Margaret River Water Recycling Water Balance and Cost Benefit Analysis

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Margaret River Water Recycling Water Balance and Cost Benefit Analysis
A study by Murdoch University Technology Centre that includes extending recycled water services to residential customers in future urban development areas of Margaret River

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Margaret River Water Recycling Water Balance and Cost Benefit Analysis

  1. 1. ETC cover page Shire of Augusta – Margaret RiverMargaret River Wastewater ReuseWater Balance & CostBenefit Analysis Report 21/2/2008
  2. 2. Margaret River Wastewater Reuse Project - Stage 1 ReportAuthors:This report has been prepared by Cameron Everard, Dr Stewart Dallas and Dr MartinAnda of the Murdoch University Environmental Technology Centre (ETC).Document Governance and Intended UsageThis document has been produced for the sole use of the client only and any use by athird party may lead to inappropriate use of information. This document is deemedcorrect at the time of publication and its accuracy and appropriateness may changewhen further knowledge becomes available. Murdoch University and theEnvironmental Technology Centre accept no responsibility for inappropriate use ofthis document and may take legal action where copying and reproduction of thematerials within this document are used for consultancy and education without writtenprior permission from the Client and the Environmental Technology Centremanagement. i
  3. 3. Margaret River Wastewater Reuse Project - Stage 1 Report Margaret River Wastewater Reuse Project - Stage 1 Water Balance and Cost Benefit Analysis ReportExecutive SummaryThe Shire of Augusta-Margaret River commissioned Murdoch University EnvironmentalTechnology Centre to conduct a study into the options for wastewater reuse in and around thetown of Margaret River. The objectives of this Stage 1 report were: • Preparation of a water balance to demonstrate the amount of water available and the area and/or number of lots that could be provided with treated wastewater; • Preparation of a cost benefit analysis to demonstrate economic viability of the project; and • Identify management plans that will be required.The water balance portrays three stages with four different scenarios and along with the netpresent value (NPV) costs are summarised below:Stages of Development Scenarios Cost NPV (Chronological) $ per kL of reused wastewaterStage 1 Scenario – 1: Existing POS Areas (28 ha) 10.49Stage 2 Scenario – 2: Margaret River Golf Course (25 ha) 13.00 Stage 3 Scenario – 3: Third Pipe to Future Urban Areas 12.50OR Stage 3 Scenario – 4: DWWTP: Part A 13.00 Scenario – 4: DWWTP: Part B (winter – recharge) 21.46 Scenario – 4: DWWTP: Part B (summer) 21.46Note: Scenarios 1-3 exclude cost of wastewater treatment. Scenario 4 includes full wastewater treatment withsome allowance for reduction in wastewater headworks and CSOs, The potential impact of both headworks andCSOs is significant and is discussed in detail in the Cost Benefit Analysis.Stage One - Scenario 1 – Existing POS areasScenario one would include irrigation of all current Shire POS areas with treated wastewaterfrom the MRWWTD, (includes schools, Gloucester Park and East Margaret River (EMR)POS (Riverslea, Rapids Landing and Brookfields) (28 ha). Does not include third pipeconnection for household toilet flushing or garden irrigation to these subdivisions.Stage Two - Scenario 2 – Margaret River Golf CourseThis scenario would comprise irrigation of all current Shire POS areas with treatedwastewater from the MRWWTD, (includes schools, Gloucester Park and EMR POS[Riverslea, Rapids Landing and Brookfields], 28 ha). This scenario also includes irrigation ofthe Margaret River Golf Course of approximately 25 ha.Scenarios 1 and 2 are also included in Scenario 3 below.Stage Three (centralised) - Scenario 3 – Third pipe to future urban areas (East and West)This scenario would include installation of a third pipe to all new subdivisions - all watersupplied from MRWWTD to subdivision households (for garden irrigation and toiletflushing) and irrigation of subdivision POS. Will require mains sewerage connection to theMRWWTD and third pipe connection to subdivision.Alternatively, the Shire may choose to pursue a decentralised option as follows:Stage Three (decentralised) - Scenario 4 - Integration of Decentralised WastewaterTreatment Plants (DWWTP) ii
  4. 4. Margaret River Wastewater Reuse Project - Stage 1 ReportScenario 4 consists of two parts, Part A comprises the existing third pipe facilities from theMRWWTD to the Shire POS areas and the MRGC undertaken in Scenarios 1 and 2. As thisinfrastructure will have already been established it is considered separate to Part B.Part B would include the establishment of DWWTP’s to each new subdivision. Allwastewater produced in the subdivision will be directed to subdivision scale DWWTP fortreatment. Treated water from this unit could be used directly for irrigating POS within thesubdivision during the summer months and supplied to the households for toilet flushing andgarden irrigation. The subdivision would be considered a closed loop system, collectingtreating and recycling the wastewater within the subdivision. Each DWWTP would bedesigned to accommodate the estimated volumes of water produced within the subdivision.In Scenario 4 excess wastewater during winter could be diverted to irrigation if practical.Third pipe connection from DWWTP will be required for summer irrigation of thesubdivision POS. As this scenario is considered to be a closed loop system it does not requirethird pipe connection from the MRWWTD and due to low winter volumes should not needmain sewerage connection. Greywater could be either treated and recycled at the householdscale or directed to the DWWTP.The Management Plans that the Shire will need to prepare for Scenarios 1 to 3 will include: • Operation and Maintenance Plan (DoH); • Nutrient and Irrigation Management Plan (DoW); • Community Consultation Outcomes Report; and • Works Approvals and Licenses (DEC).In addition if Scenario 4 is developed, independent of the Water Corporation, the Shire willneed to use the services of a licensed sewerage service provider or secure its own WaterService Providers License (Sewerage Services) from the ERA or in some instances whereappropriate require land developers to secure their own license.The ecological benefits of Stage 1 of the project include a considerable increase inenvironmental flows for the Margaret River (approximately 169,000 kL/per year) (based on2007 abstraction rates) and the associated indirect downstream ecological benefits as a resultof increased water volumes in the river. If the MRGC were supplied with treated wastewater,there would be a decrease in the groundwater abstraction from the local aquifer and thereforeassociated indirect benefits. There would also be a further reduction in future water needs asStage 3 was commissioned to supply a third pipe to new subdivisions.In addition to the ecological benefits, the project will provide social and aesthetic benefits dueto the increased river flows, these include; a healthier looking river and the potential forincreased downstream eco-tourism activities in the river during the summer months, due tothe reduction in river abstraction. The treated wastewater will secure a water source for theirrigation of parks and public facilities into the future.The project also presents a positive message to the local Margaret River community in termsof sustainable water management and urban wastewater reuse and sets a precedent for otherurban wastewater reuse projects in Western Australia. The reuse of treated wastewater hasbeen successfully undertaken by more than 60 Shire councils around Western Australia forseveral decades in order to secure sustainable water management practices. The State WaterStrategy has also set a target of reusing 20% of treated wastewater sources by 2012. iii
  5. 5. Margaret River Wastewater Reuse Project - Stage 1 Report CONTENTSExecutive Summary...................................................................................................iiIntroduction ............................................................................................................... 1 Background ........................................................................................................... 1 Recent Policy Developments.................................................................................. 1 Objectives.............................................................................................................. 2Treatment Processes .................................................................................................. 3Water Balance ........................................................................................................... 4 Water Supply - Inputs ............................................................................................ 4 Water Demand - Outputs ....................................................................................... 4Scenarios for Water Recycling................................................................................... 6 Scenario 1 – Existing POS Areas (Stage One)........................................................ 6 Scenario 2 – Margaret River Golf Course (Stage Two) .......................................... 6 Scenario 3 - Third Pipe to Future Urban Areas (Stage Three)................................. 7 Scenario 4 – Decentralised Wastewater Treatment Plant (Stage Three) ................ 10 Centralised vs Decentralised Treatment Systems.................................................. 