Home' Future Water : Future Water 2016 Contents 28 >> Future Water >> Australian Water Management Yearbook
The township of Wallan was originally serviced by Goulburn Valley
Water; however, in 2004, the government determined that Yarra
Valley Water would take over servicing responsibility for the
area. In 2006, Yarra Valley Water assumed responsibility for the
Wallan Sewage Treatment Plant, which included the Wallan 100
per cent Class C re-use scheme. This meant that recycled water
was provided to re-use customers in the area for farming use.
The implementation of the scheme involved the construction of a
winter storage lagoon on the site.
The new recycled water treatment plant uses a combination of
dual-media filters, ultrafiltration, UV disinfection and chlorination to
treat Class C effluent to Class A recycled water standard.
The existing sewage treatment plant is located adjacent to land
that was originally the Wallan Airport, but is now being developed
as a residential estate. The old lagoon-based treatment plant was
originally constructed in 1988 with a nominal capacity of above
two million litres per day. The existing treatment plant currently
utilises a series of lagoons to achieve the biological treatment
of sewage, as opposed to many other Yarra Valley Water plants,
which utilise activated sludge systems. During this process,
sewage is treated by utilising microorganisms, contained within the
sewage, that help to break down the organic matter.
The first treatment lagoon is aerated by surface aerators to provide
aeration and mixing of the sewage. Sewage then flows by gravity
through the other treatment lagoons in a predefined sequence,
which allows treatment and maturation to occur. In the lagoon,
natural biological and chemical processes aid to treat the sewage,
while the use of aerators increases the efficiency of the process.
Over the course of treatment, removal of soluble organic matter,
phosphorus, nitrogen and suspended solids will occur. Sludge
accumulates at the bottom of the lagoons. Lagoon sludge depths
are periodically tested and are desludged once the level of sludge
is near capacity. Sewage then flows into the winter storage
lagoons, and excess flows are pumped in, as well. During the
colder months of the year, winter storage lagoons are steadily
filled. During the warmer irrigation season, treated Class C effluent
is used by several re-use customers for pasture irrigation.
Construction of the new sewage treatment plant, which began in
April 2015, is now well underway, and good weather conditions
during the winter months helped to keep the project on schedule
during earthworks, piling works and construction of the concrete
tanks. During the early stages of construction, a temporary
‘Stonehenge’ was erected to form the pile base for the new
treatment plant being built. 182 steel-reinforced concrete piles
formed a solid foundation for the seven tanks that have been built
on the site. The storage tanks play an important role in the sewage-
treatment process. The piles were inserted into the ground up to
19 metres deep, with the top portion removed, both by hand and
by using machinery to create a base for the tank to be laid. Almost
2000 cubic metres of concrete and 500 tonnes of reinforcing steel
were used in the construction of the main tank.
The focus of early construction was the large tank that will be used
for the main treatment of sewage. The tank is 50 metres long and
30 metres wide, and is made from concrete supported on piles.
The concrete base slab was then poured, along with three of the
external walls, with works completed at the end of 2015. This then
allowed the mechanical and electrical fit-out to start in early 2016.
Brant Mitchell, Project Manager, Yarra Valley Water, says one of
the challenges with the project has been that while construction
is underway, the existing plant must remain operational until the
new sewage treatment plant is available. As an interim measure,
Yarra Valley Water has increased capacity at the existing facility
as much as possible by continuing to maintain and upgrade it
while the new plant is being constructed. Road access to the site
was also poor, and an upgrade was needed to allow for adequate
access facilitating construction and long-term operation.
THE NEW SEWAGE
TREATMENT PLANT WILL
FEED WATER INTO THE
ALLOWING CLASS A
WATER TO BE SUPPLIED TO
IN THE AREA
Links Archive Future Water 2015 Future Water 2017 Navigation Previous Page Next Page