Sustainable Effluent Management Strategy for Lower Hunter River
D Cho*, K Morrison**, and P Maccinante*
* Sinclair Knight Merz, 100 Christie St, St Leonards NSW 2065 Australia
** Hunter Water Corporation 36 Honeysuckle Drive Newcastle West NSW 2300 Australia
Abstract: This paper outlines the approach in developing a sustainable effluent management master
plan for five wastewater treatment plants discharging their effluent into the Hunter River directly or via
its tributaries. The master plan identifies integrated effluent management solutions and prioritises
capital works for wastewater treatment and a range of effluent reuse infrastructure. Given the
sensitivities associated with water scarcity among various users along the river, environmental
constraints and regulatory requirements, it is important to consider a broad range of stakeholder
perspectives. Central to the development of this plan is establishing a sustainable decision making
framework for prioritising effluent management scenarios for the master plan. This project
demonstrates a systematic process in formulating a sustainable effluent management master plan for a
growing region. Using the defined evaluation criteria and agreed weightings, MCA was carried out.
The results suggested that selection criteria favour scenarios which involve the upgrade of treatment
works followed by agricultural irrigation of effluent.
Keywords: Effluent Management, Sustainable Decision Making Framework, Water Recycling
Introduction
The Hunter Region covers an area of over 31,000 km2 and with over 624,000 people
is one of Australia’s largest regional populations. It includes the world’s largest coal
export port, produces over 35 percent of Australia’s aluminium, is one of Australia’s
top wine growing areas and generates 80 percent of the NSW’s electricity.
Hunter Water Corporation’s area of operations is serviced by an extensive system to
transport wastewater, including 4,477km of sewer mains, 380 pumping stations and
18 wastewater treatment Works (WWTWs). The Region will be subject to significant
population, industrial, commercial and agricultural growth over the next 30 years as
well as increasing pressure to meet water quality objectives and sustainably manage
water.
Over the last ten years water quality management in Australia has changed
dramatically. The advent of a drying climate has increased the use of alternative nontraditional water sources such as desalination and recycled water and has also seen
more localised water supplies being adopted, particularly at the household level (such
as rainwater and grey water systems). This presents water quality managers with a
new and diverse set of challenges including: managing blended waters sources such as
desalinated seawater, groundwater and surface water supplies; managing
decentralised and on-site systems of stormwater and recycled water for potable and
non-potable uses; and understanding new technologies and concepts such as managed
aquifer recharge.
The Hunter River Catchment Wastewater Management Master Plan will provide a
strategy for future investment to meet receiving water quality objectives and to
maximise reuse opportunities within sustainable economical and environmental
bounds.
Methodology
The study area covers five WWTW catchments that Hunter Water currently operates
in the lower Hunter Region. The study area is surrounded by highly productive
agricultural land with significant growth potential for residential and industrial
development. It is anticipated the population will increase from current 135,000 to
more than 200,000 in year 2025.
The baseline requirement for all effluent management scenarios is licence
compliance where Hunter Water must manage its assets so that the annual load of
pollutants released from its WWTWs stays below the fixed load limit imposed by the
regulator. Effluent management options were identified to achieve varying degrees of
pollutant load reduction, which include various additional treatment processes, as well
as recycling and alternate disposal measures.
The following lists the key constraints and opportunities presented in the vicinity of
the study area:





