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Assessment of water quality of first-flush roof runoff and harvested rainwater

Georgios D. Gikas, Vassilios A. Tsihrintzis ⇑

Laboratory of Ecological Engineering and Technology, Department of Environmental Engineering, School of Engineering, Democritus University of Thrace, 67100 Xanthi, Greece

a r t i c l e i n f o

Article history:

Received 14 March 2012

Received in revised form 19 June 2012

Accepted 11 August 2012Available online 23 August 2012

This manuscript was handled by Laurent

Charlet, Editor-in-Chief, with the assistance

of Bernhard Wehrli, Associate Editor

Keywords:

Rainwater harvesting

Roof runoff quality

First-flush

Nutrients

Microbial indicators

Principal component analysis

s u m m a r y

Six pilot rainwater harvesting systems were installed in five urban, suburban and rural houses, and on a

university campus. The systems consist of horizontal gutters to collect roof drainage, and downdrains

which end into one or two plastic storage tanks. Devices were also provided to remove first-flush water.Water quality was monitored in the storage tanks and the first-flush devices during the 2-year period

from October 2006 to November 2008. Water samples were collected at a frequency of once every 10

days, and analyzed according to potable water specifications to determine major anions (e.g., SO24 ,

NO3 , NO

2 , F, Cl) and cations (e.g., NHþ4 , Na

+, K+, Ca2+, Mg2+), total suspended solids, alkalinity, total

phosphorus and microbiological indicators (e.g., total coliforms, Escherichia coli, Streptococcus, Clostridium

perfrigens, Pseudomonas syringae and total viable counts at 22 C and 37 C). Furthermore, temperature,

pH, dissolved oxygen and electrical conductivity were measured in situ. The mean concentrations of

chemical parameters in harvested rainwater (with the exception of NHþ4 ) were below the limits set by

the 98/93/EU directive for drinking water. Total coliforms were detected in 84.4–95.8% of the collected

rainwater samples in the six tanks. E. coli, Streptococcus, C. perfrigens, P. syringae and total viable counts

at 22 C and 37 C were found at low counts in samples of collected rainwater. The collected rainwater

quality was found satisfactory regarding its physicochemical parameters, but not regarding its sanitary

quality. Therefore, rainwater harvesting systems in this area could only supply water appropriate for

use as gray water.

2012 Elsevier B.V. All rights reserved.

1. Introduction

In areas where the freshwater sources are limited (e.g., the Ae-gean islands), people from the ancient years have used traditionalmethods of collection and storage of rainwater, for potable andother uses during the dry season. The water was collected from

house terraces, roofs or specially designed paved areas (Gikasand Angelakis, 2009). This practice is being revived as an attractivesolution today, as there is increased need of freshwater due tointensive urbanization, population growth, land use transforma-

tion, pollution, and changing climate patterns (Vialle et al., 2011).

In addition to water savings, rainwater harvesting is also an eco-logical and sustainable method of water management, resultingin the reduction of urban runoff and flooding (Farreny et al.,

2011; Melidis et al., 2007).The quality of roof runoff is affected by both rainwater quality

and roof type (e.g., material, slope, length). Rainwater pollutioncan result from constituent emissions to the atmosphere, originat-

ing from industrial pollution in urban areas, combustion of fossilfuels in vehicles and buildings, and/or agricultural activities (emis-sion of pesticides) in rural areas (Melidis et al., 2007; Sazakli et al.,

2007; Rouvalis et al., 2009). Heavy metals may leach into harvestedrainwater when the roof or the drains contain metal parts (Förster,

1999). For example, heavy metals, such as Zn, Mn, Cu and Fe havebeen detected in rooftop collected rainwater (Melidis et al., 2007;Quek and Förster, 1993).

In addition, other constituents, such as inert solids and dust,

and fecal deposits from rodents and birds, accumulated on rooftopsduring dry periods, may affect the harvested rainwater quality(Ahmed et al., 2008). Microorganisms, such as total coliforms, Esch-erichia coli, fecal coliforms, Salmonella spp., Giardia lamblia have

been detected at high counts in roof runoff water (Simmons

et al., 2001; Ahmed et al., 2010). Therefore, the first-flush of roof runoff water, i.e., that occurring at the beginning of the rainfallevent, may contain pollutants at relatively increased concentra-

tions. The installation of a device to divert the first-flush wateraway from the collection system may result in improvement of the harvested water quality (Villarreal and Dixon, 2005; Mendezet al., 2011), something also tested here.

This paper presents rainfall harvesting system design, construc-

tion and operation in rural and urban areas in Thrace district,north-eastern Greece. The main objective of this research was topresent the results of the monitoring of physicochemical parame-ters both in collected rainwater and in diverted first-flush water.

Specific objectives were to: (a) present system design, aiming at

0022-1694/$ - see front matter 2012 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.jhydrol.2012.08.020

⇑ Corresponding author. Tel./fax: +30 25410 79393; mobile: +30 6974 993867.

E-mail addresses: [email protected], [email protected] (V.A. Tsihrintzis).

Journal of Hydrology 466–467 (2012) 115–126

Contents lists available at SciVerse ScienceDirect

Journal of Hydrology

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j h y d r o l

http://dx.doi.org/10.1016/j.jhydrol.2012.08.020mailto:[email protected]:[email protected]:[email protected]://dx.doi.org/10.1016/j.jhydrol.2012.08.020http://www.sciencedirect.com/science/journal/00221694http://www.elsevier.com/locate/jhydrolhttp://www.elsevier.com/locate/jhydrolhttp://www.sciencedirect.com/science/journal/00221694http://dx.doi.org/10.1016/j.jhydrol.2012.08.020mailto:[email protected]:[email protected]://dx.doi.org/10.1016/j.jhydrol.2012.08.020


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water harvesting and in-house use; (b) compare the collected rain-water quality in the storage tank to the first-flush quality, and to

drinking water standards; (c) assess the differences in water qual-ity between the different roof materials and site locations; (d) as-sess the quality (physicochemical and microbiological) of thecollected rainwater for drinking, domestic and other uses.

