2013/21: Nebo Road Water Treatment Plant (Mackay, Queensland). Pesticides: Atrazine, Dinoseb, Diuron, Hexazinone, Metolachlor

Australian Record for Diuron in drinking water

Date of Non-Compliance: February & March 2013

Date of Notification: 5 November 2013

Scheme: Mackay – Nebo Rd Treated Water – Diuron and Atrazine (pesticides)

390 μg/L & 350 μg/L. These levels are 19.5 and 17.5 times over guidelines levels.

Guideline levels for both pesticides are 20 μg/L.

Routine monitoring of drinking water detected Diuron and Atrazine in the treated water at Nebo Rd WTP at elevated levels which exceed the ADWG 2011 Health guideline value of 20 μg/L and 20 μg/L respectively. High levels of chemicals were also detected in the sample of the incoming raw water to the WTP collected on the same day as the treated water. Analysis of rainfall data for Mackay indicates that prior to the detections a significant rainfall event occurred which is likely to have washed sediments and chemicals into the Pioneer River which is the raw water source for Nebo Rd WTP.

A failure of the mass spectrometer at the Mackay Water and Waste Services Scientific and Analytical Services Laboratory (SAS) resulted in samples collected from August 2012 to April 2013 to not be analysed by SAS and instead sent to QLD Health laboratory for analysis. This resulted in a delay in obtaining results and analysing the results to identify non-compliances.

Source: Mackay Drinking Water Quality Management Plan 2013-14

Nebo Road Water Treatment Plant (Raw Water)

November 2017: Atrazine 0.2468ug/L

December 2017: Atrazine 0.8155ug/L, Diuron 0.6916ug/L

January 2018: Atrazine 0.394ug/L, Diuron 0.6148ug/L, Hexazinone 0.2612ug/L

February 2018: Atrazine 0.0755ug/L, Diuron 0.4473ug/L

March 2018: Atrazine 0.3342ug/L, Diuron 0.7559ug/L, Hexazinone 0.4089ug/L

April 2018: Atrazine 0.2038ug/L, Diuron 0.4794ug/L

May 2018: Dinoseb 0.001ug/L

2020/21: Atrazine 0.16ug/L (max), 0.03ug/L (mean)

2020/21: Hexazinone 0.24ug/L (max), 0.03ug/L (mean)

2020/21: Metolachlor 0.14ug/L (max), 0.01ug/L (mean)

Source: Mackay Drinking Water Quality Management Plan 2017-18 + 2020/21