A framework for efficient wastewater treatment and recycling systems - Gayathri Devi Mekala, Brian Davidson, Madar Samad and Anne-Maree Boland. Irrigation Australia Journal, Spring 2008. The drought conditions of the past seven years in Australia and increasing environmental awareness have led to an active promotion of wastewater recycling. The absolute and relative cost of recycling is one of the key factors that will have a big influence on the future of wastewater recycling in Australia.

1. A FRAMEWORK FOR EFFICIENT
WASTEWATER TREATMENT
AND RECYCLING SYSTEMS
Gayathri Devi Mekala, Brian Davidson, Madar Samad and Anne-Maree Boland
The drought conditions of the past
seven years in Australia and
increasing environmental
awareness have led to an active
promotion of wastewater recycling.
The absolute and relative cost of
recycling is one of the key factors
that will have a big influence on the
future of wastewater recycling in
Australia.
This article outlines the
development of a toolkit/decision
support tool for allocating wastewater
among different sectors to achieve
desired objectives in a cost-efficient
way. It deals in particular with
answering these questions:
• How can the cost-effectiveness of
wastewater recycling be judged
and budget allocated?
• For which sectors in a defined
region will wastewater recycling
be cost-efficient? A Broccoli field in Werribee Irrigation District irrigated with treated wastewater. The vegetables
Wastewater has a number of most commonly irrigated with recycled wastewater from the Western Treatment Plant in the
alternative uses and each alternative Werribee Irrigation District are broccoli, cauliflower, cabbage, onion, artichoke and lettuce.
is associated with a set of costs from
the point of treatment to the point of
use. As a result, recycling can satisfy prove to be the basis of a decision nothing). Only if the new strategy is
more than one objective such as: support tool that can be used to associated with enhanced effects and
reduce the discharge of nutrients to allocate wastewater among different higher costs, is cost-effectiveness
natural water bodies, save/substitute sectors. analysis required. It is compared
potable water, bring more land under against current practice (the “low-cost
cultivation, and save water for Cost-effectiveness analysis alternative”) in the calculation of the
environmental purposes. The Cost-effectiveness analysis (CEA) is incremental CE ratio:
methodology chosen to evaluate the one of the techniques for economic
best alternative or alternatives is evaluation in which all costs are
Cost-Effectiveness Analysis. related to a single common effect. It
The cost effectiveness of a particular is designed to compare the cost
The result might be considered as
alternative depends on what one effectiveness of an intervention and
the “price” of the additional outcome
wants to achieve. Therefore, a ranking determine if the intervention is worth
purchased by switching from the
exercise needs to be conducted for the doing. It is a technique for selecting
among competing wants wherever current practice to the new strategy.
different objectives among
stakeholders and each objective resources are limited. It was first The choice of technique depends
weighted accordingly. A further step applied to health care in the late on the nature of the benefits
may be comparing the cost- 1970s to make decisions on specified. In CEA, the benefits are
effectiveness of wastewater recycling appropriate strategies to increase expressed in non-monetary terms and
with other options like buying water health benefits or cost savings. in cost-benefit analysis they are
on the market from the agricultural In cost-effectiveness analysis, a new expressed in monetary terms. As with
sector and desalination. It is hoped strategy is compared with the current all economic evaluation techniques,
that the approach outlined above may practice (which may include doing the aim of CEA is to maximise the
32 IRRIGATION AUSTRALIA

2. CRCIF
level of benefits relative to the
resources available.
With CEA, it is normal to
distinguish between the direct costs
and the indirect costs associated with
the intervention, together with
intangible positive and negative
externalities, which although at times
difficult to quantify, are often
consequences of the intervention and
should be included in the cost profile.
The costs to be considered for CEA of
recycling projects are:
• direct costs: includes capital costs
of treatment and distribution of
recycled water
• indirect costs: e.g. groundwater
pollution of areas irrigated with
recycled water
• intangibles: includes “yuck” factor,
non-acceptability of the
wastewater irrigated products.
