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Ecological Engineering 60 (2013) 135– 139

Contents lists available at ScienceDirect

Ecological Engineering

journa l h om epage: www.elsev ier .com/ locate /eco leng

hort communication

itrogen removal from polluted river water in a novelitch–wetland–pond system

enzhong Tang, Wenqiang Zhang, Yu Zhao, Yuanyue Wang, Baoqing Shan ∗

tate Key Laboratory on Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085,hina

r t i c l e i n f o

rticle history:eceived 18 February 2013eceived in revised form 29 May 2013ccepted 4 July 2013

a b s t r a c t

To remove nitrogen from polluted river water in situ, a ditch–wetland–pond system (DWPS) with a lengthof 25 m was designed and built near the Liu River, Tianjin, China. Average ammonia (NH4

+-N), total nitrate(NO3

−-N) and nitrogen (TN) removal efficiencies of 76.90%, 54.24% and 58.71%, respectively, were attainedby the DWPS under optimum operating conditions. A DWPS application project with a length of 500 m was

eywords:itch–wetland–pond system (DWPS)itrogenperating conditionspplication

then constructed near Qilihai Wetland, Tianjin to treat polluted river water from the Chaobaixin River,and average NH4

+-N, NO3−-N and TN removal percentages of 52.04%, 33.33% and 38.66%, respectively,

were observed during monitoring. Moreover, denitrification and nitrification were found to be the mostimportant processes associated with nitrogen removal. The DWPS, which was designed to be elongatedand including duplicate units, was found to be technologically feasible and applicable to treat polluted

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water from rivers or ditch

. Introduction

Nitrogen is one of the principal pollutants that can causeutrophication and influence dissolved oxygen (DO) levels in waterodies such as lakes and rivers. In addition, nitrogen may causeoxicity to the aquatic organisms (Blankenberg et al., 2008; Saeednd Sun, 2012; Xiong et al., 2011). According to the environmentaluality standards for surface water of China, the poorest conditionslevel V) for total nitrogen (TN) and ammonia (NH4

+-N) are 2.0 mg/LChina, 2002). Currently, the water quality of many rivers in Chinaxceeds the level V standards. Indeed, more than 40% of the streamsn the Haihe Basin do not meet this standard (China, 2011). Sincehemical oxygen demand (COD) is controlled by sewage treat-ent plants, nitrogen (especially NH4

+-N) has become the mainollutant responsible for this poor water quality. Therefore, highitrogen levels in the environment and its subsequent effects onquatic ecosystems have attracted increased social attention (Dingt al., 2012).

Early treatment measures for polluted river water simplyepended on the self-purifying mechanisms of natural water bod-

es (Yuan et al., 2012). However, the concentration and volume of

astewater discharged into rivers is now too great to be treated byatural processes alone. Thus, other technologies for polluted riveremediation have been considered to enhance the self-purification

∗ Corresponding author. Tel.: +86 10 6284 9817.E-mail addresses: bqshan@rcees.ac.cn, wztang@rcees.ac.cn (B. Shan).

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925-8574/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.ecoleng.2013.07.009

situ; therefore, its use will be expanded locally and to similar areas.© 2013 Elsevier B.V. All rights reserved.

apability of rivers, including dredging, sedimentation and filtra-ion, contact oxidation, and constructed wetlands (Juang and Chen,007; Wu et al., 2009; Yuan et al., 2012). Constructed wetlandsCWs) have been receiving increased attention worldwide and areecognized as providing effective treatment of wastewater usingooted aquatic plants and media (e.g. gravel, grit, soil) (Chang et al.,012; Hu et al., 2012). As typical natural and environmental friendlyystems (Dan et al., 2011), CWs have promising potential for appli-ation in developing countries (Kivaisi, 2001). CWs can treat aariety of wastewaters (Huang et al., 2000; Zurita et al., 2009; Abou-lela and Hellal, 2012); however few studies of nitrogen removalrom polluted river water by these systems have been conductedo date, especially in situ.

