Integrated Water Systems for Sustainable Urban Landscapes

Transcription

1 Integrated Water Systems for Sustainable Urban Landscapes Josh Byrne Josh Byrne & Associates Project Number: NY09024

2 NY09024 This report is published by Horticulture Australia Ltd to pass on information concerning horticultural research and development undertaken for the nursery and turf industries. The research contained in this report was funded by Horticulture Australia Ltd with the financial support of Josh Byrne & Associates and the Nursery & Garden Industry Australia (NGIA). All expressions of opinion are not to be regarded as expressing the opinion of Horticulture Australia Ltd or any authority of the Australian Government. The Company and the Australian Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests. ISBN Published and distributed by: Horticulture Australia Ltd Level Elizabeth Street Sydney NSW 2000 Telephone: (02) Fax: (02) Copyright 2012

3 FINAL REPORT INTEGRATED WATER SYSTEMS FOR SUSTAINABLE URBAN LANDSCAPES HAL project number NY09024 author JOSH BYRNE service provider JOSH BYRNE & ASSOCIATES PTY LTD prepared for HORTICULTURE AUSRALIA LTD date 3 JANUARY 2012 Environment Design Communication phone suite 10, 16 phillimore street, fremantle wa 6160 po box 1866, fremantle wa ABN

4 HAL PROECT NUMBER: NY09024 AUTHOR CONTACT DETAILS Josh Byrne Josh Byrne & Associates Address: Suite 10, 16 Phillimore Street Fremantle WA 6160 Telephone: (08) Website: PURPOSE OF REPORT Water use in residential gardens comprises a significant proportion of household water demand in Australia. Recent drought conditions experienced in the southern and eastern regions of Australia led to the introduction of water restrictions in most capital cities as well as many towns, resulting in significant impact on the nursery and garden industry in terms of reduced plant sales and decreased consumer confidence. This project was undertaken to investigate, report and communicate the potential for lot-scale residential rainwater harvesting and greywater reuse to contribute to water conservation by reducing reliance on mains water for garden irrigation and other fit for purpose uses. Funding was used for the purchase and installation of monitoring equipment into an existing garden that incorporates industry best practice water systems infrastructure and water sensitive landscape design. The findings demonstrate that typical household water use can be reduced by around 40% through the incorporation of effective greywater reuse and rainwater harvesting, whilst still sustaining a healthy and productive garden. ACKNOWLEDGEMENTS This project has been funded by HAL using voluntary contributions from The Nursery and Garden Industry of Australia (NGIA) and Josh Byrne & Associates (JBA) and matched funds from the Australian Government. DATE OF REPORT 3 January 2012 DISCLAIMER Any recommendations contained in this publication do not necessarily represent current HAL policy. No person should act on the basis of the contents of this publication, whether as to matters of fact or opinion or other content, without first obtaining specific, independent professional advice in respect of the matters set out in this publication.

5 1. MEDIA SUMMARY TECHNICAL SUMMARY INTRODUCTION Project Background Project Aims and Objectives Study Site Description & Occupancy Mains Water Neutral Gardening Conceptual Model Study Site Water Supply & Irrigation Infrastructure Greywater Diversion Device (GDD) Rainwater Water Harvesting System Irrigation System 9 4. MATERIALS & METHODS Study Site Water Balance Greywater Volumes Irrigation Demand Rainwater Volumes Mains Water Neutral Balance Monitoring Arrangement RESULTS Greywater Volumes Water Use by Stream Serviced by Rainwater Irrigation Backyard Taps Washing Machine Toilet Mains Water Backup Valve Performance Rainfall During Study Period Compared to Recent Average Comparative Water Use by Source and Local Averages APPLICATION TO OTHER AUSTRALIAN CAPITAL CITIES Adelaide Greywater Irrigation Rainwater Mains Water Neutral 23 Josh Byrne & Associates NY09024 Final Report 1

6 6.2 Brisbane Greywater Irrigation Rainwater Mains Water Neutral Canberra Greywater Irrigation Rainwater Mains Water Neutral Melbourne Greywater Irrigation Rainwater Mains Water Neutral Perth (As per DoH 2010) Greywater Irrigation Rainwater Mains Water Neutral Sydney Irrigation Rainwater Mains Water Neutral TECHNOLOGY TRANSFER Presentations & Publications Arising from this Project RECOMMENDATIONS REFERENCES APPENDICES Appendix 1: Trial Site Irrigation Scheduling Data 37 Josh Byrne & Associates NY09024 Final Report 2

