AMIAD - AUSTRALIA & ASIA PACIFIC NEWS - VOLUME 9 - APRIL 2017 FEATURE: April 2017 Vol.9 - CaseStudy Melton Water

Case Study | Melton
Filtration of Helminth Eggs from Secondary Treated Wastewater (Class C)
prior to a Class A treatment plant and irrigation water supply
Background
The Surbiton Park Recycled Water
Plant (SPRWP) is located approximately
8 km south of Melton (50km NW of
Melbourne). The SPRWP currently
services a population of approximately
63,000 people in the Melton region
which is experiencing one of the
highest population growth rates in
Victoria. The current Average Dry
Weather Flow of the plant is
approximately 12 ML/day. The SPRWP
is an activated sludge plant that comprises primary
and secondary treatment (Class C). Western Water is
planning to increase the SPRWP capacity in stages, to
18 ML/day and ultimately to 25 ML/day by 2025, to
match the anticipated supply of wastewater in
Melbourne’s West Growth Corridor.
SPRWP disposes of the treated wastewater through
beneficial reuse via the Class A treatment facility
(capacity of 5 ML/day) and irrigation (7 ML/day).
However during the winter rainfall months there is a
constant supply of treated wastewater but little or no
demand for Class A or irrigation water, hence the need
for large winter storage dams.
Challenge
During the shoulder of the irrigation season, in the
weeks leading up to the winter rainfall season, the
objective is to irrigate as much as possible and run the
storage dams very low, to allow enough space for
storing the treated wastewater during the winter
rainfall months, when there is little or no demand for
Class A or irrigation water. The wastewater has to be
treated for the reduction of pathogenic bacteria,
viruses, protozoa and helminths, prior to irrigation on
pastures and crops.
Helminths are a worm-like invertebrate that is a
parasite of humans and other animals. Helminth eggs
have a strong shell that protects them against a range
of environmental conditions and can remain viable for
1–2 months in crops and once consumed can cause
infection to the host. Helminth eggs cannot be
inactivated with chlorine, UV light or ozone at
economical dose rates.
5 | March/April  2017
The common treatment for helminth eggs, is 25-day
storage in a dam/reservoir. According to the Australian
Guidelines for Water Recycling (May 2008), the
indicative Log Removal Value (LRV) of helminths,
through reservoir storage is 1.5 to >3 LRV. Thus, having
to store the treated wastewater for 25-days, occupies
185 ML (7.4 ML/day x 25 days) of possible winter
storage. With t he increasing supply of treated
wastewater, due to population growth in the service
area, Western Water had to either build a larger winter
storage or find an equivalent treatment for helminths
that avoids the need for 25-days storage.
Western Water was looking for a mechanical filtration
solution that would offer Helminths egg reduction of
1.5 to 2 LRV.
Solution
In a meeting with key internal stakeholders, Amiad
listed Western Water’s critical success factors,
performance metrics and evaluation criteria. Amiad
conducted an optioneering study and proposed six (6)
options, including two (2) options proposed by Western
Water, which didn’t include mechanical filtration.
Together with Western Water, each option was rated
and ranked according to the weighted evaluation
criteria, to determine the preferred option to develop
further. Amiad provided reference projects and pricing
to Western Water, to allow them to conduct their own
due diligence before engaging Amiad to design and
construct a 14 MLD, 20-micron automatic Arkal disc
filtration system.
During the detail design stage, all critical design
parameters were confirmed with a long-term onsite
pilot trial.