12 Summary of Water Reuse Scenarios .................................................................... 13Cost Benefit Analysis .............................................................................................. 14Management Plans................................................................................................... 16Community Consultation ......................................................................................... 16Ecological and Social Benefits of the Project ........................................................... 18Recommendations ................................................................................................... 19References ............................................................................................................... 21Appendix 1: Margaret River Wastewater Reuse Scenarios - Water Balance ............. 22Appendix 2: Water Balance Assumptions ................................................................ 23Appendix 3: Guidelines for the Use of Recycled Water in Western Australia........... 25Appendix 4: Net Present Value (NPV) Calculations................................................... 1 List of TablesTable 1: Current irrigated areas and volumes within the SAMR ................................. 5Table 2: Scenario 1 – Summary of water balance calculations.................................... 6Table 3: Scenario 2 – Summary of water balance calculations.................................... 7Table 4: Assumptions for predicted future urban areas............................................... 9Table 5: Scenario 3 – Summary of water balance calculations – 2026 third pipe to future urban areas............................................................................................... 9Table 6: Scenario 4: Part A – Summary of water balance calculations...................... 11Table 7: Scenario 4: Part B – Summary of water balance calculations for decentralised WWTP self contained subdivision of 650 lots .................................................. 11Table 8: Annual rainwater tank yields for Perth ....................................................... 12Table 9: Advantages and disadvantages of centralised and decentralised treatment systems ............................................................................................................ 12Table 10: Summary of water balance under each scenario........................................ 13Table 11: Summary of water balance and capital costs under each scenario ............. 14 iv
  6. 6. Margaret River Wastewater Reuse Project - Stage 1 ReportIntroduction BackgroundIn response to the increasing demand on natural potable water sources and a decrease inannual precipitation, the Shire of Augusta Margaret River (SAMR), propose to use treatedwastewater to irrigate their Public Open Space (POS), such as sports ovals and schools.The reuse of treated wastewater has been successfully undertaken by more than 60 Shirecouncils around Western Australia (Neil McGuinness, WA Department of Health, 2007) forseveral decades in order to secure sustainable water management practices. The State WaterStrategy has also set a target of reusing 20% of treated wastewater sources by 2012.It is envisaged that the treated wastewater will reduce and replace the current dependence onexisting water sources such as abstraction from the Margaret River and local groundwatersources. The SAMR are considering using the water to irrigate other POS around the townsitein the future. Investigations are under way for supplying a third pipe, to future residentialareas for toilet flushing, garden irrigation and POS. Third pipe with recycled wastewater isyet to be undertaken in Western Australia, and if implemented will set a new precedent inurban water use management. The first third pipe development in Western Australia wascompleted by Water Corporation at Brighton in the northern suburbs of Perth for the POS andhome gardens irrigation but this was only using community bore groundwater.Several studies to date have been undertaken in relation to the Project, they include: • Feasibility Investigation Report on the Margaret River Waste Water Reuse, (Wood and Grieve Engineers, 2006); • Preliminary Figures (HydroPlan Pty Ltd, 2005); and • East Margaret River Public Open Space and Landscape Development Guidelines (Shire of Augusta-Margaret River, 2007). Recent Policy DevelopmentsIt should be noted that as of September 2008 the provision for third pipe connection will bemandatory for all new subdivisions and homes in Western Australia for greywater andalternative water supply.The State Government has recently introduced the 5 Star Plus Building Code, whichencourages the reduction of water and energy use. The aims of the water use code are toreduce the consumption of water in residential homes by requiring water efficient fittings,minimising the wastage of water and facilitating the appropriate use of alternative sources ofwater such as grey water and rain water (Government of Western Australia, 2007)The installation of these alternative water sources for new subdivisions is strongly encouragedand discussed further in Section 3.6.5 Star Plus will be applicable to new homes approved for construction after 1 September2007. It is expected that the State Government will investigate measures to apply the 5 StarPlus provisions to existing homes by 2008 (Government of Western Australia, 2007).Moreover, the WA Government Department of Premier and Cabinet is currently formulatingthe State Water Recycling Strategy.The provision of recycled water to homes via third pipe will now be possible under the newWA Department of Health (DoH) regulations from the current 16 January 2007 “Guidelines 1
  7. 7. Margaret River Wastewater Reuse Project - Stage 1 Reportfor the Use of Recycled Water in Western Australia” (Appendix 3). Water is required to betreated to different standards depending on its final use. Water for irrigation of POS areas canbe treated to Class B or C, whereas water for urban non-potable use will need to be treated toClass A as specified in the DoH guidelines.At a national level the “Australian Guidelines for Water Recycling: Managing Health andEnvironmental Risks” Phase 1 (Environmental Protection Heritage Council, 2006) haverecently been finalised as a part of the National Water Quality Management Strategy. Theproject will be conducted in accordance with these guidelines. ObjectivesThe objectives of this Stage 1 report as outlined in the proposal accepted by SAMR were: • Preparation of a water balance to demonstrate the amount of water available and the area and/or number of lots that could be provided with treated wastewater; • Preparation of a cost benefit analysis to demonstrate economic viability of the project; and • Identify management plans that will be required.(NB Upon completion of this Stage 1 study it was proposed that a Stage 2 contract include:supply modelling, (components, operation funding), treatment levels, licensing requirementsand management plans).The present study has investigated and quantified the current supply of wastewater availableat the Margaret River wastewater treatment dam (MRWWTD) with the demand for irrigatingPOS within the SAMR and to assess the feasibility of various scenarios for third pipeconnections to future residential areas.Preliminary figures have been calculated on projected volumes of wastewater to quantifysupply and demand of wastewater streams up to 2026 (Scenario 3). The Water Corporation’s2026 input volumes to the MRWWTD includes sewage from the townsite of Margaret Riverand exclude Witchcliffe and Gracetown townsites. These projected figures are based oninformation provided by the Water Corporation and are considered assumptive.It is envisaged that through the implementation of this proposal that a socially acceptable,economically sound and ecologically sustainable outcome can be achieved for the localcommunity, water users and the SAMR. 2
  8. 8. Margaret River Wastewater Reuse Project - Stage 1 ReportTreatment ProcessesAt present the Water Corporation treats sewage at its Margaret River Wastewater TreatmentPlant located approximately 2.5 km north east of the Margaret River townsite.Sewage is pumped from the town via a 375 mm diameter rising main to the treatment plant.The treatment process consists of the following components: • Inlets works, complete with tanker receival facility, mechanical screening and screw- wash-press; • An Intermittent Decant Extended Aeration (IDEA) tank equipped with floating surface aerators and a decanting mechanism; • A chemical dosing facility, consisting of alum and caustic dosing; • A mechanical sludge dewatering system, including a gravity drainage deck and belt filter press; and • A treated effluent storage dam with a designed storage capacity of 450 ML.The Margaret River plant currently treats water to a Class C quality (Water Corp, 2008).Treated water is stored in the dam then sand filtered and chlorinated prior to irrigating theadjacent pine plantations. Irrigation to the pine plantations is conducted throughout the year,with irrigation rates to the pines based on soil saturation rates. The pine plantations areirrigated in winter if there is a dry period. The Water Corporation use a basic criteria of “nosurface runoff or ponding” when irrigating the adjacent plantation (Water Corporation, perscomm.). It is understood that the wastewater will not be required to undergo further treatmentto be suitable for irrigation purposes, however the chlorine dosing rate will be increased toaccount for the increased pipe distances.If treated water from the plant is to be used for a third pipe system in future urban areas forinternal non-potable purposes then further treatment and costs will be incurred due to treatingthe water from Class C to Class A. It is envisaged that an investigation of further treatmentand costs will be undertaken in the next stage of the project.Under the proposed irrigation system, the treated water will be pumped via a 250 mm pipe tobalance tanks located at the Margaret River Weir. It is expected that the existing pumping rateof 60 L/second will be sufficient to pump the water to the balance tanks. Water will bepumped to the POS areas from the balance tanks via a 150 mm pipe. Further technicalinvestigations will be necessary to ascertain pumping rates, pipe sizes and balance tank sizes. 3
