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Last Updated: Wednesday, 07 November 2018 11:53

The harmful effects of a high salinity content in Toowoomba’s wastewater means a threat to the health and productivity of our catchments, as well as a danger to our valuable rural industry. It can also affect our urban development and infrastructure such as roads and bridges, household water quality, not to mention its damaging impact to the environment.

How to help reduce salt use in the home and business

  1. Choose liquid laundry detergents over powders – this can reduce the amount of sodium in domestic wastewater by more than 200g per wash.
  2. If using laundry powders, choose concentrated powders.
  3. Don’t use more detergent than the manufacturer recommends.
  4. Try to reduce the amount of detergent used by washing full loads in both the dishwasher and the washing machine (this will also save water).
  5. Minimise the use of salt and other food additives in cooking.
  6. If you have a domestic water softener, think about whether you really need it.

For more information see Lanfax Laboratories (New window) - an independent, commercial and research organisation with special interests in soil, water and wastewater analysis.

What we are doing to manage salinity

We are actively looking for wastewater reuse opportunities including industrial and agricultural uses. However, high salinity in the wastewater makes it less attractive for these purposes because:

  1. It limits the types of crops that can be irrigated with the water and the amount of water that can be used.
  2. It restricts the types of industries that can use the wastewater and increases the  cost of treatment required to make the water suitable for reuse.
  3. Conventional wastewater treatment processes do not remove dissolved salts.

Through its trade waste policy, we are working in partnership with industry to reduce wastewater salinity. By educating residents on how our actions can adversely impact the catchment to minimise salt use and working with industry, we have taken the initiative to turn this problem around so our city becomes a leading example to other regions.

The consequences of salinity

Treated wastewater from Toowoomba discharges into the Murray Darling system via Gowrie Creek. A high level of salinity in this wastewater increases the salinity of water in the Murray Darling system and that means:

  1. Irrigation water taken from the river system by farmers contains higher levels of salinity. Irrigation with this water can contribute to soil and groundwater salinity problems for our rural sector.
  2. The quality of water available to towns and cities along the river system is poorer and the water requires more extensive and expensive treatment to make it suitable for use as drinking water.
  3. The habitat of animals, birds, fish and plants along with the general environment is adversely impacted.
  4. Opportunities to beneficially reuse our wastewater are limited, or made less attractive.

What is salinity and where does the salt come from?

Salinity refers to the presence of salts in our water and wastewater. These salts include dissolved chloride, sulphate, phosphate, carbonate, bicarbonate, sodium, calcium, magnesium, potassium and more. The Total Dissolved Salts (TDS) provide an overall measure of salinity.

The major sources come from industry, commercial operators and domestic households. Each of these sectors contributes to the salinity problem through their use of raw materials, process chemicals, cleaning chemicals, raw foodstuffs, cooking additives, dishwashing and laundry detergents, personal toiletries and domestic water softeners. Many powdered laundry and dishwasher detergents contain large amounts of fillers, which do not add any detergent action to the product, but can account for up to 40% of the sodium salts in domestic wastewater.  As well, detergents and other active ingredients are usually present in the form of sodium salts to improve their solubility in water.

Salinity in Toowoomba

The amount of TDS per head of population in Toowoomba’s wastewater is between 58% and 120% higher than for other comparable inland Australian cities. Toowoomba’s Wetalla wastewater treatment plant currently discharges TDS into the Murray Darling system via Gowrie Creek at rates of about:

  • 10,800 tonnes per year
  • 207 tonnes per week
  • 29.5 tonnes per day

18% of this TDS comes from the salts dissolved in the town water supply. The remaining, 82% (8900 tonnes per year or 24 tonnes per day), is shared between industry, commercial operators and domestic households.