2. Materials and methods

2.1. Study area and rainwater harvesting system description

For the purpose of this study, six rainwater harvesting systemswere installed in Thrace Province, Xanthi and Rhodope Prefectures,north-eastern Greece (Fig. 1, Table 1). The locations were selectedbased on: (a) the morphology of the area (i.e., urban, suburban, rur-

al); and (b) the construction material of the roof (e.g., concrete, claytile, etc.). Table 1 summarizes the characteristics of the harvestingsystems, presenting information about the location of the systems,the roof size (collection area) and the construction material, the

land use, and the number and size of the storage tanks. TS1 is lo-cated in village Kosmio, close to the industrial area of the city of Komotini, and about 2 km from a highspeed motorway (EgnatiaE90; Fig. 1). TS2 is located in Dialampi, which is a village situated

in the rural area of Rhodope Prefecture, with agricultural and farm-ing activities, and at a distance of 4 km from Egnatia. TS3 (Chrysa)and TS4 (Evmoiro) are located in the suburban area of the city of Xanthi at the foot of Rhodope Mountains; TS4 is near the industrial

area. TS5 (Xanthi) is located within the old city, in an area wherethe traffic volume is low. TS6 is located on the campus of Democr-itus University of Thrace (DUTh), about 2.5 km away from Xanthicity center. To the north of the last four sampling sites, the topog-

raphy is intense (Fig. 1). Granite, gneiss, amphibolites and marblesare the main geological formations. Erosion materials from the

mountains are carried away due to the intense north and northeastwinds which prevail in the area.

The rainwater harvesting system installed at each site consistedof: the roof and horizontal gutters and downdrains ( Fig. 2a), which

ended into one or two polyethylene storage tanks with a capacity

of 1 or 2 m

3

(Fig. 2b, Table 1). The gutters were made of zinc(Fig. 2c) and the downdrains of zinc and/or PVC. Each system, ex-cept TS6, contained a first-flush diversion system (Fig. 2a and b)

to prevent the first-flush water entrance into the storage tank.The first-flush diversion system for each tank was a 10-cm diame-ter PVC vertical pipe, the extension of the downdrain, whichtrapped a certain volume of water (Table 1) before filling to its

capacity. The lower part of this pipe ended into a cap (providingthe opportunity to remove large objects, such as leaves, debris,and dead rodents), and a valve (Fig. 2b), to empty the system after

each rainfall and also help in water sample collection. Specialplumbing was also installed for storage tank water to be used in-door (e.g., for toilet flushing and washing machine) or outdoorfor car washing and flower garden watering (Fig. 2a and d). For in-

door uses, a pump (Fig. 2e) was installed, which was equipped witha pressure sensor and could automatically stop when the toiletflushing tank was full or the washing machine did not draw water.Furthermore, connections were such to allow use of the public

water supply in case the storage tank was empty (Fig. 2d).

2.2. Water quality monitoring

Water sampling was carried out at a frequency of once every 10days from October 2006 to November 2008. To monitor waterquality, samples were collected from the outlet of the tank, i.e.,

Fig. 1. Study area and monitoring stations.

116 G.D. Gikas, V.A. Tsihrintzis / Journal of Hydrology 466–467 (2012) 115–126


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the point supplying water to the residence, and from the valve of the first-flush diversion system, which was emptied after samplingto be ready for the next rainfall. The tanks were not emptied forsampling purposes since, as mentioned, they were real tanks which

were in use in the house. Main uses included toilet-flushing and

washing machine operation. Temperature (T ), pH, electrical con-ductivity (EC) and dissolved oxygen (DO) were measured in situusing WTW 197 series instruments. Water samples were storedin a cool box and transported to the laboratory, where samples

were analyzed immediately. Total suspended solids (TSSs), alkalin-ity (ALK) and total phosphorus (TP) were measured according tostandard methods (APHA, 1998). Water samples were also ana-lyzed for anions: PO34 (OP), SO

24 , NO

3 , NO

2 , F, Cl; and cations:

Na+, K+, NHþ4 , Ca2+, Mg2+, using high pressure liquid chromatogra-

phy (DIONEX ICS-3000). Samples in the period November 2006to November 2007 were analyzed (within 24 h after the sampling)to also determine the sanitary quality both of the first-flush and of

the collected rainwater. For measuring microbiological parameters(e.g., total coliforms, E. coli, Streptococcus, Clostridium perfrigens,

Pseudomonas syringae, and total viable counts at 22 C and 37 C),which are the principal indicators for the suitability of water for

domestic and other uses, the membrane filter technique was used(APHA, 1998).

2.3. Statistical analyses

Statistical analysis was performed using nonparametric tests,because the majority of the data failed to meet the assumptionof normality (with the exception of T , pH, DO and alkalinity). Thenonparametric Kruskal–Wallis test was employed to determine

differences in concentrations among the six rainwater harvestingsystems. Where the Kruskal–Wallis test showed significant differ-ences between stations, the Mann–Whitney U test was used toevaluate pair comparisons. Spearman’s rank correlation coefficient

was used to determine the degree of association between microbi-ological and physicochemical parameters and between water qual-ity parameters themselves. The statistical significant level was setat p = 0.05. Principal component analysis (PCA) was used to detect

factors affecting rainwater characteristics. PCA is a multivariatestatistical method which is applied in environmental studies to ex-

plain data structures. The aim of PCA is to find and interpret hiddencomplexes between dataset features. It is designed to transform a

Table 1

Main characteristics of the sites, roofs and harvesting systems.

TS1 TS2 TS3 TS4 TS5 TS6

Site name Kosmio Dialampi Chrysa Evmoiro Xanthi DUTh

Longitude (N) 410500400 410501900 410705400 410604000 410804100 410804800

Latitude (E) 252404700 250900300 245105900 245104100 245303700 245500700

Land use Rural Rural Suburban Suburban Urban Campus

Distance from the city center (km) 5 22 2 4 0.5 2.5

Roof construction material Clay tiles Concrete Concrete Clay tiles Clay tiles MaxithermRoof type (slope) Sloping roof (30) Flat roof (1) Flat roof (1) Slop ing roof ( 30) Sloping roof ( 30) Sloping roof (30)

Roof surface area (m2) 180 100 75 130 100 180

Number of storage tanks 2 2 1 2 1 1

Total volume of storage tanks (L) 3000 2000 1000 2000 1000 2000

First-flush volume (L) 20 13 10 16 11 n.a.

First-flush volume (mm) 0.11 0.13 0.13 0.12 0.11 n.a.

n.a. = not available.

(a)

(c)

(b)

(e)(d)

Roof

Gutter

Various

in-house

usesPump

Overflow

Tank

Garden

Watering

Downdrain

First-Flush

storage

tank

gutter

first-flush

PVC

downdrain

valvecap

toilet flushing tank

pump

tank

public system

Fig. 2. Rainwater harvesting system: (a) schematic diagram of the pilot rainwater harvesting system; (b) storage tank and first-flush diversion system; (c) gutter and

downdrain; (d) dual connection from public water supply and storage tank to toilet flushing tank; (e) pump.

G.D. Gikas, V.A. Tsihrintzis / Journal of Hydrology 466–467 (2012) 115–126 117


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set of input variables into a set of uncorrelated variables calledprincipal components, which are linear combinations of the origi-

nal variables. The number of principal components is usually lessthan the number of original variables (Vialle et al., 2011).

