacteria

(a)

10

8

6

4

2


Different reactors

Pote

ntia

l (V

)

0

minus01

minus02

minus03

minus04


Cel

l den

sity

(107

cell g

minus1)


(b)




119877


119877


119877


119877



2


10

7

6

5

4

3

2

1

00 20 30 40 50

Reactor height (cm)

Anode Rhizosphere

PlantedUnplanted

DO

(mg L

minus1)




4



100 20 30 40

40

35

30

25

20

15

10

5

050

Reactor height (cm)

Anode Rhizosphere

TNNH3-N

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NO2minus-N


Anode


TN

40

35

30

25

20

15

10

5

0

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NH4+-N NO2

minus-N



4



4

+-N removal NH4


4




2


2


3



3




minus-N and NO3


119909


minus-N andNO3



119909



4 Discussion



Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus


and (CH2

O)119899


2

O)119899

and C6

H12

O6

(3) NH4



2

and NO3




4

+ or NO3


4


2


4


minus via NO2

minus by


3

minus (1198641015840120579NO3

N2


2





119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


10

04

03

02

01

0

8

6

4

2


Different reactors

Cathode potentialPo

tent

ial (

V)

Cel

l den

sity

(107

cell g

minus1)

Bacteria

(a)

10

8

6

4

2


Different reactors

Pote

ntia

l (V

)

0

minus01

minus02

minus03

minus04


Cel

l den

sity

(107

cell g

minus1)


(b)




119877


119877


119877


119877



2


10

7

6

5

4

3

2

1

00 20 30 40 50

Reactor height (cm)

Anode Rhizosphere

PlantedUnplanted

DO

(mg L

minus1)




4



100 20 30 40

40

35

30

25

20

15

10

5

050

Reactor height (cm)

Anode Rhizosphere

TNNH3-N

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NO2minus-N


Anode


TN

40

35

30

25

20

15

10

5

0

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NH4+-N NO2

minus-N



4



4

+-N removal NH4


4




2


2


3



3




minus-N and NO3


119909


minus-N andNO3



119909



4 Discussion



Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus


and (CH2

O)119899


2

O)119899

and C6

H12

O6

(3) NH4



2

and NO3




4

+ or NO3


4


2


4


minus via NO2

minus by


3

minus (1198641015840120579NO3

N2


2





119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


100 20 30 40

40

35

30

25

20

15

10

5

050

Reactor height (cm)

Anode Rhizosphere

TNNH3-N

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NO2minus-N


Anode


TN

40

35

30

25

20

15

10

5

0

Con

cent

ratio

n (m

g Lminus1)

NO3minus-N

NH4+-N NO2

minus-N



4



4

+-N removal NH4


4




2


2


3



3




minus-N and NO3


119909


minus-N andNO3



119909



4 Discussion



Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus


and (CH2

O)119899


2

O)119899

and C6

H12

O6

(3) NH4



2

and NO3




4

+ or NO3


4


2


4


minus via NO2

minus by


3

minus (1198641015840120579NO3

N2


2





119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Cathode

Bacteria

Anode

H2O O2

N2

O2

CO2

CO2

(CH2O)n

C6H12O6

NO3minus

NO3minus

NH4+ NO2

minus


and (CH2

O)119899


2

O)119899

and C6

H12

O6

(3) NH4



2

and NO3




4

+ or NO3


4


2


4


minus via NO2

minus by


3

minus (1198641015840120579NO3

N2


2





119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



119877




5 Conclusions



Acknowledgment


References








O3

Fe2

O3





O4
















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of














































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article power generation enhancement by utilizing...

Documents