2001/18 – Forrest Beach (Queensland) – Iron

2016/17: Forrest Beach (Queensland) – Iron 0.5mg/L (max), 0.36mg/L (av.)

2017/18: Forrest Beach (Queensland) – Iron 0.37mg/L (max), 0.31mg/L (av.)

Iron levels in raw water are quite scattered with the historical maximum sample of 0.39 mg/L. Iron levels in the treated and reticulated water have often exceeded the guideline. The maximum reticulation sample taken for iron had a reading of 0.77 mg/L. There have been five historical instances that have exceeded the ADWG:
• 0.65 mg/L – 20th June 2001 sample taken from water tower (Turbidity levels were also exceeded in this sample).
• 0.9 mg/L – 24 January 2002 sample taken from water tower.
• 0.9 mg/L – 16 July 2002 sample taken from Beatts Road.
• 0.31 mg/L – 8th January 2003 sample taken from water tower.
• 0.39 mg/L – 17 June 2009 sample taken from Pangola Street (pH exceeded guideline in same sample).
We note a number of obvious data entry errors in the results and will be resolved in a future data update. It is expected that raw water source selection will largely resolve this issue

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

Forrest Beach (Queensland) – Turbidity

The raw water has high levels of turbidity. Bore 6 has the highest level of turbidity with a maximum value of 215 NTU. Treated water shows scattered levels of turbidity that all fall below the guideline. There was one occurrence where the turbidity level was 5 NTU. Reticulated water had five instances where the sample for  turbidity exceeded the guideline aesthetic limit:
• 4.3 NTU – 23 June 2001, sample taken from water tower (Iron levels were also exceeded in this sample).
• 16.5 NTU – 23 January 2002, sample taken from water tower.
• 17.5 NTU – 24 January 2002, sample taken from water tower.
• 15 NTU – 6 March 2002, sample taken from water tower.
• 16 NTU – 10 September 2008, sample taken from water tower.
There were numerous results in the reticulated water where the turbidity was above 1 NTU. Source selection is planned to treat this issue however further work is planned to investigate chlorine disinfection increases to  address this issue and is an RMIP action.

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

Colour levels in raw water at Forrest Beach are scattered, as shown in , but there are some samples that are quite high. An historical abnormal result of 249 HU occurred in September 2006, but it is hard to determine if this is operator error or a rare occurrence. Colour in treated water has been sampled to be below the guideline, but levels are quite high with many samples being over 10 HU. Reticulated water showed a similar result with one ample being 17 HU. Selection of raw water sources may have a positive effect on this issue. Soda Ash is used in Scheme 2 and may be replicated here, however to minimise expense, switching raw water sources in currently considered the most appropriate solution.