3. Results and discussion

3.1. Descriptive statistics of physicochemical parameters

Statistics of measured physicochemical parameters and nutri-ent (N, P) concentration values, in storage tank (TS1–TS6) and

first-flush water (FS1–FS5) for all sites and field campaigns, arepresented in Table 2. Fig. 3 presents Box–Whisker plots of the mea-sured values of T , pH, EC, DO and nutrient concentrations. The capsat the end of each box indicate the extreme values (minimum and

maximum), the box is defined by the lower and upper quartiles,and the line at the center of the box is the median value. Meantemperature values of both storage tank and first-flush water werenormal depending on season and air temperature (Table 2; Fig. 3a).

Mean pH in the six sampling sites ranged in storage tanks between6.63 and 6.99 (mean value for all tanks: 6.74) and in first-flush be-tween 6.44 and 7.04 (mean value: 6.59). The findings are in agree-

ment with other studies in rural and urban areas in Greece(Rouvalis et al., 2009) and in France (Vialle et al., 2011). Box–Whis-

ker plots of pH (Fig. 3b) show that there are not obvious differencesbetween stations. Although the mean value of pH was withindrinking water standards (6.5–9.5; EU, 1998), there were valuesbelow the lower limit (Fig. 3b), indicating the presence of acid sub-

stances in the atmosphere in some cases. In a previous study in the

area, Melidis et al. (2007) measured in roof drainage a mean pH va-lue of 7.77, while in rainwater the mean value was 7.44, indicatinghigher amount of calcium and magnesium in their samples.

Mean EC values in the storage tanks and in the first-flush ran-ged from 31lS/cm (at TS6) to 143 lS/cm (at TS3) and from67 lS/cm (at FS5) to 394 lS/cm (at FS1), respectively (Table 2).Fig. 3c shows differences of EC values between the first-flush and

the corresponding storage tank; differences were also statisticallysignificant (Mann Whitney U test for all data set: p < 0.001). Morespecifically, the mean EC values of FS1, FS2, FS3, FS4 and FS5 were

6.2, 3.7, 1.9, 5.5 and 1.4 times greater than those of TS1, TS2, TS3,TS4 and TS5, respectively (Table 2). This suggests that severalmaterials, which accumulate on the roof, increase the conductivity,and highlights the usefulness of the first-flush device to improve

the collected rainwater quality. At all sites, EC values were lower

Table 2

Descriptive statistics for concentrations of physicochemical parameters and nutrients (N, P).

Parameter Storage tanks First-flush

TS1 TS2 TS3 TS4 TS5 TS6 FS1 FS2 FS3 FS4 FS5

T (C) DWS: not mentioned

Mean 18.3 18.2 17.2 18.4 17.4 17.1 17.1 17.9 16.0 20.1 15.3

SD 5.4 6.3 4.9 6.3 6.4 5.9 6.0 6.5 4.8 6.6 4.3

n 76 70 68 61 46 73 52 35 34 35 17

pH DWS: 6.5 – 9.5

Mean 6.75 6.64 6.99 6.65 6.63 6.76 6.49 6.55 7.04 6.45 6.44

SD 0.46 0.58 0.57 0.51 0.49 0.63 0.34 0.40 0.67 0.42 0.38

n 76 68 68 61 45 72 53 44 35 42 15

EC (lS/cm) DWS: 2500 lS/cmMean 63 68 143 37 46 31 394 256 272 203 67

SD 31 20 25 10 22 13 212 137 90 143 35

n 74 64 64 60 43 70 50 41 31 40 13

DO (mg/L) DWS: not mentioned

Mean 1.34 1.53 1.25 1.44 1.39 1.31 0.65 1.10 1.48 0.79 1.17

SD 0.80 0.86 0.86 0.94 0.92 0.90 0.90 0.96 1.11 0.78 1.05

n 73 66 65 58 43 70 50 42 32 39 14

TSS ( mg/ L) D WS: not ment ione d

Mean 2.6 1.7 1.4 4.2 4.2 2.0 39.5 10.5 9.5 12.9 10.2

SD 2.6 2.2 1.0 2.1 6.2 2.6 35.4 15.1 11.4 7.0 12.1

n 12 11 8 8 5 12 9 6 4 4 4

NO 3–N (mg/L) DWS: 11.29 mg N/L

Mean 0.83 0.84 0.58 0.71 0.66 0.58 0.46 0.68 0.62 0.36 0.59

SD 0.71 0.71 0.52 0.57 0.51 0.55 0.44 0.70 0.64 0.36 0.44

n 72 67 71 61 44 74 46 39 34 36 12

NO 2–N (mg/ L) D WS: 0.15 mg N/ LMean 0.08 0.05 0.05 0.03 0.04 0.01 0.14 0.15 0.04 0.08 0.12

SD 0.10 0.12 0.10 0.07 0.10 0.02 0.20 0.17 0.04 0.14 0.28

n 71 68 69 61 45 65 49 44 36 39 10

NH 4–N ( mg/ L) D WS: 0.5 mg/L

Mean 3.18 2.06 1.33 1.82 1.38 1.24 32.97 8.31 2.37 10.84 1.71

SD 2.17 1.64 1.69 2.10 1.82 1.32 17.17 5.60 1.75 9.99 0.83

n 75 67 66 60 44 72 40 36 30 28 10

OP (mg/L) DWS: not mentioned

Mean 0.27 0.23 0.09 0.15 0.14 0.09 2.14 0.48 0.20 1.22 0.23

SD 0.32 0.35 0.16 0.22 0.32 0.16 1.74 0.58 0.32 1.18 0.21

n 73 67 64 61 40 64 49 44 31 40 10

TP (mg/L) DWS: not mentioned

Mean 1.37 0.90 0.86 1.35 0.99 0.64 7.16 2.23 1.33 2.98 1.21

SD 1.36 1.11 1.14 1.54 1.47 0.76 5.48 1.92 1.25 2.04 1.06

n 77 72 72 62 46 75 53 48 40 44 14

SD: standard deviation; n: number of measured values; DWS: Drinking Water Standard set by EU (1998).



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than drinking water standards set by the European Union (2.5 mS/cm; EU, 1998). Conductivity values in the storage tanks were com-

parable to those of other studies (Rouvalis et al., 2009; Farrenyet al., 2011; Vialle et al., 2011). DO concentrations, both in storagetank and first-flush, were measured at low levels, and there werenot any remarkable differences between stations (Table 2;

Fig. 3d). TSS concentrations were small in all storage tanks (mean

TSS < 4.2 mg/L; Table 2). On the contrary, TSS concentration washigh in first-flush and ranged from 9.5 mg/L (in FS3) to 39.5 mg/L

(in FS1). Furthermore, TSS contents in first-flush of the slopingroofs were greater than those of the flat roofs ( Tables 1 and 2).

