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Water Resour Manage (2010) 24:25–36 DOI 10.1007/s11269-009-9435-0 Alternative Water Resources for Rural Residential Development in Western Australia Yan Zhang · Andrew Grant · Ashok Sharma · Donghui Chen · Liang Chen Received: 28 July 2008 / Accepted: 13 April 2009 / Published online: 5 May 2009 © Springer Science+Business Media B.V. 2009 Abstract Rainwater collected from residential roofs and greywater generated from domestic uses except toilets are viewed as possible substitutes for high grade water sources which supply nonpotable indoor uses and irrigation in Australia. This paper searches for alternatives by adopting roofwater and greywater in residential envelope as per Australian water standards. A water balance model Aquacycle was applied to determine storage capacities and to evaluate the percentage reduction in water supplying, stormwater run-off and wastewater disposal, as well as volume of rainwater use and greywater reuse. This study provides the results of greywater recycling, which contributes to the greater saving of mains water supply than rain- water use, and which reduces more than half of the wastewater to receiving waters in the rural township of Cranbrook, Western Australia. The results of this study provide greywater usage (maximum reduction 32.5%) more significantly reduces scheme water supply than rainwater harvesting (maximum reduction 25.1%). Use of greywater on individual residential lots has the dramatic effect for drainage system by reduction approximately 54.1% or 88.1 m 3 /lot/year. The results of rainwater use analysis show explicitly that rainwater tanks are much more effective in intercepting Y. Zhang College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China Y. Zhang (B ) · A. Grant · A. Sharma Land and Water, Commonwealth Scientific and Industrial Research Organization (CSIRO), P.O. Box 56, Graham Rd., Highett, Victoria 3190, Australia e-mail: [email protected] D. Chen Shanghai Institute of Technology, 120 Caobao Rd., Shanghai 200235, China L. Chen Putuo Environmental Protection Bureau of Shanghai, 1668 Daduhe Rd., Shanghai 200333, China

Alternative Water Resources for Rural Residential Development in Western Australia

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Water Resour Manage (2010) 24:25–36DOI 10.1007/s11269-009-9435-0

Alternative Water Resources for Rural ResidentialDevelopment in Western Australia

Yan Zhang · Andrew Grant · Ashok Sharma ·Donghui Chen · Liang Chen

Received: 28 July 2008 / Accepted: 13 April 2009 /Published online: 5 May 2009© Springer Science+Business Media B.V. 2009

Abstract Rainwater collected from residential roofs and greywater generated fromdomestic uses except toilets are viewed as possible substitutes for high grade watersources which supply nonpotable indoor uses and irrigation in Australia. Thispaper searches for alternatives by adopting roofwater and greywater in residentialenvelope as per Australian water standards. A water balance model Aquacycle wasapplied to determine storage capacities and to evaluate the percentage reductionin water supplying, stormwater run-off and wastewater disposal, as well as volumeof rainwater use and greywater reuse. This study provides the results of greywaterrecycling, which contributes to the greater saving of mains water supply than rain-water use, and which reduces more than half of the wastewater to receiving watersin the rural township of Cranbrook, Western Australia. The results of this studyprovide greywater usage (maximum reduction 32.5%) more significantly reducesscheme water supply than rainwater harvesting (maximum reduction 25.1%). Use ofgreywater on individual residential lots has the dramatic effect for drainage systemby reduction approximately 54.1% or 88.1 m3/lot/year. The results of rainwater useanalysis show explicitly that rainwater tanks are much more effective in intercepting

Y. ZhangCollege of Environmental Science and Engineering,Donghua University, Shanghai 201620, China

Y. Zhang (B) · A. Grant · A. SharmaLand and Water, Commonwealth Scientific and Industrial Research Organization (CSIRO),P.O. Box 56, Graham Rd., Highett, Victoria 3190, Australiae-mail: [email protected]

D. ChenShanghai Institute of Technology,120 Caobao Rd., Shanghai 200235, China

L. ChenPutuo Environmental Protection Bureau of Shanghai,1668 Daduhe Rd., Shanghai 200333, China

26 Y. Zhang et al.

roof runoff, with the maximum stormwater reduction 48.1% or 68.3 m3/lot/year. Thisresearch endeavours to offer a typical paradigm for an integrated water system in therural residential sectors.