7 1. MEDIA SUMMARY The objective of this research project has been to assess the effectiveness of both greywater and rainwater as alternative water sources for reducing mains water use in residential gardens when incorporated as part of an integrated landscape and water system design. The study also examined the potential for mains water savings achieved through using rainwater for toilet flushing and washing machine use for the purpose of determining the potential for these internal savings to offset summer irrigation demand when rain water may be unavailable. This potential for offsetting has been expanded into a novel water demand management conceptual model termed Mains Water Neutral Gardening. HAL funding was used for the purchase and installation of monitoring equipment into an existing garden that incorporates industry best practice water systems infrastructure and water sensitive landscape design. The findings demonstrated that typical household water use can be reduced by around 40% through the incorporation of effective greywater reuse and rainwater harvesting, whilst still sustaining a healthy and productive garden. Monitoring of energy usage of the system pumps indicated that this water was supplied at a significantly reduced energy cost to that of large scale desalination plants. Experienced gained from the study period has informed the modelling of estimated plant water demand, greywater generation volumes and shortfalls, as well as rainwater tank sizing guidelines to offset summer mains water irrigation usage for capital cities around Australia, based on the Trial Site design. These guidelines will be published and made available to both industry, as well as the broader community, through a Nursery and Garden Industry Association Nursery Paper publication. 2. TECHNICAL SUMMARY Water use in residential gardens comprises a significant proportion of household water demand in Australia. In Perth, Western Australia, for example, typical household garden water use represents 44% of total mains water demand (Water Corporation, 2010). Drought conditions experienced in recent years in the southern and eastern regions of Australia led to the introduction of water restrictions in most capital cities as well as many towns, which in turn led to an increase in the innovation and dissemination of water conservation technologies and practices including greywater reuse, rainwater harvesting and efficient irrigation equipment. It can be assumed that the greatest potential for water use efficiency in terms of both application and resource substitution will be achieved when there is an integrated approach to the design and operation of these technologies, however a review of the literature indicates that the effectiveness of mains water savings through such an approach is poorly quantified. This report presents the findings of a detailed monitoring program that was designed to assess the water savings potential of both greywater and rainwater as alternative water sources for reducing mains water use in residential gardens when incorporated as part of an integrated landscape and water system design. Monitoring of the Study Site was undertaken between July 2010 and June 2011 and included volumetric metering and data logging of the following: All water sources (property mains supply, rainwater tank and greywater system). All fixtures / appliances being serviced by these water sources (irrigation system, garden taps, toilet, washing machine and greywater irrigation field). Rainwater and mains water back up supply to the rain water / mains water back up valve. All household water streams contributing to greywater generation (shower, washing machine, laundry trough and hand basins). The results showed that the overall mains water use of the Trial Site was approximately 40% less than the surrounding South Fremantle average, whilst the water demand of the established garden was met. The internal water use was similar to the local average, however of the average figure of 298 litres per day of water that was used to irrigate the garden at the Trial Site (including Josh Byrne & Associates NY09024 Final Report 3

8 178 litres of greywater and 34 litres of rainwater), only 86 litres was mains water, compared to the local average of 250 litres of mains water. An unexpected finding from the study was the inefficiency of the mains water backup valve, with results indicating that the model used had an average system inefficiency of 12%. That is, during periods of normal operation when rainwater was available, approximately 20 litres per day of mains water was used, compared to 123 litres per day of rainwater used. It is understood that some shandying of mains and rain water is typical with most automatic mains water back up valves on the market however the amount is not clearly communicated on product information. Personal communication between the author and several product manufacturers indicate that this is a system design issue that is currently being addressed. Monitoring of the energy usage associated with both the greywater system and the rainwater system indicated an approximate energy cost of 0.5 kilowatt hours per kilolitre (kwh/kl) of greywater supplied and 2.5 kwh/kl of rainwater supplied. It should be noted that the energy cost of both these systems is well below that of large scale desalination plants which typically operate in the range of kwh/kl of water produced (Hauber-Davidson & Shortt, 2011). Experienced gained from the study period has informed the modelling of estimated plant water demand, greywater generation volumes and shortfalls, as well as rainwater tank sizing guidelines to offset summer mains water irrigation usage for capital cities around Australia, based on the Trial Site design. Results from this study were presented at two recent national industry conferences. In addition, these guidelines will be published and made available to both industry, as well as the broader community, through a Nursery and Garden Industry Association Nursery Paper publication. 3. INTRODUCTION 3.1 Project Background Water use in residential gardens comprises a significant proportion of household water demand in Australia. In Perth, Western Australia, for example, typical household garden water use represents 44% of total mains water demand (Water Corporation, 2010). Drought conditions experienced in recent years in the southern and eastern regions of Australia led to the introduction of water restrictions in most capital cities as well as many towns, which in turn led to an increase in the innovation and dissemination of water conservation technologies and practices including greywater reuse, rainwater harvesting and efficient irrigation equipment. It can be assumed that the greatest potential for water use efficiency will be achieved when there is an integrated approach to the design and operation of these technologies, however a review of the literature indicates that the effectiveness of mains water savings through such an approach is poorly quantified. This report presents the findings of a detailed monitoring program that was designed to assess the performance of an established garden that incorporates such water technologies and practices. 3.2 Project Aims and Objectives The objective of this research project has been to assess the effectiveness of both greywater and rainwater as alternative water sources for reducing mains water use in residential gardens when incorporated as part of an integrated landscape and water system design. The study also examined the potential for mains water savings achieved through using rainwater for toilet flushing and washing machine use for the purpose of determining the potential for these internal savings to offset summer irrigation demand when rain water may be unavailable. This potential for offsetting has expanded into a novel water demand management conceptual model termed Mains Water Neutral Gardening. Experienced gained from the study period has informed the modelling of estimated plant water demand, greywater generation volumes and shortfalls, as well as rainwater tank sizing guidelines Josh Byrne & Associates NY09024 Final Report 4