The mean TSS values of FS1, FS2, FS3, FS4 and FS5 were 15.2, 6.2,6.8, 3.0 and 2.4 times greater than those of TS1, TS2, TS3, TS4and TS5, respectively (Table 2), which indicates that the TSS origi-nate from accumulated materials on the roof rather than from

rainwater.

Nitrates (NO

3 ) and nitrites (NO

2 ) in rainwater are products of fossil fuel combustion (Mouli et al., 2005). Mean nitrate nitrogen

(a) (b)

(c) (d)

(e) (f)

(g) (h)

Fig. 3. Box–Whisker plots of physicochemical parameters and nutrients (N, P) in harvested rainwater (TS1–TS6) and in first-flush of roof runoff (FS1–FS5).



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concentrations in the harvested water and in the first-flush rangedbetween 0.58 mg/L and 0.84 mg/L, and between 0.36 mg/L and

0.68 mg/L, respectively (Table 2). Mean nitrite nitrogen concentra-tions in the harvested water and in the first-flush ranged between0.01 mg/L and 0.08 mg/L, and between 0.04 mg/L and 0.15 mg/L,respectively (Table 2). Box–Whisker plot of NO x–N (NO3–

N + NO2–N) concentration (Fig. 3b) shows that there were not

any obvious differences between stations, and there was also notsignificant difference (Mann Whitney U test: p > 0.05) of NO x–Nconcentration between the first-flush and the corresponding stor-

age tank. Mean nitrate and nitrite nitrogen concentrations in thestorage tanks were below the EU (1998) drinking water maximumcontaminant limit of 11.29 mg/L (for NO3–N) and 0.15 mg/L (forNO2–N). Mean ammonium nitrogen (NH4–N) concentration in

the harvested water and in the first-flush ranged between1.24 mg/L and 3.18 mg/L, and between 1.71 mg/L and 32.97 mg/L,respectively (Table 2). In areas with low industrial activity, ammo-

nium and phosphorus concentrations in roof runoff are normally of natural origin (e.g., bird and rodent excrement, moss and lichens,etc.). This partly explains the high concentration of NH4–N infirst-flush, particularly in rural areas (TS1, TS2; Table 2). Fig. 3f

shows that there was difference, which was also statistically signif-icant (Mann Whitney U test: p < 0.001), for NH4–N values betweenthe first-flush and the corresponding storage tank. More specifi-cally, the mean NH4–N concentration in FS1, FS2, FS3, FS4 and

FS5 were 10.4, 4.0, 1.8, 5.9 and 1.4 times greater than TS1, TS2,TS3, TS4 and TS5, respectively (Table 2). Ammonium has also anactive role in the definition of final value of pH, as well as in thefinal concentration of nitrate in the harvested water (ammonium

transformed to nitrate) resulting in an increase compared to thevalue in the first-flush water (Table 2). At all sites, ammonium con-centrations were over drinking water standards set by EU (0.5 mg/L; EU, 1998).

Mean OP concentration in the harvested water and in the first-flush ranged between 0.09 mg/L and 0.27 mg/L, and between0.23 mg/L and 2.14 mg/L, respectively (Table 2). Mean TP concen-

tration in the harvested water and in the first-flush ranged be-tween 0.64 mg/L and 1.37 mg/L, and between 1.21 mg/L and7.16 mg/L, respectively (Table 2). The mean OP concentration inFS1, FS2, FS3, FS4 and FS5 were 7.9, 2.1, 2.2, 8.1 and 1.6 timesgreater than TS1, TS2, TS3, TS4 and TS5, respectively. The mean

TP concentration in FS1, FS2, FS3, FS4 and FS5 were 5.2, 2.5, 1.5,2.2 and 1.2 times greater than TS1, TS2, TS3, TS4 and TS5, respec-tively (Table 2). As in the case of NH4–N, higher concentrations of OP and TP were measured in first-flush in rural areas. Box–Whisker

plots of OP and TP concentrations (Fig. 3g and h) show differences,which were also statistically significant (Mann Whitney U test: p < 0.001), for OP and TP values between the first-flush and the cor-responding storage tank. Consequently, several substances (atmo-

spheric dry deposits), which accumulate on the roof, may increase

phosphorus concentration in roof runoff water. The increased con-centration of OP and TP in first-flush is attributed mainly to birdexcrements (Göbel et al., 2007). In the rural areas (TS1, TS2; Ta-ble 1), the nitrate, nitrite and ammonium ions, OP and conductivity

show higher values than those in the suburban and urban areas,both in storage tanks and in first-flush (Table 2).

Alkalinity and concentration values of main anions and cationsin the storage tanks (TS1–TS6) and in the first-flush (FS1–FS5) for

all sites and field campaigns, are presented in Table 3. Fig. 4 pre-sents Box–Whisker plots of the measured values of alkalinity(ALK) and concentrations of anions (F, Cl, SO24 ) and cations(Mg2+, Ca2+, Na+, K+). Alkalinity is taken as an indication of the

hydroxide (OH), bicarbonate (HCO3 ) and carbonate (CO23 ), but

also includes other basic compounds, such as phosphate and sili-

cates. Mean alkalinity values ranged between 8.2 mg CaCO3/L (atTS6) and 44.7 mg CaCO3/L (at TS3) for the harvested water and be-

tween 17.0 mg CaCO3/L (at FS5) and 100.9 mg CaCO3/L (at FS2) forthe first-flush. Box–Whisker plots of alkalinity (Fig. 4a) shows

obvious differences, which were also statistically significant (MannWhitney U test: p < 0.001), for alkalinity values between the first-flush and the corresponding storage tank. Taking into account therange of pH values of harvested and first-flush water (6.44–7.04),

bicarbonate is the dominant anion. Fluoride was measured in the

storage tank and in the first-flush water at low concentrations(0.06 mg/L – 0.14 mg/L; Table 3). At all sites, fluoride concentrationwas lower than drinking water standards (1.5 mg/L; EU, 1998).

Box–Whisker plot of F concentration (Fig. 4b) shows that therewere no obvious differences (and no statistically significant; MannWhitney U test: p > 0.05) between stations for both harvestedwater and first-flush; there was also no significant difference of

F concentration between the first-flush and the correspondingstorage tank at all stations.