It is important to specify the costs to Werribee Park Tourism Precinct: All these five public areas now use recycled water for
be included in a CEA and those which irrigation from Western Treatment Plant.
should not to reduce the risk of
misinterpreting the findings. A
distinction must be made between which by definition are uncertain, the recycling infrastructure only if they
those interventions that are level of confidence that can be placed are financially viable and it is worth
completely independent, i.e. where in them need to be identified. In a the risk. Therefore, the cost of
the costs and effects of one dynamic market, both the costs and supplying recycled water becomes a
intervention are not affected by the the effects can change. Sensitivity crucial determinant of overall project
introduction or otherwise of other analysis tests all assumptions used in viability. It is important to recognise
interventions, and those that are the model and enables the impact of that the direct costs of providing
mutually exclusive, i.e. where the best-case and worse-case settings recycled water will depend on the
implementing one intervention means on the baseline findings to be specific nature of the project and the
that another cannot be implemented, investigated. use to which the recycled water will be
put.
or where the implementation of one
intervention results in changes to the Procedure for conducting the ACIL Tasman broadly categorised
costs and effects of another. cost-effectiveness analysis the infrastructure related costs
The four sectors where wastewater can associated with recycling as:
For the current study, wastewater
be recycled and for which the CEA can • capital costs for new or upgrading
recycling was considered to be an
be conducted are: treatment plants, and subsequent
independent programme. Using CEA
• household/residential operating costs
with independent programmes
• industry • installing and operating
requires that cost-effectiveness ratios
• recreational irrigation reticulation and trunk delivery
(CERs) are calculated for each
• agriculture. systems
programme and ranked.
• storage capacity where needed to
The cost-effectiveness of using
match seasonal variations in
recycled water for each of the sectors
production and demand
is obtained by summing the costs of
Interventions with the least CER • costs incurred by users in
using recycled water for each of the
should be given priority but to decide accessing recycled water, e.g.
options (which includes the cost of
which programme to implement, the converting equipment, plumbing,
treatment to comply with the EPA
extent of resources available must be and extra on-site storage or
standards for each of the specific uses
considered. In mutually exclusive treatment.
and to take it to the point for use) and
interventions, incremental cost- Other costs of supply include:
dividing this cost by the intended
effectiveness ratios (ICERs) are used: • project planning and regulatory
impact it creates depending upon the
approvals
objective one chooses to attain.
• marketing, public education and
Costs to be included for CEA. In consultation programs
Alternative interventions are ranked 2005 ACIL Tasman Pty Ltd conducted • capital and operating costs of any
according to their effectiveness on the stakeholder consultations to identify additional treatment and waste-
basis of securing maximum effect the impediments to recycling. stream treatment following
rather than considering cost, and Seventy-seven per cent of stakeholders recycled water use
ICERs are calculated. identified the cost of infrastructure as • ongoing monitoring and
The results of CEA should be an important impediment to the compliance with regulatory
subjected to a sensitivity analysis. supply side of the recycled water requirements and other risk
Since the CERs are point estimates, market. Water companies can invest in management measures
IRRIGATION AUSTRALIA 33

3. CRCIF
• contingent liabilities for possible Table. Possible objectives of recycling and the expected effect.