9 to offset summer mains water irrigation usage for capital cities around Australia, based on the Study Site design. 3.3 Study Site Description & Occupancy Located in Fremantle, Western Australia, the Study Site can be described as a 330m2, green title, semi detached dwelling. It includes a WA Department of Health approved greywater diversion system, which irrigates approximately 27m2 of garden beds; and a 3,500L in-ground rain water tank (with pump and mains water back up valve), which services garden irrigation (pots and vegetable bed), garden taps, as well as the household toilet and washing machine supply. Installation has been done to relevant regulatory and industry standards and incorporates a number of best practice sustainable landscape design features as illustrated in Figure 1. Established in 2007, the Site is well suited for the study because the integrated water systems were incorporated in to the landscape design from the outset, with consideration given to an overall water balance. The garden is also established which provides an indication of water requirements at maturity. As a two bedroom house, occupancy varied between one to three persons during the study period. All occupants were between the ages of years and included both males and females. Figure 1: Study Site Landscape Layout Plan and Key Features 1. Native dryland verge garden 2. Nesting boxes for birds & bats 3. Salvaged brick paving 4. Salvaged timber bench seats 5. Mains water backup valve 6. Leaf trap & first flush device for rainwater collection 7. Succulent bed - unirrigated 8. Worm farm and potting bench 9. 3,500L in-ground rainwater tank beneath decking 10. Sedimentation tank-type greywater system beneath decking 11. Outdoor laundry 12. 2,000L Slimline rainwater tank (used for drinking & cooking only) 13. Leaf strainer and manual diverter valve for rainwater collection 14. Outdoor kitchen 15. Pizza oven 16. Raised pots for ground dwelling edible plants 17. Taller herbs & companion plants irrigated by greywater 18. Raised vegetable bed 19. Trellised fruit trees 20. Mobile chook pen in rotation with veggie crops 21. Aquatic pot for fish and frog habitat 22. Fruit trees & ornamental shrubs 23. Grape vines on trellis 24. Pots for additional vegetable production 25. Composting bins 26. 1,000L Slimline rainwater tank for poultry water supply 27. Outdoor bath 28. Outdoor shower 29. Studio 30. Clothesline Josh Byrne & Associates NY09024 Final Report 5

10 3.4 Mains Water Neutral Gardening Conceptual Model Underpinning the landscape design is a new, site responsive, systems based approach to water management in urban gardens termed Mains Water Neutral Gardening (MWNG), which has been conceived by the author. This novel water demand management tool integrates water efficient technologies, appropriate behavioural practices and local environmental conditions to establish a holistic residential water budget that is capable of meeting plant water demand requirements as part of a water sensitive landscape design. The model is based on the following assumptions: Greywater is used to provide irrigation to suitable hydrozones in line with relevant regulatory guidelines (e.g. trees, shrubs, lawn, annuals etc). The size of these zones is determined by matching the actual daily greywater volumes with estimated peak plant water demand to ensure garden water needs are met. Rainwater harvesting supplies water for garden irrigation zones not suited to untreated greywater application (e.g. ground dwelling vegetables and herbs) as well as selected internal uses (toilet and washing machine). Tank storage is sized via daily time step supplydemand side modelling. Mains water is only used as a back up to rain water for irrigation where the mains water used can be paid back through normal indoor water usage patterns during wet weather periods, during which time it is readily available but not required for irrigation. Best practice water efficient hardware and behaviour for both internal uses and irrigation is assumed. Additional garden areas outside the established water budget are designated as dryland plantings, that is they are unirrigated, with suitable species being chosen on the basis of being able to survive on rainfall alone. The model uses Bureau of Meteorology rainfall and evaporation data to determine rainwater availability and plant water demand on a daily time step basis. These are balanced with daily inhouse water demand and greywater production volumes. It should be noted that whilst irrigation demand does factor in changing monthly evaporation rates, it does not factor in rainfall, therefore is irrigation demand is calculated independently of rainfall. Even though actual rainfall may negate the need for irrigation in many cases, experience has shown that some garden areas will remain dry after rainfall events due to rain shadows created by trees, eaves or other structures. It can also be assumed that rainwater will be available in the tanks during these periods so mains water will not be wasted. Figure 2 provides a schematic description of the MWNG model. Figure 2: Schematic diagram of the Mains Water Neutral Gardening model indicating water sources and fit for purpose applications. Josh Byrne & Associates NY09024 Final Report 6