The anions with the higher concentrations were Cl and sulfate

SO24 (Table 3). The mean Cl concentrations of FS1, FS2, FS3, FS4

and FS5 were 1.3, 2.1, 1.7, 1.7 and 0.9 times greater than those of TS1, TS2, TS3, TS4 and TS5, respectively (Table 3; Fig. 4c). This sug-gests, particularly at stations TS2, TS3 and TS4, that Cl is not only

of sea-origin (all the sites are at a distance less than 20 km from thenorth Aegean sea, and are all affected by south winds), but alsooriginates from several materials (e.g., soil erosion products),which are transferred by wind and accumulate on the roof, and in-

crease the Cl concentration in first-flush. Basak and Alagha (2004)also found that Cl in rainwater may have other sources except thesea water. The mean SO24 concentrations of FS1, FS2, FS3, FS4 andFS5 were 1.5, 1.6, 2.0, 1.4 and 0.9 times greater than TS1, TS2, TS3,

TS4 and TS5, respectively (Table 3). Box–Whisker plots of SO24concentrations (Fig. 4d) at TS2 and TS3 stations and statistical anal-yses (Mann Whitney U test: p < 0.001) show that there was signif-icant difference for sulfate concentrations between the first-flush

and the corresponding storage tank. The SO24 =NO

3 ratios of 3.27and 3.84 for the rural and suburban, and urban areas, respectively,indicate the higher contribution of sulfate concentration in the for-

mation of the pH value. In general, SO24 and NO3 are derivatives of industrial, traffic and central heating emissions, as a result of fossilfuel combustion (Farreny et al., 2011). In this case, sulfate concen-trations can be attributed to the use of fossil fuels in cars andhouses; the high sulfate concentrations measured at sites TS2

and TS3 (Table 3; Fig. 4d) can also be attributed to the constructionactivities (dust of gypsum) in these areas. Both chloride and sulfateconcentrations at all stations were lower than the limits set by EU(1998) for drinking water (for both chloride and sulfate: 250 mg/L).

Mean Mg2+ concentration in the harvested water and in thefirst-flush ranged between 1.11 mg/L and 1.88 mg/L, and between2.25 mg/L and 5.24 mg/L, respectively (Table 3). Mean Ca2+ concen-tration in the harvested water and in the first-flush ranged be-

tween 8.07 mg/L and 18.98 mg/L, and between 11.46 mg/L and

32.52 mg/L, respectively (Table 3). Mg2+ and Ca2+ mainly are prod-ucts of erosion of mountain rocks and roof construction materials.This partly explains the high concentration of Mg2+ and Ca2+ in the

first-flush, particularly in rural areas (TS1, TS2; Table 3). Figs 4e,f and statistical analyses (Mann Whitney U test: p < 0.001) showthat there was significant difference for Mg2+ and Ca2+ concentra-tions between the first-flush and the corresponding storage tank.The mean Mg2+ concentration in FS1, FS2, FS3, FS4 and FS5 were

3.1, 2.4, 1.7, 2.1 and 1.2 times greater than TS1, TS2, TS3, TS4 andTS5, respectively, and the mean Ca2+ concentration in FS1, FS2,FS3, FS4 and FS5 were 2.4, 2.3, 1.7, 2.1 and 1.1 times greater thanTS1, TS2, TS3, TS4 and TS5, respectively (Table 3).

Mean Na+ concentration in the harvested water and in the first-flush ranged between 3.26 mg/L (in TS4) and 6.91 mg/L (in TS3),

and between 4.05 mg/L (in FS5) and 13.52 mg/L (in FS3), respec-tively. The mean sodium concentration in FS1, FS2, FS3, FS4 and



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FS5 were 1.3, 2.0, 1.9, 1.6 and 1.1 times greater than those of TS1,TS2, TS3, TS4 and TS5, respectively (Table 3). Mean K+ concentra-tions in the harvested water and in the first-flush ranged between1.77 mg/L (in TS4) and 7.98 mg/L (in TS3), and between 1.60 mg/L

(in FS5) and 13.76 mg/L (in FS3), respectively. The mean K+ concen-tration in FS1, FS2, FS3 and FS4 were 3.1, 2.2, 1.7 and 2.0 timesgreater than those of TS1, TS2, TS3, and TS4, respectively (Table 3).Fig. 3g shows that there was obvious difference of Na+ concentra-

tions between the first-flush and the corresponding storage tank atstation TS3. There was also significant difference (Mann Whitney Utest: p < 0.001) for K+ concentration between the first-flush and thecorresponding storage tank at stations TS1, TS2, TS3 and TS4(Fig. 4h). The increased values of Na+ and K+ in first-flush water

are attributed to the erosion materials accumulated on roofs atTS1, TS2 stations, and in construction activities in the area of TS3station.

From all the above, it is obvious that the diversion of first-flush

away from the storage tanks may improve the harvested waterquality. The volume of the first-flush may also play an importantrole in collected water quality. In this study, the first-flush devicevolume was set at about 10 L for each storage tank, and rangedin stored volume from 0.11 to 0.13 mm. The first-flush volume

(in mm) was calculated by dividing the volume of the collectedwater in the first-flush device by the corresponding catchment area(Table 1). Further investigation would be necessary to proposeappropriate design values. It can also be stated that the quality of

harvested water based on physicochemical parameters is good,

with violations in potable water quality standards only forammonium.

3.2. Microbial concentration in first-flush and in collected rainwater

Fecal materials, mainly from birds, rodents and lizards are theprimary source of pathogens in rainwater harvesting systems. To-tal coliforms (TCs) were measured in the first-flush and in the col-

lected rainwater at all sites with the exception of FS5. Themicrobiological analysis results are presented in Table 4. TCs weredetected in 73.3%, 81.8%, 83.3% and 100.0% of the first-flush sam-ples at FS1, FS2, FS3 and FS4, respectively. Spearman’s rank corre-

lation between TC and chemical parameter concentrations in first-flush water showed a significant relation between TC and OP(0.494, p < 0.05), suggesting that TC and OP have probably thesame source of origin (e.g., bird droppings, as mentioned before).

Although, only a part of roof runoff was diverted away from thetanks, the sanitary quality of collected rainwater in the storagetanks was not good, indicating the need for increased capacity of the first-flush device. TCs were detected in 84.4%, 87.1%, 92.3%,95.8%, 87.5% and 88.2% of the collected rainwater samples at TS1,

TS2, TS3, TS4, TS5 and TS6, respectively. The TC counts ranged be-tween 0/100 mL and 7750/100 mL, a result in accordance with aprevious study in Auckland district, New Zealand (Simmonset al., 2001), but it is one order of magnitude higher than values

found in Kefalonia, Greece (Sazakli et al., 2007). In addition, corre-lation between the TC in the first-flush and in the collected rainwa-ter showed a significant relation (0.648, p < 0.001), which suggeststhat the microbial contamination is a result of contact with the roof

materials or probably the existence of microbes in rainwater.

