Margaret River Water Recycling Water Balance and Cost Benefit Analysis

ETC cover page

Shire of Augusta – Margaret River

Margaret River Wastewater Reuse
Water Balance & Cost
Benefit Analysis Report
21/2/2008

Margaret River Wastewater Reuse Project - Stage 1 Report

Authors:
This report has been prepared by Cameron Everard, Dr Stewart Dallas and Dr Martin
Anda of the Murdoch University Environmental Technology Centre (ETC).

Document Governance and Intended Usage
This document has been produced for the sole use of the client only and any use by a
third party may lead to inappropriate use of information. This document is deemed
correct at the time of publication and its accuracy and appropriateness may change
when further knowledge becomes available. Murdoch University and the
Environmental Technology Centre accept no responsibility for inappropriate use of
this document and may take legal action where copying and reproduction of the
materials within this document are used for consultancy and education without written
prior permission from the Client and the Environmental Technology Centre
management.

i


Margaret River Wastewater Reuse Project - Stage 1
Water Balance and Cost Benefit Analysis Report

Executive Summary
The Shire of Augusta-Margaret River commissioned Murdoch University Environmental
Technology Centre to conduct a study into the options for wastewater reuse in and around the
town 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 net
present value (NPV) costs are summarised below:

Stages of Development Scenarios Cost NPV
(Chronological) $ per kL of reused wastewater
Stage 1 Scenario – 1: Existing POS Areas (28 ha) 10.49
Stage 2 Scenario – 2: Margaret River Golf Course (25 ha) 13.00
Stage 3 Scenario – 3: Third Pipe to Future Urban Areas 12.50
OR Stage 3 Scenario – 4: DWWTP: Part A 13.00
Scenario – 4: DWWTP: Part B (winter – recharge) 21.46
Scenario – 4: DWWTP: Part B (summer) 21.46
Note: Scenarios 1-3 exclude cost of wastewater treatment. Scenario 4 includes full wastewater treatment with
some allowance for reduction in wastewater headworks and CSOs, The potential impact of both headworks and
CSOs is significant and is discussed in detail in the Cost Benefit Analysis.

Stage One - Scenario 1 – Existing POS areas
Scenario one would include irrigation of all current Shire POS areas with treated wastewater
from the MRWWTD, (includes schools, Gloucester Park and East Margaret River (EMR)
POS (Riverslea, Rapids Landing and Brookfields) (28 ha). Does not include third pipe
connection for household toilet flushing or garden irrigation to these subdivisions.

Stage Two - Scenario 2 – Margaret River Golf Course
This scenario would comprise irrigation of all current Shire POS areas with treated
wastewater from the MRWWTD, (includes schools, Gloucester Park and EMR POS
[Riverslea, Rapids Landing and Brookfields], 28 ha). This scenario also includes irrigation of
the 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 water
supplied from MRWWTD to subdivision households (for garden irrigation and toilet
flushing) and irrigation of subdivision POS. Will require mains sewerage connection to the
MRWWTD 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 Wastewater
Treatment Plants (DWWTP)

ii


Scenario 4 consists of two parts, Part A comprises the existing third pipe facilities from the
MRWWTD to the Shire POS areas and the MRGC undertaken in Scenarios 1 and 2. As this
infrastructure 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. All
wastewater produced in the subdivision will be directed to subdivision scale DWWTP for
treatment. Treated water from this unit could be used directly for irrigating POS within the
subdivision during the summer months and supplied to the households for toilet flushing and
garden irrigation. The subdivision would be considered a closed loop system, collecting
treating and recycling the wastewater within the subdivision. Each DWWTP would be
designed 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 the
subdivision POS. As this scenario is considered to be a closed loop system it does not require
third pipe connection from the MRWWTD and due to low winter volumes should not need
main sewerage connection. Greywater could be either treated and recycled at the household
scale 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 will
need to use the services of a licensed sewerage service provider or secure its own Water
Service Providers License (Sewerage Services) from the ERA or in some instances where
appropriate require land developers to secure their own license.

The ecological benefits of Stage 1 of the project include a considerable increase in
environmental flows for 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 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 therefore
associated indirect benefits. There would also be a further reduction in future water needs as
Stage 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 due
to the increased river flows, these include; a healthier looking river and the potential for
increased downstream eco-tourism activities in the river during the summer months, due to
the reduction in river abstraction. The treated wastewater will secure a water source for the
irrigation of parks and public facilities into the future.

