Orange STP Chorination Interim Upgrade Concept Design

  • ASpect’s Client: Orange City Council
  • Head Client: Orange City Council
  • Plant Configuration: MLE
  • Plant Size: 60,000 EP
  • Project Value: $21k (ASpect Fee $21k)
  • Project Duration: August 2013 to November 2013

Orange STP Chlorination Interim Upgrade Concept Design for OCC (NSW).

Orange STP is a 40,000 EP facility that services the majority of the city of Orange in NSW.  Orange STP utilises gaseous chlorination for disinfection, with the majority of the disinfected effluent pumped to the Cadia mine for re-use.  Changes in licence conditions made it difficult to simultaneously meet discharge limits for free chlorine residual and faecal coliforms.  A re-use risk assessment also suggested that additional barriers may be required to attain the degree of re-use safety that OCC desired.  An options report had narrowed the solution to providing UV as an additional barrier either upstream or downstream of the existing chlorination facility.  Depending on the solution, dechlorination may also be required for discharge.  Both options included a common set of recommendation for improving the monitoring, critical control and alarming of the existing chlorination and re-use pumping systems.  OCC decided to implement these common recommendations ahead of the disinfection upgrade t0 realise immediate incremental improvement.  The scope included additional instrumentation (ammonia, total and free chlorine residual), implementing duty/assist dosing, improved feedback control, better alarming and more sophisticated monitoring.  The interim upgrade also targetted additional critical control of re-use pumping to isolate re-use automatically if there is a risk of sub-optimal disinfection.  The scope of work included a review and recommendation of additional instrumentation, improvements to automated control, process and instrumentation diagrams and a detailed operating and control philosophy.