  9. 9. Margaret River Wastewater Reuse Project - Stage 1 ReportWater BalanceThe following key tasks have been calculated as a part of the water balance (Refer toAppendix 1): 1. Quantification of incoming wastewater and incident rainfall flows and evaporation from the treatment dam (Supply); and 2. Future public and urban areas to be irrigated (Demand). Water Supply - InputsAs of April 2007 approximately 1,768 dwellings were connected to the main sewer of 2734available (Water Corporation, pers comm.), which feed into the MRWWTD.During the summer and public holidays there will be an increase in tourist numbers visitingthe town and therefore an increase in inflows to the treatment dam. The Margaret RiverVisitor Centre reported that the months of highest visitation was January, April andDecember. It is understood that most visitors to the Shire would be spread acrossaccommodation facilities located in sewered and unsewered areas. Wastewater generatedfrom visitors to the sewered areas would already be accounted for in the inflow volumes tothe treatment dam. Visitors to unsewered areas are not likely to contribute to the increase inflows to the dam as wastewater from these accommodation facilities would treated through aseptic tank or alternative treatment system approved by the SAMR. The summer holidaymonths of December, January and April usually correspond to higher inflow volumes at thetreatment dam.The increase in absentee land owners occupying properties in sewered areas during thesummer months will also increase inflow volumes to the treatment dam.The wastewater treatment dam is located approximately 2.5 kms from town and receivesapproximately 359,000 kL of wastewater per year (982 kL per day). The treatment dam has adesigned storage capacity of 450,000 kL.Rainfall to the MRWWTD minus evaporation reduces the volume of water by 14,000 kL peryear on average. Therefore, the approximate volume of water available for use in theMRWWTD is 345,000 kL (345 ML) per year. The area of the MRWWTD has been estimatedat 30,000m2.The treated wastewater from the MRWWTD is currently drip irrigated to the adjacent pineplantation at approximately 323,000 kL/per year. Informal discussions with the WaterCorporation in June 2007 have identified that the Forest Products Commission plan to harvestthe surrounding pine plantations that are currently irrigated in 2009. Therefore an alternativeuse for the water will need to be established by this time. Current volume of water available for irrigation = 345,000 kL (345 ML) per year. Water Demand - OutputsThe SAMR currently abstracts water from the Margaret River Weir for irrigation purposes.The water is pumped via an automated system (150mm pipe) to irrigate schools, POS andovals. Irrigation of the ovals occurs twice per week, approximately 30mm/per week 4
  10. 10. Margaret River Wastewater Reuse Project - Stage 1 Report(15mm/session). The main irrigation pump has been designed to pump at 12.25L/second at600kPa.Water required for irrigating schools, POS and ovals (except Riverslea Subdivision) is134,000 kL/per year (17.8 ha) or approximately 7,528 kL/ha/year.Based on the above irrigation rate, approximately 35,000 kL/per year is abstracted from theMargaret River for the Riverslea Subdivision. Therefore it is estimated that approximately169,000 kL/per year is currently abstracted for the irrigation of 22.4 ha of Shire POS. Abreakdown of the POS areas that are irrigated by the SAMR, their size and irrigation volumesare provided in Table 1.Table 1 does not include the POS areas of Brookfield and Rapids Landing. It is understoodthat these areas are not currently irrigated by river water. These two additional areas havebeen included in the water balance calculations for Scenario 1 and total 28 ha (refer to Table2).Table 1: Current irrigated areas and volumes within the SAMR Irrigated Areas Hectares (ha) Approximate Volume (kL) (based on 7,528 kL/ha/yr)Gloucester park 11 83,000Reuther park/ bowling green 1 7,500Two state schools 5.8 44,000Riverslea subdivision 4.6 34,500Total (approximate) 22.4 169,000Table 1 highlights the importance of a wastewater reuse scheme; approximately 169 ML ayear will need to be abstracted from the Margaret River in 2008 for irrigation of the aboveareas. It is understood that the SAMR are currently renewing their water abstraction licenceadministered through the Department of Water (DoW). Abstraction of river water could stillbe used to offer a supplementary supply, provided volumes were within DoW licensed limits.The assumptions used in the water balance are provided in Appendix 2. 5
  11. 11. Margaret River Wastewater Reuse Project - Stage 1 ReportScenarios for Water RecyclingThe water balance is presented in Appendix 1 and portrays three stages with four differentscenarios. The four scenarios have been created and refined from several discussions with theSAMR. It is understood that the SAMR will implement the three stages in succession. Thescenarios are summarised below and described in detail in this section:Stages of Development (Chronological) ScenariosStage 1 Scenario – 1: Existing POS Areas (28 ha) Stage 2 Scenario – 2: Margaret River Golf Course (25 ha) Stage 3 Scenario – 3: Third Pipe to Future Urban Areas OR Stage 3 Scenario – 4: DWWTP: Part A Scenario – 4: DWWTP: Part B (winter – recharge) Scenario – 4: DWWTP: Part B (summer) Scenario 1 – Existing POS Areas (Stage One)Scenario 1 includes the irrigation of all current Shire POS and existing subdivisions (EastMargaret River EMR POS) from the MRWWTD. Table 2 below summarises the outcomes ofthe water balance calculations. Under this scenario, approximately 134,000 kL of waterwould be available for other irrigation purposes, such as the adjacent pine plantation or thirdpipe applications.Table 2: Scenario 1 – Summary of water balance calculationsIrrigated Areas Approximate Volume (kL) paTotal available water for irrigation in MRWWTD 345,000Shire irrigation 28 ha (schools, ovals, EMR POS) 211,000Dam level and water available for other irrigation 134,000following irrigation of Shire POSThe current average irrigation rate for other POS and turfed areas in the SAMR is in the orderof 7528 kL/ha/year. On this basis, approximately 17 ha of POS could potentially be irrigatedwith the remaining water available in the dam. Scenario 2 – Margaret River Golf Course (Stage Two)Further opportunities to use treated wastewater include the Margaret River Golf Course(MRGC), which is located approximately 5.3 km by road from Gloucester Park. The MRGCcurrently obtains water from on-site dams and groundwater bores and is assessing the costsand benefits of pumping treated wastewater for irrigation purposes.A report undertaken by Hydroscapes Australia Pty Ltd in June 2007 estimated the currentdesigned irrigation system can deliver up to 396,000 kL/per year (over 9 months), howeveractual water usage rates for the MRGC are in the order of 188,000 kL/per year (based on7500 kL/ha/year for 25 ha). No irrigation is undertaken at the golf course during the wintermonths.Scenario 2 includes the irrigation of all current Shire POS areas with treated wastewater fromthe MRWWTD, (includes schools, Gloucester Park and EMR POS) and irrigation of theMRGC (approximately 25 ha).Table 3 below summarises the outcomes of the water balance calculations. In this scenarioapproximately 54,000 kL of additional water would be required to be derived from other 6
  12. 12. Margaret River Wastewater Reuse Project - Stage 1 Reportsources such as bore or river water for the months of February, March and April. It isrecommended that the MRGC investigate ways of reducing overall water use based oncurrent best practice in the industry.Table 3: Scenario 2 – Summary of water balance calculationsIrrigated Areas Approximate Volume (kL) paTotal available water for irrigation in MRWWTD 345,000Shire irrigation 28 ha (schools, ovals, EMR POS) 211,000Margaret River Golf Course (25 ha) 188,000Total water required 399,000Water required from other sources 54,000Based on data extrapolated from Water Corporation predictions, preliminary calculationsindicate that the 400,000 kL of irrigation water required for Scenario 2 could be available by2009 (refer to Figure 1 below). Scenario 3 - Third Pipe to Future Urban Areas (Stage Three)Scenario 3 consists of installing a third pipe connection system to all new subdivisions. Waterwould be supplied from the MRWWTD to the subdivision for irrigation of the POS andinclude connection to each household for garden irrigation and toilet flushing. This scenariohas not factored in the installation of household onsite greywater systems.The new subdivisions will require mains sewerage and third pipe connection to theMRWWTD. Volumes of water required for scenarios 1 and 2 are also included in the scenario3 calculations.Predicted inflow volumes to the MRWWTD have been obtained from the Water Corporationand are as follows: 2007 = 358,526 kL per year (982 kL/ per day) (actual recorded volume); 2015 = 550,000 kL (1507 kL/ per day) (Water Corporation prediction); and 2026 = 910,000 kL (2493 kL/ per day) (Water Corporation prediction).According to the SAMR the population of Margaret River in June 2007 was approximately5,400. The current inflow into the MRWWTD is 358,526 kL/per year, with approximately1768 connections (or 203 kL/connection/year).The Water Corporation has projected a steady increase reaching approximately 550,000kL/per year in 2015 to 910,000 kL/per year by 2026, based on a population of approximately12,500.Based on these figures, approximately 4,482 connections would be contributing to theMRWWTP in 2026. However, it should be noted that there is likely to be an increase inhousehold water usage over time associated with increasing standards of living, e.gdishwashers and spa baths. This would result in similar volumes of water with fewerconnections. Therefore this figure is considered assumptive.Various occupancy rates are available ranging from 2.4 – 2.7 occupants per dwelling, for thepurpose of this report an average 2.6 occupants per dwelling has been selected in line with therecent Rapids Landing development.Additions from rainfall and losses through evaporation were calculated at approximately14,000 kL per year. The following estimates have been made with respect to wateravailability for third pipe usage in the future urban areas: 7