Keywords Rural residential development · Rainwater harvesting ·Greywater reuse · Integrated water management

1 Introduction

In terms of the average residential water consumption, the volumes can be or-dered as 380 L/day (USA), 340 L/day (Canada), 265 L/day (Spain), 181 L/day(Australia), 85 L/day (Lithuania; EEA 2003; Loh and Coghlan 2003; Racoviceanu2005). Augmentation of water supply in both urban and rural areas is continuing(Lazarova et al. 2003). It is a great challenge to ensure the supply of high-quality andsufficient water for all domestic water use because of climate change, surface andground water pollution, rapidly growing water consumption, as well as financial cost.For all residential water use, only a small portion serves potable quality purpose,which covers approximately 9% of indoor water use in Western Australia (Loh andCoghlan 2003). The remaining non-potable uses, such as toilet flushing, clotheswashing and garden irrigating, can satisfactorily be supplied with alternative watersources. In this way reducing the costs associated with water supply, stormwater andwastewater discharge, ultimately lead to a more sustainable use of natural waterresource and the protection of the ecological balance in aquatic ecosystems. Cap-turing rainwater and reusing greywater are increasing practices in the area of waterresearch in the last decade, particularly in countries where regulations encouragethese practices and by-laws, such as US, Australia and Germany (Racoviceanu 2005).

Previous studies on rainwater and greywater chiefly focus on urban area(Christova-Boal et al. 1996; Herrmann and Hasse 1997; Dixon 2000; Eriksson et al.2002; Brown 2003; Friedler 2006; Grant et al. 2006; Coombes 2007; Ghisi and Ferreira2007; Madungwe and Sakuringwa 2007). Some researchers are interested in county-side rainwater contaminant study and the impact on agriculture (Chang et al. 1997;Wei et al. 2005). In contrast, this paper seeks for explored water sources supplyingtoilet flushing and landscape watering in the rural town of Cranbrook, Western Aus-tralia. Tank capacities, imported water saving, stormwater discharge and wastewaterdisposal have been estimated. It endeavours to achieve a paradigm shift especiallyfor newly built rural residential developments, with promoting rainwater adoptingand greywater recycling as parts of integrated water management.

This paper is one part of the project Water for a Healthy Country which is anational research project mainly undertaken by CSIRO.

2 Methodology

2.1 Description of Study Area and Climate Data

The township of Cranbrook is located in the Great Southern Region, WesternAustralia, at coordinates of 34◦18′ S and 117◦33′ E. Figure 1 provides the location

Alternative Water Resources for Rural Residential Development 27

Fig. 1 Location andresidential land use ofCranbrook

Cranbrook

of the study catchment and residential land use details. The population densities forresidential large, residential medium and residential small are 300–700, 201–299 and1–200 km−2 respectively.

The historical daily climate data over 57 years (from 1950 to 2006) is used formodelling purposes in this case. The average annual rainfall for this climate series is490 mm ranging from 310 to 682 mm and the average annual pan evaporation is 1,439from 1,267 to 1,577 mm. The monthly maximum temperature is 30.0◦C which occursin January and the minimum temperature is 5.3◦C in July. Figure 2 shows annualaverage rainfall and evaporation.

Table 1 indicates the relevant properties associated with modelling and analysis inthis case study.

Fig. 2 Annual average rainfalland evaporation of Cranbrook

200

400

600

800

1000

1200

1400

1600

1800

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Mill

imet

res

(mm

)

rainfall yearly Evaporation yearly

28 Y. Zhang et al.

Table 1 Properties of Cranbrook

Properties Values

Rainfall (mm)a 490Evaporation (mm)a 1,439Populationb 270Study area (ha)c 29.6Water consumption (ml/year)d 33.4aClimate data was adopted from SILO Data Drill (http://www.nrw.qld.gov.au/silo/datadril, dataedited as per reference (Jeffrey et al. 2001))bPopulation data was sourced from the Australian Bureau of Statistics, 2007cTopographical data was supplied by Western Australian Department of Planning & InfrastructuredWater consumption data was stemmed from Water Corporation of Western Australia

2.2 Alternative Options

Six proposed alternatives were selected to achieve the expected water reductionduring the study period, which was based on the indoor end-uses (Table 2).

A summary of the scenarios being modelled is shown in Table 3.

