GSP-WW: Toxicity of Influent

GSP-WW: Toxicity of Influent


Western Water (WW) provides water, sewerage and recycled water services to 61,000 properties with a population of 162,000 across a region of 3,000 square kilometres to the north-west of Melbourne. Since the authority’s establishment 20 years ago, Western Water has seen its service population more than double. This strong growth rate is projected to continue as suburbs around Melton and Sunbury develop over the coming decade. Nearly all towns in the service area now have a secure water supply through provision of alternate supplies to local water. These include interconnection to adjoining supply systems as well as access to Melbourne water.


To develop a method to model the risk of potential toxins (with a focus on tree root foam) into Western Water’s Recycled Water Plants (RWPs). These toxins may add stress to the biomass of the activated sludge, which would decrease the effectiveness of the treatment process. ATP is used as a stress indicator of the biomass.


  • Assess the feasibility of ATP as a test method to determine the toxicity of influent. If successful, implement testing across Western Water’s RWPs to minimise the loss of biomass, and protect the plant operations, quality of recycled water and biosolids.
  • Verify a threshold value for root foaming chemicals in the influent to assist the field operation team in the planning of root foaming activities in the sewer.

Toxcity of influent is a critical issue to Western Water business for the following reasons;

  1. The current tree root foam we use is no longer available requiring us to adopt the use of a different foam.
  2. We are experiencing some blockages in our network due to tree roots and are therefore going to commence a program of using tree root foam in our network.
  3. We wish create a model to determine whether the tree root foam program will increase the toxicity of our influent and adversely affect the performance of our recycled water plant.


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