(Potable system–Non Potable Zone (Bac and Chem)

Mimili (South Australia) – Nitrate

5 August 2014: Mimili (South Australia) – Nitrate + Nitrite as NO3: 89.5mg/L

10 August 2015: Mimili (South Australia) – Nitrate + Nitrite as NO3: 114mg/L

10 August 2015: Mimili TS Drinking Water (South Australia) – Nitrate + Nitrite as NO3: 52.3mg/L

26/8/19: Mimili Nitrate + Nitrite as NO3 45.19mg/L (max), 38.51mg/L (av)

25/2/20: Mimli Nitrate + Nitrite as CO3 65.12mg/L (potable/non-potable)

23/2/21: Mimili Nitrate + Nitrate as NO3 76.2mg/L (Potable System – Non Potable Zone)

8/3/22: Mimili NDW TS Non Potable Nitrate + Nitrite 61.13mg/L (max)

Excessive nitrates in the diet reduce blood’s ability to carry oxygen. In infants, this can cause the potentially life-threatening Blue Baby Syndrome, where the skin takes on a bluish colour and the child has trouble breathing. Housing provides bottled water for infants under three months in communities with high nitrates. Long term solutions would likely include asset replacements or upgrades or finding new water sources, or a combination of these.

Child Heath Levels Nitrate: 50mg/L. Adult Heath Levels Nitrate: 100mg/L

Mimili (South Australia) – Fluoride

19 November 2012: Mimili (South Australia) – Fluoride 1.9mg/L

19 August 2013: Mimili (South Australia) – Fluoride 2.1mg/L

5 August 2014: Mimili (South Australia) – Fluoride 2.1mg/L

10 August 2015: Mimili (South Australia) – Fluoride 2.5mg/L

25/2/20: Mimili (South Australia) Fluoride 2.1mg/L

23/2/21: Mimili (South Australia) Fluoride 2.1mg/L

8/3/22: Mimili NDW TS Non Potable Fluoride  2.2mg/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

Mimili (South Australia) – Chloride

19 November 2012: Mimili (South Australia) Chloride 341mg/L

25/2/20: Mimili Chloride 340mg/L (potable/non-potable)

“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

Mimili (South Australia) – Silica

19 August 2013: Mimili (South Australia). Silica 93.3mg/L

5 August 2014: Mimili (South Australia). Silica 86.5mg/L

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