Load Base licence – regulatory framework that limits the annual pollutant load released
from each WWTW to the receiving environment;
Possible industrial customers up to 70 km from the study area;
BASIX – NSW government initiative that mandates all new residential development to
save up to 40% of base water demand. Whilst non-descriptive, this forces new dwellings
to be provided with alternate water supply, generally in the form of reticulated recycled
water or rainwater tanks;
Agricultural irrigation – There are a large number of river water users in the vicinity of
the study area. Applications include irrigated agriculture, private irrigation districts
(including numerous boutique vineyards) and golf courses etc;
Main water supply system comprising water supply dams, connecting infrastructure and
groundwater bore fields
Scenarios
Options were developed by integrating components into an effluent management
portfolio for the Lower Hunter Region based on the opportunities and constraints
presented. These options were then grouped together for analysis and comparison.
Table 1 summarises and compares scenarios considered for this project. Figure 1
shows examples scenarios developed for this projects.
Table 1 Scenarios considered
Scenarios
Description
S1 Treat and
Release
Most conventional approach whereby treatment is upgraded to meet the regulatory
requirement. One plant requires advance treatment (RO or equivalent) to meet
licence conditions.
Provides flexibility for any future initiative for beneficial reuse schemes
Water quality modelling indicates that it would have the highest predicted nutrient
content in the Hunter River
Likely to be accepted by communities, as it would be similar to what is currently
being practiced. Construction impact would be generally confined to the existing
plant sites
Order of cost : ~ AUD$ 30 Million
S2. Industrial
recycling
Additional treatment with UF prior to recycling at nearby power plant, approximately
70km north west of the study area. Requires lengthy transfer system.
Nutrient loads essentially eliminated from discharging into the river and river
extraction being substituted with recycled water. Substantial improvement in water
quality is expected in the Hunter River
Construction impact of the transfer system
Order of Cost: ~ $320 M
S3. Intercatchment
transfer for
ocean disposal
A portion of effluent flow would be transferred to the nearest ocean discharging plant.
This requires up to 50 km of transfer pipeline from two plants. No further treatment is
required.
No improvement to water quality in the Hunter River expected (only partial transfer to
meet the load based licence)
Likely to cause limited construction impact mainly via pipeline
Order of Cost: ~ $30 M
S4 & S5 Nonpotable
recycling for
new
development
Effluent from the wastewater treatment plant is further treated to a suitable standard
and sent to new residential developments for reuse. This involves extensive
networks of recycled water distribution and reticulation systems. This scenario has
two sub-scenarios where for Scenario 4, recycled water is provided to only part of
the new development to comply with the licence condition and scenario 5 provides
recycled water to all new development within the study area.
This requires relatively high up-front capital investment and is inflexible to any future
changes. Reduction in pollutant loads are expected as more development is
provided with recycled water.
Order of Cost: $60M (meet licence requirement, S4) to $150M (service all new
development, S5)
S6. Agricultural
reuse
S6a – local
agricultural
reuse
S6b – reuse in
private irrigation
district (PID)
S7.
Potable
Recycling
Treated effluent is sent to agricultural areas, either at for local irrigation (Scenario 6a)
or to a private irrigation district (PID, Scenario 6b). Minor improvement to effluent
quality is required.
Benefits can be realised with respect to water quality
improvement in the river as well as reduction in river water extractions. It should be
noted that full benefit can only be realised if treated effluent is preferentially used
over river water for irrigation.
Order of Cost: $51 M (local recycling) or $41 M (private irrigation district)
Effluent from each plant is sent to a centralised location and receives advanced
treatment (UF/RO) before entering to the potable water system. Public acceptance
is likely to be the key impediment for this scenario. There are three variants within
this Scenario as follows:
Scenario 7a – Indirect potable recycling to Grahamstown Dam (local water
reservoir)

Scenario 7b – Direct Potable recycling into the water distribution system

Scenario 7c – Indirect potable recycling to Tomago Sandbed (currently used as
a potable groundwater bore field)
This has the most benefit with respect to potable water saving as well as reducing
pollutant loads discharged into Hunter River
Order of Cost: $130 M - $ 210 M
(a) S6b – Agricultural Reuse in Private Irrigation District
(b) S7 – Potable Recycling
Figure 1 Examples of scenarios considered: (a) S6b-Agricultural reuse scheme to PID; (b) S7- Potable
recycling
Evaluation
Critical to the process is the establishing a sustainable decision making framework,
to incorporate social, economic, technical and environmental considerations in the
decision making process. The basic methodology comprises a Multi-Criteria Analysis
(MCA) process. The principles of the MCA approach are:
Options are identified and aggregated into scenarios. The scenarios are developed
to the point where the main features are understood;