The project also presents a positive message to the local Margaret River community in terms
of sustainable water management and urban wastewater reuse and sets a precedent for other
urban wastewater reuse projects in Western Australia. The reuse of treated wastewater has
been successfully undertaken by more than 60 Shire councils around Western Australia for
several decades in order to secure sustainable water management practices. The State Water
Strategy has also set a target of reusing 20% of treated wastewater sources by 2012.

iii


CONTENTS

Executive Summary...................................................................................................ii
Introduction ............................................................................................................... 1
Background ........................................................................................................... 1
Recent Policy Developments.................................................................................. 1
Objectives.............................................................................................................. 2
Treatment Processes .................................................................................................. 3
Water Balance ........................................................................................................... 4
Water Supply - Inputs ............................................................................................ 4
Water Demand - Outputs ....................................................................................... 4
Scenarios 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 .................................................................... 13
Cost Benefit Analysis .............................................................................................. 14
Management Plans................................................................................................... 16
Community Consultation ......................................................................................... 16
Ecological and Social Benefits of the Project ........................................................... 18
Recommendations ................................................................................................... 19
References ............................................................................................................... 21
Appendix 1: Margaret River Wastewater Reuse Scenarios - Water Balance ............. 22
Appendix 2: Water Balance Assumptions ................................................................ 23
Appendix 3: Guidelines for the Use of Recycled Water in Western Australia........... 25
Appendix 4: Net Present Value (NPV) Calculations................................................... 1

List of Tables

Table 1: Current irrigated areas and volumes within the SAMR ................................. 5
Table 2: Scenario 1 – Summary of water balance calculations.................................... 6
Table 3: Scenario 2 – Summary of water balance calculations.................................... 7
Table 4: Assumptions for predicted future urban areas............................................... 9
Table 5: Scenario 3 – Summary of water balance calculations – 2026 third pipe to
future urban areas............................................................................................... 9
Table 6: Scenario 4: Part A – Summary of water balance calculations...................... 11
Table 7: Scenario 4: Part B – Summary of water balance calculations for decentralised
WWTP self contained subdivision of 650 lots .................................................. 11
Table 8: Annual rainwater tank yields for Perth ....................................................... 12
Table 9: Advantages and disadvantages of centralised and decentralised treatment
systems ............................................................................................................ 12
Table 10: Summary of water balance under each scenario........................................ 13
Table 11: Summary of water balance and capital costs under each scenario ............. 14

iv


Introduction

Background
In response to the increasing demand on natural potable water sources and a decrease in
annual precipitation, the Shire of Augusta Margaret River (SAMR), propose to use treated
wastewater 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 Shire
councils around Western Australia (Neil McGuinness, WA Department of Health, 2007) for
several decades in order to secure sustainable water management practices. The State Water
Strategy 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 on
existing water sources such as abstraction from the Margaret River and local groundwater
sources. The SAMR are considering using the water to irrigate other POS around the townsite
in the future. Investigations are under way for supplying a third pipe, to future residential
areas for toilet flushing, garden irrigation and POS. Third pipe with recycled wastewater is
yet to be undertaken in Western Australia, and if implemented will set a new precedent in
urban water use management. The first third pipe development in Western Australia was
completed by Water Corporation at Brighton in the northern suburbs of Perth for the POS and
home 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 Developments
It should be noted that as of September 2008 the provision for third pipe connection will be
mandatory for all new subdivisions and homes in Western Australia for greywater and
alternative water supply.

The State Government has recently introduced the 5 Star Plus Building Code, which
encourages the reduction of water and energy use. The aims of the water use code are to
reduce 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 of
water such as grey water and rain water (Government of Western Australia, 2007)

The installation of these alternative water sources for new subdivisions is strongly encouraged
and discussed further in Section 3.6.

5 Star Plus will be applicable to new homes approved for construction after 1 September
2007. It is expected that the State Government will investigate measures to apply the 5 Star
Plus provisions to existing homes by 2008 (Government of Western Australia, 2007).

Moreover, the WA Government Department of Premier and Cabinet is currently formulating
the State Water Recycling Strategy.

The provision of recycled water to homes via third pipe will now be possible under the new
WA Department of Health (DoH) regulations from the current 16 January 2007 “Guidelines

1


for the Use of Recycled Water in Western Australia” (Appendix 3). Water is required to be
treated to different standards depending on its final use. Water for irrigation of POS areas can
be treated to Class B or C, whereas water for urban non-potable use will need to be treated to
Class A as specified in the DoH guidelines.

At a national level the “Australian Guidelines for Water Recycling: Managing Health and
Environmental Risks” Phase 1 (Environmental Protection Heritage Council, 2006) have
recently been finalised as a part of the National Water Quality Management Strategy. The
project will be conducted in accordance with these guidelines.

Objectives
The 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 requirements
and management plans).

The present study has investigated and quantified the current supply of wastewater available
at the Margaret River wastewater treatment dam (MRWWTD) with the demand for irrigating
POS within the SAMR and to assess the feasibility of various scenarios for third pipe
connections to future residential areas.

Preliminary figures have been calculated on projected volumes of wastewater to quantify
supply and demand of wastewater streams up to 2026 (Scenario 3). The Water Corporation’s
2026 input volumes to the MRWWTD includes sewage from the townsite of Margaret River
and exclude Witchcliffe and Gracetown townsites. These projected figures are based on
information 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 local
community, water users and the SAMR.