11 Key to the MWNG concept is effective hydrozoning that groups together plants with similar water demand and allocated a suitable water supply stream based on fit for purpose quality and quantity. Figure 3 identifies the hydrozones for the Study Site. Details on the water systems providing the water are provided in section 3.5 Study Site Water System Design. Figure 3: Study Site Hydrozone Plan 3.5 Study Site Water Supply & Irrigation Infrastructure Greywater Diversion Device (GDD) Greywater is the component of domestic wastewater that is produced by the bathroom (bath/shower, hand basin), laundry (washing machine, laundry trough) and kitchen (sink, dishwasher). Kitchen wastewater is typically excluded due to the relatively high concentration of contaminants including fats, oils and food waste. Regulations governing greywater reuse vary from state to state, however they are based on the Australian Standard AS/NZS Greywater reuse systems can be classified as either diversion devices, or treatment systems. Treatment systems are typically higher cost and enable water to be stored for extended periods of time, as well as increase the range of end uses. It should be noted that greywater reuse system needs to be approved for use on a state by state basis, with approval of a specific system being assessed at a state government department level, and the actual installation and operation approved at the local government level. (Malawaraarachchi et al, 2011). In Western Australia greywater reuse falls under the jurisdiction of both the WA Department of Health (DoH) and the relevant Local Government. Installation and operation of greywater reuse systems must comply with the DoH Code of Practice for the Reuse of Greywater in Western Australia, 2010 (DoH 2010). The greywater diversion device installed at the Study Site is a proprietary system known as the GRS Water Save by Greywater Reuse Systems ( - WA Department of Health approval number GW0403). It is currently only approved for use in Western Australia. The system is best described as a twin tank collection, sedimentation and pump out type. The advantage of tank type systems is that they are able to capture all incoming greywater, unlike systems that rely on intercepting traps where greywater will automatically divert to sewer if inflow exceeds pump output capacity. The inclusion of a sedimentation process also clarifies the water prior to being pumped through the filter, which reduces the frequency of filter cleaning required. Another benefit of tank collection and pump out type systems is that the greywater is discharged at once, meaning that all irrigation lines are fully charged and water is applied across the dispersal zone uniformly. This also means that the pump runs more efficiently rather than regularly stopping and starting as with interception type greywater systems which leads to increased power consumption. Josh Byrne & Associates NY09024 Final Report 7

12 The greywater is pumped from the system via a float switch activated submersible pressure pump (Grundfos Hilift 35 A-1) with a power demand of 0.76 kw. Following filtration water is applied to designated garden areas via lilac poly pipe and drip line (Netafim Tiran) in accordance with DoH 2005 and as noted in Figure 6. The key system components and operational features are described above as identified in Figure 4. Installation specifications are as per the WA Department of Health Code of Practice for the Reuse of Greywater in Western Australia, 2005 (DoH 2005), which was current at the time of system installation. The most significant change between the 2005 and 2010 versions of the Code of Practice has been the reduction of the maximum daily greywater application rate from 10mm per day (DoH 2005) to 5mm per day (DoH 2010), which is in line with the recommended application rates under AS/NZS-1547 for free draining soils. The implications of this in terms of irrigation performance and meeting peak plant water demand for a system being installed in Perth now, as well as how this has been translated across to the modelled design guidelines for other capital cities is further addressed under Section 6 of this Report. Figure 4: Key components and operational features of the Study Site greywater system Rainwater Water Harvesting System Rain is harvested off a 200m 2 roof catchment via a standard roof guttering arrangement. Leaf traps and first flush devices with manual drain valves are located on all gutter pops to prevent debris from entering the tank. Rainwater is stored in a 3,500L in-ground rainwater tank (Bluescope ThinkTank) with overflow diverted to a soak well as described in Figure 5. The tank is fitted with a float switch activated pressure pump (Davey submersible) with a power demand of approximately 1000W. Pressurised rainwater is supplied to the end use fixtures and appliances (washing machine, toilet, irrigation system and garden taps) via a mains water back up valve (Davey Rainbank). The rainwater harvesting system has been designed and installed as per AS HB Rainwater Tank Design & Installation Handbook and AS/NZS Plumbing & Drainage Water Services. Josh Byrne & Associates NY09024 Final Report 8

13 Figure 5: In-ground rainwater tank arrangement at the Study Site Irrigation System As described in the previous sections, the landscape water demand is met by a combination of greywater, rainwater and mains water, based on fit for purpose application and availability of the respective water sources. The Study Site irrigation system has been designed to service the landscape hydrozones automatically via a programmable irrigation controller, with the exception area serviced by greywater which is supplied directly from the greywater system which discharges on a volumetric basis as described in Section A dedicated greywater top up line supplies water (rainwater with mains water backup) for periods when the house is unoccupied and irrigation is still required. Design and installation of the irrigation complies with Irrigation Australia design and installation standards (Irrigation Australia 2010). The general irrigation layout and irrigation emitter types are described in Figure 6. Further details on irrigation scheduling for Trial Site are provided in Section and Appendices 1. Figure 6: Key elements and layout of the Study Site irrigation system Josh Byrne & Associates NY09024 Final Report 9

