2016/17 – MICC Town High (Mt Isa – Queensland) – Trichloroacetic Acid

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 tri-chloroacetic 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.

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).

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.

Mt Isa Drinking Water Quality Management Plan 2016/17

ADWG Guideline: 0.1mg/L (100µg/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