DESALINATION

www.elsevier.com/locate/desalDesalination 247 (2009) 28–35

Water reuse and resources recovery: the role of constructedwetlands in the Ecosan approach

Fabio Masi*

IRIDRA Srl, via Lorenzo il Magnifico 70, Florence, 50129, ItalyTel: +39 055 47 07 29; Fax: +39 055 47 55 93; email: masi@iridra.com

Received 20 September 2007; revised 19 December 2007; accepted 07 March 2008

Abstract

This chapter highlights some of the possible additional advantages of the use of constructed wetlands (CWs)for wastewater treatment joined to the Ecosan approach; reuse of treated wastewater, nutrients recovery and bio-mass production are the targets that can be kept in mind while designing a sustainable water cycle in several com-mon scenarios.

Keywords: Constructed wetlands; Water reuse; Nutrients recovery; Biomass production; Ecosan

1. Introduction

Our modern wastewater management approachhas made a crucial contribution to health, welfareand environment; nevertheless, very often conven-tional wastewater treatment systems have weak-nesses that should be more critically examined.For example, useful substances are not always sep-arated from harmful ones in these systems, andtherefore the resulting nutrient-rich sludge con-tains a relevant amount of pollutants and is oftenbadly managed during its final disposal.

The paradigm shift of sustainable water man-agement or ecological sanitation (Ecosan) isbased on a combination of traditional techniques

and new approaches such as water saving,wastewater reuse and recycling, nutrients recov-ery and biomass production for energy. Themain technical topics are, therefore, how toreduce fluxes at every consumption point, howto treat used water in the most efficient way tobe able to use it as ‘‘service water’’ for domesticor urban usages, how to reuse treated wastewaterfor agricultural irrigation, how to segregate dif-ferent sources of wastewater (black/grey) aswell as useful substances such as nutrients(nitrogen and phosphorus) or organic matter,and finally what kind of growths could be irri-gated to obtain valuable quantities of availablebiomass for energy production.

As an example of how a sustainable approachin the water cycle management can yield*Corresponding author.

Presented at Multi Functions of Wetland Systems, International Conference of Multiple Roles of Wetlands, June 26–29, 2007, Legnario (Padova) Italy

0011-9164/08/$– See front matter � 2009 Elsevier B.V. All rights reserved

valuable results, MEDA Water Project Zer0-mhas recently elaborated a feasibility study for atourist facility located near Tangier on the Med-iterranean Sea. Due to the seasonal water scar-city, which is typical in this area, a strongeffort for reducing water consumption has beenworked out, always keeping in mind, at thesame time, the reduction of pollutants dischargein the sea itself. With a traditional approach,direct treatment of the whole flow (48 m3/d) bya constructed wetland (CW) has been evaluated(Fig. 1).

The adoption of some Ecosan concepts, suchas rainwater harvesting and its temporary stor-age, black and grey water segregation, reuse ofthe treated grey water, together with an estima-tion of the losses by evaporation and evapotrans-piration during the treatments in sequencingbatch reactor (grey water) and constructed wet-land (black water), produces a complex flow dia-gram, as shown in Fig. 2.

A remarkable reduction in the usage of drink-ing water from 48 to 18.5 m3/d is the first impor-tant finding, immediately followed by the absenceof any discharge in the sea; only a small amountof water, containing some nutrients, could beused in fact for landscape or crop irrigation.

Constructed wetlands (CWs) can represent avalid option as grey water treatment systems,due to their specific capabilities and the particularchemical characterization of the grey water itself;it is well known [1] that the biodegradation rate ismuch higher for grey waters than for black ormixed waters (combination of black and grey).Due to a higher BOD5/COD ratio which is com-mon in grey wastewater and a lower content innutrients, especially for nitrogen, only 1–2 daysof hydraulic retention time (HRT) is needed intemperate climates for obtaining reusable waterby submerged flow CWs such as horizontal orvertical flow reed beds.