Coombes et al. (2002) found Pseudomonas aeruginosa in rainwater,before its contact to roof surfaces, while E. coli and enterococci

Table 3

Descriptive statistics for alkalinity and concentrations of measured anions and cations.

Parameter Storage tanks First-flush

TS1 TS2 TS3 TS4 TS5 TS6 FS1 FS2 FS3 FS4 FS5

ALK (mg CaCO 3 /L) DWS: not mentioned

Mean 14.7 14.3 44.7 8.3 12.2 8.2 99.0 100.9 83.7 54.2 17.0

SD 14.4 10.4 25.5 6.3 6.4 6.6 60.2 73.5 42.7 40.2 10.0

n 68 61 65 54 43 63 49 41 33 38 13

F (mg/L) DWS: 1.5 mg/L

Mean 0.09 0.08 0.12 0.08 0.06 0.07 0.14 0.14 0.07 0.12 0.09

SD 0.08 0.07 0.09 0.07 0.06 0.08 0.12 0.07 0.05 0.12 0.08

n 60 57 61 54 49 59 26 22 18 20 7

Cl (mg/L) DWS: 250 mg/L

Mean 7.29 5.05 4.16 3.54 3.48 3.61 10.05 10.65 6.91 6.17 2.93

SD 3.97 2.93 2.81 2.25 3.28 2.28 6.33 6.38 3.31 4.47 1.78

n 65 59 65 58 50 64 27 25 20 21 7

SO24 (mg/L) DWS: 250 mg/L

Mean 10.65 13.56 15.70 8.28 8.84 10.25 16.60 22.24 30.86 11.88 8.63

SD 3.14 4.34 6.43 2.69 5.31 3.98 9.94 9.93 12.83 5.55 4.85

n 64 59 64 58 50 63 28 25 20 21 7

Mg 2+ (mg/L) DWS: not mentioned

Mean 1.67 1.57 1.88 1.11 1.85 1.36 5.24 3.72 3.16 2.32 2.25

SD 0.63 0.81 0.75 0.69 1.19 0.89 1.82 1.02 0.54 0.86 0.90

n 66 60 63 57 41 62 27 25 20 21 7

Ca 2+ (mg/L) DWS: not mentioned

Mean 10.08 14.00 18.98 8.07 10.46 10.35 24.92 32.52 31.61 17.00 11.46

SD 3.73 5.18 4.21 4.04 4.73 4.42 9.39 7.82 5.52 5.12 1.45

n 65 59 63 57 42 62 27 24 19 20 8

Na+ (mg/L) DWS: not mentioned

Mean 5.15 4.42 6.91 3.26 3.78 4.15 6.89 8.85 13.52 5.37 4.05

SD 2.08 1.57 1.90 1.89 2.14 1.77 3.30 5.06 6.24 2.41 1.74

n 66 60 64 58 44 63 28 25 20 21 8

K + (mg/L) DWS: not mentioned

Mean 3.08 2.57 7.98 1.77 1.87 2.87 9.44 5.71 13.76 3.58 1.60

SD 1.22 1.55 1.74 1.16 1.67 1.55 3.42 1.94 2.41 1.42 0.59

n 66 60 64 58 44 63 28 25 20 21 8

SD: standard deviation; n: number of measured values; DWS: Drinking Water Standard set by EU (1998).



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were not found (Fewtrell and Kay, 2007). In this study, no samplesof rainwater were collected and measured, something that could

confirm or refute the hypothesis of microbes in rainwater.Furthermore, samples of collected rainwater at TS1, TS2 and TS3

storage tanks were analyzed for E. coli, Streptococcus, C. perfrigens,P. syringae and total viable counts at 22 C and 37 C. Results of

these measures are presented in Table 5. The higher number of

microbial indicators was measured in TS1 storage tank with theexception of P. syringae that was measured at high count at TS3.

These results show that the quality of collected rainwater does

not meet the standards for the microbiological parameters set byEU (1998) for potable water (Tables 4 and 5); therefore, rainwaterharvesting systems could transmit microorganisms that cause ill-

ness in humans when used as a potable water supply. It is obvious

(a) (b)

(c) (d)

(e) (f)

(g) (h)

Fig. 4. Box–Whisker plots of alkalinity and measured ions in harvested rainwater (TS1–TS6) and in first-flush of roof runoff (FS1–FS5).



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that the first-flush system cannot protect the microbe contamina-

tion of collected rainwater without further treatment. In Greece,there are no regulations relating the microbial quality of collectedrainwater for non-potable or potable uses. The recent MinisterialDecision 145116/2-3-2011, which refers to the reuse of treated

wastewater, defines a limit for various uses only for E. coli. Specif-ically, for unrestricted application on legumes and crops whoseproducts are eaten raw, the limit is 65/100 mL for 80% of samplesand650/100 mL for 95% of samples. For urban use in recreational

areas, and for washing streets and sidewalks, the limit is62/

100 mL for 80% of samples and 6 20/100 mL for 95% of samples.Furthermore, recent regulations by WHO (2006), which refers tosafe reuse of water, do not provide specific limits for microorgan-

isms, but describe a methodology for setting appropriate guide-lines at the local and regional level. Consequently, disinfectionmeasures should be implemented to improve the sanitary quality

of the collected rainwater if it was to be used as potable water.Such measures could be the diversion of a greater volume of first-flush water away from the rainwater harvesting tank and/orthe chlorination of water before its use (Villarreal and Dixon,

2005; Sazakli et al., 2007).

3.3. Differences in collected rainwater quality of various stations

The Kruskal–Wallis test indicated that the differences in col-lected rainwater quality between the stations were not significant

( p > 0.05) for T , DO and NO x–N (Table 6). However, significant dif-

ferences were found ( p < 0.05) between stations for all the otherparameters (Table 6). The Mann–Whitney U test was used to findbetween which stations the differences were significant, and theresults are also presented in Table 6. For example, the median val-

ues in TS1 storage tank were significantly higher than those in theother tanks (e.g., TS3, TS4, TS5 and TS6) for ammonia nitrogen, OPand Cl. There were no significant differences between TS1 and TS2stations for all parameters with the exception of SO24 and Ca

2+. The

roof construction materials of TS1 and TS2 stations are clay tiles

and concrete, respectively, and both of them are in rural areas (Ta-ble 1). The higher concentrations of NH4–N, OP and TP that weremeasured in first-flush of TS1 were attributed to bird excrements,

moss and lichens (as mentioned before). Therefore, it is suggestedthat the local conditions of the harvesting system location, is amore important factor compared to the roof construction material

for the quality of collected rainwater.Furthermore, the median values in storage tank TS3 were higher

than those in other stations for EC, ALK, SO24 , Ca2+, Na+ and K+. The

high concentrations of these pollutants in collected rainwater at

TS3 station was attributed to dust in the atmosphere, as a resultof intensive land development construction activities in this areaduring the monitoring period. The house where the TS3 harvestingsystem was installed was newly constructed, and residues of mate-

rials, such as lime, gypsum, etc., on the roof also have affected theroof runoff quality. TS3 and TS4 harvesting rainwater systems are

Table 4

Descriptive statistics for total coliforms.

