Mittagong STP Design Review

  • ASpect’s Client: Hunter H2O
  • Head Client: Wingecarribee Shire Council
  • Plant Configuration: FSB
  • Plant Size: 21,000 EP
  • Project Value: $30M (ASpect Fee $25k)
  • Project Duration: April 2021 to Current

Mittagong STP Detailed Design, with Hunter H2O for Wingecarribee Shire Council (NSW).

Wingecarribee Shire Council (WSC) own and operate a number of STPs in the NSW Southern Highlands Region.  This is a growing region in the south west corridor out of Sydney.  The region is characterised by a number of large towns and cities in a cool climate, situated in the drinking water catchment of Sydney.  The location within the catchment places a number of constraints on discharge from their STPs.  One of these is that the load of pollutants, including nutrients, are capped at historical quanta.  Therefore, all amplifications and upgrades must achieve a neutral or beneficial effect (NorBE) on the recieving waters.  As the population increases, the performance targets tighten.  Mittagong STP is projected to have significant growth.  This means that the NorBE targets will be extremely tight.  The original concept, prepared by others, involved the expansion of the STP using existing IDEA style bioreactors.  The NorBE requirements were proposed to be met by post IDEA add on technologies.  It became clear during the proposal stage that such technology would be incapable of reliably meeting possiblre future NorBE requirements, especially for total nitrogen (TN).  The future TN targets required the most advanced nitrogen removal technology, being four stage bardenpho (FSB).  The proposed bioreactors could be operated as MLE or FSB as NorBE limits tightened.  The MLE configuration could be used in the interim, utilising the spare capacity to provide a very high wet weather treatment capacity or to defer future stages.  Mittagong STP is also the regional STP designated to accept tankered waste comprising septage and commercial wastes.  The concept is to retain the existing sludge lagoons for septage storage and thickening while treating other wastes through the process via storage tanks.  ASpect’s role in the project was to provide process design review, including current and future loads, process modelling and process uniy sizing, P&ID review, functional description, designer’s report and operations manual.