2


Treatment Processes

At present the Water Corporation treats sewage at its Margaret River Wastewater Treatment
Plant 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 the
adjacent 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 are
irrigated in winter if there is a dry period. The Water Corporation use a basic criteria of “no
surface runoff or ponding” when irrigating the adjacent plantation (Water Corporation, pers
comm.). It is understood that the wastewater will not be required to undergo further treatment
to be suitable for irrigation purposes, however the chlorine dosing rate will be increased to
account for the increased pipe distances.

If treated water from the plant is to be used for a third pipe system in future urban areas for
internal non-potable purposes then further treatment and costs will be incurred due to treating
the water from Class C to Class A. It is envisaged that an investigation of further treatment
and 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 to
balance tanks located at the Margaret River Weir. It is expected that the existing pumping rate
of 60 L/second will be sufficient to pump the water to the balance tanks. Water will be
pumped to the POS areas from the balance tanks via a 150 mm pipe. Further technical
investigations will be necessary to ascertain pumping rates, pipe sizes and balance tank sizes.

3


Water Balance
The following key tasks have been calculated as a part of the water balance (Refer to
Appendix 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 - Inputs
As of April 2007 approximately 1,768 dwellings were connected to the main sewer of 2734
available (Water Corporation, pers comm.), which feed into the MRWWTD.

During the summer and public holidays there will be an increase in tourist numbers visiting
the town and therefore an increase in inflows to the treatment dam. The Margaret River
Visitor Centre reported that the months of highest visitation was January, April and
December. It is understood that most visitors to the Shire would be spread across
accommodation facilities located in sewered and unsewered areas. Wastewater generated
from visitors to the sewered areas would already be accounted for in the inflow volumes to
the treatment dam. Visitors to unsewered areas are not likely to contribute to the increase in
flows to the dam as wastewater from these accommodation facilities would treated through a
septic tank or alternative treatment system approved by the SAMR. The summer holiday
months of December, January and April usually correspond to higher inflow volumes at the
treatment dam.

The increase in absentee land owners occupying properties in sewered areas during the
summer months will also increase inflow volumes to the treatment dam.

The wastewater treatment dam is located approximately 2.5 kms from town and receives
approximately 359,000 kL of wastewater per year (982 kL per day). The treatment dam has a
designed storage capacity of 450,000 kL.

Rainfall to the MRWWTD minus evaporation reduces the volume of water by 14,000 kL per
year on average. Therefore, the approximate volume of water available for use in the
MRWWTD is 345,000 kL (345 ML) per year. The area of the MRWWTD has been estimated
at 30,000m2.

The treated wastewater from the MRWWTD is currently drip irrigated to the adjacent pine
plantation at approximately 323,000 kL/per year. Informal discussions with the Water
Corporation in June 2007 have identified that the Forest Products Commission plan to harvest
the surrounding pine plantations that are currently irrigated in 2009. Therefore an alternative
use 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 - Outputs
The 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 and
ovals. Irrigation of the ovals occurs twice per week, approximately 30mm/per week

4


(15mm/session). The main irrigation pump has been designed to pump at 12.25L/second at
600kPa.

Water required for irrigating schools, POS and ovals (except Riverslea Subdivision) is
134,000 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 the
Margaret River for the Riverslea Subdivision. Therefore it is estimated that approximately
169,000 kL/per year is currently abstracted for the irrigation of 22.4 ha of Shire POS. A
breakdown of the POS areas that are irrigated by the SAMR, their size and irrigation volumes
are provided in Table 1.

Table 1 does not include the POS areas of Brookfield and Rapids Landing. It is understood
that these areas are not currently irrigated by river water. These two additional areas have
been included in the water balance calculations for Scenario 1 and total 28 ha (refer to Table
2).

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 83,000
Reuther park/ bowling green 1 7,500
Two state schools 5.8 44,000
Riverslea subdivision 4.6 34,500
Total (approximate) 22.4 169,000

Table 1 highlights the importance of a wastewater reuse scheme; approximately 169 ML a
year will need to be abstracted from the Margaret River in 2008 for irrigation of the above
areas. It is understood that the SAMR are currently renewing their water abstraction licence
administered through the Department of Water (DoW). Abstraction of river water could still
be 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


Scenarios for Water Recycling
The water balance is presented in Appendix 1 and portrays three stages with four different
scenarios. The four scenarios have been created and refined from several discussions with the
SAMR. It is understood that the SAMR will implement the three stages in succession. The
scenarios are summarised below and described in detail in this section:

Stages of Development (Chronological) Scenarios
Stage 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 (East
Margaret River EMR POS) from the MRWWTD. Table 2 below summarises the outcomes of
the water balance calculations. Under this scenario, approximately 134,000 kL of water
would be available for other irrigation purposes, such as the adjacent pine plantation or third
pipe applications.

Table 2: Scenario 1 – Summary of water balance calculations
Irrigated Areas Approximate Volume (kL) pa
Total available water for irrigation in MRWWTD 345,000
Shire irrigation 28 ha (schools, ovals, EMR POS) 211,000
Dam level and water available for other irrigation 134,000
following irrigation of Shire POS

The current average irrigation rate for other POS and turfed areas in the SAMR is in the order
of 7528 kL/ha/year. On this basis, approximately 17 ha of POS could potentially be irrigated
with 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 MRGC
currently obtains water from on-site dams and groundwater bores and is assessing the costs
and benefits of pumping treated wastewater for irrigation purposes.

