Investigation now focuses on raw water source

TasWater is making progress in identifying the cause of irregularities in the taste and odour in the greater Hobart water supply, with test results today confirming the most likely source of the issue coming from raw water drawn from the Derwent River near New Norfolk and treated at the Bryn Estyn water treatment plant.

After extensive water tests, General Manager Works Delivery, Dr Dharma Dharmabalan said that this gives us greater direction for our investigation and the commencement of measures to mitigate the problem.

‘Tests show the raw water entering the system contains naturally occurring compounds of geosmin and methylisoborneol (MIB) and produced by certain types of algae which can indicate a musty and earthy taste from around 10 nanograms per litre,’ he said.

The water still continues to meet Australian Drinking Water Guidelines and is safe to consume.

‘The raw water going into the Bryn Estyn plant in recent weeks has been fluctuating between 10 and 30 nanograms per litre and the intermittent nature of the complaints across the system can most likely be attributed to this variability,’ Dr Dharmabalan said.

‘This is a problem commonly experienced in other states across Australia and our Bryn Estyn treatment plant is not configured to handle such levels of geosmin and MIB because of the high quality water,’ Dr Dharmabalan said.

‘We are now testing water further upstream of the treatment plant in the Derwent River to undertake further investigation,’ Dr Dharmabalan said.

This development gives TasWater maintenance crews a focus to start working to clear the system of the taste and odour issues.

Crews are undertaking a raft of extra measures to clean filters and wash out tanks and pipes at the Bryn Estyn water treatment plant.

‘There are teams now investigating how quickly and effectively we can introduce measures to remove the taste and odour issues at the Bryn Estyn water treatment plant,’ Dr Dharmabalan said.

However Dr Dharmabalan stressed unfortunately there is still no concrete timeframe for a solution for customers.

Anyone experiencing irregularities in their water is urged to call the TasWater call centre on 13 6992.

Updates on the situation are on the TasWater website http://www.taswater.com.au/Community—Environment/Current-Alerts/Taste-odour-updates

Background Information – Hobart’s water supply

Number of complaints received by TasWater:
 532 since 1 January; the majority in the past week.
Greater Hobart’s three primary water catchments:
 River Derwent, through Bryn Estyn Water Treatment Plant – around 60% of supply, supplying Greater Hobart, Glenorchy, eastern shore and Sorell, and Bridgewater, Kempton & Campania
 Lake Fenton – through Bryn Estyn Water Treatment Plant – around 20% of supply for parts of Glenorchy and Hobart
 Mount Wellington – around 20% of supply for parts of Glenorchy and Hobart an all of Kingborough
Treatment facilities
 One water treatment plant – Bryn Estyn Water Treatment Plant (located outside New Norfolk)
 16 dosing stations (disinfection)
Storages
 Nine reservoir dams in the supply system
 96 storage sites (excluding those in water treatment plants)
Bulk water mains (pipelines)
 419 km in length
 Average age 52 years; earliest records go back to 1917
Reticulation pipelines
 2,172km in length
 Average age 34 years; earliest records go back to 1920
No. of connections in greater Hobart
 85,218
Number of drinking water tests
 6,100 per annum
Number of water test sites
 80
Simon Pilkington, TasWater