Several recent studies have demonstrated thegood performances of horizontal submergedflow CWs applied for the treatment of segre-gated blackwater/greywater (bw/gw): the highquality of the final effluent is the most appropri-ate for reuse practices even at domestic level[2,3]; also, the number of papers on bw/gwcharacterization is decidedly increasing nowa-days [4]. The segregation of bw/gw seems tobe one of the best practices for minimizing treat-ment costs, when the final target is reuse of thewastewater itself.

An interesting multi-purpose approach relatedto the use of CWs is the combination of the waste-water treatment with the production of useful bio-masses for energy or for direct utilization asvaluable materials. The plants that are growingin CWs, most commonly reeds (Phragmites aus-tralis), can in fact be utilized as follows:

– biomass fuel (renewable source of energy)– construction material for housing– high-strength fibre– pulp and paper production– livestock forage– soil conditioner (due to a slow release of the

nutrients standing stock).

Certain bamboo species are considered topossess characteristics similar to those of

Drinking water

CW

to sea

48.3

Fig. 1. Example of conventional approach to the watercycle for tourist facility (estimated daily flow for con-sumed water = 48.3 m3/d).

F. Masi / Desalination 247 (2009) 28–35 29

reeds, but with some advantages [5]. These spe-cies are markedly adaptable plants that can toler-ate a wide range of climatic conditions. They areusually fast growing and highly productive, andare one of the most widely utilized naturalresources in the world [6–8]. The above-citedworks conclude that there is a high potentialfor the use of bamboo in CWs, in particular attertiary treatment stage, and for a further devel-opment of such systems in Europe and in theMediterranean countries.

2. Wastewater Fluxes Segregation forReuse Optimization

The simplest segregation is obtained withthe construction of two different collectingsystems, as shown in Fig. 3, for the grey andblack waters. Normally, grey water means allwastewater from a household except the flush-ing water with faeces and urine (black water).But for special purposes, that is, to get moreunspoiled grey water, it can be collected only

from showers, bath and washing machine andthe whole water from kitchen sinks or dish-washer is added to black water. Another optionis to install a degreaser before the septic tanksand to treat the whole grey water, including itskitchen fraction.

Additionally, black water can be morediverted. Using water-free urinals and/or urineseparation toilets, the urine can be collectedand discharged separately and the faeces canbe treated separately or combined with thegrey water. Figure 4 shows one possibility of adiverting technology for black water [9].

An interesting case of grey water treatmentby CWs is ‘‘La Cava’’ camping site near Arezzo(Central Italy), a small camping site recentlyestablished and designed according to the sus-tainable water management principles (watersaving, reuse and recycling). Black and greywaters are segregated and treated by a CW;treated grey water is recycled for toilet flushing,while the treated black water is reused for land-scape irrigation.

Rainwater

Drinking water

5,8

4,8

3,4

3,81,0

1,0Evaporation

Laundry1,0 Cleaning7,5 Irrigation1,0 Outside7,0 WC

18,5 16,9 Bath

Greywatertreatment

all flows are given in m3 per day

2,6

8,4

Irrigation

11,0 Blackwatertreatment in CW

7,5 7,5

15,0

7,5

Evapo-transpiration

3,5

Fig. 2. Example of water balance obtained with a sustainable water management approach (all flows are given in m3/d).

30 F. Masi / Desalination 247 (2009) 28–35

The camping complex covers an area of about20,000 m2, with wood, green terraces and parkingplaces for a total of 25 cars. The CW area occu-pies only 3.5% (700 m2) of the camping area.The camping is only open during summer months(from July to September). The produced waste-water has to be treated on-site because the nearestsewer to the municipality treatment plant islocated at a distance of approximately 6000 m.Wastewater is collected by a gravity system. Sim-ilarly to other touristic sites, wastewater produc-tion has a high weekly fluctuation, ranging from0.3 to 7 m3/d. Grey water is treated at an HLRof 8.26 cm/d (a flow rate of 9.5 m3/d passingthrough a horizontal sub-surface flow wetlandcell [HF] with a surface area of 115 m2). Blackwater is treated at a smaller HRT of 5.16 cm/d

(flow rate of an average 6.5 m3/d passing throughan HF wetland cell, whose surface area is126 m2). The entire wetland treatment system(Fig. 5-6) is continuously fed by gravity, withoutenergy consumption.

