Clean water takes effort
OUTSIDE times of drought and flood or news about contamination and waterborne health outbreaks, clean water is often taken for granted.
This precious resource is crucial in our daily lives. The human body is 6075 per cent water; 97 per cent of water on Earth is salty and 2 per cent is frozen. So, despite 80 per cent of the world being covered by water, only 1 per cent is suitable for human use. Unless consuming tank or bore water, we can only drink what has been chemically treated from this 1 per cent.
It’s not uncommon to hear the argument “It’s my water. I paid for it and I’ll use it as I please.” On the surface that seems logical. Scientifically, no one can “own” a single drop. Every molecule is 4.6 billion years old, recycling endlessly in the hydrological cycle. All we can do, through various technologies and depending on location, is to capture, store, divert, transport, treat, consume, conserve, release and recycle water. It is a finite resource.
Natural water supplies can contain high levels of insoluble impurities such as clay, microbes, colloidal content, dissolved impurities such as salt, nitrates and chemical compounds. These change the colour and hardness while sulphur compounds give it an unpleasant flavour or taste. Many supplies do not meet minimum standards set by the WHO. It would be extremely expensive to treat all substandard water supplies, so it is vital to preserve the good quality catchments and to use our treated supply wisely.
Townsville has three water treatment plants. Ross Dam supplies the Douglas Water Treatment Plant ( DWTP) with up to 220ML of raw untreated water per day. The Northern WTP near Rollingstone is about 30km south of Paluma Dam. A third small treatment plant supplies Cungulla and draws water from the Giru Weir. The NWTP can only treat “good quality” raw water which is a natural feature of the Paluma and Crystal Creek. The system is combined with Paluma able to be pumped to AIMS and Douglas able to pump to Rollingstone. Paluma is not connected to Paluma Dam but supplied by a small weir on the coastal side of the main road. Problems with water quality are being resolved with installation of a $ 500,000 transportable unit. The rate of growth in the region further justifies improved infrastructure to pump an increased volume of Burdekin water when Ross and Paluma dams are low.
Two pumping stations supply water to the Douglas and Mount Louisa reservoirs before it is distributed through the city’s reservoirs, pipes, drains and meters to our taps, at great expense to supply and maintain. The main Douglas plant is fully automated, computer- controlled by a Supervisory Control and Data Acquisition ( SCADA) System. This allows the daily flow rate, tank levels, chemical dose rates and other plant operating criteria to be set as required. The plant is controlled by one of two programmable logic controllers ( PLCs), one operating and one on standby if the other fails. The plant can also be controlled remotely using the Process Controllers’ laptop computers. An automatic dialler alerts the Process Controller on duty in the event of a fault or plant breakdown.
Townsville’s treatment facilities are managed by TRILITY, an Australian and New Zealand company. What happens at water treatment plants? Raw water is pumped from a storage area. Both of our conventional plants need the water to settle first so larger ( turbid) particles do not enter the system. The water is pumped upwards into the plants for aeration, followed by thorough mixing in vertical turbine towers. Next, coagulation where pinsized chemicals are added to destabilise harmful particles. The resulting ‘ floc’ clumps settle out as sedimentation. The liquid on top is passed through a multilayered filtering system that traps smaller, even microscopic, particles.
Chlorine is added to disinfect any bio- contamination and finally, fluoride is added which greatly reduces the incidence of dental decay. Water from the Crystal Creek Intake- Paluma Dam system is combined with water from Douglas and distributed through the network. In 2008 the State Government committed $ 33.3 million to upgrades of the two key treatment plants; $ 25.58 million went to Mount Spec to provide an average of 20ML per day.
In 2015- 16 a new 22.5ML steel reservoir was installed alongside two others at Mount Louisa. This new facility complements 33 other water reservoirs with combined storage of 273ML, about three days of treated supply for the city when on Level 3 restrictions. Council has not begun the proposed new treatment plant at Toonpan to process the increased volume that the new two- staged pipeline will deliver. The technology for Toonpan will be able to treat turbid Burdekin water directly without the settling process in Ross Dam with its very high evaporation rate.
Townsville Laboratory Services ( TLS) has been monitoring the council’s potable water system for more than 25 years with a range of services available to council, hospitals, the university and schools, the general community and other institutions in the North Queensland area. The laboratory can analyse samples from open waters, treated drinking water, trade waste, sewage, soils and other environmental sources. On average in Townsville 70 per cent of household consumption goes on outdoor use! This practice has to change in our dry tropics location. Smart grasses, more trees, better detection of leakage in the reticulation network, and best- practice council covenants for all new developments.
Living in the driest inhabited continent on Earth, we need to think about water use every day.
As climate change escalates and the world’s population grows, concentrated in high- density centres, supplying adequate treated drinking water will be an increasing challenge.
Governments must prioritise and plan well ahead to provide infrastructure for water security including hi- tech treatment facilities.
This must be complemented by ongoing education so everyone is committed to treating our precious drinking supply properly.