A set of criteria by which the scenarios can be evaluated is defined;

The criteria are weighted to reflect their perceived importance;

Each scenario is allocated a score against each criterion;

The ‘scores’ for each scenario are computed and compared; and

Preferred scenarios are identified and carried forward for more detailed analysis.
Table 2 summarises the decision criteria used for comparing options.
Table 2 Sustainable Decision Making Framework
Primary
Criteria
Secondary
Criteria
Community
Impacts
Social
Community
Acceptance
Customer
Uptake
Use of nonrenewable
resources
Environmental
Technical
This criterion represents the willingness of customers to take
recycled water and incorporates an assessment of the risk that the
customer will cease to require recycled water into the future. The
more certainty about the customer's future demand for recycled
water, then the higher the score for this criterion.
This is a measure of the quantity of non-renewable resources
associated with each scenario. Examples include the quantity of
chemical usage, non-renewable construction materials, quantity of
waste generation etc
Receiving
Water Health
(Water Quality
Objectives)
Consistent with ANZECC 2000 Guidelines, water quality objectives
include the protection of: Aquatic ecosystems; Visual amenity;
Primary and Secondary contact recreation and; Aquatic foods.
This also includes protection of groundwater resources.
Receiving
Water Health
(River Flow
Objectives)
Consistent with water sharing plans and may include maintaining
wetland and floodplain inundation; natural flow variability;
groundwater etc.
Emission to air
This criterion is an estimate of greenhouse gas emissions.
It is estimated using CO2 emitted for each scenario based on
estimated power consumption.
Implementation
Risk
(Flexibility and
Adaptability)
Complexity
Whole of the
life cost
Description
A measure of community impact due to construction and operation
of infrastructure associated with each scenario, including visual,
noise and odour impacts, land acquisition, as well as disruptions
caused by construction (e.g. truck movements) and O&M activities
(post construction activities, etc)
This criterion refers to community acceptance of a particular
scheme. For example, schemes that increase the utilisation or
improve public facilities such as sporting fields (municipal nonpotable reuse) will score higher than those that don’t or agricultural
reuse may be considered more acceptable than ocean release.
Present Value
This criterion is based on an assessment of the risk factors
associated with implementing a scheme. These factors include
the ability to implement a scheme progressively in stages and so
minimise capital risk, potential for expansion to serve growth, the
ability to migrate to a different path without stranded assets and
flexibility to meet future regulatory requirements.
This criterion relates to the complexity of the scheme from both a
construction and operational perspective. For example, third pipe
systems may involve more complex treatment and distribution than
agricultural or industrial reuse.
This criterion relates to financial costs associated with each
scenario and includes capital and operating costs over the life of
the project
Numerous workshops were been carried out with key stakeholders – participants
included representatives from various departments within Hunter Water, regulatory
authorities (environmental, health, agriculture, and treasury), local government and
consultants. The workshops were critical to the evaluation process in defining and
developing the measures for evaluation as well as identifying and recognising
limitations of the measures adopted for each criteria. This ensures transparency is
maintained in the evaluation process.
One of the key variables in any MCA process is weightings on evaluation criteria
which was determined among the workshop participants via Paired Analysis. The
agreed weightings on the evaluation criteria are shown in Figure 2.
Figure 2 Adopted Weighting
Project Outcome and Discussion
The projected load and flow analysis indicated that with the exception of one WWTW,
the regulatory requirements for pollutant discharge will be met with minor
improvements in the treatment process. Therefore the regulatory drivers could not be
used as the sole driver for the master plan; rather beneficial reuse of treated effluent
and how this is perceived by the various stakeholders will likely form the basis of the
preferred scenario for the master plan.
Within the context of this study, effluent management scenarios were compared
against relevant criteria. The combined attributes for each option were then assessed
against the weighted evaluation criteria to provide input to the formulation of the
preferred strategy. The result of the MCA is shown in Figure 3.
100
Technical
Environmental
Social
Financial
90
80
70
60
50
40
30
20
10
S2 - Transfer to MB
S7a - Potable Recycling to
GTD (max)
S7b - Potable Recycling
to CTGM (max, direct)
S5 - Non Potable
Recycling (max)
S7c - Potable Recycling to
TSB (20 ML/d)
S4 - Non Potable
Recycling (min)
S3 - Partial Transfer to BB
S6b - Agricultura
Recycling (Local)
S6a - Agricultura
Recycling (Pokolbin)
S1 - Treat and Release
0
Figure 3 Result of MCA – Scenario Ranking
The MCA results indicate that there is a clear distinction between two groups of
scenarios. The higher scoring group comprises the following scenarios:

