1997/1999 + 2012/21 – Yunyarinyi (South Australia) – Fluoride, Silica, Hardness, Total Dissolved Solids

Non Potable Drinking Water Supply

Yunyarinyi (South Australia) – Fluoride

15/8/16: Yunyarinyi (South Australia) – Fluoride 1.6mg/L

28/8/19: Yunyatinyi (South Australia) – Fluoride 1.6mg/L

26/8/20: Yunyarinyi (South Australia) – Fluoride 1.6mg/L

9/8/21: Yunyarinyi NDW TS Non Potable Fluoride 1.6mg/L (max)

“Fluoride occurs naturally in seawater (1.4 mg/L), soil (up to 300 parts per million) and air (from volcanic gases and industrial pollution). Naturally occurring fluoride concentrations in drinking water depend on the type of soil and rock through which the water drains. Generally, concentrations in surface water are relatively low (<0.1–0.5 mg/L), while water from deeper wells may have quite high concentrations (1–10 mg/L) if the rock formations are fluoride-rich.” 2011 ADWG. Health Guideline: 1.5mg/L

Yunyarinyi (South Australia) – Silica

19 August 2013: Yunyarinyi (South Australia). Silica 82mg/L

5 August 2014: Yunyarinyi (South Australia). Silica 78.9mg/L

To minimise an undesirable scale build up on surfaces, silica (SiO2) within drinking waters should not exceed 80 mg/L.
Silica present in water is usually referred to as amorphous silica (i.e. lacking any crystalline structure). When silica is dissolved within water it forms monosilicic acid:
SiO2 + 2H2O à Si(OH)4
When the concentrations of monosilicic acid increase, polymerisation of the silica occurs, forming polysilicic acids followed by formation of colloidal silica. Monosilicic acid and polysilicic acids are the forms of silica analysed when determining dissolved silica content.
The deposition of silica from solutions can occur via various mechanisms. The deposition of silica that can cause the most problems for the water industry is via silica’s ability to deposit on solid surfaces that have hydroxyl (OH) groups present. Surfaces that commonly have hydroxyl groups present are glass and metallic surfaces. For example, dissolved silica will react with the surfaces of glass and begin to form a white precipitate. The silica forms silicates on the surface, resulting in silica build-up. In cases where customer complaints occur due to scale build-up, water hardness and silica concentrations should be investigated to determine the cause.
Silica can be a problem in water treatment due to its ability to cause fouling of reverse osmosis (RO) membranes (Sheikholeslami and Tan, 1999, Ning 2002, Sahachaiyunta and Sheikholeslami 2002). This occurs when the dissolved silica of the concentrate becomes super-saturated, causing silicates to form in the presence of metals, and these deposit on the membrane surface. The silicate then dehydrates, forming hard layers on the membrane that reduce the effectiveness of the process… 2011 ADWG

Yunyarinyi (South Australia) – Hardness

2012/16: Yunyarinyi (South Australia) – Hardness average 254.4mg/L (5 detections out of 5 above guideline)

9/8/21: Yunyarinyi TS NDW Non Potable Total Hardness 9/8/21 258mg/L (max)


“To minimise undesirable build‑up of scale in hot water systems, total hardness (as calcium
carbonate) in drinking water should not exceed 200 mg/L.

Hard water requires more soap than soft water to obtain a lather. It can also cause scale to form on hot water pipes and fittings. Hardness is caused primarily by the presence of calcium and magnesium ions, although other cations such as strontium, iron, manganese and barium can also contribute.”

Yunyarinyi (Kenmore Park) 1997-1999

The salinity of these groundwaters is 540-670 mg/L . TDS with nitrate concentrations of 22-44 mg/L and fluoride concentrations of 1.5 mg/L. Salinity is within the Australian Drinking Water Guidelines (1996) although water quality with respect to fluoride is marginal. The 1997 water quality investigation detected total coliform counts in two of the bores possibly indicating the presence of biofilms in the bore casing which will need to be cleaned out (Fitzgerald et al.,

Total Dissolved Solids 1997-1999

“No specific health guideline value is provided for total dissolved solids (TDS), as there are no
health effects directly attributable to TDS. However for good palatability total dissolved solids
in drinking water should not exceed 600 mg/L.

Total dissolved solids (TDS) consist of inorganic salts and small amounts of organic matter that are dissolved in water. Clay particles, colloidal iron and manganese oxides and silica, fine enough to pass through a 0.45 micron filter membrane can also contribute to total dissolved solids.