14 4. MATERIALS & METHODS 4.1 Study Site Water Balance The following section outlines the water balance methodology for the trial site, specifically estimated greywater volumes, irrigation demand and estimated rainwater availability. This methodology has then been applied to other capital cities around Australia, taking into consideration local conditions, and the findings presented in Section Greywater Volumes Sizing the greywater dispersal area is a key part of system installation approval and is based on estimated household greywater generation volumes, which is calculated by multiplying average greywater figures per individual by the number of bedrooms in the house (assuming two people in the first bedroom and one person in each additional bedroom) as per DoH 2005 and Under DoH 2005, the volume of greywater applied to the garden should not exceed 10L per square meter per day, which equates to an irrigation application rate of 10mm. In addition to meeting the minimum dispersal area, accurately estimating the volume of greywater generated from the household and matching this to landscape water requirements is important to ensure satisfactory plant performance. Often greywater systems underperform as a source of irrigation because the actual volume of greywater generated is significantly less than the DoH design figures, due to under occupancy or the incorporation of water efficient fixtures and appliances. Table 1 presents the estimated daily greywater generation volumes (in litres per person per day) used in the DoH 2005 design guidelines, as well as what is likely to be generated using waterefficient fixtures and appliances. Table 1: Comparison of estimated greywater volumes DoH CoP 2005 Water efficient Greywater volumes volumes stream L/p/d L/p/d Laundry Bathroom Kitchen 0 0 The water efficient laundry figure is based on new data from the Perth Residential Water Use Study (Water Corporation, 2010) which reflects the reduced water use achieved from the take up of front loading washing machines, since the previous 2003 Loh and Coghlan study. The water efficient bathroom figure is based on a 55% reduction in bathroom greywater since the 2003 Loh and Coghlan study by installing water-efficient shower and tap fixtures (assuming a reduction from 14 litres per minute to 9 litres per minute and 9 litres per minute to 6 litres per minute respectively), combined with water saving behaviour change practices such as shorter showers and turning off taps whilst brushing teeth or shaving. Table 2 shows realistic estimated greywater generation volumes (in litres per household per day) based on multiplying the reduced per person greywater volumes assuming full occupancy of three residents. Table 2: Greywater volumes and applications rate Greywater stream Streams Volume Volume L/p/d L/hh/d Washing machine Laundry trough 2 6 Bathroom Total (L/hh/d) Actual irrigation area (m 2 ) 27 Application rate (mm/m 2 ) 6.3 Josh Byrne & Associates NY09024 Final Report 10

15 (mm/m 2 ) Figure 7 expresses the realistic estimated daily household greywater generated of 170.7L per day, as an irrigation application rate of 6.3mm per day over the 27m2 area. Running alongside is the monthly water demand of landscaping, assuming a plant crop factor of 0.7. It can be seen that during the peak of summer (December to March), there is insufficient water to meet the irrigation demand and so additional water will need to be provided as greywater top up GW Irrigation Demand App. Rate (Realistic) App. Rate (DoH CoP 2005) May Jul Aug Oct Dec Jan Mar May Jun Aug Figure 7: Greywater application rates versus estimated plant water demand. Josh Byrne & Associates NY09024 Final Report 11

16 4.1.2 Irrigation Demand The irrigation areas were divided into 4 hydrozones for the purposes of calculating the garden water demands. Table 3 outlines the key information used in the modelling for each hydrozone including the primary water source to be used. Note Hydrozone 3 was split across two stations to ensure adequate water pressure and flow rate. Table 3: Hydrozone description Hydrozone 1 2 3a 3b 4 Parameter Fruit trees Pots Pots Pots Vegetables & shrubs exposed 1 exposed 2 shade Irrigation area (m 2 ) Crop factor Root depth (m) Canopy cover (%) Irrigated by RW GW RW RW RW Then by MW MW MW MW MW Note: RW = Rainwater GW = Greywater MW = Mains water Table 4 presents estimated irrigation water use for each hydrozone in kilolitres (kl) per month. Full scheduling data used to determine these volumes is provided in Appendix 1. Table 4: Irrigation Demand Hydrozone Total 1 2 3a 3b 4 irrigation Month Fruit trees Pots Pots Pots Vegetables water use & shrubs exposed 1 exposed 2 shade kl/mth kl/mth kl/mth kl/mth kl/mth kl/mth January February March April May June July August September October November December Total Note: 1kL = 1,000L Josh Byrne & Associates NY09024 Final Report 12