Scenario 1 – Treat and Release

Scenario 6a – Agricultural recycling to PID

Scenario 6b – Local agricultural recycling

Scenario 3 – Partial Transfer to Burwood Beach for Ocean Disposal
Sensitivity analysis suggests that the results of the scenario groupings is robust.
Any change to the weighting on one or more evaluation criteria did not change the
grouping.
The results highlight potential limitations of the MCA process in developing a long
term master plan. Scenarios that utilise existing infrastructure tend to be favoured due
to sunk costs that target existing EPL requirements but do not encourage innovation
or account for significant changes in the regulatory environment.
For example, potable reuse scored poorly against a number of criteria (e.g.
community acceptance, implementation risk, complexity etc) and also incurs high
costs. The MCA scoring was based on the views expressed by workshop attendees;
however an alternate view could be that potable reuse may become a proven and
accepted method of managing wastewater within the planning horizon of the Master
Plan. In addition, incorporation of criteria such as the volume of potable water
savings or volume of effluent recycled may have resulted in a more favourable
outcome for potable water recycling scenarios when assigned with appropriate
weightings.
Based on these findings, a number of actions were recommended for various
planning horizons. For the near term these included:
Process upgrade at one of the plants (Farley WWTW) to improve nutrient removal.

Should performance not meet the target effluent nitrogen concentrations, then there will
be a need to provide further advanced treatment or to implement agricultural recycling to
Private Irrigation District, subject to detailed feasibility assessment.

To develop water quality modelling to assist in developing water quality objectives

Further investigation of the feasibility of supply of recycled water to the Private
Irrigation District
Conclusions
During development of the Hunter River Catchment Effluent Management Master
Plan a series of effluent management scenarios were identified and evaluated using
MCA. Importantly, the MCA was based a set of evaluation criteria which were
developed in close consultation with key stakeholders. Involvement of key
stakeholders in defining and weighting the evaluation criteria ensured a well informed
and transparent options assessment process.
Based on the adopted evaluation criteria and their weightings, the two highest
ranked scenarios were:

Scenario 1 – Treat and Release

Scenario 6a – Agricultural recycling to Private Irrigation District
The study outcomes demonstrate that upgrading existing WWTWs will provide the
most effective result by meeting the effluent management objectives without wasted
investment or stranded assets. It also suggests that supplying recycled water to the
Private Irrigation District offers the most attractive alternative to current practice and
should be fully evaluated. Based on this finding a list of action items were outlined in
meeting effluent management objectives.
It should be noted that the outcome is largely driven by the current regulatory
framework and community expectations. Future changes to regulatory frameworks
and community expectations and advances in treatment technology may favour
alternate scenarios such as large scale non-potable and potable recycling.
Hunter water is currently undertaking a separate planning exercise, “Lower Hunter
Water Plan” to secure adequate water supplies for the regions’ growth in population
and industry. The recycled water opportunities identified in this study will provide
input to this planning exercise.