A report undertaken by Hydroscapes Australia Pty Ltd in June 2007 estimated the current
designed irrigation system can deliver up to 396,000 kL/per year (over 9 months), however
actual water usage rates for the MRGC are in the order of 188,000 kL/per year (based on
7500 kL/ha/year for 25 ha). No irrigation is undertaken at the golf course during the winter
months.

Scenario 2 includes the irrigation of all current Shire POS areas with treated wastewater from
the MRWWTD, (includes schools, Gloucester Park and EMR POS) and irrigation of the
MRGC (approximately 25 ha).

Table 3 below summarises the outcomes of the water balance calculations. In this scenario
approximately 54,000 kL of additional water would be required to be derived from other

6


sources such as bore or river water for the months of February, March and April. It is
recommended that the MRGC investigate ways of reducing overall water use based on
current best practice in the industry.

Table 3: Scenario 2 – Summary of water balance calculations
Margaret River Golf Course (25 ha) 188,000
Total water required 399,000
Water required from other sources 54,000

Based on data extrapolated from Water Corporation predictions, preliminary calculations
indicate that the 400,000 kL of irrigation water required for Scenario 2 could be available by
2009 (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. Water
would be supplied from the MRWWTD to the subdivision for irrigation of the POS and
include connection to each household for garden irrigation and toilet flushing. This scenario
has not factored in the installation of household onsite greywater systems.

The new subdivisions will require mains sewerage and third pipe connection to the
MRWWTD. Volumes of water required for scenarios 1 and 2 are also included in the scenario
3 calculations.

Predicted inflow volumes to the MRWWTD have been obtained from the Water Corporation
and 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 approximately
5,400. The current inflow into the MRWWTD is 358,526 kL/per year, with approximately
1768 connections (or 203 kL/connection/year).

The Water Corporation has projected a steady increase reaching approximately 550,000
kL/per year in 2015 to 910,000 kL/per year by 2026, based on a population of approximately
12,500.

Based on these figures, approximately 4,482 connections would be contributing to the
MRWWTP in 2026. However, it should be noted that there is likely to be an increase in
household water usage over time associated with increasing standards of living, e.g
dishwashers and spa baths. This would result in similar volumes of water with fewer
connections. Therefore this figure is considered assumptive.

Various occupancy rates are available ranging from 2.4 – 2.7 occupants per dwelling, for the
purpose of this report an average 2.6 occupants per dwelling has been selected in line with the
recent Rapids Landing development.

Additions from rainfall and losses through evaporation were calculated at approximately
14,000 kL per year. The following estimates have been made with respect to water
availability for third pipe usage in the future urban areas:

7


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 – 2026

Note: Volumes include additions from rainfall and losses from evaporation.

Note that with the increasing acceptance of greywater reuse and water conservation strategies
at all levels of government and the community, there could be a reduction in the volume of
wastewater discharged into the main sewerage system. On the contrary, a doubling of the
residential population may actually result in more wastewater inflows due to additional
connections to the main sewerage system within existing developed areas due to sewerage
infill.

The MRWWTD has a designed capacity of 450,000 kL, based on current increases in inflow
volumes it will be at full capacity by 2010. An alternative reuse/disposal option will need to
be assessed and commissioned as the adjacent pine plantations are earmarked for harvesting
in 2009. However with the commencement of irrigation of POS and golf course and
commissioning of a third pipe to future urban areas the volume of dam water will be reduced
and therefore provide increased capacity. Controlled releases to water courses from winter
storage dams may also be feasible subject to water quality objectives.

The recent Rapids Landing subdivision (formerly termed Lot 27 subdivision) has been used
as a standard subdivision template. The Rapids Landing subdivision is expected to house
approximately 1,690 people and comprises a total land area of 82.5 ha of which 6 ha have
been allocated for POS. The area has been subdivided into 650 lots with an occupancy rate of
2.6 per lot (Simon Munckton, Lester Group, pers comm.).

In the absence of any planning data (except population increases) for future subdivisions, the
Rapids Landing subdivision figures were extrapolated to account for an increase in
population.

8


Future total population figures have been based on Water Corporations projections of
approximately 12,500 in 2026. It has been assumed that this would consist of approximately
7,000 from existing town areas, infill and EMR areas and approximately 5,500 in future urban
areas (new subdivisions). It has been assumed that of the 4,482 connections potentially
available in 2026, approximately 44% or 1,972 connections could be connected to future
urban 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. Therefore
an 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 be
approximately 11,600, the Water Corporation has used an occupancy rate of 2.7 (12,100). The
SAMR has estimated that the population in 2026 will be between 10,200 and 12,900. A
population of 12,500 has been selected in line with the Water Corporation, however is
considered assumptive at this stage. Inflow volumes for dwellings have been assumed at
approximately 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 areas
Element 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 3
POS (ha) 6 18
Occupancy rate per lot 2.6 2.6

Table 5 below summarises the results of the water balance calculations. In this scenario
approximately 68,000 kL would be available for other uses (9 ha of POS). The volumes in
table 5 for third pipe for toilet, irrigation and POS are only for the 3 subdivisions in new areas
and not for existing areas (town, infill and EMR area). At this stage these figures should be
considered assumptive.