In this study, a ditch–wetland–pond system (DWPS), whichncluded a pilot-scale DWPS and a full-scale DWPS, was designednd constructed to investigate nitrogen removal from pollutediver water in situ. The main objectives of this paper were: (1) tovaluate the capacity and long-term stability of DWPS for the treat-ent of polluted river water and (2) to demonstrate the potential

pplication and spread of DWPS in local and similar areas.

. Materials and methods

.1. System configuration

A pilot-scale DWPS composed of two wetland–pond–wetlandnits and one ditch unit was set up within the vicinity of Liuiver of Tianjin, China (Fig. 1). To enable better application to

136 W. Tang et al. / Ecological Engineering 60 (2013) 135– 139

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Fig. 1. Configuration (units: mm) an

ivers or ditches in situ, the system was designed to be elon-ated and have duplicate units (wetland–pond–wetland). The twoetland–pond–wetland units were mainly used for the treatment

f polluted river water, while the ditch unit was for runoff. Theilot-scale DWPS was 25 m long, 2 m wide, and 1 m deep, while theour wetland units were all 3.5 m long, 0.875 m wide at the top and.075 m wide at the bottom. In addition, the units were 0.8 m high,

ncluding a 0.3 m layer of gravel ( ̊ 40–60 mm) at the bottom, a.2 m layer of gravel ( ̊ 10–30 mm) and a 0.2 m layer of grit in theeddle, and a 0.1 m layer of soils on the top, where reeds were

lanted.The full-scale DWPS (an application project) was constructed

ear Qilihai Wetland in Tianjin to treat polluted river waterrom the Chaobaixin River in 2011 (Fig. 3). The applicationroject (500 m long, 20 m wide, and 2 m deep) consisted of threeetland–pond–wetland units and one ditch unit.

.2. Operation of the system

Fig. 1 also shows the operational arrangements of the pilot-scaleWPS. The experiment was started in June 2010 and completed inctober 2011. During this time, polluted river water was directlyumped from the Liu River into the system. Operation of the sys-

em was divided into three periods, a startup period, optimizationeriod (I, II and III), and steady state. The operating conditions wereet based on reference to the water level and flow rate of the Liuiver.

o

c

rational arrangements of the DWPS.

.3. Sampling and analysis

To monitor the performance of the DWPS, water samples of thenfluent and effluent were taken periodically every week for analy-is (Fig. 1) during optimization of operating conditions and steadytate operation. Before sampling, T, pH, Eh and DO were moni-ored in situ using an Orion 4-star pH/ISE portable meter, a triodelectrode (Orion 9197 BNMD) and a YSI 550A portable dissolvedxygen meter, respectively. After the indexes were measured, threeeplicate samples were collected and analyzed for NH4

+-N, nitrateNO3

−-N), TN and COD using a Digital Reactor Block 200 and HACHR 2800 spectrophotometer according to the standard procedure

HACH TNT test tube method) recommended by the supplier.In addition, triplicate surface soils were collected from each

etland–pond–wetland unit of the DWPS application project andnalyzed for the potential nitrification rate (PNR) and potentialenitrification rate (DNR) using the chlorate inhibition methodKurola et al., 2005) and acetylene inhibition method (Wang et al.,012), respectively.

. Results and discussion

.1. Overall performance of the system during optimization of

perating conditions

Table 1 shows the pollutant removal profiles (in terms of con-entration), and removal efficacy (expressed as percentages) across

W. Tang et al. / Ecological Engineering 60 (2013) 135– 139 137

Table 1Mean pollutant concentration across DWPS during optimization of operating conditions.

