1980’s-2010’s: Malpas Dam Armadale (NSW) – Microcystis aeruginosa

Armidale – Malpas Dam


Armidale Water Treatment Plant (WTP) has a treated water production capacity of 40 ML/d and comprises coagulation, flocculation, sedimentation, monosand open gravity filtration, fluoridation and chlorination. Raw water is sourced from Malpas Dam. Characteristics of the raw water are provided in Table 1. Cyanobacterial events in Malpas Dam are common, with generally at least one bloom occurring per year. Generally the events occur between November and March, however high levels of cyanobacteria have been recorded as early as August and persisted at times until July.

During the algal blooms, contamination of the raw water source with taste and odour compounds is common, and at times algal toxins have been detected. Recently the predominant genus is Anabaena circinalis, which is capable of releasing the neurotoxin Saxitoxin. Algal counts in the order of 1.75 x 106 cells/mL of Microcystis aeruginosa and 4 x 106 cells/mL of Anabaena circinalis have been recorded. High levels of Microcystis aeruginosa in Malpas Dam in the 1980s were linked to liver damage in the Armidale community [1]. The primary taste and odour compound of concern from Malpas Dam has been geosmin, with levels as high as 1000 ng/L measured.

Red alert at Malpas Dam as algae blooms

Jan 17 2015


Residents are being urged to limit their recreational use of the dam, which is Armidale’s main supply of water.

An Armidale Dumaresq Council spokeswoman said the bloom did not affect tap water.

“The water treatment process takes all of that out [of the water] so it is safe to drink,” she said. “In terms of recreational use, you can use it if you really want but it won’t be very pleasant.”

The algae may be toxic to humans so contact should be avoided.

It can cause skin and eye irritation and stomach upset if consumed without being boiled or treated.

The alerts are based on how many cells are present in a millilitre of water.

A red or high alert means there are more than 50,000 cells present.

Amber or medium is between 5000 and 50,000, and the lowest green alert is 500 to 5000.

The levels often varied and it was not unusual for blooms to occur.

“As the dam levels are lower and it has been warm we have seen the levels of blue-green algae increase,” she said.