Table 5: Scenario 3 – Summary of water balance calculations – 2026 third pipe
to future urban areas
Future 3 rd pipe to subdivisions (3 sub) (toilet, irrigation) 294,000
Future 3 rd pipe to subdivisions (3 sub) (POS, 18 ha) 135,000
Dam level/ available water 68,000

Inflow volumes outlined in Table 5 have been sourced from the Water Corporation’s 2026
predictions (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 inflow
volumes.

9


If scenario 3 only included Shire POS, MRGC and POS with the future residential areas (18
ha), 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 the
MRWWTD to the Shire POS areas and the MRGC. As this infrastructure will have already
been established it is considered separate to Part B. As Part A would be operational, Part B
would run concurrently as each subdivision was approved and constructed. As Part B is
considered a closed looped system in terms of wastewater treatment and reuse the stand alone
development 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 homes
or communities at or near the point of generation (Tchobanoglous, 1995). Centralised
treatment on the other hand, consist of conventional systems (sewers), centralised treatment
plants 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 scale
DWWTP for treatment. Treated water from this unit could be used directly for irrigating POS
within the subdivision during the summer months and supply households with non-potable
water for toilet flushing and garden irrigation.

The subdivision would be considered a closed loop system, collecting treating and recycling
the wastewater within the subdivision. Each DWWTP would be designed to accommodate the
estimated volumes of water produced within the subdivision.

Excess treated wastewater during the winter could be diverted to an irrigation/pasture area or
reinjected into the local aquifer through a Managed Aquifer Recharge (MAR) process.
Alternatively, if practical, the water could be discharged into a constructed wetland area or
engineered 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 into
consideration issues associated with winter storage of treated wastewater.

Third pipe connection from the DWWTP will be needed for summer irrigation of POS. This
scenario does not require third pipe connection from the MRWWTD and ideally should not
need main sewerage connection due to low volumes of water produced in winter and the
potential for onsite reuse. Greywater treatment systems could be installed at the household
level to irrigate private gardens or connected to the DWWTP.

If newly approved subdivisions do adopt this closed loop water management strategy they are
likely to be self sufficient in terms of water treatment capacity and irrigation reuse. There will
be 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 current
2007 inflow volumes (345,000 kL/per year) plus an extra 30,000 kL per year to account for
additional connections from the existing Cowaramup townsite and infill within the Margaret
River townsite, as no additional water would be discharged back to the MRWWTD from the
new subdivisions.

10


Creating future subdivisions that are closed looped and self sufficient in terms of water
treatment and reuse would shift more responsibility onto the developer to provide appropriate
water 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 Rapids
Landing. This assumes the subdivision has approximately 1,690 people with 6 ha of POS and
650 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 calculations
Irrigated Areas Approximate Volume (kL)
Total available water for irrigation in MRWWTD 345,000 + 30,000
Water required from other sources 24,000

Table 7: Scenario 4: Part B – Summary of water balance calculations for
decentralised WWTP self contained subdivision of 650 lots
Irrigated Areas Approximate Volume (kL)
Total available water for irrigation from DWWTP* 119,000
3rd pipe from DWWTP within subdivision (for toilet)* 26,000
3rd pipe from DWWTP within subdivision (for irrigation)* 69,000
3rd pipe from DWWTP within subdivision (for POS 6 ha)* 45,000
Water to be irrigated/recharged locally (winter) 38,000
Water 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 be
somewhat higher than the assumed 30,000 kL, in which there would be enough water
available to irrigate the Shire POS areas and the MRGC. It is anticipated that sufficient water
will 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 stored
during 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 and
constraints presented at each individual subdivision. Further feasibility studies would need to
be undertaken early in the planning stages to allow for the integration of these systems. For
example additional POS or a designated wetland landscaped area with high water and nutrient
uptake plants could be included in the subdivision design.

During summer, approximately 60,000 kL of additional water will be required for irrigation
of the POS, toilet flushing and garden irrigation within each subdivision of approximately 650
lots. The majority of this water will be used for household garden irrigation during summer
and could be reduced if strict water conservation measures are applied to households in line
with other states.

This scenario has the potential to save up to 119,000 kL of scheme water per year, per
subdivision of this size (similar to Rapids Landing) and could easily accommodate irrigation
of the subdivision POS.