Parameter Storage tanks First-flush Standarda

TS1 TS2 TS3 TS4 TS5 TS6 FS1 FS2 FS3 FS4

Total coliforms (N/100 mL) 0/100 mL

Median 525 204 200 350 300 125 303 305 200 280

Min 0 0 0 0 0 0 0 0 0 80

Max 7750 3250 2800 2050 1600 4700 6550 2100 900 2700

n 33 31 14 24 14 17 15 11 8 16

a Standard for drinking water quality set by EU (1998).

Table 5

Descriptive statistics for microbial indicators.

Parameter TS1 TS2 TS3 Standarda

Faecal coliforms (Escherichia coli) (N/100 mL) Median 10 0 0 0/250 mL

Min 5 0 0

Max 200 3 2

n 10 10 10

Streptococcus (N/100 mL) Median 25 5 0 n/m

Min 25 0 0

Max 62 40 9

n 10 10 10

Total count at 22 C (N/mL) Median 1000 35 22 100/mL

Min 1000 30 20

Max 10,000 100 30

n 10 10 10

Total count at 37 C (N/mL) Median 1000 250 10 20/mL

Min 1000 240 8

Max 10,000 10,000 60

n 10 10 10

Clostridium perfrigens (N/100 mL) Median 0 0 0 0/100 mL

Min 0 0 0

Max 43 1 0

n 10 10 10

Pseudomonas syringae (N/250 mL) Median 12 2 5 n/m

Min 10 0 0

Max 77 50 200

n 10 10 10

a Standard for drinking water quality set by EU (1998); n/m: not mentioned.



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in a suburban area and the roof type and construction material areflat and concrete for TS3, and sloping and clay tiles for TS4. Mann–Whitney U test showed that there were significant differences be-

tween the quality in TS3 and TS4 stations for EC, ALK, SO24 , Ca2+,

Na+ and K+ (Table 6), presenting higher pollution levels for allparameters in TS3. Again the local conditions (e.g., constructionactivities) seem to play an important role in harvesting rainwater

quality.TS4, TS5 and TS6 rainwater harvesting systems are located in

suburban, urban and campus areas, respectively, and their roofsare clay tiles for TS4 and TS5, and maxitherm for TS6; all roofs

are sloping (Table 1). The three roofs did not show significant dif-ferences for any of the parameters, except for Mg2+ where the med-ian value of TS5 was significantly greater than this of TS4 (Table 6).

These results suggest that, regarding the physicochemical parame-ters, the collected rainwater quality in these three rainwater har-vesting systems is similar.

3.4. Relations between physicochemical parameters

Spearman’s rank correlation was applied to the results of phys-icochemical parameters of all datasets in storage tank rainwater.

The results of this analysis are presented in Table 7. Significant cor-relations were found between EC and ions concentrations (e.g., F,SO24 , Mg

2+, Ca2+, Na+, K+; p < 0.01; Table 7), showing that EC de-pends mainly on these ions. NO x (NO

3 þ NO

2 ) showed significantpositive correlation ( p < 0.01) with SO24 , Cl

, OP and TP, indicating

that they have the same source of origin. The negative correlationbetween NO x and DO ( p < 0.01) was expected, since the oxygen of collected rainwater is consumed during transformation of nitrite tonitrate that takes place in the storage tanks. Positive significant

( p < 0.01) correlations were observed between NHþ4 and other cat-ions (e.g., Mg2+, Ca2+, Na+), as well as anions (e.g., OP, Cl). The po-sitive significant correlation ( p < 0.05) between ammonia and SO24agrees with the findings by Rouvalis et al. (2009). No relation was

detected between ammonia and NO x. This result is consistent with

that obtained by Farreny et al. (2011); thus, one can conclude thatammonia and NO x do not have the same origin. Additionally, sig-nificant correlations ( p < 0.01) were found between marine derivedspecies, such as Na+, Cl and Mg2+. Soil derived species, such asCa2+, K+, Mg2+, were also significantly ( p < 0.01) correlated to eachother.

Principal component analysis was also performed on the corre-lation matrix. Kaiser–Meyer-Olkin (KMO) and Bartlett’s test were

performed in order to examine the suitability of data for factoranalysis. The results of this test showed that the dataset is suitablefor factor analysis, as the KMO value was 0.70 (it is noticed that avalue of 0.6 is suggested as the minimum value for a good factor

analysis), and Bartlett’s test of sphericity was significant( p < 0.001). Based on the scree plot, with eigenvalues greater or

equal to 1, four principal components (PCs) were obtained. PC1,PC2, PC3, PC4 represent 29.7%, 14.2%, 10.9%, 10.4%, respectively,

Table 6

Kruskal–Wallis test results for various collecting rainwater tanks.