  13. 13. Margaret River Wastewater Reuse Project - Stage 1 Report 2007 = 345,000 kL per year 2015 = 536,000 kL per year 2026 = 896,000 kL per year(Calculations are provided in Appendix 1)Figure 1 below shows a gradual increase in the volume of water available for reuse.Figure 1. Available wastewater volumes from MRWWTP 1998 – 2026Note: Volumes include additions from rainfall and losses from evaporation.Note that with the increasing acceptance of greywater reuse and water conservation strategiesat all levels of government and the community, there could be a reduction in the volume ofwastewater discharged into the main sewerage system. On the contrary, a doubling of theresidential population may actually result in more wastewater inflows due to additionalconnections to the main sewerage system within existing developed areas due to sewerageinfill.The MRWWTD has a designed capacity of 450,000 kL, based on current increases in inflowvolumes it will be at full capacity by 2010. An alternative reuse/disposal option will need tobe assessed and commissioned as the adjacent pine plantations are earmarked for harvestingin 2009. However with the commencement of irrigation of POS and golf course andcommissioning of a third pipe to future urban areas the volume of dam water will be reducedand therefore provide increased capacity. Controlled releases to water courses from winterstorage dams may also be feasible subject to water quality objectives.The recent Rapids Landing subdivision (formerly termed Lot 27 subdivision) has been usedas a standard subdivision template. The Rapids Landing subdivision is expected to houseapproximately 1,690 people and comprises a total land area of 82.5 ha of which 6 ha havebeen allocated for POS. The area has been subdivided into 650 lots with an occupancy rate of2.6 per lot (Simon Munckton, Lester Group, pers comm.).In the absence of any planning data (except population increases) for future subdivisions, theRapids Landing subdivision figures were extrapolated to account for an increase inpopulation. 8
  14. 14. Margaret River Wastewater Reuse Project - Stage 1 ReportFuture total population figures have been based on Water Corporations projections ofapproximately 12,500 in 2026. It has been assumed that this would consist of approximately7,000 from existing town areas, infill and EMR areas and approximately 5,500 in future urbanareas (new subdivisions). It has been assumed that of the 4,482 connections potentiallyavailable in 2026, approximately 44% or 1,972 connections could be connected to futureurban areas.When a population of 5,500 was applied to the future urban areas at an occupancy rate of 2.6(comparable with Rapids Landing) approximately 2,115 lots/connections resulted. Thereforean average of 2000 connections for future urban areas has been assumed for this scenario.Based on 4,482 connections and an occupancy rate of 2.6 the population would beapproximately 11,600, the Water Corporation has used an occupancy rate of 2.7 (12,100). TheSAMR has estimated that the population in 2026 will be between 10,200 and 12,900. Apopulation of 12,500 has been selected in line with the Water Corporation, however isconsidered assumptive at this stage. Inflow volumes for dwellings have been assumed atapproximately 203 kL per year.The following assumptions (Table 4) were made regarding the future urban areas up to 2026.Table 4: Assumptions for predicted future urban areasElement Rapids Landing Subdivision Future Urban Areas (with 3rd pipe) – 2026 (Actual) (Predicted)Population 1,690 5,500 (Total MR popln: approx 12,500)No. of lots/connections 650 2,115 (approx 2000)No. of subdivisions 1 3POS (ha) 6 18Occupancy rate per lot 2.6 2.6Table 5 below summarises the results of the water balance calculations. In this scenarioapproximately 68,000 kL would be available for other uses (9 ha of POS). The volumes intable 5 for third pipe for toilet, irrigation and POS are only for the 3 subdivisions in new areasand not for existing areas (town, infill and EMR area). At this stage these figures should beconsidered assumptive.Table 5: Scenario 3 – Summary of water balance calculations – 2026 third pipeto future urban areasIrrigated Areas Approximate Volume (kL) paTotal available water for irrigation in MRWWTD 896,000Shire irrigation 28 ha (schools, ovals, EMR POS) 211,000Margaret River Golf Course (25 ha) 188,000Future 3 rd pipe to subdivisions (3 sub) (toilet, irrigation) 294,000Future 3 rd pipe to subdivisions (3 sub) (POS, 18 ha) 135,000Total water required 828,000Dam level/ available water 68,000Inflow volumes outlined in Table 5 have been sourced from the Water Corporation’s 2026predictions (assuming additional 3 subdivisions for future residential areas).Preliminary estimates show that the total required water to accommodate scenario 3(approximately 828,000 kL) could be available by 2025, based on Water Corporations inflowvolumes. 9
  15. 15. Margaret River Wastewater Reuse Project - Stage 1 ReportIf scenario 3 only included Shire POS, MRGC and POS with the future residential areas (18ha), then 534,000 kL per year would be required. This volume could be available by 2015. Scenario 4 – Decentralised Wastewater Treatment Plant (Stage Three)Scenario 4 consists of two parts; Part A comprises the existing third pipe facilities from theMRWWTD to the Shire POS areas and the MRGC. As this infrastructure will have alreadybeen established it is considered separate to Part B. As Part A would be operational, Part Bwould run concurrently as each subdivision was approved and constructed. As Part B isconsidered a closed looped system in terms of wastewater treatment and reuse the stand alonedevelopment can be considered in isolation to the other scenarios.Part B would include the establishment of Decentralised Wastewater Treatment Plants(DWWTPs) to each new approved subdivision.Decentralised systems involve the collection, treatment and reuse of wastewater from homesor communities at or near the point of generation (Tchobanoglous, 1995). Centralisedtreatment on the other hand, consist of conventional systems (sewers), centralised treatmentplants and disposal/reuse of the treated effluent, usually far from the point of origin(Tchobanoglous, 1996).All wastewater produced in each new subdivision will be directed to a subdivision scaleDWWTP for treatment. Treated water from this unit could be used directly for irrigating POSwithin the subdivision during the summer months and supply households with non-potablewater for toilet flushing and garden irrigation.The subdivision would be considered a closed loop system, collecting treating and recyclingthe wastewater within the subdivision. Each DWWTP would be designed to accommodate theestimated volumes of water produced within the subdivision.Excess treated wastewater during the winter could be diverted to an irrigation/pasture area orreinjected into the local aquifer through a Managed Aquifer Recharge (MAR) process.Alternatively, if practical, the water could be discharged into a constructed wetland area orengineered water feature and allowed to naturally infiltrate into the local superficial aquifer.The most appropriate method would have to be assessed on a site-by-site basis taking intoconsideration issues associated with winter storage of treated wastewater.Third pipe connection from the DWWTP will be needed for summer irrigation of POS. Thisscenario does not require third pipe connection from the MRWWTD and ideally should notneed main sewerage connection due to low volumes of water produced in winter and thepotential for onsite reuse. Greywater treatment systems could be installed at the householdlevel to irrigate private gardens or connected to the DWWTP.If newly approved subdivisions do adopt this closed loop water management strategy they arelikely to be self sufficient in terms of water treatment capacity and irrigation reuse. There willbe no need for main sewerage connection and therefore no contributions to the MRWWTD.Predicted inflows into the MRWWTD for Part A of this scenario have been based on current2007 inflow volumes (345,000 kL/per year) plus an extra 30,000 kL per year to account foradditional connections from the existing Cowaramup townsite and infill within the MargaretRiver townsite, as no additional water would be discharged back to the MRWWTD from thenew subdivisions. 10