11


Rainwater tanks could be fitted and plumbed to each house to harvest rainwater for in-house
and ex-house purposes. Due to the Mediterranean climate experienced in the south west of
Western Australia, winters are wet and cold, while summers are dry and hot, rainwater tanks
are most useful when plumbed for in-house use to take advantage of high winter rainfall. This
water can be used for toilet flushing and washing machines and contributes to the overall
reduction of scheme water over the year. In addition, a small amount of rainwater could be
used 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 yields
from various roof areas and rainwater tanks plumbed for in-house and ex-house use. The
results summarised below in Table 8 are based on Perth rainfall and therefore are considered
slightly 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 84
Adapted from Marsden Jacob Associates (2007)

Houses with a 50m2 roof area and 2,000 L rainwater tank would yield approximately 29,000
L a year. Larger houses with a roof area of 200m2 would yield approximately 58,000 kL per
year. On this basis, the installation of rainwater tanks plumbed to the house for in-house and
ex-house use should be strongly encouraged in new subdivisions.

Installing rainwater tanks to all new houses would also reduce the demand for scheme water
supply to the subdivision. If rainwater tanks where installed to supply 100% of the needs of
internal potable water use (drinking, washing, etc), then a roof area between 200 and 250 m2
and 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 Systems
The water balance calculations have identified that there is sufficient water to proceed with
Stages 1 and 2 of the project. There are two possible options that could be considered for the
future urban areas (Stage 3).

Two different scenarios have been assessed for the development of Stage 3. Scenario 3
involves a conventional centralised treatment system requiring main sewerage and third pipe
connection to all new subdivisions. Scenario 4 involves provision for subdivision scale
decentralised systems and would involve subdivisions to be self sufficient in water treatment
and reuse. Table 9 below briefly summarises the advantages and disadvantages of centralised
and decentralised systems.

Table 9: Advantages and disadvantages of centralised and decentralised
treatment systems
Treatment System Advantages of system Disadvantages of system
• Shire can defer responsibility for • Cost and energy use for installation and
Scenario – 3
management of the expanded operation;
Centralised Third-Pipe
system to Water Corporation; • Conventional and expensive deep
System 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


Subdivision scale and nutrients treated and reused develop new internal systems or
Decentralised onsite; subcontract arrangements to
Treatment 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 over
150 commercially available DWWTPs from around Australia and the world and categorised
them in terms of their treatment type and application.

Summary of Water Reuse Scenarios

The water available or required under each scenario is summarised in Table 10 and discussed
below.

Table 10: Summary of water balance under each scenario
Scenarios Available water per year Water required from other
(kL) sources per year (kL)
Scenario – 1: Existing POS Areas (28 ha) 134,000 0
Scenario – 2: Margaret River Golf Course (25 ha) 0 54,000*
Scenario – 3: Third Pipe to Future Urban Areas 2026 68,000 0
Scenario – 4: DWWTP: Part A – 1 subdivision 0 24,000*
Scenario – 4: DWWTP: Part B (winter – recharge) 38,000 0
Scenario – 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 is
available for further irrigation use. This could be disposed to the adjacent pine plantation until
2009 or treated to a suitable quality for aquifer recharge.

Scenario 2 - approximately 54,000 kL of additional water would need to be derived from
other sources such as groundwater for the months of February, March and April to
supplement the third pipe water.

Scenario 3 – no additional water is required and approximately 68,000 kL would be available
for other uses in 2026. Estimates show that the total required water to accommodate scenario
3 (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 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 and constraints
presented at each individual subdivision.

During summer, approximately 60,000 kL of additional water will be required for irrigation
of the POS, toilet flushing and garden irrigation within the subdivision. The majority of this
water will be used for household garden irrigation. The additional water could be obtained
from a combination of sources such as groundwater and rainwater tanks plumbed to the house
for in-house and ex-house use.

13


Cost Benefit Analysis

The water available or required and associated capital costs under each scenario are
summarised 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 scenario
Scenarios 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) wastewater
Scenario – 1
Existing POS Areas (28 211,000 134,000 0 2.21 10.49
ha)
Scenario – 2
Margaret River Golf 399,000 0 54,000* 5.18 13.00
Course (25 ha)
Scenario – 3
Third Pipe to Future 828,000 88,000 0 10.34 12.50
Urban Areas
Scenario – 4
399,000 0 24,000* 5.18 13.00
DWWTP: Part A
Scenario – 4
DWWTP: Part B (winter 38,000 0 21.46
– recharge)
140,000 2.56
Scenario – 4
DWWTP: 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 decentralised
systems. 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 present
values (NPV) have been calculated assuming an effective life of 25 years (with depreciation
to 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 treated
wastewater. Annual pumping costs have been calculated but are relatively minor. Other costs
to be incurred but not as yet quantified are ongoing water quality monitoring costs as required
by the relevant regulatory authorities. Sale of the treated wastewater (third pipe water and
golf 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 capital
outlay. This is due to the efficiencies to be gained in Scenario 3 due to the increased volumes
being supplied, again nearly double.

14


Scenario 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 some
rebate’ 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 a
true comparison of the various scenarios on an economic basis is necessary therefore that the
true cost of wastewater treatment either be added to these scenarios (1-3) OR deducted from
Scenario 4. The latter approach has been taken here. CSOs were identified as a significant
issue in the Gracetown Development Project (GHD, 2007).