Paramet er Krusk al Wallis t est Mann–Whit ney U t est

Chi-square p Compared sites p

T 2.94 0.709

DO 4.94 0.423

NO x–N 10.04 0.074

pH 21.24 0.001 TS3–TS2 0.002TS3–TS4 0.024

TS3–TS5 0.014

EC 2.54 0.001 TS1–TS4 0.001

TS1–TS5 0.001

TS1–TS6 0.001

TS2–TS4 0.001

TS2–TS5 0.001

TS2–TS6 0.001

TS3–TS1 0.001

TS3–TS2 0.001

TS3–TS4 0.001

TS3–TS5 0.001

TS3–TS6 0.001

NH4–N 61.69 0.001 TS1–TS3 0.001

TS1–TS4 0.001

TS1–TS5 0.001

TS1–TS6 0.001

OP 54.87 0.001 TS1–TS3 0.001

TS1–TS4 0.014

TS1–TS5 0.001

TS1–TS6 0.001

TS2–TS3 0.004

TS2–TS6 0.017

TP 23.83 0.001 TS1–TS6 0.001

ALK 117.54 0.001 TS3–TS1 0.001

TS3–TS2 0.001

TS3–TS4 0.001

TS3–TS5 0.001

TS3–TS6 0.001

F 19.56 0.002 TS3–TS5 0.014

TS3–TS6 0.011

Cl

61.65 0.001 TS1–TS3 0.001TS1–TS4 0.001

TS1–TS5 0.001

TS1–TS6 0.001

SO24 91.08 0.001 TS1–TS4 0.001

TS2–TS1 0.001

TS2–TS4 0.001

TS2–TS5 0.001

TS2–TS6 0.001

TS3–TS1 0.001

TS3–TS4 0.001

TS3–TS5 0.001

TS3–TS6 0.001

Mg2+ 47.91 0.001 TS4–TS1 0.001

TS4–TS2 0.010

TS4–TS3 0.001

TS4–TS5 0.003Ca2+ 141.36 0.001 TS2–TS1 0.001

TS2–TS4 0.001

TS2–TS5 0.001

TS2–TS6 0.003

TS3–TS2 0.002

TS3–TS1 0.001

TS3–TS4 0.001

TS3–TS5 0.001

TS3–TS6 0.001

Na+ 102.69 0.001 TS1–TS4 0.001

TS1–TS5 0.001

TS3–TS1 0.003

TS3–TS2 0.001

TS3–TS4 0.001

TS3–TS5 0.001

TS3–TS6 0.001

Table 6 (continued)

Paramet er Krusk al Wallis t est Mann–Whitney U test

Chi-square p Compared sites p

K+ 181.52 0.001 TS1–TS4 0.001

TS1–TS5 0.001

TS3–TS1 0.001

TS3–TS2 0.001

TS3–TS4 0.001TS3–TS5 0.001

TS3–TS6 0.001



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of the total variance. The four factors were rotated using Varimaxrotation procedure and the results are presented in Table 8. Thevariables that contributed to PC1 were potassium, calcium, so-

dium, sulfate and magnesium that relate to environmental condi-tions. PC2 and PC3 were mainly related to ions attributed toanthropogenic activities, as they comprise NO x , SO

24 , NH

þ

4 andOP. Finally, PC4 was mainly related to TP and F. OP was also

loaded on PC4 due to its positive correlation with TP ( Table 8).

4. Conclusions

The tested roof rainwater harvesting systems provided a sup-ply of relatively good quality water in terms of physicochemicalparameters. However, the microbiological quality of this waterwas inferior. Pollutant concentrations were below drinking water

standards with the exception of NHþ4 . Regarding the microbialparameters, the storage tank water did not meet the drinkingwater standards set by EU. The installation and use of a first-flushsystem improves the physicochemical quality of collected rainwa-

ter, but it cannot avoid microbial contamination of stored rainwa-ter; therefore, appropriate designs and disinfection strategies tominimize contamination should be undertaken, for potable useof rainwater. The good quality of the collected rainwater, regard-

ing its physicochemical parameters, makes the roof runoff in thisstudy area appropriate for domestic use as gray water (e.g., toilet

flush-tank, garden irrigation, etc.), with no need for on-sitetreatment.

Acknowledgements

This study was funded through the EU INTERREG IIIB-MEDOCCproject ‘‘Reseau Durable d’ Amenagement des Ressources Hydraul-iques (HYDRANET)’’ (2005–2007). The authors are also grateful to

Ms. Varveri Aikaterini and Ms. Spinou Despina for their help in col-lection and analysis of rainwater samples. Microbial analyses wereconducted at the Laboratory of Hygiene and Environmental Protec-tion, Medical School, Democritus University of Thrace, Alexand-

roupolis, under the guidance of Assoc. Professor Th. Constantinidis.

References

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Ahmed, W., Vieritz, A., Goonetilleke, A., Gardner, T., 2010. Health risk from the useof roof-harvested rainwater in Southeast Queensland, Australia, as potable ornonpotable water, determined using quantitative microbial risk assessment.Appl. Environ. Microbiol. 76 (22), 7382–7391.

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Table 7

Spearman’s rho correlation coefficients between the collected rainwater physicochemical parameters.

T pH EC DO NO x NHþ4 TP OP ALK F Cl SO24

Mg2+ Ca2+ Na+ K+

T 1

pH 0.029 1

EC 0.167* 0.099 1

DO 0.116* 0.152** 0.037 1

NO x 0.198**

0.050 0.048 0.218** 1

NHþ4 0.065 0.172*

0.061 0.083 0.017 1TP 0.282** 0.173** 0.102* 0.062 0.199** 0.074 1

OP 0.043 0.108* 0.016 0.059 0.195** 0.185** 0.297** 1

ALK 0.109* 0.102 0.508** 0.202** 0.065 0.014 0.041 0.133* 1

F 0.241** 0.179** 0.208** 0.094 0.003 0.084 0.131* 0.022 0.304** 1

Cl 0.210** 0.028 0.122* 0.155** 0.292** 0.239** 0.008 0.120* 0.160** 0.196** 1

SO24 0.169**

0.050 0.411** 0.015 0.274** 0.117* 0.050 0.090 0.338** 0.191** 0.481** 1

Mg2+ 0.102 0.028 0.358** 0.086 0.194** 0.288** 0.111* 0.023 0.418** 0.236** 0.331** 0.291** 1

Ca2+ 0.009 0.113* 0.567** 0.027 0.089 0.220** 0.187** 0.045 0.497** 0.218** 0.220** 0.481** 0.733** 1

Na+ 0.190** 0.118* 0.346** 0.106 0.097 0.189** 0.127* 0.027 0.345** 0.133* 0.393** 0.410** 0.562** 0.654** 1

K+ 0.014 0.112* 0.481**‘ 0.119* 0.022 0.098 0.011 0.027 0.493** 0.200** 0.240** 0.390** 0.492** 0.650** 0.695** 1

** Correlation is significant at the 0.01 level (2-tailed).* Correlation is significant at the 0.05 level (2-tailed).

Table 8

Rotated component matrix in the total data set of collected rainwater.

Variables Component

PC1 PC2 PC3 PC4

K+ 0.849

Ca2+ 0.838

Na+ 0.788

SO24 0.639 0.398

Mg2+ 0.592

NO x 0.826

Cl 0.546 0.470

OP 0.431 0.427

NHþ4 0.833

TP 0.774

F+ 0.711



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Simmons, G., Hope, V., Lewis, G., Whitmore, J., Gao, W., 2001. Contamination of potable roof-collected rainwater in Auckland, New Zealand. Water Res. 35 (6),1518–1524.

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Villarreal, E.L., Dixon, A., 2005. Analysis of a rainwater collection system fordomestic water supply in Ringdansen, Norrkoping, Sweden. Build. Environ. 40,1174–1184.

WHO (World Health Organization), 2006. Guidelines for the Safe Use of Wastewater, Excreta and Greywater. Geneva, Switzerland.


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