Bulahdelah (New South Wales) – Trihalomethanes

Bulahdelah (New South Wales): Trihalomethanes: 250μg/L (max), 191.2μg/L (average)

Midcoast Water: DRINKING WATER QUALITY MANAGEMENT SYSTEM ANNUAL REPORT SUMMARY 2016-2017

Bulahdelah (New South Wales): Trihalomethanes: 257μg/L (max), 190.76μg/L (average)

Bulahdelah water supply achieved 97.7% of water quality results in the reticulation system meeting ADWG, compared to 100% during 2016 – 2017. There were 349 analytes tested for verification monitoring within the Bulahdelah system.

Total THMs were above the ADWG value on two occasions during summer. Increased levels of naturally occurring dissolved organic carbon in Crawford River during the warmer months contributed to the higher levels of THMs.

Midcoast Water: DRINKING WATER QUALITY MANAGEMENT SYSTEM ANNUAL REPORT SUMMARY 2017-2018

Trihalomethanes Australian Guideline Level 250μg/L (0.25mg/L)

Why and how are THMs formed?
“When chlorine is added to water with organic material, such as algae, river weeds, and decaying leaves, THMs are formed. Residual chlorine molecules react with this harmless organic material to form a group of chlorinated chemical compounds, THMs. They are tasteless and odourless, but harmful and potentially toxic. The quantity of by-products formed is determined by several factors, such as the amount and type of organic material present in water, temperature, pH, chlorine dosage, contact time available for chlorine, and bromide concentration in the water. The organic matter in water mainly consists of a) humic substance, which is the organic portion of soil that remains after prolonged microbial decomposition formed by the decay of leaves, wood, and other vegetable matter; and b) fulvic acid, which is a water soluble substance of low molecular weight that is derived from humus”. US EPA

Trihalomethanes Australian Guideline Level 250μg/L (0.25mg/L)

Why and how are THMs formed?
“When chlorine is added to water with organic material, such as algae, river weeds, and decaying leaves, THMs are formed. Residual chlorine molecules react with this harmless organic material to form a group of chlorinated chemical compounds, THMs. They are tasteless and odourless, but harmful and potentially toxic. The quantity of by-products formed is determined by several factors, such as the amount and type of organic material present in water, temperature, pH, chlorine dosage, contact time available for chlorine, and bromide concentration in the water. The organic matter in water mainly consists of a) humic substance, which is the organic portion of soil that remains after prolonged microbial decomposition formed by the decay of leaves, wood, and other vegetable matter; and b) fulvic acid, which is a water soluble substance of low molecular weight that is derived from humus”. US EPA

2017/18 – Bulahdelah (New South Wales) – Iron

2017/18 – Bulahdelah (New South Wales) – Iron 0.324 (max), 0.036 (av.)

On six occasions from March – May, concentrations of metals (aluminium, iron and manganese) were above ADWG values in this supply. This was due to an exceptional water quality event in Crawford River, including low dissolved oxygen and high metals. A full explanation is provided in 6.1 Bulahdelah water quality incident.

ADWG Guideline: 0.3mg/L

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