Healesville Sewage Treatment Plant
Introduction
Around 93% of the sewage that Yarra Valley Water collects
is transferred to Melbourne Water for treatment at either
the Western or Eastern Treatment Plants.
However, the remaining 7% of wastewater is treated in
small treatment plants, which we own and operate, located
in suburban and semi-rural areas, such as the Healesville
STP. The water from these treatment plants is released
into rivers and streams, or reused and must therefore
undergo a high standard of treatment.
The Healesville STP was initially commissioned as a small
neighbourhood plant in 1987 however; it was replaced in
1990 by the larger current plant. Over the following years, a
chemical dosing facility was installed and once the plant
came close to reaching capacity, the decommissioned
aeration tanks from the Whittlesea STP were relocated to
the Healesville STP.
The plant is located on the outskirts of Healesville on
Argoon Road; it is EPA licensed and treats sewage from
the Healesville Township and surrounding areas; with the
treated effluent being discharged into the Yarra River in
accordance with EPA standards.
The Treatment Process
The treatment process includes an influent pump station,
an inlet screen, biological treatment utilising an oxidation
ditch and two treatment reactors, secondary clarification,
upward flow clarification and UV disinfection.
The oxidation ditch is a horseshoe-shaped basin where
incoming effluent is mixed with return sludge from a
secondary clarifier. The ditch provides a mechanism for
circulation and oxygen transfer promoting the growth of
micro-organisms that consume organic matter to
breakdown and release nitrogen. Alum is dosed to the
sewage at the inlet to the oxidation ditch to aid phosphorus
removal.
Capacity
The current design and licensed capacity of the Healesville
treatment plant are shown below:
Parameter
Organic Capacity
Equivalent Population
Average Dry Weather Flow
Licensed Mean Daily Flow Rate
Value
720 kg/d BOD
10,000
1.5 ML/d
1.4 ML/d
Healesville Sewage Treatment Plant
Healesville STP Treatment Process
Sewage is pumped into the treatment plant
Fig 1 (right): Briefly describes the main treatment processes that occur at the plant
Fig 2 (below): A schematic diagram of the plant’s treatment process
Preliminary Treatment
Influent from Healesville
Branch Sewer
Screenings to
Landfill
The flow of sewage passes through screens so that
rubbish and other large objects can be removed
Alum is dosed to the sewage at the inlet to the
oxidation ditch to aid phosphorus removal
Caustic soda is dosed into the oxidation ditch to
maintain a neutral pH
Influent
Pump
Station
Inlet Screens
Secondary Treatment
Alum
Caustic Soda
Oxidation Ditch
Sludge
Thickening
Tank
RAS
Aeration
Tanks
WAS
Secondary
Clarifier
Educt off-site to
Brushy Creek STP
Secondary treatment involves the use of an oxidation
ditch and two sidestream reactors. The mixed liquor is
then piped back to the oxidation ditch from the
reactors.
Removal of soluble organic matter; nitrogen and some
phosphorus occurs.
The effluent then flows into the secondary clarifier,
where settling occurs to remove suspended solids
Waste sludge is thickened and then transported to
Brushy Creek for disposal into Melbourne Water’s
sewage system
Tertiary Treatment
The effluent then flows through the upward flow
clarifiers, for further removal of suspended solids
Following clarification, the effluent undergoes UV
disinfection to inactivate and destroy any disease
causing pathogens that are still present
Upward Flow
Clarifier
Now the effluent is of an acceptable standard to be
discharged into the Yarra River, without causing harm
to the environment
UV Disinfection
System
Yarra River