17 4.1.3 Rainwater Volumes Rainwater harvesting modelling was performed using average daily rainfall data to ascertain the optimal size rainwater tank and roof catchment area required for effective rainwater harvesting based on the following system design parameters: Rainwater is to be used for toilet flushing and filling the washing machine (cold water supply), as well as garden irrigation for selected hydrozones, with automatic mains water backup. The minimum tank size is to be determined by the volume of rainwater that can be effectively used to meet toilet and washing machine demand during periods of regular rainfall, to the extent where this volume offsets the equivalent amount of mains water used for external uses, effectively making this external house demand mains water neutral. Table 5 present the roof catchment and internal water demand data used to generate tank storage options. Table 5: Rainwater harvesting modelling inputs Rainfall modelling inputs Catchment area (m 2 ) 200 Catchment efficiency (%) 80 Loss to adsorption (mm/event) 0.2 Occupancy rate 3 Toilet demand (L/p/d) 27.4 Washing machine demand (L/p/d) 21.9 Table 6 presents the modelling results, including estimated rainwater used under the different tank size scenarios. Table 6: Rainwater harvesting modelling outputs Rainfall modelling outputs Tank volume (kl) Total water available (kl/year) Efficiency + adsorption loss (kl/year) Total demand (kl/year) Reliability (time) 51% 57% 60% 64% 67% Satisfaction (volume) 48% 54% 57% 60% 64% Rainwater used (kl/year) Josh Byrne & Associates NY09024 Final Report 13

18 4.1.4 Mains Water Neutral Balance Table 7 compares the internal demand (toilet and washing machine) met by rainwater, with the amount of additional mains water required to meet irrigation demand (including greywater top up) during periods when rainwater is unavailable. These volumes are presented for a range of tank sizes and the percentage of pay back, or Mains Water Neutrality is provided. Table 7: Internal rainwater demand compared with mains water irrigation top up for various tank sizes Inhouse volume Rainwater Greywater Tank Mains Water supplied by irrigation mains irrigation scheme volume Neutral rainwater top-up required top-up required (kl) (kl) (kl) (kl) % It can be seen that even with a small 2kL tank, the volume of water supplied to the toilet and washing machine exceeds the volume of mains water required for rainwater irrigation top up (including greywater top up). The performance, or efficiency of the system, in terms of savings versus tank storage volume, diminishes rapidly due to Perth s Mediterranean summer-dry climate where most of the savings are made from late autumn through to early spring when the majority of rainfall occurs. Similarly, irrigation demand is mainly during the dry summer months where tanks are typically empty across all the tank sizes presented, which is why the irrigation top up volumes remain relatively constant. 4.2 Monitoring Arrangement Monitoring of the Study Site was undertaken between July 2010 and June The following list describes the monitoring equipment installed and its application. All external meters and sensors were connected to a multi channel Datataker DT80 data logging unit with a Datataker CEM20 channel expansion module. The hot and cold water supplies to the kitchen sink and bathroom basin could not be connected to the main data logger due to difficulties accessing plumbing lines, so these were logged using individual Onset Hobo Pendent Event data loggers. 19 water meters comprising of 15 x 20mm Elster V100 cold water meters and 4 x 20mm Kent S130 warm water meters were fitted to monitor the property water usage on a daily time-step basis, including: All water sources (property mains supply, rainwater tank and greywater system). All fixtures / appliances being serviced by these water sources (irrigation system, garden taps, toilet, washing machine and greywater irrigation field). Rainwater and mains water back up supply to the rain water / mains water back up valve. All household water streams contributing to greywater generation (shower, washing machine, laundry trough and hand basins). 50mm in-line Arkal 40 mesh disc filters were installed on both rainwater and greywater supply lines to prevent the water meters from fouling and affecting readings. Mercoid Series SBLT2 Submersible level transmitters were been installed in the rainwater tank and greywater pump out tanks to provide a real time indication of tank volumes for the purpose of comparing periods of rainwater availability with rainwater supply to fixtures and appliances. Josh Byrne & Associates NY09024 Final Report 14

19 APCS WHT290 Watt-hour transducers were been installed on the pumps associated with the greywater and rainwater systems to monitoring energy usage. A Decagon ECH20 ECRN-100 self tipping rainwater gauge was installed to provide an accurate record of site rainfall. 18 Decagon 10HS capacitance soil moisture probes (100mm) were installed to monitor the soil moisture content across landscape hydrozones to provide an indication of soil moisture levels on a daily time-step basis. Josh Byrne & Associates NY09024 Final Report 15

20 5. RESULTS 5.1 Greywater Volumes Table 8 presents the actual greywater volumes (per person per day) for the trial site against AS/NZS1547 and estimated volumes from a water efficient household. Of note is that the actual greywater generated is close to the AS/NZS1547 figure indicating that despite the use of water efficient fixtures and appliances, internal water use is still fairly typical. (This is further illustrated in Figure 13). Table 8: Comparative greywater volumes AS/NZS 1547 Water efficient Trial Site L/p/d L/p/d L/p/d Washing machine Laundry trough 2 2 Subtotal - laundry Bathroom basin 11 Shower 68 Subtotal - bathroom Total Note: The trial site greywater volumes were calculated during periods where household occupancy was three people to provide a reasonable average. 5.2 Water Use by Stream Serviced by Rainwater Table 9 presents the water use for each stream supplied by rainwater by month, as well as the total percentage split. Of note is that mains water is still used during periods when rainwater is available in the tank. The balance between mains water and rainwater usage for each stream is presented in Figures Table 9: Average water use by month 2010/11 (litres) Stream Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total Irrigation Backyard tap Washing machine Toilet Total (L) RW MW RW MW RW MW RW MW RW MW Total (MW+RW) Total (%) RW MW Note: RW = Rainwater MW = Mains water Josh Byrne & Associates NY09024 Final Report 16

