Residents assured drinking water safe
Moranbah and Nebo residents, south-west of Mackay in north Queensland, are being assured their water is safe to drink, after the discovery of benzene in three coal seam gas wells last week.
A spokesman for the Isaac Regional Council says Moranbah is supplied from groundwater supplies from the Burdekin and Eungella dam, and not from underground supplies.
He says Nebo’s supply is from an underground aquifer.
Arrow Energy says trace levels of benzene have been found in the three wells outside Moranbah and is unlikely to pose a public health risk.
Nebo (Queensland) – Dissolved Oxygen
2016/17: Nebo (Queensland) Dissolved Oxygen 85.9% (max), av. 70.7%. 11 exceedences during year.
2015/16: Nebo (Queensland) Dissolved Oxygen 80.5% (max), av. 65.482%. 5 exceedences during year.
Based on aesthetic considerations, it is desirable that the dissolved oxygen concentration in drinking water be greater than 85% saturation.
No health-based guideline value has been set for dissolved oxygen.
Drinking water will generally contain an adequate concentration of dissolved oxygen; however, under some circumstances the oxygen concentration may be reduced. This may occur, for instance, where water has been drawn from deep storages, where there is considerable growth of microorganisms in a distribution system, or following prolonged periods of high water temperature.
Low oxygen concentrations or anoxic conditions enable nuisance anaerobic microorganisms to grow, producing by-products that affect the aesthetic quality of the water and increase corrosion of pipes and fittings.
There are a number of such nuisance microorganisms. Manganese-reducing bacteria produce black manganese deposits which can slough off pipes and soil laundry. Sulfate-reducing bacteria can produce hydrogen sulfide, giving drinking water a ‘rotten egg’ smell. Nitrate-reducing bacteria can produce nitrite. Iron-reducing bacteria can increase the concentration of ferrous ion in solution which will lead to the deposition of insoluble ferric salts when aeration is increased.
Localised pH changes associated with the growth of nuisance microorganisms can cause rapid corrosion in metal pipes.
Water from groundwater sources will generally have low oxygen concentrations and while this may cause no difficulties for most supplies, some supplies may need aeration to improve water quality (e.g. taste and odour). ADWG 2011
Nebo – (Queensland) – Hardness
2016/17: Nebo (Queensland) – Hardness 487.57mg/L (Highest Detection), (258.08mg/L av)
6 exceedences during year
“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
2016/17 – Nebo (Queensland) – Total Dissolved Solids
“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.