  16. 16. Margaret River Wastewater Reuse Project - Stage 1 ReportCreating future subdivisions that are closed looped and self sufficient in terms of watertreatment and reuse would shift more responsibility onto the developer to provide appropriatewater treatment facilities during the design and costing of the subdivision.The volumes used for Scenario 4 Part B are based on a single subdivision such as RapidsLanding. This assumes the subdivision has approximately 1,690 people with 6 ha of POS and650 lots. A summary of the water balance calculations is provided in Tables 6 and 7 below.Table 6: Scenario 4: Part A – Summary of water balance calculationsIrrigated Areas Approximate Volume (kL)Total available water for irrigation in MRWWTD 345,000 + 30,000Shire irrigation 28 ha (schools, ovals, EMR POS) 211,000Margaret River Golf Course (25 ha) 188,000Total water required 399,000Water required from other sources 24,000Table 7: Scenario 4: Part B – Summary of water balance calculations fordecentralised WWTP self contained subdivision of 650 lotsIrrigated Areas Approximate Volume (kL)Total available water for irrigation from DWWTP* 119,0003rd pipe from DWWTP within subdivision (for toilet)* 26,0003rd pipe from DWWTP within subdivision (for irrigation)* 69,0003rd pipe from DWWTP within subdivision (for POS 6 ha)* 45,000Total water required 140,000Water to be irrigated/recharged locally (winter) 38,000Water required from other sources (summer) 60,000*Volumes based on Water Corporation’s Domestic Water Use Study, 2001.Based on the assumption of an additional 30,000 kL contribution of wastewater for Part A,24,000 kL of water would be required from other sources. In reality, this figure could besomewhat higher than the assumed 30,000 kL, in which there would be enough wateravailable to irrigate the Shire POS areas and the MRGC. It is anticipated that sufficient waterwill be available for Part A, due to a yearly increase of approximately 30,000 kL.For Part B, approximately 7,500 kL of water per month will need to be reused or storedduring the May to September period or approximately 38,000 kL over the 5-month period.This water could be reused in several different ways depending on the opportunities andconstraints presented at each individual subdivision. Further feasibility studies would need tobe undertaken early in the planning stages to allow for the integration of these systems. Forexample additional POS or a designated wetland landscaped area with high water and nutrientuptake plants could be included in the subdivision design.During summer, approximately 60,000 kL of additional water will be required for irrigationof the POS, toilet flushing and garden irrigation within each subdivision of approximately 650lots. The majority of this water will be used for household garden irrigation during summerand could be reduced if strict water conservation measures are applied to households in linewith other states.This scenario has the potential to save up to 119,000 kL of scheme water per year, persubdivision of this size (similar to Rapids Landing) and could easily accommodate irrigationof the subdivision POS. 11
  17. 17. Margaret River Wastewater Reuse Project - Stage 1 ReportRainwater tanks could be fitted and plumbed to each house to harvest rainwater for in-houseand ex-house purposes. Due to the Mediterranean climate experienced in the south west ofWestern Australia, winters are wet and cold, while summers are dry and hot, rainwater tanksare most useful when plumbed for in-house use to take advantage of high winter rainfall. Thiswater can be used for toilet flushing and washing machines and contributes to the overallreduction of scheme water over the year. In addition, a small amount of rainwater could beused in the garden to offset a portion of the water required by the third pipe system.A study undertaken by Marsden Jacob and Associates in March 2007 shows rainwater yieldsfrom various roof areas and rainwater tanks plumbed for in-house and ex-house use. Theresults summarised below in Table 8 are based on Perth rainfall and therefore are consideredslightly conservative.Table 8: Annual rainwater tank yields for Perth Tank Size 2 kL 5 kL 10 kL Roof Area 50m2 200m2 50m2 200m2 50m2 200m2 Annual Yield (KL) 29 58 30 74 30 84Adapted from Marsden Jacob Associates (2007)Houses with a 50m2 roof area and 2,000 L rainwater tank would yield approximately 29,000L a year. Larger houses with a roof area of 200m2 would yield approximately 58,000 kL peryear. On this basis, the installation of rainwater tanks plumbed to the house for in-house andex-house use should be strongly encouraged in new subdivisions.Installing rainwater tanks to all new houses would also reduce the demand for scheme watersupply to the subdivision. If rainwater tanks where installed to supply 100% of the needs ofinternal potable water use (drinking, washing, etc), then a roof area between 200 and 250 m2and a tank size between 45 kL and 70 kL would need to be established in order for the 99%reliability criteria to be met (GHD, 2007). Centralised vs Decentralised Treatment SystemsThe water balance calculations have identified that there is sufficient water to proceed withStages 1 and 2 of the project. There are two possible options that could be considered for thefuture urban areas (Stage 3).Two different scenarios have been assessed for the development of Stage 3. Scenario 3involves a conventional centralised treatment system requiring main sewerage and third pipeconnection to all new subdivisions. Scenario 4 involves provision for subdivision scaledecentralised systems and would involve subdivisions to be self sufficient in water treatmentand reuse. Table 9 below briefly summarises the advantages and disadvantages of centralisedand decentralised systems.Table 9: Advantages and disadvantages of centralised and decentralisedtreatment systemsTreatment System Advantages of system Disadvantages of system • Shire can defer responsibility for • Cost and energy use for installation andScenario – 3 management of the expanded operation;Centralised Third-Pipe system to Water Corporation; • Conventional and expensive deepSystem from • Preferred by WA Dept of Health. sewerage with pump stations;MRWWTP • Disturbance to townsite during installation.Scenario – 4 • Closed loop system, whereby water • Shire and/or developers may need to 12
  18. 18. Margaret River Wastewater Reuse Project - Stage 1 ReportSubdivision scale and nutrients treated and reused develop new internal systems orDecentralised onsite; subcontract arrangements toTreatment Plant • Reduced pumping and energy costs; manage and maintain the DWWTP; • Less expensive shallow sewerage • Need to develop winter storage or and fewer pump stations; recharge facilities on a case by • Reduced disturbance to townsite case basis; during installation; • Water Service Providers License may • In the event of a breakdown, only the be required from ERA; subdivision is impacted. • Regular monitoring and reporting to regulatory authorities.The Murdoch University Environmental Technology Centre has prepared a database of over150 commercially available DWWTPs from around Australia and the world and categorisedthem in terms of their treatment type and application. Summary of Water Reuse ScenariosThe water available or required under each scenario is summarised in Table 10 and discussedbelow.Table 10: Summary of water balance under each scenarioScenarios Available water per year Water required from other (kL) sources per year (kL)Scenario – 1: Existing POS Areas (28 ha) 134,000 0Scenario – 2: Margaret River Golf Course (25 ha) 0 54,000*Scenario – 3: Third Pipe to Future Urban Areas 2026 68,000 0Scenario – 4: DWWTP: Part A – 1 subdivision 0 24,000*Scenario – 4: DWWTP: Part B (winter – recharge) 38,000 0Scenario – 4: DWWTP: Part B (summer) 0 60,000** Water required from other sources (e.g. river water, rainwater tanks or dam water)Scenario 1 – no additional water is required and approximately 134,000 kL of water isavailable for further irrigation use. This could be disposed to the adjacent pine plantation until2009 or treated to a suitable quality for aquifer recharge.Scenario 2 - approximately 54,000 kL of additional water would need to be derived fromother sources such as groundwater for the months of February, March and April tosupplement the third pipe water.Scenario 3 – no additional water is required and approximately 68,000 kL would be availablefor other uses in 2026. Estimates show that the total required water to accommodate scenario3 (approximately 828,000 kL) could be available by 2025.Scenario 4 - approximately 7,500 kL of water per month will need to be reused during theMay to September period or approximately 38,000 kL over the 5-month period. This watercould be reused in several different ways depending on the opportunities and constraintspresented at each individual subdivision.During summer, approximately 60,000 kL of additional water will be required for irrigationof the POS, toilet flushing and garden irrigation within the subdivision. The majority of thiswater will be used for household garden irrigation. The additional water could be obtainedfrom a combination of sources such as groundwater and rainwater tanks plumbed to the housefor in-house and ex-house use. 13