21 Water used (L) Water used (L) Irrigation Table 8 presents the monthly irrigation volumes as a proportion supplied by rainwater and mains water. Of note that March is the only month where rainwater did not make up any part of the irrigation water supply Rainwater Mainswater Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Figure 8: Monthly irrigation volumes showing balance of mains water and rainwater Backyard Taps Table 9 presents the monthly volumes of water used in the backyard taps (for hand watering) as proportion supplied by rainwater and mains water. Again, March was the only month where rainwater was unavailable for use. 350 Rainwater Mainswater Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Figure 9: Monthly backyard tap volumes showing balance of mains water and rainwater Josh Byrne & Associates NY09024 Final Report 17

22 Water used (L) Water used (L) Washing Machine Figure 10 presents the monthly volumes of water used to fill the washing machine as a proportion of rainwater and mains water. Again, March was the only month where rainwater was unavailable for use Rainwater Mainswater Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Figure 10: Monthly washing machine showing balance of mains water and rainwater Toilet Figure 11 presents the monthly volumes of water used to fill the toilet as a proportion of rainwater and mains water. Again March is the only month where rainwater is unavailable Rainwater Mainswater Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Figure 11: Monthly toilet volumes showing balance of mains water and rainwater Josh Byrne & Associates NY09024 Final Report 18

23 5.2.5 Mains Water Backup Valve Performance As indicated above, mains water was still used in the operation of the fixtures and appliances services by that supply, despite rainwater being available. Of the available Water Mark approved mains water back up valves, most do indicate that a small amount of scheme water is used during operation based on the system design, however volumes or percentages are not given. Table 10 presents a summary of the performance (described as inefficiency) of the mains water backup valve installed at the Trial Site. The inefficiency figure was calculated by dividing the daily volume of mains water used, by the combined total of mains water and rainwater used for that day. The average percentage of mains water used was then calculated over a sample period as noted below. The results indicate that the Rainbank had an average system inefficiency of 12%, with approximately 20 litres per day of mains water used, compared to 123 litres per day of rainwater used. Table 10: Analysis periods and results for Rainbank performance Time period Avg. Rain Avg. Rain Avg No. Bank MWS Bank RWS MW days (L) (L) (%) 20 Jul - 13 Sept Oct Oct-5 Nov Jan Apr-6 May May June All time periods MWS = Mains water supply RWS = Rainwater supply MW = Mains water Notes: Rainbank inefficiency (i.e. percentage of mains water used when rainwater was available) was calculated over random time periods where rainwater was available for greater than three days from 20/7/ /6/2011, across periods of mixed occupancy. Only days that rainwater was available for the full day was used in the calculation, i.e. the first day in which rainwater became available was not included because mains water would have already been used. Josh Byrne & Associates NY09024 Final Report 19

24 Rainfall (mm) Rainfall During Study Period Compared to Recent Average Figure 12 presents the local rainfall during the study period with the recent average for the same location. The average annual rainfall for was 709 mm and total annual rainfall for the study period was 641 mm. Of note is that the average monthly rainfall was lower during the study period when compared to the long term average for most months. Although rainfall was greater in May, June and July during the study period, the rainwater tank was full anyway so the extra rainfall doesn t result in increased rainwater use. 200 Average monthly rainfall ( ) Total rainfall during study period (July 2010-June 2011) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 12: Comparison of rainfall during study period and recent average ( ) Josh Byrne & Associates NY09024 Final Report 20