Segregation of fluxes allows for a safe reuseof the treated grey water, which is pumped backto the buildings for toilet flushing. Water-savingmeasures have been adopted in all buildings(double-choice flushing toilets, taps, showers).The treated black water is reused for dropirrigation of green areas. Very efficient COD(89%) and NH4

+ (92%) reductions have beenachieved in the grey water HF CW, providingimportant information about the high removalefficiency by CWs when used for grey watertreatment [10].

Black water

Grey water

KitchenLavoratory

Bathroom

Fig. 3. Black and grey water segregation at household level.

Urine tank

Urine separationtoilet

Faecal bin

Grey water

Fig. 4. Black water diverting technologies at household level.

F. Masi / Desalination 247 (2009) 28–35 31

Fig. 5. The two reed beds (before plantation of P. australis) for the treatment of black and grey water at La Cavacamping site – Poppi – Italy.

CWs

Septic tank Well WellHorizontal flow RBTS

Degreaser

Pumpingsystem

Out

Reuse

Blackwater

Greywater

Well WellHorizontal flow RBTS

Fig. 6. Location of the two reed beds (horizontal sub-surface flow CWs or reed bed treatment systems – RBTS) andrespective sketches for the treatment of the segregated wastewater at La Cava camping site.

32 F. Masi / Desalination 247 (2009) 28–35

3. Nutrients Recovery and BiomassProduction

Looking at the wastewater components suchas BOD, nitrogen, phosphorus and potassiumin black and grey water, their specific composi-tion differs remarkably in urine and faeces. Thisis the most important reason for using separationtechnologies to promote more efficient ways forwastewater treatment, nutrient reclamation andwater saving.

Figure 7 clearly shows that the main dif-ference between grey and black water lies inthe amount of nitrogen as well as BOD. Thecontents of nutrients such as N, P and K are3–10 times higher in black water. It is wellknown that detergents are specific pollutantsof the grey water. Some of them, in particularlynon-ionic polyethoxylates surfactants, canproduce environmentally harmful biodegrada-tion products, such as bisphenols, which needto be removed before reusing the treatedwastewater.

Anyway it is very clear that grey water treat-ment is not affected by concerns about nitrogen

removal, which is one of the most economicaland technically difficult steps in a wastewatertreatment process. Figure 8 depicts the composi-tion of black water from its main sources, faecesand urine. Urine contains almost 91% of nitro-gen, 69% of phosphorus and 69% of potassium,besides hormones and pharmaceutical substan-ces from drugs [9]. Faeces can be describedmainly by BOD and bacteria, pathogens andnon-pathogens.

The segregation of the different fluxes ofmaterials, such as urine or faeces (by urineseparating toilets, composting toilets, vacuumtoilets and water-free urinals), involves the pro-duction of low polluted wastewater, mainly greywater, making its treatment easier and certainlycheaper than the common treatment of mixedwastewater. Moreover, the recovered substancescan be used as fertilizers in selected agriculturalproductions (i.e. biomass fuels).

A research project performed in Italy byRegione Lombardia and called ‘‘Nature WaterEnergy’’ has demonstrated that reeds can be con-sidered a valid biomass fuel, with an energyyield of about 14,000 kJ/kg of dry matter.

BOD 49,3

BOD 27,4BOD 21,9

N 13,4

N 1,4N 12,1

P 2,2

P 0,5P 1,6

K 4,1

K 0,5K 3,6

0

10

20

30

40

50

60

70

80

Total Black Grey

g/d

K

P

N

BOD

Fig. 7. Daily production of nutrients (BOD = biodegradable organics; N = nitrogen; P = phosphorus, K = potassium) bya single person in mixed (total), black and grey wastewater.

