2004/14 – Bermagui (New South Wales) – Turbidity, Iron

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2004/14 – Bermagui (New South Wales) – Turbidity

From a total of 62 samples, 2 exceedances occurred from 1 Jan 2004 to 31 Mar 2014. The
highest exceedance of 8.8 NTU was recorded on 1 May 2012 at sample site 709 in
Bermagui. The other exceedance was 5.1 NTU on 16 Feb 2010 at sample site 719 in
Bermagui. Iron exceedances were also recorded in the samples.

Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.

Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
consumer’s tap

2004/14 Bermagui (New South Wales) – Iron

From a total of 52 samples, there were 35 exceedances from 1 Jan 2004 to 31 Mar 2014.
The ADWG value for iron is based on aesthetic considerations is 0.3 mg/L. Iron has a taste
threshold of about 0.3 mg/L, gives the water a rust brown appearance and can cause
staining of laundry and plumbing fittings. This high number of exceedences suggests iron in
the distribution system is a persistent problem.

Based on aesthetic considerations (precipitation of iron from solution and taste),
the concentration of iron in drinking water should not exceed 0.3 mg/L.
No health-based guideline value has been set for iron.

Iron has a taste threshold of about 0.3 mg/L in water, and becomes objectionable above 3 mg/L. High iron concentrations give water an undesirable rust-brown appearance and can cause staining of laundry and plumbing fittings, fouling of ion-exchange softeners, and blockages in irrigation systems. Growths of iron bacteria, which concentrate iron, may cause taste and odour problems and lead to pipe restrictions, blockages and corrosion. ADWG 2011