2007/18 – Hopetoun (Western Australia) – Hardness, Total Dissolved Solids, Chloride, Sodium, Silica

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Hopetoun – Western Australia – Hardness

2007/08: Hopetoun (Western Australia) – Hardness 222mg/L (Highest Detection Only)

2009/10: Hopetoun (Western Australia) – Hardness 210mg/L (Highest Detection Only)

2011/12 Hopetoun (Western Australia) Hardness 210mg/L (max), 134mg/L (av)

2016/17 Hopetoun (Western Australia) Hardness 220mg/L (max), 137mg/L (mean)

GUIDELINE

“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.”

Australian Drinking Water Guidelines 2011

Hopetoun – Western Australia – Total Dissolved Solids

2007/08: Hopetoun (Western Australia) – Total Dissolved Solids 682 mg/L (Maximum Level)

2008/09: Hopetoun (Western Australia) – Total Dissolved Solids 709 mg/L (max), 618mg/L (mean)

2009/10: Hopetoun (Western Australia) – Total Dissolved Solids 768 mg/L (max)

2011/12 Hopetoun (Western Australia) Total Dissolved Solids 678mg/L (max), 649mg/L (av)

2013/14 Hopetoun (Western Australia) Total Dissolved Solids  833mg/L (max), 640mg/L (av)

2014/15 Hopetoun (Western Australia) Total Dissolved Solids 641mg/L (max), 599mg/L (av)

2015/16 Hopetoun (Western Australia) Total Dissolved Solids 624mg/L (max), 546mg/L (av)

2016/17 Hopetoun (Western Australia) Total Dissolved Solids 723mg/L (max), 621mg/L (av)

2017/18 Hopetoun (Western Australia) Total Dissolved Solids 654mg/L (max), 609mg/L (av)

GUIDELINE

“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.

Total dissolved solids comprise: sodium, potassium, calcium, magnesium, chloride, sulfate, bicarbonate, carbonate, silica, organic matter, fluoride, iron, manganese, nitrate, nitrite and phosphates…” Australian Drinking Water Guidelines 2011

Hopetoun (Western Australia) – Chloride

2013/14 Hopetoun (Western Australia) Chloride 400mg/L (max), 254mg/L (av)

2014/15 Hopetoun (Western Australia) Chloride 270mg/L (max), 225mg/L (mean)

2015/16 Hopetoun (Western Australia) Chloride 260mg/L (max), 204mg/L (mean)

2016/17 Hopetoun (Western Australia) Chloride 260mg/L (max), 226mg/L (mean)

2017/18 Hopetoun (Western Australia) Chloride 265mg/L (max), 196.3mg/L (mean)

“Chloride is present in natural waters from the dissolution of salt deposits, and contamination from effluent disposal. Sodium chloride is widely used in the production of industrial chemicals such as caustic soda, chlorine, and sodium chlorite and hypochlorite. Potassium chloride is used in the production of fertilisers.

The taste threshold of chloride in water is dependent on the associated cation but is in the range 200–300 mg/L. The chloride content of water can affect corrosion of pipes and fittings. It can also affect the solubility of metal ions.

In surface water, the concentration of chloride is usually less than 100 mg/L and frequently below 10 mg/L. Groundwater can have higher concentrations, particularly if there is salt water intrusion.

Based on aesthetic considerations, the chloride concentration in drinking water should not exceed 250 mg/L.

No health-based guideline value is proposed for chloride.” 2011 Australian Drinking Water Guidelines

Hopetoun (Western Australia) – Sodium

2013/14 Hopetoun (Western Australia) Sodium 250mg/L (max), 158mg/L (av)

2014/15 Hopetoun (Western Australia) Sodium 180mg/L (max), 139mg/L (av)

“Based on aesthetic considerations (taste), the concentration of sodium in drinking water
should not exceed 180 mg/L….The sodium ion is widespread in water due to the high solubility of sodium salts and the abundance of mineral deposits. Near coastal areas, windborne sea spray can make an important contribution either by fallout onto land surfaces where it can drain to drinking water sources, or from washout by rain. Apart from saline intrusion and natural contamination, water treatment chemicals, domestic water softeners and
sewage effluent can contribute to the sodium content of drinking water.” ADWG 2011

2017/18 – Hopetoun (Western Australia) – Silica

2017/18 Hopetoun (Western Australia) Silica 150mg/L (max), 121.3mg/L (mean) (listed as Silicon in Water Corporation Water Quality Report 2017-18)

To minimise an undesirable scale build up on surfaces, silica (SiO2) within drinking waters should not exceed 80 mg/L.
GENERAL DESCRIPTION
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