Carmila (Queensland) – Dissolved Oxygen
2016/17: Carmilla (Queensland) Dissolved Oxygen 100% (max), av. 83.49%. 9 exceedences during year.
2017/18: Carmilla (Queensland) Dissolved Oxygen 104.39% (max), av. 94.31 (av.) 2 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