Page 4212 - Week 12 - Thursday, 1 December 2022

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(9) especially as the sewers react to stormwater ingress almost as quickly as the normal stormwater system.

(10) What is the population that LMWQCC can treat if the treatment capacity has not increased in 50 years.

Mr Rattenbury: The answer to the member’s question is as follows:

1. Icon Water advises that the Lower Molonglo’s original design capacity was 270,000 equivalent persons (EP). The original plant was designed to be augmented in three stages to an ultimate capacity of 1,000,000 EP. In 2010, Icon Water augmented the Lower Molonglo Water Quality Control Centre (LMWQCC), increasing capacity to treat up to 100 megalitres per day, which is equivalent to approximately 550,000 EP.

In 2012, Icon Water undertook a capacity assessment which highlighted that the plant was sensitive to primary treatment variability, particularly sludge settleability, which significantly impacted the secondary treatment process capacity. This report made several recommendations for operational approaches to improve overall performance, which have been implemented.

2. Icon Water advises that since the 2012 review, Canberra’s population has grown more rapidly, and Icon Water is beginning to see the impact of a changing climate on the wastewater system. This has brought forward the requirement for augmentations of some systems at LMWQCC.

Several major projects were initiated in the 2013 2018 and 2018 2023 regulatory periods to increase capacity in the secondary treatment and solids handling systems. They are now included in Icon Water’s 2023 2028 pricing submission for construction. These projects are currently moving from concept design phase to planning and detailed design, having been through a rigorous options assessment to identify suitable technologies that are able to satisfy Icon Water's operating and performance requirements. The projects have been developed with an ultimate design horizon of 2070 and a forecast population of 1,000,000 EP.

3. Icon Water advises that since the completion of the LMWQCC bypass storage dam, there have been 11 release events associated with major wet weather events:

During these major wet weather events the releases of partially treated effluent typically constituted less than 1 per cent of the river flow.

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