  19. 19. Margaret River Wastewater Reuse Project - Stage 1 ReportCost Benefit AnalysisThe water available or required and associated capital costs under each scenario aresummarised in Table 11 and discussed below (Refer to Appendix 4 for NPV calculations).Table 11: Summary of water balance, NPV and NPV/kL under each scenarioScenarios Reused Available Water NPV ($m) NPV ($) over wastewater water p.a. (kL) required from over 25 25 years at (kL) other years at 10% per kL of sources p.a. 10% recycled (kL) wastewaterScenario – 1Existing POS Areas (28 211,000 134,000 0 2.21 10.49ha)Scenario – 2Margaret River Golf 399,000 0 54,000* 5.18 13.00Course (25 ha)Scenario – 3Third Pipe to Future 828,000 88,000 0 10.34 12.50Urban AreasScenario – 4 399,000 0 24,000* 5.18 13.00DWWTP: Part AScenario – 4DWWTP: Part B (winter 38,000 0 21.46– recharge) 140,000 2.56Scenario – 4DWWTP: Part B 0 60,000* 21.46(summer) • Water required from other sources (e.g. groundwater, river water, rainwater tanks or dam water) • Note CSO and headworks reductions for Scenario 4B. Refer text below.The costs presented in Table 11 build on the previous costing done by Wood and Grieve(2006) with additional development to account for in-house third pipe and decentralisedsystems. Wood and Grieve (2006) estimated an “order of magnitude” capital cost of$1,890,000 (plus GST) for a 135ML/year reuse system.In order to normalise the capital and operating costs for the various scenarios net presentvalues (NPV) have been calculated assuming an effective life of 25 years (with depreciationto 10%) and 10% discount rate. A sensitivity analysis was conducted with 7%, 10% and 15%discount rates.Supply mains as expected are the single largest component of these costs for all scenarios,except Scenario 4, due to the relatively large distances involved in the transfer of treatedwastewater. Annual pumping costs have been calculated but are relatively minor. Other coststo be incurred but not as yet quantified are ongoing water quality monitoring costs as requiredby the relevant regulatory authorities. Sale of the treated wastewater (third pipe water andgolf course) can be expected to contribute to offsetting these annual operating costs.Scenarios 2 and 3 are comparable in terms of dollars per kilolitre of wastewater treated($13/kL and $12.5/kL respectively) despite the near doubling in size of infrastructure capitaloutlay. This is due to the efficiencies to be gained in Scenario 3 due to the increased volumesbeing supplied, again nearly double. 14
  20. 20. Margaret River Wastewater Reuse Project - Stage 1 ReportScenario 4B represents a near doubling ($21.46/kL) in the cost of treated wastewater on a$/kL basis when compared to Scenarios 2 and 3 on a pure ‘infrastructure only with somerebate’ basis. The external factors which have a significant impact on this outcome are: • Cost of treating the wastewater and providing potable water. All other scenarios do not include the cost of treating the wastewater (Customer Service Obligations (CSO) are currently borne by Water Corp/State Government and are typically $3,000-$4,000 pa/connection for water and wastewater service); • Headworks charges. Headworks per lot are water = $3,278, wastewater = $1,514 at full rates; and • Increasing tariffs. It can be assumed that the cost to the consumer for the provision of potable water and wastewater treatment is likely to rise above historic rates in the near future.Scenarios 1-3 do not include the cost of wastewater treatment by the Water Corporation,typically $3,000-$4,000 pa/connection for water and wastewater service. In order to allow atrue comparison of the various scenarios on an economic basis is necessary therefore that thetrue cost of wastewater treatment either be added to these scenarios (1-3) OR deducted fromScenario 4. The latter approach has been taken here. CSOs were identified as a significantissue in the Gracetown Development Project (GHD, 2007).On this basis for Scenario 4 an annual CSO equivalent of $1,000pa/connection has beenapplied with a full one-off headwork reduction for wastewater of $1,514. That is, noreductions in potable water and full reductions (100%) for wastewater have been applied.Despite this the NPV/kL is still approximately twice the other scenarios.Of note however is the significant impact that would occur with reductions in headworks andCSOs for potable water. This has been illustrated as Scenario 4B with full water rebate asshown in Appendix 4 and reveals a NPV of +$95/kL. The implication of this for futurestandalone developments is that subdivisions that are able to operate completely independentof the Water Corporation and receive headworks reductions and CSO returns under thecurrent rebate policy would return a positive cashflow to the developer (or community).Several additional issues that may need to be addressed include: a) The state of the existing pump station at the Margaret River crossing. Wood and Grieve (2006) have allowed a provisional $50,000 to upgrade however this may be inadequate in the short term and certainly in the medium term; b) The hours during which irrigation with treated effluent may occur. Experience from the McGillvray Oval scheme indicates that subject to DoH conditions, and the high use of the Gloucester Park ovals, increased main sizes may be required to ensure all irrigation occurs in a reduced irrigation time window. This has a significant cost implication; c) Gypsum injection is often recommended for treated wastewater irrigation schemes and while it represents additional costs (capital and on-going) there exist merits for its consideration. 15
  21. 21. Margaret River Wastewater Reuse Project - Stage 1 ReportManagement PlansThe Health Act 1911 contains a number of provisions that regulate the use of recycled water.The WA Department of Health (DoH) requires the preparation of the following documentsfor approval of the Project: • Operation and Maintenance Plan; • Monitoring Plan; and • Reporting regime.The DoH has recently published guidelines on providing homes with recycled water via thirdpipe systems. The “Guidelines for the Use of Recycled Water in Western Australia”(Appendix 3) were released in January 2007. In summary the guidelines provide informationto planners, designers, installers and users of recycled water systems, with the objectives of: • Encouraging and providing guidance on the beneficial use of recycled water; • Reducing impact to public health and the environment; • Providing guidance for the planning, design, operation and monitoring of recycled water systems; and • Outlining statutory approvals needed for reuse schemes. (Department of Health, 2007).For wastewater reuse schemes the DoW has two Water Quality Protection Notes (WQPN)that outline procedures that should be followed: • WQPN 22, July 2006 Irrigation with nutrient-rich wastewater; and • WQPN 33, July 2006 Nutrient and irrigation management plans.Nutrient and irrigation management plans (NIMPs) are detailed guidelines for theestablishment and growing of crops, gardens, trees or turf. NIMPs demonstrate that inputssuch as water and fertiliser should be well matched to the plant growth cycle resulting inminimal contaminant leaching into the surrounding environment. The DoW requires NIMPsfor rural and recreational land areas exceeding 5,000 square metres where vegetation isirrigated, fertiliser is applied, animals are held intensively in paddocks and/or organic solidscontaining nutrients are spread onto the land. NIMPs are also suited to sites where industrialor municipal wastewater rich in nitrogen (N) and phosphorus (P) is applied to foster thegrowth and maintenance of healthy vegetation. They may be required for lesser areas wherelocal water values are particularly sensitive to nutrient contamination.If the Shire decides to run the DWWTP itself independent from Water Corporation it willneed to use a licensed subcontractor or secure a Water Service Providers License (SewerageServices) from the Economic Regulation Authority of Western Australia (ERA). This willrequire preparation of all of the plans above beforehand and approvals from the agenciesmentioned above before the licence can be granted. These provisions are listed under theWater Services Licensing Act 1995.Community ConsultationA community consultation program for the Project has been initiated by the SAMR. To datevarious publications, surveys and information have been distributed to the community ofMargaret River. These include: • Specific stakeholder consultation with developers and catchment groups; 16
  22. 22. Margaret River Wastewater Reuse Project - Stage 1 Report • Articles in the local newspaper; • Discussions with local radio; • Inclusion of water recycling in the 2007 community survey; and • Articles in local shire briefs/publications.Informal discussions with the SAMR have indicated that the Margaret River community hasbeen very supportive of the Project so far. Ongoing consultation will be required by theSAMR and a Community Consultation Outcomes Report submitted to the relevant agenciesin order to proceed through the approvals process. 17
  23. 23. Margaret River Wastewater Reuse Project - Stage 1 ReportEcological and Social Benefits of the ProjectThe ecological benefits of the project include a considerable increase in environmental flowsfor the Margaret River (approximately 169,000 kL/per year) (based on 2007 abstraction rates)and the associated indirect downstream ecological benefits as a result of increased watervolumes in the river. If the MRGC were supplied with treated wastewater, there would be adecrease in groundwater abstraction from the local aquifer (up to approximately 188,000kL/per year, 2007 rates) and therefore associated indirect benefits.In addition to the ecological benefits, the project will provide social benefits due to theincreased river flows, these include; a healthier looking river and the potential for increaseddownstream eco-tourism activities in the river during the summer months, due to thecessation of river abstraction. The quality of recreational facilities will also be able tomaintained by the SAMR as a secure source of treated water will available for irrigationpurposes.The project also presents a positive message to the local Margaret River community in termsof sustainable water management and urban wastewater reuse and sets a precedent for otherurban wastewater reuse projects in Western Australia. 18
