Orange STP Carbon Dosing Options

  • ASpect’s Client: Orange City Council
  • Head Client: Orange City Council
  • Plant Configuration: MLE
  • Plant Size: 60,000 EP
  • Project Value: $7k (ASpect Fee $7k)
  • Project Duration: September 2019 to Current

Orange STP Carbon Dosing Options for Orange City Council (NSW).

Orange STP is a 60,000 EP facility that services the majority of the city of Orange in NSW.  When the last upgrade was commissioned in 1998, the sewage conditions were favourable to denitriication.  This allowed the existing primary sedimentation tanks and anaerobic digester to be retained while still meeting effluent total nitrogen (TN) limits.  Since then, closures and pre-treatment of trade waste discharges have resulted in a loss of beneficial carbon in the form of soluble biodegradable COD (SBCOD).  Orange City Council (OCC) were also having operational and maintenance issues with their pre-fermenter, resulting in it being mothballed.  These factors combined to reduce the denitrification effectiveness of the secondary treatment process (MLE).  OCC commissioned ASpect to undertake an options report into supplementary carbon dosing.  The aim was to select the most appropriate form of SBCOD to dose to the anoxic zone of the bioreactor to assist TN removal performance.  ASpect selected four carbon dosing compounds commonly dosed in Australia (sucrose, acetic acid, methanol and ethanol) plus glycerol.  ASpect used first principle stoichiometric chemistry, plus standard heterotrophic kinetics to determine and compare the usage of each compound.  ASpect liaised with local chemical suppliers to determine the specification and cost of chemical solutions that could be delivered to Orange.  The five compounds were then compared using the criteria of operating cost, capital costs, hazards, risks, viscosity, freezing, acclimation and response.  Surprisingly, glycerol was found to be the most appropriate and cost effect compound.  ASpect is working with OCC and chemical suppliers to prepare a customised glycerol solution for trialling.  This has the potential to revolutionise carbon dosing in Australia.