2.3 Water Balance Method

A water modelling software ‘AQUACYCLE’ (Mitchell et al. 2001) is adopted tocompute water balance results for each of various water servicing options consideredin this paper. This computer model which runs on daily time step views water supply,stormwater flows and waste water network as a more holistic framework in terms ofintegrated water management. The water consumption of ketch, bathroom, laundryand toilet are considered. Calibration parameters are determined by comparing theactual water consumption derived from Water Corporation of Western Australiato modelled data. Two measures of performance were used to judge the model’sability to simulate flows during the verification period: SIM/REC and the coefficientof efficiency, E. A running calibration parameter set fitted to the water balancemodelling is listed in Table 4.

3 Results

The modelled and statistical results for the residential development of Cranbrookare shown as Figs. 3, 4, 5, 6 and 7 for rainwater harvesting options and Figs. 8, 9, 10and 11 for greywater recycling system.

Table 2 Estimated residentialindoor end use breakdown(Loh and Coghlan 2003)

End use L/capita/day

Toilet 38Laundry 58Bathroom 69Kitchen 16Total 181

Alternative Water Resources for Rural Residential Development 29

Table 3 Water servicing options to be modelled

Options Description of options

Base case A Traditional water systemRain water use B Adopting rainwater for garden irrigation

C Adopting rainwater for toilet flushingD Adopting rainwater for toilet flushing & garden irrigation

Grey water reuse E Reuse treated greywater for garden irrigationF Reuse treated greywater for toilet flushing & garden irrigationGa Direct untreated greywater subsurface irrigation

aWater from shower, hand sinks and laundry rinse

3.1 Rainwater Use

3.1.1 Dimensions of Rainwater Tank

Volumetric reliability herein is defined as the percentage of total demand met overthe logging period. The optimum dimensions of tanks are assumed to correspondto that tank size where further increases in size produced only a small increase inreliability.

When only rainwater is considered, the curves in Fig. 3 illustrate reaching themaximum volumetric reliability for option B (80%), C (100%) and D (62%) withtank sizes 147, 12 and 75 m3, respectively. It can also be observed that option Cis much more likely to meet the most amount of water demand, which probablyhappens due to the water end-use for toilet flushing is low. As a compromise amongvolumetric efficiency, final cost and available space, tank sizes for these describedthree options have been adopted as 30, 12 and 30 m3 respectively.

3.1.2 Water Balance Results

In the scope of this study, imported water, stormwater and wastewater are consideredas an integrated water system instead of separate ones. Water balance results

Table 4 Aquacycleparameters

Parameters Values

Area of pervious soil store 1 (%) 50Capacity of soil store 1 (mm) 50Capacity of soil store 2 (mm) 120Roof area maximum initial loss (mm) 1Effective roof area % 95Paved area maximum initial loss (mm) 1.5Effective paved area % 10Road area maximum initial loss (mm) 1.5Effective road area % 20Base flow index (ratio) 0.1Base flow recession constant (ratio) 0Infiltration index (ratio) 0Infiltration store recession constant (ratio) 0% surface runoff as inflow 0Garden trigger to irrigate (ratio) 0.22Rainwater tank first flush (L) 0

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Fig. 3 Volumetric reliabilityof rainwater storage forvarying tank size

Tank Size (m3)

0 50 100 150 200 250 300

Volu

met

ric

Rel

iabil

ity

0.0

0.2

0.4

0.6

0.8

1.0

Option B

Option C

Option D

Fig. 4 Water balance ofoption A (conventionalend-of-pipe water system). IWimported water; SWstormwater; WW wastewater

Fig. 5 Water balance ofoption B. RWTU rainwatertank use

Alternative Water Resources for Rural Residential Development 31

Fig. 6 Water balance ofoption C

Fig. 7 Water balance ofoption D

Fig. 8 Volumetric reliabilityof greywater storage forvarying tank size

Tank Size (m3)

0 50 100 150 200 250 300

Vol

umet

ric

Rel

iabi

lity

0.0

0.2

0.4

0.6

0.8

1.0

Option EOption F

32 Y. Zhang et al.

Fig. 9 Water balance ofoption E. GWTU greywatertank use; GWTP greywatertreatment plant

obtained from the computer programme are based on average roof area 249 m2 and2.4 persons for an average block.