  24. 24. Margaret River Wastewater Reuse Project - Stage 1 ReportRecommendationsThe following recommendations are provided: • Undertake further feasibility studies to identify potential opportunities and constraints of centralised and decentralised wastewater treatment systems in future subdivisions (Scenario 3 and 4); • The MRGC investigate ways of reducing overall water use based on current best practice in the industry; • Plan to incorporate sustainable water use options in all future residential areas. A comparison of the costs/benefits of mandatory onsite greywater treatment units, water efficient appliances and domestic rainwater tanks (plumbed) for future subdivisions would be of merit; • The SAMR formulate strategies for reducing and phasing out river abstraction in consultation with the DoW and other key stakeholders; and • Investigate concerns/issues that the public may have with respect to the implementation of DWWTP and third pipe projects through a community consultation process.Future tasks would include: • Supply modelling - Identify the necessary supply elements from source to final application including hardware, supply organisations’ and consumers’ responsibilities in terms of operation and maintenance; • Treatment level - Investigate current and possible treatment levels with existing infrastructure, treatment levels required for different supply models; • Determine the existing and likely future legal requirements pertaining to Customer Service Obligations. Refer ERA (2007); • Regulatory requirements under various State legislation such as: o Environmental Protection Act 1986 (Works Approval and Operating Licence) administered under DEC; o Health Act 1911 (Guidelines for the Use of Recycled Water) administered under DoH; and o Water Services Licensing Act 1995 (Water Service Providers License) administered under ERA. • Prepare appropriate management plans for government regulatory departments, these include, Nutrient and Irrigation Management Plan (DoW) and an Operation and Maintenance Plan (DoH).Following the findings of this report, it is recommended that the SAMR move towards the useof recycled water for non-potable purposes such as irrigation of POS and the golf course(scenarios 1 and 2). 19
  25. 25. Margaret River Wastewater Reuse Project - Stage 1 ReportIn the longer term, the SAMR should consider the integration of current best practice andplanning into all new future residential areas with the aim that newly developed areas are selfsufficient in terms of water treatment and reuse based on decentralised treatment systems, orprovision for a third pipe, where practical. Rainwater harvesting for internal potable purposesshould also be considered as a part of the overall water management strategy of future urbanareas. 20
  26. 26. Margaret River Wastewater Reuse Project - Stage 1 ReportReferencesDepartment of Health (2007) Guidelines for the Use of Recycled Water in Western Australia.January 2007.Environmental Protection Heritage Council (2006) Australian Guidelines for WaterRecycling: Managing Health and Environmental Risks” Phase 1. National Water QualityManagement Strategy. November 2006.Economic Regulation Authority (2007). Draft Report. Inquiry on Competition in the Waterand Wastewater Services Sector. ERA WA.GHD (2007) Gracetown Development Project - Phase 1 Sustainable Water and WastewaterServices. Prepared for Landcorp. August 2007.Government of Western Australia (2007) 5 Star Plus – Energy Use in Houses Code andWater Use in Houses Code. Department of Housing and Works. May 2007.HydroPlan (2005) Preliminary Figures. HydroPlan Pty Ltd. November 2005.Marsden Jacob and Associates (2007) The Cost-Effectiveness of Rainwater Tanks in UrbanAustralia. Prepared for the Australian Government National Water Commission. March 2007.Shire of Augusta-Margaret River (2007) East Margaret River Public Open Space andLandscape Development Guidelines. Prepared by the Shire of Augusta-Margaret River 2007.Tchobanoglous, G. (1995) Decentralised Systems for Wastewater Management. Presented atthe Water Environment Association of Ontario Annual Conference, Toronto, Canada.Tchobanoglous, G. (1996) Appropriate Technologies for Wastewater Treatment and Reuse,Australian Water and Wastewater Association. Water Journal, Vol.23, No.4.Water Corporation (2001) Domestic Water Use Study in Perth, Western Australia 1998 –2001. March 2001.Wood and Grieve (2006) Margaret River Waste Water Reuse Feasibility InvestigationReport. Prepared for the Lester Group. May 2006. 21
  27. 27. Margaret River Wastewater Reuse Project - Stage 1 ReportAppendix 1: Margaret River Wastewater Reuse Scenarios - WaterBalance 22
  28. 28. Margaret River Wastewater Reuse Project - Stage 1 ReportAppendix 2: Water Balance AssumptionsThe following assumptions and calculations have been applied to the water balance model: 1. No industrial wastewater is included in the volumes; 2. Estimated area of wastewater treatment dam - 300m x 100m = 30,000m2; 3. Water required for irrigation of schools and ovals (except Riverslea subdivision) (2007) approximately 134,000 kL/per year (17.8 ha) or 7528 kL/per ha/per year (7 months); 4. Irrigation of Shire POS areas (including Riverslea subdivision) = 168,626 kL (22.4 ha) for 7 months (note April and October halved and added to summer months December and January); 5. 2026 Population projections - 12,500 (Source: Water Corporation); 6. Wastewater inflow volumes (Source: Water Corporation) 2007 = 358,526 kL per year (982 kL per day); 2015 = 550,000 kL per year (1507 kL per day); 2026 = 910,000 kL per yer (2493 kL per day); 7. Available wastewater volumes (plus rainfall - evaporation) minus 14,000 kL per year 2007 = 345,000 kL per year (945 kL per day); 2015 = 536,000 kL per year (1468 kL per day); 2026 = 896,000 kL per year (2455 kL per day); 8. Scenario 3: Third pipe water usage for toilet flushing and irrigation at future urban areas = 2000 houses within approximately 3 subdivisions; Toilet flushing = 112 L/hse/day, garden irrigation (ex-house) = 500 L/hse/day = 612 L/hse/day. (Data derived from single residential figures [Perth Domestic Water Study] and Water Corporation figures; Summer: Oct - Apr = 612 L/hse/day x 2000 hse/lots = 1224 kL/day x 212 days = 260,000 kL/year (toilet flushing and irrigation); Winter: May - Sep = 112 L/hse/day x 2000 hse/lots = 224 kL/day x 153 days = 34,000 kL/year (toilet flushing, no irrigation); Total = 294,000 kL/per year for toilet flushing and garden irrigation (ex-house activities); Summer garden irrigation only = 500 L/hse/day x 2000 hse/lots x 212 days = 212,000 kL (summer) (Source: Perth Domestic Water Study, Water Corporation 2001); 23
  29. 29. Margaret River Wastewater Reuse Project - Stage 1 Report Scenario 3: Third pipe water usage for POS at future urban areas (Stage 3), 18 ha @ 7528 kL/ha/year = 135,000 kL/year. An irrigation year = 7 months or 212 days (No irrigation May - Sep); Scenario 3 - Future population (2026) = 7,000 (MR Town, infill and EMR area) + 5,500 (Future Residential Areas) = 12,500;9. Scenario 4: Total in-house water use (1 subdivision to DWWTP) (based on single residential figures + Water Corporation) = 500 L/hse/day x 365 days x 650 hse/lots = 118,625 kL/year; Blackwater = 112 L/hse/day (toilet) + 75 L/hse/day (Tap), Greywater = 170 L/hse/day (Bath and Shower) + 130 L/hse/day (Washing Machine), Other = 13 L/hse/day. Total = 500 L/hse/day (Water Corporation projections);10. Scenario 4 - treated water usage: Toilet flushing = 112 L/hse/day, garden irrigation (ex-house use) = 500 L/hse/day = 612 L/hse/day (Data based on single residential figures - Perth Domestic Water Study); Summer: Oct - Apr = 612 L/hse/day x 650 houses/lots = 398 kL/day x 212 days = 84,376 kL/year (toilet flushing and irrigation, ex-house); Winter: May - Sep = 112 L/hse/day x 650 houses/lots = 72.8 kL/day x 153 days = 11,138 kL/year (toilet flushing, no irrigation); Total yearly for 1 subdivision (650 lots) = 95,514 kL/per year for toilet flushing and garden irrigation; Yearly volume - toilet flushing = 112L/hse/day x 650 houses/lots x 365 days = 26,572 kL/year; Yearly volume - irrigation, ex-house (Oct-Apr) = 500L/hse/day x 650 houses/lots x 212 days = 68,900 kL/year;11. Rapids Landing (Lot 27 subdivision), total land area 82.5 ha, 650 lots @ 2.6 occupants per lot = 1690 persons (Simon Munckton Lester Group, pers comm);12. Third pipe water usage for POS (6 ha) at Rapids Landing subdivision, 7528 kL/ha/year = 45,168 kL/year. Irrigation year consists of 7 months or 212 days (No irrigation between May and September);13. BoM data (rainfall and evaporation) sourced from Witchcliffe and Jarrahwood respectively; and14. Margaret River Golf Course irrigation rates based on 25 ha @ 7500 kL/ha = 187,500 KL no winter watering between June and August. Note May and September halved and added to summer months December and January. 24
  30. 30. Margaret River Wastewater Reuse Project - Stage 1 ReportAppendix 3: Guidelines for the Use of Recycled Water in WesternAustralia 25
