Case

Stu

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Bartlett’s Environmental Pty LtdAsset, Liquid Waste & Environmental Management

PO Box 3105 Geelong VIC 3220Tel: 03 5248 7955 Fax: 03 5248 7677info@bartlettsenvironmental.com.auwww.bartlettsenvironmental.com.au

Melbourne Zoo: Desludging of the Japanese Lake at the Melbourne ZooThe ornamental lake in the Japanese Garden at Melbourne Zoo was built by the Zoo in 1991

and is home to many birds, turtles and koi fish. It has an overlooking conference centre and

visitors to the Zoo often sit and eat their lunch beside the lake.

The Issue: Over the years, a thick sludge gradually builds up in the lake due to the breakdown of

plant and animal waste. The sludge is fully organic consisting of broken down leaves, trees

and plants, dirt and animal waste. While not a direct threat to wildlife the sludge increases

nutrient levels in the lake causing algal blooms, increased turbidity and dramatically reducing

the aesthetic value of the lake. This is a natural process that Melbourne Zoo has previously

addressed through draining and refilling the lake with fresh water. As has previously been

done, Melbourne Zoo scheduled the ornamental lake to be restored to its pristine condition,

so that visitors could enjoy improved visibility of fish and turtles.

The Solution: To address the problem of excessive sludge in the lake, Melbourne Zoo engaged the help of

Bartlett’s Environmental. When asked why it was he chose Bartlett’s for the project, Ben Zarb,

Water Technician at the Zoo said “I continue to use Bartlett’s due to their great customer service,

modern machinery and their ability to be flexible”.

Due to the eventful nature of the Zoo, a timeframe of three days was given to complete this

project. The lake had been drained by Zoo staff over a two day period by opening the valve in

the floor drain. The koi fish and turtles were removed and temporarily relocated as the water

level fell. Unluckily the day before Bartlett’s were to begin work, there was a heavy downpour

of rain. As the storm water drains into the lake, it inevitably re-filled with water. This was a

major setback to the project and resulted in the deadline being extended to five days. After

the fifth day, the lake needed to be refilled whether the job was finished or not.

An entire day was spent re-vacuuming and draining over 850,000 litres of water from the

lake. The water was sent to the Zoo’s treatment plant for treatment and storage with the

recycled water used to refill the lake. Being the first time in ten years the lake had been

drained, it became evident as the water lowered that approximately 40% of the lake was full

of sludge and organic matter. In some areas the sludge was up to one metre deep.

The thick sludge was extracted using Bartlett’s industrial vacuum unit. A four wheel motor

bike with specially designed squeegees as well as hand held squeegees were used to push

the sludge into piles, making vacuuming easier and increasing efficiency. High pressure

Project

Desludging of the Japanese

Lake at the Melbourne Zoo

Client

Melbourne Zoo

Service

Liquid Waste Management

Date

February 2010

Case

Stu

dy

Bartlett’s Environmental Pty LtdAsset, Liquid Waste & Environmental Management

PO Box 3105 Geelong VIC 3220Tel: 03 5248 7955 Fax: 03 5248 7677info@bartlettsenvironmental.com.auwww.bartlettsenvironmental.com.au

water was used to clean any remaining sludge from the bottom of the lake, along the sides

and around the rocks.

Refilling the lake began on the final day before the deadline. Once it was filled, it took several

days for sediments in the water to completely settle. The animals were then returned to their

home.

The Outcome: 100 tonnes of sludge was removed from the lake. The sludge was transported to the Werribee

Zoo where it was reused as valuable organic compost. Of the 40 cubic metres of organic

material removed, a portion of it was composted on site with the remainder taken to an

organic recycling facility.

The water quality improved dramatically and there was a significant difference in the clarity

of the water. The ornamental lake has been restored for visitors of the Zoo to admire and

they have better visibility of the outstanding koi fish and turtles swimming around.

Versatility and flexibility were extremely important with this project. It was a challenging task

due to the unforeseen volume of sludge in the lake - there was almost triple that of what was

expected. This, along with the setback of the rain and the limited timeframe to complete the

project, meant that the result was beyond expectations.

Project

Desludging of the Japanese

Lake at the Melbourne Zoo

Client

Melbourne Zoo

Service

Liquid Waste Management

Date

February 2010