Period Parameter Unit Influent concentration Effluent concentration % removal

Optimization of operating conditions

I

pH 8.17 ± 0.09 8.64 ± 0.41 –DO mg/L 4.58 ± 1.51 12.41 ± 0.25 –Eh mV 473.00 ± 83.54 583.67 ± 44.63 –NH4

+-N mg/L 3.64 ± 0.45 1.10 ± 0.51 69.78NO3

−-N mg/L 2.18 ± 0.76 1.72 ± 0.70 21.10TN mg/L 6.67 ± 1.50 3.37 ± 0.41 49.47

II

pH 8.73 ± 0.10 8.76 ± 0.08 –DO mg/L 9.44 ± 1.40 8.39 ± 1.06 –Eh mV 177.66 ± 46.60 243.66 ± 59.58 –NH4

+-N mg/L 0.88 ± 0.31 0.23 ± 0.12 73.86NO3

−-N mg/L 2.64 ± 0.73 0.58 ± 0.11 78.03TN mg/L 5.02 ± 1.96 2.06 ± 0.31 58.96

III

pH 8.58 ± 0.27 8.50 ± 0.09 –DO mg/L 11.79 ± 1.16 10.48 ± 1.20 –Eh mV 104.00 ± 37.32 99.66 ± 29.87 75.56NH4

+-N mg/L 3.11 ± 1.52 0.76 ± 0.42mg/mg/

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Dwrt

3

NO3−-N

TN

he DWPS under different operating conditions. Overall, high NH4+-

removal percentages (>69%) within the range of variations inydraulic loading, water level and influent pollutant concentra-ion were observed, indicating that NH4

+-N removal in the DWPSas due to intense nitrification (Saeed et al., 2012). The COD val-es of polluted river water were lower (mean 38.64 mg/L) than thenvironmental quality standards for surface water (V, 40.00 mg/L)

China, 2002), and showed no obvious changes across DWPS. Themall fluctuations in COD concentrations in effluent may haveeen due to differences in the polluted river water during differ-nt periods. TN removal rates, an important standard to measure

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40

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Fig. 2. Pollutant removal performance across t

L 1.94 ± 0.61 1.23 ± 0.63 36.59L 7.08 ± 1.61 4.43 ± 1.92 37.43

WPS efficiency, indicated that the optimum operating conditionsere as follows: high water level 0.85 m, low hydraulic loading

ate 0.06 m/day, under which the DWPS had a higher residenceime.

.2. Overall performance of the system during steady operation

To evaluate the long-term stability of the DWPS, the pollutantemoval performance was investigated from July 2011 to October011 under optimum operating conditions. During this period, therimary pollutant in the river water was NH4

+-N (mean 59.68%),

1 2 3 4 5 6 7 8 9 10 11 12 13 14

N

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60

80

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oval (%

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oval (%

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he DWPS during steady state operation.

138 W. Tang et al. / Ecological Engineering 60 (2013) 135– 139

iency

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Fig. 3. Pollutant removal effic

ndicating that nitrification is the first step in nitrogen transfor-ation in the DWPS (Saeed and Sun, 2012). As shown in Fig. 2,

he DWPS all maintained high NH4+-N removal efficiencies ran-

ing from 71.51% to 81.88%, with an average of 76.90% throughouthe steady state period. During DWPS, denitrification, the major

echanism of TN removal in constructed wetlands (Chung et al.,008; Matheson and Sukias, 2010; Reilly et al., 2000), was also stim-lated. Specifically, TN removals of 52.89–63.24% with an averagef 58.71% and NO3

−-N removals of 42.25–61.61% with an averagef 54.24% were attained. In contrast, COD removal remained poorcross the DWPS, with an average of only 11.06%.

When compare with traditional constructed wetlands, theWPS was designed to be elongated (length:width = 12.5:1) andave duplicate units (wetland–pond–wetland) (Fig. 1) for betterpplication to rivers or ditches in situ. In the DWPS, pollutediver water flowed into wetland–pond–wetland units repeatedlyor repeated treatment, and the transformation and removal ofitrogen was accomplished by biological (e.g. nitrification, denitri-cation, plant uptake), and physicochemical routes (e.g. ammoniaolatilization, and adsorption) (Hu et al., 2012; Saeed and Sun,012; Sun et al., 2012). The effective and steady removal of TNFig. 2) implies that DWPS can be applied to rivers or ditches well.