legal claims arising from
inappropriate use of the recycled Objective Criteria for Effectiveness (AUD*/effect)
water
• metering, billing, and other To reduce the nitrogen load released AUD/tons of nitrogen discharge
customer-related costs. into the bay/river reduced into bay/river
The capital and operating costs of To save potable water or create AUD/gallons (GL) of potable water
treating wastewater to a standard alternative or new sources of water saved
suitable for its intended use will to complement the existing sources
depend on factors such as the quality
To reduce the costs of treatment by AUD/kilolitres of wastewater treated
of the effluent, the quality of the
treating the water to a lower level
recycled water required, the
technology adopted or required for To promote regional development in AUD/number of people employed
the appropriate level of treatment, new areas through employment
and the extent of economies of scale. generation and promotion of primary
The general position is that the industries
higher the level of treatment, the
* Australian dollars
higher the cost. The relative cost-
effectiveness of recycled water
schemes in terms of cost per environment, and inadequate acceptability of using recycled water
megalitre varies a lot from project to community consultation on the is higher for non-edible crops than
project, with a high volume of issue. for edible crops. For edible crops,
industrial or agricultural schemes 2. Lack of trust in technology: in a preference is towards crops that must
benefiting from economies of scale. 1999 study by Sydney Water, the lack be peeled or washed before human
A common issue raised by suppliers of trust in technology was the second consumption like oranges and
consulted in this research was the most frequently stated reason given sweetcorn.
challenge and costs associated with by participants who opposed using However, a 1988 study using
overcoming the spatial separation of reclaimed water for agricultural salient options, which specifically
supply. irrigation. described how and when the recycled
Objectives of wastewater 3. Social pressure and fear of social water was to be used in a
recycling. State governments have a backlash: a heightened need for new community, found that the degree of
variety of objectives for recycling. water sources does not automatically contact was not related to how
Depending on the objective, the warrant the acceptability of acceptable people perceived a certain
results of the CEA will vary. The wastewater recycling. Drought- use option to be. Rather participants
different possible objectives are affected Werribee farmers were favoured specific-use options which
shown in the table. offered a deal to access water from conserved water, enhanced health
the Thompson Dam by the Victorian and reduced treatment and
Depending on the objective (see
Government in 2004, in return for distribution costs. After all the
the table) that an institution/
which they were required to sign up factors that influenced overall public
community wants to achieve, the
to a program to take reclaimed water perceptions of use were collated as
sector to which the recycled water is
the following year. Only half of the (1) degree of human contact and (2)
allocated would vary and so would
farmers have so far accepted the deal. the five factors (i.e., health,
the costs and its effectiveness. It is
environment, treatment, distribution
also possible that governments and Others are reluctant because of fears
and conservation) it was concluded
communities will have a number of of possible community backlash.
that the first component only had a
objectives that they want to achieve 4. Fear of losing markets: the greatest
greater effect when people were
through recycling. In such instances, concern for growers is maintenance
asked about general use options,
there is a need to weight and rank of markets, i.e. continued access and
whereas when the specific use
the different objectives based on assured price. A recent survey by the
scheme was used, the second
their perceived importance. Department of Primary Industries
component had greater impact on
asked consumers if they would be
Weighting objectives of people’s perceptions.
willing to buy vegetables grown in
recycling Therefore, it is essential to weigh
Werribee with recycled water. The
the different objectives of the
The options for wastewater recycling results were as follows:
government for recycling options in
are varied and contentious because of • Yes - 35% - Support the use of
coordination with user and consumer
its nature of origin and issues and recycled water; trust the
acceptability and preference and
perceptions related to health and authorities to do the right thing
accordingly select the recycling
safety. The local communities have • Not sure - 55% - If the water is
projects which are most likely to be
rejected a number of wastewater treated properly; if safety is
accepted by the community and
recycling projects by the government guaranteed
therefore make the project
and water boards around the world • No - 10% - Don’t like the idea of
implementation successful. The
and in Australia. A number of social using recycled water
different weighting methods include
reasons have been found to be Literature review and previous equal weighting of all attributes, rank
associated with the rejection: studies have consistently shown that order weighting and ratio weighting.
