Mt Isa (Queensland) – Lead
2013/4: Mt Isa (Queensland) – Lead
Lead Australian Drinking Water Guideline 0.01mg/L
“… Lead can be present in drinking water as a result of dissolution from natural sources, or from household plumbing systems containing lead. These may include lead in pipes, or in solder used to seal joints. The amount of lead dissolved will depend on a number of factors including pH, water hardness and the standing time of the water.
Lead is the most common of the heavy metals and is mined widely throughout the world. It is used in the production of lead acid batteries, solder, alloys, cable sheathing, paint pigments, rust inhibitors, ammunition, glazes and plastic stabilisers. The organo-lead compounds tetramethyl and tetraethyl lead are used extensively as anti-knock and lubricating compounds in gasoline…
Mt Isa (Queensland) – Trihalomethanes
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
Mount Isa (Queensland) – Chloroacetic Acids
Of the samples collected for THAAs, 4 exceeded the ADWG for trichloroacetic acid of 100μg/l. The results ranged from 16 to 130μg/l. The results are shown in Appendix A – Table 2, and further detail is given in section 5. In November 2016 Queensland Health published a new guideline limit for Total Haloacetic Acids of 0.1mg/L, ADWG does not define a limit for this group. Thirteen samples exceeded the Queensland Health defined Total Haloacetic Acid limit of 0.1mg/l, ranging from 0.07 to 0.21mg/l
Exceedance of Trichloroacetic acid (previous financial year)
Incident description: On 7th June 2016, the result for trichloroacetic acid at sampling location MICC Town High (S29) was 110 μg/L. This result exceeded the ADWG health guideline limit of 100 μg/L. The result was reported to the DEWS Water Supply Regulation and recorded as incident DWI-7-199-00045. This incident remained open into the new financial year, with a further four tests returning high results in the trichloroacetic acid concentration noted on 4th July, 11th July, 13th July and 19th July 2016; with the results being 119, 130, 100 and 102 μg/L respectively. Concurrently Total Haloacetic Acids were also high for all samples between July 5 and August 2, 2016. The THAA exceedances were assessed against the new November 2016 revision of the ADWG and the incident was closed.
Corrective and preventative actions: MIWB informed the DEWS Water Supply Regulation of the incident within the incident notification timeframe. The MIWB’s operations and maintenance Contractors were informed of the incident. Chlorine grab sample results of free and total chlorine were monitored and found to be within the ADWG health guideline limit. Closer monitoring of chlorine residuals was initiated in an effort to reduce formation of DBP’s without compromising bacteriological disinfection. Investigation steps included a chlorine reduction trial in the storage tanks, frequent monitoring of chlorine residuals and sampling at various points in the system; in addition to the final discharge points.
Exceedance of total Haloacetic acids
Incident Description: On January 31, 2017 the result for Total Haloacetic Acid (THAA) at sampling location MICC Town High (S29) was 0.2mg/l (152 μg/l) which exceeded the Queensland Health advised guideline limit of 0.1mg/l. The result was reported to the DEWS Water Supply Regulation and recorded as incident DWI-7-199-0046.
Corrective and preventative actions: MIWB informed the DEWS Water Supply Regulation of the incident within the incident notification timeframe. The MIWB’s operations and maintenance contractor was informed of the incident. Chlorine contact times were calculated for the primary disinfection tank and the target residual chlorine level was reduced in an effort to reduce the THAA formation. While the incident remained open, two further high readings were noted; one on February 21, and one on February 28, 2017. Both readings were 0.2mg/l (162μg/l each).
Exceedance of total Haloacetic acids
Incident Description: On April 24, 2017 the result for Total Haloacetic Acid (THAA) at sampling location MICC Town High (S29) was 0.2mg/l (154 μg/l) which exceeded the Queensland Health advised guideline limit of 0.1mg/l. The result was reported to the DEWS Water Supply Regulation; and recorded as incident DWI-7-199-0047.
Corrective and preventative actions: MIWB informed the DEWS Water Supply Regulation of the incident within the incident notification timeframe. The MIWB’s operations and maintenance Contractors were informed of the incident. Contact times were calculated in the primary disinfection tank and the target residual chlorine level was reduced. During the incident remaining open, four further high readings were noted on 23rd May, 29th May, 5th June and 13th June, 2017 with all of the results being 0.2mg/l (160, 158, 163 and 151 μg/L respectively). THAA sampling frequency was increased from monthly to weekly, and was incorporated into the new verification monitoring plan for the next financial year. An on-line chlorine analyser had also been installed to monitor the semi-treated water extracted from the 50ML tank. This allows more regular monitoring of the cool weather impacts of chlorine contact times which appear to be a key factor in DBP formation.
Australian Guidelines Trichloroacetic Acid 0.100mg/L, Dichloroacetic Acid 0.100mg/L
“Chloroacetic acids are produced in drinking water as by-products of the reaction between chlorine and naturally occurring humic and fulvic acids. Concentrations reported overseas range up to 0.16mg/L and are typically about half the chloroform concentration. The chloroacetic acids are used commercially as reagents or intermediates in the preparation of a wide variety of chemicals. Monochloroacetic acid can be used as a pre-emergent herbicide, dichloroacetic acid as an ingredient in some pharmaceutical products, and trichloroacetic acid as a herbicide, soil sterilant and antiseptic.” Australian Drinking Water Guidelines – National Health and Medical Research Council…
There are no epidemiological studies of TCA carcinogenicity in humans. Most of the human health data for chlorinated acetic acids concern components of complex mixtures of water disinfectant by-products. These complex mixtures of disinfectant by-products have been associated with increased potential for bladder, rectal, and colon cancer in humans [reviewed by Boorman et al. (1999); Mills et al. (1998)].” Ref: tmp/Trichloroacetic acid (TCA) CASRN 76-03-9 IRIS US EPA.htm
Mt Isa (Queensland) – Cyanobacteria