.3. Application performance of the system

A DWPS application project was constructed to treat pollutediver water from the Chaobaixin River (Fig. 3). Polluted river waterowed directly or was pumped from the Chaobaixin River intohe system, which was operated at a water level of 1.50 m and

hydraulic loading rate 0.60 m/day. The nitrogen removal per-

ormance of the DWPS application project was monitored everywo weeks from April to September 2012. The average NH4

+-, NO3

−-N and TN removal percentages were 52.04%, 33.33%nd 38.66%, respectively, which were higher than the values

R

A

of DWPS application project.

eported in other studies (Saeed and Sun, 2011; Zhao et al., 2011).oreover, the PNR of the surface soils in wetland units reached

7.42–117.29 nmol N/(g dry weight soil·h), while the DNR was1.23–73.56 nmol N/(g dry weight soil·h). These findings indicatehat denitrification and nitrification were the most important pro-esses responsible for nitrogen removal in the DWPS applicationroject (Saeed and Sun, 2012). These results indicate that DWPS cane implemented in situ for the treatment of polluted river water.ndeed, its use has been approved by local water conservation andnvironmental protection departments.

. Conclusions

Nitrogen was effectively removed from polluted river watercross the DWPS via biological (especially denitrification and nitri-cation) and physicochemical routes, and the optimum operatingonditions were a high water level and low hydraulic loading rate.WPS, which is designed to be elongated and includes duplicatenits (wetland–pond–wetland), can be applied to rivers or ditches

n situ. The DWPS application project for the treatment of pollutediver water from the Chaobaixin River achieved good results, andill therefore be employed locally and in similar areas.

cknowledgements

This research was supported by the National Natural Scienceoundation of China (No. 21107126), and the National Water Pol-ution Control Program (No. 2012ZX07203-002).

eferences

bou-Elela, S.I., Hellal, M.S., 2012. Municipal wastewater treatment using verticalflow constructed wetlands planted with Canna, Phragmites and Cyprus. Ecol.Eng. 47, 209–213.

Engine

B

C

C

CC

D

D

H

H

J

K

K

M

R

S

S

S

S

W

W

X

Y

Z

W. Tang et al. / Ecological

lankenberg, A.G.B., Haarstad, K., Sovik, A.K., 2008. Nitrogen retention in constructedwetland filters treating diffuse agriculture pollution. Desalination 226, 114–120.

hang, J.J., Wu, S.Q., Dai, Y.R., Liang, W., Wu, Z.B., 2012. Treatment performance ofintegrated vertical-flow constructed wetland plots for domestic wastewater.Ecol. Eng. 44, 152–159.

hina, M.E.P., 2002. Environmental quality standards for surface water (GB 3838-2002).

hina, W.R.P.B.H.B., 2011. Water resources bulletin of Haihe Basin.hung, A.K.C., Wu, Y., Tam, N.F.Y., Wong, M.H., 2008. Nitrogen and phosphate

mass balance in a sub-surface flow constructed wetland for treating municipalwastewater. Ecol. Eng. 32, 81–89.

an, T.H., Quang, L.N., Chiem, N.H., Brix, H., 2011. Treatment of high-strengthwastewater in tropical constructed wetlands planted with Sesbania ses-ban: horizontal subsurface flow versus vertical downflow. Ecol. Eng. 37,711–720.

ing, Y., Song, X.S., Wang, Y.H., Yan, D.H., 2012. Effects of dissolved oxygen andinfluent COD/N ratios on nitrogen removal in horizontal subsurface flow con-structed wetland. Ecol. Eng. 46, 107–111.

