❓ A WA parliamentary question addresses water quality concerns at Mullaloo Beach, focusing on data access, faecal contamination sources, and ammonia discharge from the Beenyup Wastewater Treatment Plant. The Minister's response provides data access details, attributes contamination to animal sources, and outlines ammonia management measures.
AnsweredQoN 177Legislative Council
QuestionView source ↗
(1) I refer to the report titled ‘Independent Investigation into Water Quality and Local Current Flows at Mullaloo Beach’, prepared by MetOcean for the Department of Water and Environmental Regulation, issued on 24 January 2025 (the O2 Report), and I ask: (a) can the Minister confirm whether the Water Corporation provided full access to raw, unredacted telemetry and historian data from the Beenyup Wastewater Treatment Plant to the authors of the O2 Report; (b) if yes to (a), did this data include all minute-by-minute flow rates and chemical dosage levels; (c) if no to (a), why was this data withheld; and (d) can the Minister provide the monthly treated wastewater discharge data from the Beenyup Wastewater Treatment Plant for the 2023–2024 reporting period, including the following: (i) volume discharged; (ii) nutrient concentrations; (iii) organic particulate levels; and (iv) any other parameters monitored by the Water Corporation? (2) In reference to (1), I refer to Table 14 on page 56 of the O2 Report which sets out multiple instances of faecal contamination (Enterococci levels) exceeding acceptable recreational water quality thresholds at Mullaloo Beach and Pinnaroo Point, and I ask: (a) can the Minister advise where this faecal contamination is originating from; (b) what investigations have been undertaken to identify the source; (c) what measures have been taken to protect public health; and (d) has the Minister undertaken any corrective actions in response to the increased organic load? (3) I refer to the Environmental Protection Authority’s Report 1751 (2023), 'Beenyup Wastewater Ocean Outlets into Marmion Marine Park', which confirms that ammonia levels in the wastewater discharge have risen to 12 milligrams per litre, substantially higher than earlier approvals, and I ask: (a) can the Minister provide a full breakdown of ammonium and ammonia used by the Water Corporation for flushing and cleaning; and (b) can the Minister explain what measures are in place to limit ammonia discharge?
AnswerView source ↗
Answered
25 June 2025
Responded by
Leader of the House representing the Minister for Water
Response time
8 days
(1)
(a)
Yes. Water Corporation provided all requested and available information and data to DWER to support the development of the O2 Report.
(b)– (c)
The data was Beenyup Water Resource Recovery Facility (WRRF) Ocean Outfall flow data and composite sampling taken at 30-minute increments. No chemical dosage information was provided as Beenyup WRRF does not dose any chemicals directly into the ocean outfall.
(d)
All parameters tested by Water Corporation, and data results, are available in the Perth Long Term Ocean Outlet Monitoring Program (PLOOM) 2023-24 Annual Report which is publicly available on the Water Corporation website at https://www.watercorporation.com.au/Our-water/Wastewater/Ocean-outfall/Perth-monitoring-program
(2)
a) as described by the O2 report, it is likely detectable concentrations of Enterococci can be attributed to animal sources.
b) as sample results have not exceeded the National Health and Medical Research Council primary contact guideline level routine monitoring continues to occur.
c) as above.
d) No, Water Corporation has not taken any corrective actions as no notifiable exceedances have occurred.
(3)
(a)
Neither ammonium nor ammonia is used at Beenyup WRRF or at Beenyup Advanced Water Recycling Plant for flushing and cleaning purposes.
(b)
The Beenyup WRRF treats ammonium and ammonia via the secondary treatment system. There are various points of control to manage performance during this process, ensuring that the final effluent complies with the licence regulations under the Department of Water and Environmental Regulation.
(a)
Yes. Water Corporation provided all requested and available information and data to DWER to support the development of the O2 Report.
(b)– (c)
The data was Beenyup Water Resource Recovery Facility (WRRF) Ocean Outfall flow data and composite sampling taken at 30-minute increments. No chemical dosage information was provided as Beenyup WRRF does not dose any chemicals directly into the ocean outfall.
(d)
All parameters tested by Water Corporation, and data results, are available in the Perth Long Term Ocean Outlet Monitoring Program (PLOOM) 2023-24 Annual Report which is publicly available on the Water Corporation website at https://www.watercorporation.com.au/Our-water/Wastewater/Ocean-outfall/Perth-monitoring-program
(2)
a) as described by the O2 report, it is likely detectable concentrations of Enterococci can be attributed to animal sources.
b) as sample results have not exceeded the National Health and Medical Research Council primary contact guideline level routine monitoring continues to occur.
c) as above.
d) No, Water Corporation has not taken any corrective actions as no notifiable exceedances have occurred.
(3)
(a)
Neither ammonium nor ammonia is used at Beenyup WRRF or at Beenyup Advanced Water Recycling Plant for flushing and cleaning purposes.
(b)
The Beenyup WRRF treats ammonium and ammonia via the secondary treatment system. There are various points of control to manage performance during this process, ensuring that the final effluent complies with the licence regulations under the Department of Water and Environmental Regulation.
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