1. Lack of coordination between the the closer one moved on the contact In a 1993 simulation study it was
authorities involved in planning continuum, the less acceptable the
health, water supply and recycling option became. The Continued over page
34 IRRIGATION AUSTRALIA

4. IRRIGATION RESEARCH
IRRIGATION RESEARCH
RECYCLED WATER SAVING VITICULTURE
Belinda Rawnsley, Senior Research Officer, South Australian Research & Development Institute
Recycled water is droughtproofing Comparison of selected quality parameters of recycled and mains water used to irrigate
McLaren Vale, keeping it one step vines in McLaren Vale, South Australia.
ahead of other regions affected by
water shortages. Parameter Unit Recycled Mains
The use of recycled water in the pH 7.4 7.4
McLaren Vale region has observable
benefits by alleviating pressure on Boron mg/L 0.23 0.33
naturally available water resources and Calcium mg/L 42 41
is up to 40% cheaper per kilolitre than
mains water. Environmentally, the Chloride mg/L 270 138
amount of wastewater discharged out Potassium mg/L 25 7
to sea is reduced which minimises the
harmful impact on the marine Sodium mg/L 190 88
environment in the Gulf St Vincent. Total Nitrogen mg/L 20 0.3
Recycled water quality is constantly
Total Phosphorus mg/L 8 0.08
monitored. Compared to mains water,
recycled water tends to have a higher Total Dissolved Solids (TDS) mg/L 807 373
salt content and nutrient load (see
E. coli /100ml 18 0
table). Nitrogen (N) and phosphorus
(P) are higher in recycled water than Source: Christies Beach Wastewater Treatment Plant and Myponga system, SA Water 2006.
mains water so additional fertiliser use
may not be necessary. There are
common concerns that recycled water
contains excessive levels of boron, yet between vines irrigated with recycled nutrients that can reduce grower
there is no evidence of this (see table). or mains water. This research has fertiliser costs.
The use of recycled water has many shown that irrigation with recycled I also have conducted research on
obvious benefits and ongoing water does not cause nutrient the effect of recycled water on the soil
research, led by Dr Michael McCarthy imbalance and does not impede yield. environment, particularly the level of
(SARDI), has shown that there is no Recycled water appears to provide a microbes in the soil and whether soil
difference in yield or wine quality good source of plant available pathogens pose a problem.
Continued from previous page Bruvold, W. 1988. Public opinion on pp. 1-6. http://www.evidence-based-
water use options. Journal WPCF 60(1): medicine.co.uk
found that ratio weights and rank 45-49.
order weights were much superior to PMSEIC (Prime Minister’s Science,
D’Angelo Report. 1998. See Using Engineering and Innovation Council).
the equal weights method.
Reclaimed Water to Augment Potable
2003. Recycling Water for Our Cities.
Water Resources. Public Information
References Paper prepared by an independent
Outreach Programs (Special Publication,
ABC online. 2004. Werribee farmers get working group for PMSEIC. 28
Salvatore D’Angelo, Chairperson).
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January 9, 2004
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ACIL Tasman Pty Ltd. 2005. Economics
Association. recycled water. Sydney.
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Eddy. D. M. 2000. Effective Clinical
recycled water and impediments to
recycled water investment. Report
Practice. Journal of American Medical About the authors
Association 3(5): 253-255. Gayathri Devi Mekala works with
prepared for the Australian
Government Department of Jia, J.; Fischer, G. W.; Dyer, J. S. 1993. the CRCIF, University of Melbourne
Agriculture, Fisheries and Forestry on Attribute Weighting Methods and
and International Water
behalf of the Natural Resource Policy Decision Quality in the Presence of
Management Institute, Brian
and Programs Committee. June 2005, Response Error: A Simulation Study.
Davidson with the CRCIF and
pp 1-82. Journal of Behavioral Decision Making.
May 1993. University of Melbourne, Madar
Boland, A. 2005. The use of recycled water
Phillips, C.; Thompson, G. 2001. What is
Samad with the International Water
in Australian horticulture Keynote
address at Irrigation 2005 – Irrigation cost-effectiveness? Published by Management Institute, and Anne-
Association of Australia Conference, Hayward Medical Communications. Maree Boland with RM Consulting
Townsville. Aventis House. Volume 1, Number 3. Group.
IRRIGATION AUSTRALIA 35