u, Y.S., Zhao, Y.Q., Zhao, X.H., Kumar, J.L.G., 2012. High rate nitrogen removal inan alum sludge-based intermittent aeration constructed wetland. Environ. Sci.Technol. 46, 4583–4590.

uang, J., Reneau, R.B., Hagedorn, C., 2000. Nitrogen removal in constructed wet-lands employed to treat domestic wastewater. Water Res. 34, 2582–2588.

uang, D.F., Chen, P.C., 2007. Treatment of polluted river water by a new constructedwetland. Int. J. Environ. Sci. Technol. 4, 481–488.

ivaisi, A.K., 2001. The potential for constructed wetlands for wastewater treatmentand reuse in developing countries: a review. Ecol. Eng. 16, 545–560.

urola, J., Salkinoja-Salonen, M., Aarnio, T., Hultman, J., Romantschuk, M., 2005.Activity, diversity and population size of ammonia-oxidising bacteria in oil-contaminated landfarming soil. FEMS Microbiol. Lett. 250, 33–38.

atheson, F.E., Sukias, J.P., 2010. Nitrate removal processes in a constructed wetlandtreating drainage from dairy pasture. Ecol. Eng. 36, 1260–1265.

Z

ering 60 (2013) 135– 139 139

eilly, J.F., Horne, A.J., Miller, C.D., 2000. Nitrate removal from a drinking water sup-ply with large free-surface constructed wetlands prior to groundwater recharge.Ecol. Eng. 14, 33–47.

aeed, T., Afrin, R., Al Muyeed, A., Sun, G.Z., 2012. Treatment of tannery wastewaterin a pilot-scale hybrid constructed wetland system in Bangladesh. Chemosphere88, 1065–1073.

aeed, T., Sun, G.Z., 2011. Enhanced denitrification and organics removal in hybridwetland columns: comparative experiments. Bioresour. Technol. 102, 967–974.

aeed, T., Sun, G., 2012. A review on nitrogen and organics removal mechanisms insubsurface flow constructed wetlands: dependency on environmental param-eters, operating conditions and supporting media. J. Environ. Manage. 112,429–448.

un, G.Z., Zhu, Y.F., Saeed, T., Zhang, G.X., Lu, X.G., 2012. Nitrogen removal and micro-bial community profiles in six wetland columns receiving high ammonia load.Chem. Eng. J. 203, 326–332.

ang, C.X., Zhu, G.B., Wang, Y., Wang, S.Y., Yin, C.Q., 2012. Nitrous oxide reductasegene nosZ and N2O reduction along the littoral gradient of a eutrophic freshwaterlake. J. Environ. Sci. 24, 1–9.

u, W.Z., Liu, Y., Zhu, Q., Wei, C.J., Wang, J.L., 2009. Remediation of polluted riverwater by biological contact oxidation process using two types of carriers. Int. J.Environ. Pollut. 38, 223–234.

iong, J.B., Guo, G.L., Mahmood, Q., Yue, M., 2011. Nitrogen removal from secondaryeffluent by using integrated constructed wetland system. Ecol. Eng. 37, 659–662.

uan, X.C., Qian, X., Zhang, R.B., Ye, R., Hu, W., 2012. Performance and microbialcommunity analysis of a novel bio-cord carrier during treatment of a pollutedriver. Bioresour. Technol. 117, 33–39.

hao, Y.Q., Babatunde, A.O., Hu, Y.S., Kumar, J.L.G., Zhao, X.H., 2011. Pilot field-scale

demonstration of a novel alum sludge-based constructed wetland system forenhanced wastewater treatment. Process Biochem. 46, 278–283.

urita, F., De Anda, J., Belmont, M.A., 2009. Treatment of domestic wastewater andproduction of commercial flowers in vertical and horizontal subsurface-flowconstructed wetlands. Ecol. Eng. 35, 861–869.