  31. 31. Appendix 1Wastewater Reuse Study - Water BalanceShire of Augusta Margaret RiverMain Sewer connections 1768Available sewer connections 2734(Source: Water Corporation) (2007)Wastewater treatment dam - surface area 30,000 (m2)Evaporation factor of storage area 1Max designed capacity of treatment dam 450,000 (kL)Vegetation type of irrigated area TurfCrop factor 0.6Irrigation efficiency 85 (%)Total irrigated area (Shire area 07/08) 28 (ha)Monthly Rainfall and Evaporation Data May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr TotalMonthly rainfall (mm) - Witchcliffe 2006 50.8 88.6 139.8 194 73.2 66.6 68.8 10 18.2 3.8 26.4 35.4 776Monthly evaporation (mm) - Jarrahwood 2006 (sum of -56 -38.6 -52.2 -65.6 -71.1 -120.4 -133.4 -183.1 -158 -148 -135.6 -66.6 -1,229availble daily totals) (Source: BoM)Rainfall to treatment dam minus evap (kL)(-ve -156 1,500 2,628 3,852 63 -1,614 -1,938 -5,193 -4,194 -4,326 -3,276 -936 -13,590values represents evaporation from dam)Wastewater May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr TotalWastewater inflow at treatment dam (kL) 28,582 26,070 27,280 33,821 29,610 30,938 30,540 30,256 31,372 27,720 31,527 30,810 358,526Wastewater inflow at treatment dam (kL/day) 922 869 880 1,091 987 998 1,018 976 1,012 990 1,017 1,027 982(Source: Water Corporation)Total monthly wastewater plus rainfall-evap 28,426 27,570 29,908 37,673 29,673 29,324 28,602 25,063 27,178 23,394 28,251 29,874 344,936(Available for irrigation) (kL) No Shire irrigation undertaken during winterIrrigation Requirements May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr TotalShire irrigation POS Stage 1 (28 ha) (kL) 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784Golf course irrigation requirements (25 ha) (kL) 10,416 0 0 0 10,416 20,833 20,833 31,249 31,249 20,833 20,833 20,838 187,500Future urban areas third pipe (toilet/garden) (kL) 5,300 5,300 5,300 5,300 5,300 38,175 38,175 38,175 38,175 38,175 38,175 38,175 293,725Future urban areas third pipe (for POS, 25.8 ha) (kL) 0 0 0 0 0 13,873 27,746 41,619 41,619 27,746 27,746 13,873 194,222Total irrigation requirements 15,716 5,300 5,300 5,300 15,716 87,937 116,866 156,211 156,211 116,866 116,866 87,942 886,231(Source: SoAMR)Current pine plantation irrigation May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr TotalTotal monthly wastewater available 28,426 27,570 29,908 37,673 29,673 29,324 28,602 25,063 27,178 23,394 28,251 29,874 344,936Pine irrigation (Source:Water Corporation) 30,028 0 2,070 36,435 49,003 14,894 37,409 34,361 34,884 24,539 34,061 26,013 323,697Dam level (kL) -1,602 27,570 27,838 1,238 -19,330 14,430 -8,807 -9,298 -7,706 -1,145 -5,810 3,861 21,239Scenario 1 - Shire POS (28 ha) May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr TotalSupply StartTotal available wastewater for irrigation (kL) Dam 28,426 27,570 29,908 37,673 29,673 29,324 28,602 25,063 27,178 23,394 28,251 29,874 344,936Demand LevelPine plantation irrigation 06/07 (not included) 0 30,028 0 2,070 36,435 49,003 14,894 37,409 34,361 34,884 24,539 34,061 26,013 323,697Existing Shire irrigation POS (28 ha) (kL) (kL) 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784Dam level/avail for pines (kL) cumulative 28,426 55,996 85,904 123,577 153,250 167,518 166,008 145,903 127,913 121,195 119,334 134,152 134,152Scenario 2 -Shire POS (28 ha) + Golf Course (25 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Totalha)Supply StartTotal available water for irrigation (kL) Dam 28,426 27,570 29,908 37,673 29,673 29,324 28,602 25,063 27,178 23,394 28,251 29,874 344,936Demand LevelExisting Shire irrigation POS Stage 1 (28 ha) (kL) 0 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784Golf course irrigation requirements (25 ha) (kL) (kL) 10,416 0 0 0 10,416 20,833 20,833 31,249 31,249 20,833 20,833 20,838 187,500Total water required (kL) 10,416 0 0 0 10,416 35,889 50,945 76,417 76,417 50,945 50,945 35,894 398,284Dam level (kL) cumulative 18,010 45,580 75,488 113,161 132,418 125,853 103,510 52,156 2,917 -24,634 -22,694 -6,020 0Water required from other sources - approx -24,634 -22,694 -6,020 -53,348Scenario 3 - third pipe to future urban areas (3 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Totalsubdivisions-18 ha POS) 2026 (+ scenario 1 and2)SupplyTotal available water for irrigation (kL) Start 74,666 74,666 74,666 74,666 74,667 74,667 74,667 74,667 74,667 74,667 74,667 74,667 896,000Demand Dam
  32. 32. Existing Shire irrigation POS Stage 1 (28 ha) (kL) Level 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784Golf course irrigation requirements (25 ha) (kL) 0 10,416 0 0 0 10,416 20,833 20,833 31,249 31,249 20,833 20,833 20,838 187,500Future urban areas third pipe (for toilet/garden) (kL) (kL) 6,800 6,800 6,800 6,800 6,800 37,142 37,143 37,143 37,143 37,143 37,143 37,143 294,000Future urban areas third pipe (for POS, 18 ha) (kL) 0 0 0 0 0 9,644 19,286 28,927 28,927 19,286 19,286 9,644 135,000Total water required (kL) 17,216 6,800 6,800 6,800 17,216 82,675 107,374 142,487 142,487 107,374 107,374 82,681 827,284Dam level (kL) cumulative 57,450 125,316 193,182 261,048 318,499 310,491 277,784 209,964 142,144 109,437 76,730 68,716 68,716Water required from other sources - approx 0Scenario 4 - Part A existing third pipe facilites May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Totalfrom MRWWTD to POS + MRGC.Part B - DWWTP + third pipe from DWWTP forfuture urban areas (1 subdivision only) POS (6ha) + household toilet and gardenPart ASupply (2007 volumes plus additional 30,000 kL/per year)Total available water for irrigation (kL) (2007 volumes) Start 31,250 31,250 31,250 31,250 31,250 31,250 31,250 31,250 31,250 31,250 31,250 31,250 375,000Demand DamExisting Shire irrigation POS Stage 1 (28 ha) (kL) Level 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784Golf course irrigation requirements (25 ha) (kL) 0 10,416 0 0 0 10,416 20,833 20,833 31,449 31,449 20,833 20,833 20,838 187,900Total water required (kL) (kL) 10,416 0 0 0 10,416 35,889 50,945 76,617 76,617 50,945 50,945 35,894 398,684Dam level (kL) cumulative 20,834 52,084 83,334 114,584 135,418 130,779 111,084 65,717 20,350 655 -19,040 -4,644 0Water required from other sources - approx -19,040 -4,644 -23,684Part BSubdivision scale water balance (stand alone) -based on 650 persons per 1 subdivision (DWWTP)SupplyWastewater from subdivision to DWWTP (In-house 9,885 9,885 9,885 9,885 9,885 9,885 9,885 9,885 9,885 9,885 9,885 9,890 118,625blackwater and greywater) (kL)DemandFuture subdivision third pipe from DWWTP for 2,228 2,228 2,228 2,228 2,226 12,053 12,053 12,053 12,053 12,053 12,053 12,058 95,514toilet/garden (kL)Future subdivision third pipe from DWWTP for POS (6 0 0 0 0 0 2,845 6,453 10,061 10,061 6,453 6,453 2,845 45,168ha) (kL) (Based on 7528 kL/per ha/per year)Total water required (kL) 2,228 2,228 2,228 2,228 2,226 14,898 18,506 22,114 22,114 18,506 18,506 14,903 140,682Available water after reuse 7,657 7,657 7,657 7,657 7,659 -5,013 -8,621 -12,229 -12,229 -8,621 -8,621 -5,013Water to be recharged locally (Winter) 7,657 7,657 7,657 7,657 7,659 0 0 0 0 0 0 0 38,287Water required from other sources - approx 0 0 0 0 0 -5,013 -8,621 -12,229 -12,229 -8,621 -8,621 -5,013 -60,344(summer)Summary - Irrigation ScenariosStage 1Scenario 1 - existing Shire POS areas (28 ha) includes schools, gloucester park and EMR POS (Riverslea, Rapids Landing and Brookfield)Stage 2Scenario 2 - existing Shire POS areas (28 ha) includes schools, gloucester park and EMR POS (Riverslea, Rapids Landing and Brookfield) - Golf Course (25 ha)Stage 3Scenario 3 - existing Shire POS areas (28 ha) includes schools, gloucester park and EMR POS (Riverslea, Rapids Landing and Brookfield) - Golf Course (25 ha) OR - third pipe to future urban areas (approx 3 subdivisions) POS (18 ha), and household toilet flushing and garden irrigation from MRWWTP (2026)Scenario 4 - Part A - existing Shire POS areas (28 ha) includes schools, gloucester park and EMR POS (Riverslea, Rapids Landing and Brookfield) - Golf Course (25 ha) - Part B - Installation of Decentralised Wastewater Treatment Plant (DWWTP) to each new subdivision - third pipe from DWWTP to POS (6 ha) and toilet flushing and garden irrigation, local irrigation, no third pipe from MRWWTD
  33. 33. Margaret River Wastewater Reuse Project - Stage 1 ReportAppendix 4: Net Present Value (NPV) Calculations ECONOMIC ASSESSMENT OF MARGARET RIVER WASTEWATER REUSE Assumptions Description ValueMains electricity price ($/kWh) 0.13Synergy buyback price ($/kWh) 0.13 Not usedMains water price ($/kL) 0.60 Not usedDiscount rate 0.10 All cash flows are incremental, replacing baseline or default equipment NPV Model Maintenance Headworks Revenue cost - Value of Salvage value Effective life savings ($) - Capital cost ($/yr) - Operational nominal energy/water ($ @ end of NPV Volumes Item (yrs) Note 1 ($) Note 2 cost ($/yr) ($/yr) saved ($/yr) life) ($) (ML) NPV ($/kL) Development scenarios 10% Scenario W&G 25 Payable $1,925,000 $3,700 $1,000 $1 $192,500 -$1,949,886 135 -$14.444 Scenario 0 25 Payable $1,925,000 $4,700 $1,000 $1 $192,500 -$1,958,963 170 -$11.523 Scenario 1 25 Payable $2,126,549 $10,750 $1,000 $1 $212,655 -$2,213,568 211 -$10.491 Scenario 2 25 Payable $5,020,693 $22,200 $1,000 $1 $502,069 -$5,184,932 399 -$12.995 Scenario 3 25 Payable $10,112,100 $34,500 $1,000 $1 $1,011,210 -$10,340,995 827 -$12.504 Scenario 4A 25 Payable $5,020,693 $22,200 $1,000 $1 $502,069 -$5,184,932 399 -$12.995 Scenario 4B 25 $984,100 $7,135,000 650,000 $260,000 $1,000 $1 $713,500 -$2,554,069 119 -$21.463 Scenario 4B with full water rebate 25 $3,114,800 $4,020,200 1,950,000 $260,000 $1,000 $1 $402,020 $11,348,035 119 $95.362Note 1: Headworks cost savings/lot assuming no reduction for water and 100% reduction for wastewater ($1514). Full potential reduction for water (100% = $3278).Note 2: Annual CSO equivalent of wastewater has been assumed at 100% (=$1000pa). Allow 0% reduction in potable water due to recycled water for potable water supply for Scenario 4.Total potential CSO is $3,000pa/connection for water ($2000) and wastewater ($1000). 26
  34. 34. Guidelines for the Use of Recycled Water in Western Australia 16 January 2007Guidelines for the use of Recycled Water in Western Australia -30/08/06 Page 1 of 66

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