On this basis for Scenario 4 an annual CSO equivalent of $1,000pa/connection has been
applied with a full one-off headwork reduction for wastewater of $1,514. That is, no
reductions 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 and
CSOs for potable water. This has been illustrated as Scenario 4B with full water rebate as
shown in Appendix 4 and reveals a NPV of +$95/kL. The implication of this for future
standalone developments is that subdivisions that are able to operate completely independent
of the Water Corporation and receive headworks reductions and CSO returns under the
current 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


Management Plans
The 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 documents
for 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 third
pipe systems. The “Guidelines for the Use of Recycled Water in Western Australia”
(Appendix 3) were released in January 2007. In summary the guidelines provide information
to 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 the
establishment and growing of crops, gardens, trees or turf. NIMPs demonstrate that inputs
such as water and fertiliser should be well matched to the plant growth cycle resulting in
minimal contaminant leaching into the surrounding environment. The DoW requires NIMPs
for rural and recreational land areas exceeding 5,000 square metres where vegetation is
irrigated, fertiliser is applied, animals are held intensively in paddocks and/or organic solids
containing nutrients are spread onto the land. NIMPs are also suited to sites where industrial
or municipal wastewater rich in nitrogen (N) and phosphorus (P) is applied to foster the
growth and maintenance of healthy vegetation. They may be required for lesser areas where
local water values are particularly sensitive to nutrient contamination.

If the Shire decides to run the DWWTP itself independent from Water Corporation it will
need to use a licensed subcontractor or secure a Water Service Providers License (Sewerage
Services) from the Economic Regulation Authority of Western Australia (ERA). This will
require preparation of all of the plans above beforehand and approvals from the agencies
mentioned above before the licence can be granted. These provisions are listed under the
Water Services Licensing Act 1995.

Community Consultation

A community consultation program for the Project has been initiated by the SAMR. To date
various publications, surveys and information have been distributed to the community of
Margaret River. These include:

• Specific stakeholder consultation with developers and catchment groups;

16


• 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 has
been very supportive of the Project so far. Ongoing consultation will be required by the
SAMR and a Community Consultation Outcomes Report submitted to the relevant agencies
in order to proceed through the approvals process.

17


Ecological and Social Benefits of the Project

The ecological benefits of the project include a considerable increase in environmental flows
for 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 water
volumes in the river. If the MRGC were supplied with treated wastewater, there would be a
decrease in groundwater abstraction from the local aquifer (up to approximately 188,000
kL/per year, 2007 rates) and therefore associated indirect benefits.

In addition to the ecological benefits, the project will provide social benefits due to the
increased river flows, these include; a healthier looking river and the potential for increased
downstream eco-tourism activities in the river during the summer months, due to the
cessation of river abstraction. The quality of recreational facilities will also be able to
maintained by the SAMR as a secure source of treated water will available for irrigation
purposes.

The project also presents a positive message to the local Margaret River community in terms
of sustainable water management and urban wastewater reuse and sets a precedent for other
urban wastewater reuse projects in Western Australia.

18


Recommendations

The 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 use
of recycled water for non-potable purposes such as irrigation of POS and the golf course
(scenarios 1 and 2).

19


In the longer term, the SAMR should consider the integration of current best practice and
planning into all new future residential areas with the aim that newly developed areas are self
sufficient in terms of water treatment and reuse based on decentralised treatment systems, or
provision for a third pipe, where practical. Rainwater harvesting for internal potable purposes
should also be considered as a part of the overall water management strategy of future urban
areas.

20


References

Department of Health (2007) Guidelines for the Use of Recycled Water in Western Australia.
January 2007.

Environmental Protection Heritage Council (2006) Australian Guidelines for Water
Recycling: Managing Health and Environmental Risks” Phase 1. National Water Quality
Management Strategy. November 2006.

Economic Regulation Authority (2007). Draft Report. Inquiry on Competition in the Water
and Wastewater Services Sector. ERA WA.

GHD (2007) Gracetown Development Project - Phase 1 Sustainable Water and Wastewater
Services. Prepared for Landcorp. August 2007.

Government of Western Australia (2007) 5 Star Plus – Energy Use in Houses Code and
Water 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 Urban
Australia. Prepared for the Australian Government National Water Commission. March 2007.

Shire of Augusta-Margaret River (2007) East Margaret River Public Open Space and
Landscape Development Guidelines. Prepared by the Shire of Augusta-Margaret River 2007.

Tchobanoglous, G. (1995) Decentralised Systems for Wastewater Management. Presented at
the 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 Investigation
Report. Prepared for the Lester Group. May 2006.