25 Mean water use (L/day) 5.3 Comparative Water Use by Source and Local Averages Figure 13 compares the water use for the Trial Site (split into indoor and irrigation (irrigation plus garden taps), as well as by source) with the Perth average and the local South Fremantle average (split into indoor and irrigation) on a per household basis. Block sizes in South Fremantle tend to be smaller than the Perth average so this has been included for fair comparison. Of note is that the overall mains water use of the Trial Site is approximately 40% less the surrounding average. The internal water use for the study site (mains water plus rainwater) of 299 litres per day is similar to the local average of 302 litres per day. However of the 298 litres per day of water used to irrigate the garden at the Trial Site (including 178 litres of greywater and 34 litres of rainwater), only 86 litres was mains water, compared to the locale average of 250 litres of mains water used per day for irrigation. Monitoring of the energy usage associated with both the greywater system and the rainwater system indicated an approximate energy cost of 0.5 kilowatt hours per kilolitre (kwh/kl) of greywater supplied and 2.5 kwh/kl of rainwater supplied. The greater efficiency of the greywater, in terms of water volume supplied per unit of energy expended, is due to the difference in pump operation between the two systems. The greywater system pump is switched on in response to the pump out tank filling up and then switching off until the tank refills again, typically one to two days later. Conversely the rainwater tank pump continuously switches on and off according to demand from any fixtures or appliances connected to it, resulting in multiple pump start ups and shut downs which consumes additional power. It should be noted that the energy cost of both these systems is well below that of large scale desalination plants which typically operate in the range of kwh/kl of water produced (Hauber-Davidson & Shortt, 2011) Irrigation: greywater Irrigation: rainwater Irrigation: mainswater Indoor: rainwater Indoor: mainswater Perth South Fremantle McLaren St Figure 13: Comparative water use by source and local average Note: The Perth average water use figures were obtained from the 2008/09 Perth Residential Water Use Study (2010). The South Fremantle average was obtained from data supplied by the Water Corporation on water bills covering the period January 2007-Dec The ratio of indoor to irrigation was calculated by applying the ratio obtained from the Perth Residential Water Use Study (2010) data. Josh Byrne & Associates NY09024 Final Report 21

26 (mm/m 2 ) 6. APPLICATION TO OTHER AUSTRALIAN CAPITAL CITIES The following section presents the water balance data for each Australian capital city as outlined in Section 4.1. Greywater application rates were set at 5mm per day to comply with AS/NZS1547. For the purpose of this exercise, this was done by multiplying the estimated greywater volumes for a water efficient house (as per section Table 8), applied to a 34m2 dispersal area. This increases the likelihood of meeting plant water demand with greywater across the year with and therefore reduces the volume of top up water required. Rainfall data for determining rainwater harvesting potential, and evaporation rates used to estimate plant water demand obtained from the nearest Bureau of Meteorology weather station to the relevant cities General Post Office that supplied the data. Soil type for determining irrigation scheduling was deemed to be free draining loam for all cities except Perth, which was deemed to be improved sand (sandy loam). 6.1 Adelaide Greywater Figure 14 plots the estimated irrigation demand against the maximum allowable greywater application rate of 5mm as per AS/NZS1547, as well as the potential application rate using the standard AS/NZS1547 design figures. Note that at 5mm application rate, only a small amount of greywater top up is required to meet peak plant water demand from December to March, however using standard design figures, top up irrigation is required from September through to April. 8.0 GW Irrigation Demand App. Rate (Realistic) App. Rate (AS/NZS-1547) May Jul Aug Oct Dec Jan Mar May Jun Aug Figure 14: Greywater application rates versus estimated plant water demand Josh Byrne & Associates NY09024 Final Report 22

27 6.1.2 Irrigation Table 11 presents estimated irrigation water use for each hydrozone in kilolitres (kl) per month. Table 11: Irrigation Demand Hydrozone Total 1 2 3a 3b 4 irrigation Month Fruit trees & Pots Pots Pots Vegetables water use shrubs exposed 1 exposed 2 shade kl/mth kl/mth kl/mth kl/mth kl/mth kl/mth January February March April May June July August September October November December Total Rainwater Table 12 presents the rainwater modelling results for Adelaide, including estimated rainwater used under the different tank size scenarios. Table 12: Rainwater harvesting modelling outputs Rainfall modelling outputs Tank volume (kl) Total water available (kl/year) Efficiency + adsorption loss (kl/year) Total demand (kl/year) Reliability (time) 54% 61% 65% 69% 72% Satisfaction (volume) 55% 62% 65% 69% 72% Rainwater used (kl/year) Mains Water Neutral Table 13 compares the internal demand (toilet and washing machine) met by rainwater, with the amount of additional mains water required to meet irrigation demand (including greywater top up) during periods when rainwater is unavailable. These volumes are presented for a range of tank sizes and the percentage of pay back, or Mains Water Neutrality is provided. Table 13: Water balance by tank size Inhouse volume Rainwater irrigation Tank supplied by mains top-up volume rainwater required Greywater irrigation scheme top-up required Mains Water Neutral (kl) (kl) (kl) (kl) % Josh Byrne & Associates NY09024 Final Report 23

28 (mm/m 2 ) 6.2 Brisbane Greywater Figure 15 plots the estimated irrigation demand against the maximum allowable greywater application rate of 5mm as per AS/NZS1547, as well as the potential application rate using the standard AS/NZS1547 design figures. Note that at 5mm application rate, greywater matches plant water demand year round, however using standard design figures, top up irrigation is required from August to April. 8.0 GW Irrigation Demand App. Rate (Realistic) App. Rate (AS/NZS-1547) May Jul Aug Oct Dec Jan Mar May Jun Aug Figure 15: Greywater application rates versus estimated plant water demand Josh Byrne & Associates NY09024 Final Report 24