1890 Effluent Disposal Review · MCU20/0022

3.4   Effluent Quality
      In accordance with the Department of Natural Resources (DNR) – “On-site Sewerage
      Code”, the appropriate method of on-site disposal is proportional to the effluent quality.
      Effluent quality is defined by three broad categories:


      Primary effluent - typically outflow from a septic tank will be disposed in a conventional
      absorption trench system.

      Secondary effluent - where aerobic microorganisms biologically degrade organic matter.
      (AWTS - aerated wastewater treatment system / aerobic sand filtration).

      Advanced Secondary effluent - a modified secondary treatment system where the
      nutrients including nitrogen and phosphorous are reduced to environmentally
      acceptance levels.

      Effluent Quality

                                                                 “Modified” Advanced
                                                                  Secondary Effluent
                                                                         mg/L
                    Biochemical Oxygen Demand                            <10
                    Suspended Solids                                     <30
                    Total Nitrogen                                       <25
                    Total Phosphorus                                     <10
                    Thermotolerant Coliform (org/100mL)                   <10



3.5   For each given effluent quality, the criteria for exclusion and separation also varies,
      with reference to the Queensland Plumbing and Wastewater Code, 2019:

      Recommended horizontal separation distances for subsurface land application areas

                                                                                  Horizontal Separation
                                     Feature
                                                                                      Distance (m)

       Property boundaries, pedestrian paths and walkways,                                  2
       recreation areas

       Water edge of a swimming pool                                                        6

       Dwellings, recreation areas                                                         10*

       Notes: For primary effluent, the distance from an in-ground portable water tank must be 15 metres.
      The separation distances are based on a spray plume with a diameter not exceeding 1m or a plume height
      not exceeding 0.3m above the finished surface level. Distances are given in metres from the edge of the
      irrigate wetted area to any point of thefeature.

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