21


Appendix 1: Margaret River Wastewater Reuse Scenarios - Water
Balance

22


Appendix 2: Water Balance Assumptions

The 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);


2026 = 910,000 kL per yer (2493 kL per day);

7. Available wastewater volumes (plus rainfall - evaporation) minus 14,000 kL per year




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


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; and

14. 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


Appendix 3: Guidelines for the Use of Recycled Water in Western
Australia

25

Appendix 1

Wastewater Reuse Study - Water Balance
Shire of Augusta Margaret River

Main Sewer connections 1768
Available sewer connections 2734
(Source: Water Corporation) (2007)

Wastewater treatment dam - surface area 30,000 (m2)
Evaporation factor of storage area 1
Max designed capacity of treatment dam 450,000 (kL)

Vegetation type of irrigated area Turf
Crop factor 0.6
Irrigation 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 Total
Monthly rainfall (mm) - Witchcliffe 2006 50.8 88.6 139.8 194 73.2 66.6 68.8 10 18.2 3.8 26.4 35.4 776
Monthly 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 -1,229
availble 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 -13,590
values represents evaporation from dam)

Wastewater May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Total
Wastewater 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 30,810 358,526
Wastewater 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 winter
Irrigation Requirements May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Total
Shire irrigation POS Stage 1 (28 ha) (kL) 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784
Golf 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 20,838 187,500
Future 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 38,175 293,725
Future 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 13,873 194,222
Total 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 Total
Total 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 29,874 344,936
Pine 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 26,013 323,697
Dam 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 21,239

Scenario 1 - Shire POS (28 ha) May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Total
Supply Start
Total 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 29,874 344,936
Demand Level
Pine 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 26,013 323,697
Existing Shire irrigation POS (28 ha) (kL) (kL) 0 0 0 0 0 15,056 30,112 45,168 45,168 30,112 30,112 15,056 210,784
Dam level/avail for pines (kL) cumulative 28,426 55,996 85,904 123,577 153,250 167,518 166,008 145,903 127,913 121,195 119,334 134,152 134,152

Scenario 2 -Shire POS (28 ha) + Golf Course (25
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Total
ha)
Supply Start
Total 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 29,874 344,936
Demand Level
Existing 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 15,056 210,784
Golf 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 20,838 187,500
Total water required (kL) 10,416 0 0 0 10,416 35,889 50,945 76,417 76,417 50,945 50,945 35,894 398,284
Dam 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 0
Water required from other sources - approx -24,634 -22,694 -6,020 -53,348

Scenario 3 - third pipe to future urban areas (3 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Total
subdivisions-18 ha POS) 2026 (+ scenario 1 and
2)
Supply
Total 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 74,667 896,000
Demand Dam

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 15,056 210,784
Golf 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 20,838 187,500
Future 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 37,143 294,000
Future 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 9,644 135,000
Total 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 82,681 827,284
Dam 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 68,716
Water required from other sources - approx 0

Scenario 4 - Part A existing third pipe facilites May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Total
from MRWWTD to POS + MRGC.
Part B - DWWTP + third pipe from DWWTP for
future urban areas (1 subdivision only) POS (6
ha) + household toilet and garden

Part A
Supply (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 31,250 375,000
Demand Dam
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 15,056 210,784
Golf 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 20,838 187,900
Total water required (kL) (kL) 10,416 0 0 0 10,416 35,889 50,945 76,617 76,617 50,945 50,945 35,894 398,684
Dam 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 0
Water required from other sources - approx -19,040 -4,644 -23,684

Part B

Subdivision scale water balance (stand alone) -
based on 650 persons per 1 subdivision (DWWTP)
Supply
Wastewater 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 9,890 118,625
blackwater and greywater) (kL)
Demand
Future 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 95,514
toilet/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 45,168
ha) (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 14,903 140,682
Available 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 -5,013
Water to be recharged locally (Winter) 7,657 7,657 7,657 7,657 7,659 0 0 0 0 0 0 0 38,287
Water 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 Scenarios

Stage 1

Scenario 1 - existing Shire POS areas (28 ha) includes schools, gloucester park and EMR POS (Riverslea, Rapids Landing and Brookfield)

Stage 2

- Golf Course (25 ha)

Stage 3

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)

- 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


Appendix 4: Net Present Value (NPV) Calculations

ECONOMIC ASSESSMENT OF MARGARET RIVER WASTEWATER REUSE

Assumptions
Description Value
Mains electricity price ($/kWh) 0.13
Synergy buyback price ($/kWh) 0.13 Not used
Mains water price ($/kL) 0.60 Not used
Discount 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 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 $95.362
Note 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

Guidelines for the
Use of Recycled Water
in Western Australia

16 January 2007

Guidelines for the use of Recycled Water in Western Australia -30/08/06 Page 1 of 66

Margaret River Water Recycling Water Balance and Cost Benefit Analysis

Margaret River Water Recycling Water Balance and Cost Benefit Analysis

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Andere mochten auch

Andere mochten auch (9)

Ähnlich wie Margaret River Water Recycling Water Balance and Cost Benefit Analysis

Ähnlich wie Margaret River Water Recycling Water Balance and Cost Benefit Analysis (20)

Mehr von Wayne Prangnell

Mehr von Wayne Prangnell (9)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Margaret River Water Recycling Water Balance and Cost Benefit Analysis