Option A is the traditional water system (base case) with imported water,stormwater and wastewater decentralized (end-of-pipe solution). On the contrary,option B, C and D are sustainable alternatives which are promoted as a compre-hensive framework to analyse total scheme water saving and discharge reduction toreceiving waters.

It can be noted that the annual imported water quantities for option A, B, C andD are 297.6, 238.9, 261.1 and 222.8 m3, and wastewater discharge is around 161 m3. Ithas been seen that yearly stormwater runoff predicts in the Figs. 5–7 are 85.8, 105.3and 71.3 m3, and storage rainwater use is 68.14, 32.7 and 68.3 m3 for option B, C andD, respectively.

3.2 Greywater Reuse

The supplied water consumption data for Cranbrook recommend the quantity oftoilet flushing covering 21% of all indoor water use. Using greywater for toiletflushing only would be marginally necessary because of large volumes of overflow.In order to take full advantage of greywater, the authors deem a combination oftoilet flushing and garden irrigating in the household scene as more viable.

Untreated greywater flowing directly to subsurface irrigation as a simple and safemeans is acceptable by Australian water authorities and residents. This will decreasehuman exposure to the used water. Immediate reuse (storage time not more than24 h) is a key factor for greywater avoiding anaerobic state.

Fig. 10 Water balance ofoption F

Alternative Water Resources for Rural Residential Development 33

Fig. 11 Water balance ofOption G

The following is a discussion of greywater recycling in residential subdivisionCranbrook.

3.2.1 Dimensions of Greywater Tank

Figure 8 gives clear volumetric reliability changing trend with adoption of greywaterfor garden irrigation and toilet flushing and garden irrigation. It states that in order toachieve the most adequate efficiency for options E and F, the necessary tank volumesshould be 75 and 55 m3. Assuming it to be an appropriate balance among greywatertank storage, reliability and costing, tank size 3 m3 is chosen for these two options.The same tank volumes are adopted for option G.

3.2.2 Water Balance Results

Water from the kitchen, bathroom and laundry can be reused for garden wateringand toilet flushing in options E and F with necessity of greywater treatment plant.

The estimated annual imported water quantities are 221.2, 201.0 and 238.1 m3

for these three scenarios, with stormwater discharge around 137 m3. It can also beformulated to show yearly wastewater discharge of 92.9, 74.8 and 108.8 m3, withtreated greywater reuse quantities 69.9 and 88.1 m3 for options E and F respectively,54.0 m3 untreated greywater directly reused for option G.

3.3 Reduction in Potable Water, Wastewater Discharge and Stormwater Runoff

Reduction evaluates the alternatives performance of this residential sector. Usingthe appropriate tank sizes and statistical analysis method, results of average annualpercentage reduction in scheme water supply, wastewater and stormwater dischargefor all proposed scenarios comparison to base case are given in Table 5.

Table 5 Reduction ofimported water supply,wastewater and stormwaterdischarge

Options ReductionImported Wastewater Stormwaterwater (%) discharge (%) runoff (%)

Rain water use B 19.7 1.2 37.6C 12.3 0.6 23.4D 25.1 1.3 48.1

Grey water reuse E 25.7 43.0 0.2F 32.5 54.1 0.2G 20.0 33.2 0.2

34 Y. Zhang et al.

It has been seen that the percentage saving on imported water supply for rainwaterusage options spans from 12.3% to 25.1% comparison with greywater reuse 20.0% to32.5%. Reduction on wastewater discharge ranges from 33.2% to 54.1% by adoptinggreywater. Stormwater runoff reduction percentage is from 23.4% to 48.1% forrainwater scenarios.

4 Discussion

4.1 Water Quality

Scientific evidence has confirmed that water obtained from residential roofs isacceptable for most household uses. A study undertaken in Queensland, Australia(Coombes 2003) reported that the quality of rainwater collected from roofs wassuitable for toilet flushing and hot water uses. Also it is stated (Herrmann 1999)that the use of rainwater for clothes washing is safe. In this case study, using a fine-mesh intank filtration over all inlets and outlets and sedimentation in the tank toremove debris and minimise the need for maintenance. Rainwater harvesting fortoilet flushing and garden watering in residential scope is considered a feasible watersource or conservation measure in Cranbrook.