F. Masi / Desalination 247 (2009) 28–35 33

Reeds can be harvested twice a year, eventhough a start-up period for growth is neededbefore the first harvest, which in case ofnutrient-poor soil can be even 2–3 years long.Reeds also accumulate nutrients as standingstock, in the order of 0.1–0.45 tons/ha for nitro-gen and 0.01–0.07 tons/ha for phosphorus.These considerable amounts can be used bymulching the biomass and by mixing it withthe top layer of agricultural soil, leading to soilconditioning due to the slow release of thenutrients to the soil itself.

Acknowledgments

This study is partially funded by the EuropeanCommission under the MEDA programme, proj-ect ‘‘Zer0-m’’ n8 ME8/AIDCO/2001/0515/59768(www.zer0-m.org). The author is solely responsi-ble for the content of this paper that does not rep-resent the opinion of the Community. TheEuropean Community is not responsible for anyuse that might be made of data appearing therein.

References

[1] E. Olson, Residential Wastewater, The SwedishNation Institute for Building Research, Box 27S-102 52 Stockholm 27, Sweden, 1968.

[2] F. Masi and N. Martinuzzi, Constructed Wetlandsfor the Mediterranean countries: Hybrid systemsfor water reuse and sustainable sanitation, Desali-nation, 215 (2007), 44–55.

[3] B. El Hamouri, J. Nazih and J. Lahjouj, Subsurface-horizontal flow constructed wetland for sewagetreatment under Moroccan climate conditions,Desalination, 215 (2007), 153–158.

[4] E. Nolde, Grey water recycling systems inGermany: Results, experiences and guidelines,Wat. Sci. Tech., 51 (10) (2005), 203–210.

[5] J. De Vos, Potential of bamboo in phytoremediation– the Portuguese technology, VII World BambooCongress, New Delhi, 2004.

[6] J. De Vos, Bamboo for Europe – final reportEEC Brussels, Part 2. European Economic Com-munity, report number FAIR-CT96-1747, 2000,1–35.

[7] P. Whish-Wilson and S. Maley, Preliminaryassessment of product & market opportunitiesfor the bamboo industry in far north Queen-sland, Bamtek and Kleinhardt FGI Pty Ltd,2002, 1–66.

K

P

N

BOD

BOD 21,9

BOD 8,2

BOD 13,7

N 12,1

N 11,0N 1,1

P 1,6

P 1,1

P 0,5

K 3,6

K 2,5

K 1,1

0

10

5

15

20

25

30

35

40

45

Black Faeces Urine

g/d

Fig. 8. Daily production of nutrients (BOD = biodegradable organics; N = nitrogen; P = phosphorus, K = potassium)by a single person in black wastewater, faeces and urine.

34 F. Masi / Desalination 247 (2009) 28–35

[8] B.C. Wolverton, R.C. McDonal and W.R. Duffer.Microorganisms and higher plants for wastewatertreatment, J. Environ. Qual., 12(2) (1983), 236–242.

[9] M. Regelsberger, K. Bahlo, G. Conte, B. Ebeling,F. Masi, G. Mitterer-Reichmann, C. Platzer, B.Regelsberger, L. Urtane and G. Wach, Guidelinesfor Sustainable Water Management in Tourism

Facilities, ISBN 3-901425-99-3, published byArbeitsgemeinschaft Erneuerbare Energie Gmbh,Gleisdorf, 2005.

[10] F. Masi, N. Martinuzzi, R. Bresciani, L. Giovannelliand G. Conte, Tolerance to hydraulic and organicload fluctuations in constructed wetlands, Wat.Sci. Tech., 56(3) (2007), 39–48.

F. Masi / Desalination 247 (2009) 28–35 35