Water Science & Technology Vol 43 No 9 pp 133–144 © IWA Publishing 2001
The use of artificial oxygenation to reduce nutrient availability in the Canning River, Western Australia
B. Greenop*, K. Lovatt** and M. Robb***
*Aquatic Sciences Branch, Water and Rivers Commission, Level 2 Hyatt Centre, 3 Plain St, East Perth, Western Australia 6004, Australia
**Aquatic Sciences Branch, Water and Rivers Commission, Level 2 Hyatt Centre, 3 Plain St, East Perth, Western Australia 6004, Australia
***Aquatic Sciences Branch, Water and Rivers Commission, Level 2 Hyatt Centre, 3 Plain St, East Perth, Western Australia 6004, Australia
ABSTRACT
Artificial oxygenation has been used for two summer periods to improve the
water quality of the Canning River in Perth, Western Australia. The project
is part of the Swan Canning Cleanup Program, which aims to reduce the
frequency and severity of nuisance and toxic algal blooms in the
Swan-Canning estuary. The trials have proved that oxygenation has increased
the dissolved oxygen concentrations in the water column, particularly in the
bottom waters where dissolved oxygen concentrations are frequently below a
critical level of three milligrams per litre. Oxygenation has had a positive
impact on nutrient concentrations in the water column and nitrogen cycling
processes. Reductions in nutrient concentrations were highlighted by drops
in ammonium and total phosphorus concentrations of 97% and 64% following the
recommencement of oxygenation after a plant shutdown. Results of a
microbiological study combined with the data analysis indicate that the
number of nitrifying microbes have increased due to oxygenation. However,
comparisons between oxygenated and control areas were inconclusive about the
ability of the oxygenation plant to reduce total nitrogen and phosphorus
levels. This could be explained by factors such as spatial variability,
water flow during the trials and measurement limitations in the monitoring
program. Future work will concentrate on assessing the impact of the
oxygenation plant on nutrient concentrations.
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