Greywater contains fewer pathogens and 90% less nitrogen than toilet water.Therefore, the greywater treatment process is less complex and cheaper than sewerwastewater. Research reports that the common greywater treatment mechanisms areconstructed wetlands, modified sand filters, wet composting, amended soil filter, basictwo-stage systems (coarse filtration plus disinfection), biological systems (membranebioreactors (MBR), biologically aerated filters (BAF) and rotating biological con-tactor (RBC; Al-Jayyousi 2003; Madungwe and Sakuringwa 2007). In comparison totraditional treatment methods, these technologies are simpler, cheaper. The qualityof effluent from greywater treatment plants (Nolde 1999; Al-Jayyousi 2003; Winwardet al. 2007) shows that technologies documented above are competent for coping withAustralian domestic recycling water standards. In this project, the recommended on-site greywater treatment technology is MBR followed by ultraviolet disinfection dueto the small footprint and high quality of effluent. Treated greywater is believed tobe reliable and consistent for garden irrigation and toilet flushing and irrigation inCranbrook.

4.2 Tank Capacities

The curves (Figs. 3 and 8) reveal percentage reflection of the available water con-sumption and the water needed in per residential lot. Rainwater tank and greywatertank capacities ideally are taken at the points where the curves begin to flattenwith consideration of volumetric efficiency, costing and space. The explanation ofthese different reliability trends is that the extreme variation in rainfall patternsand irrigation consumption for scenarios B, D, E and F comparison of option C.The curves demonstrate that greywater reuse holds the significant potential to caterfor selected water use. A possible reason is the steady and higher water provision.It should be noted that the high garden irrigation demand mitigates the differencebetween the effectiveness of options B and D, as well as options E and F.

Alternative Water Resources for Rural Residential Development 35

4.3 Water Balance

Figures and tables surrounding water balance and annual reduction for alternativesimply that greywater reuse outperforms rainwater use in saving imported potablewater with smaller tank volumes. This is the reflection of higher usage for storagewater in these two options. It is apparent that greywater recycling is more beneficialto decrease wastewater discharge to water bodies. It is also obviously seen thatrainwater has greater impact on reducing stormwater runoff than greywater reusewhich would mitigate drainage system stress.

4.4 Further Alternatives for Rainwater and Greywater Use

The most common use of rainwater and treated greywater is for indoor and outdoornon-potable purposes, the second major application being crop irrigating, othersinclude tree nurseries, fire sprinklers, cleaning, car washing and livestock watering.Further alternatives should focus on reducing urban salinity which is the problemthat Cranbrook and other sites in Western Australia are suffering.

4.5 Existing Issues

It may be necessary to have dual water systems to use both rainwater/greywater andscheme water when the tank level is low due to dry weather or high usage. Thisensures a reliable water supply that will still provide significant scheme water savingsand stormwater management benefits, but increasing final costing at the same time.

Using fluctuant rainfall would be confronted with the condition that the marginallyeffectiveness in much rainfall days and limitation use in insufficiency precipitationperiod. Reuse of treated greywater in residential development is still to be a greatchallenge of community confidence in reliability and trustworthiness of this recyclingsystem. The economic feasibility is indeed the barrier for recycled greywater uptake.

5 Conclusions

Harvesting rainwater and reclaimed greywater holds the potential for fresh waterconserving, wastewater and stormwater discharge reducing, and should also beconsidered in terms of its contribution to integrated water management system.

Six possible options adopting rainwater and greywater separately were estimatedfor rural residential development in the township of Cranbrook.

The results of this study provide greywater usage (maximum reduction 32.5%)more significantly reduces scheme water supply than rainwater harvesting (maximumreduction 25.1%). Use of greywater on individual residential lots has the dramaticeffect for drainage system by reduction approximately 54.1% or 88.1 m3/lot/year.The results of rainwater use analysis show explicitly that rainwater tanks are muchmore effective in intercepting roof runoff, with the maximum stormwater reduction48.1% or 68.3 m3/lot/year.

To achieve water resources conservation, other measures such as water efficientdomestic appliances, revised garden landscaping, leakage control, pricing policiesand social water reduction education would also contribute greatly.

36 Y. Zhang et al.

Acknowledgement The authors gratefully thank Mr. Steve Marvanek for providing the land useinformation data of Cranbrook.

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