Bucasia Wastewater Treatment Plant

Bucasia Waste Water Treatment Plant is located approximately 12 km northwest of Mackay and services a population of 8,000.  This represents approximately 89% of its 9,000 capacity. It is an extended aeration (continuous) plant.

Influent enters a screening chamber where the wastewater passes through two large vertical primary bar screens and a secondary bar screen.  Screens are manually raked but plans include installation of a mechanical step screen.  Smaller inorganic particulate matter and finer organic matter settle in the grit chamber and are removed by council's vacuum truck. 

Wastewater from the grit chamber enters a distribution chamber and is directed to one of two oxidation ditches for primary treatment.  The oxidation ditches operate on separate lines, with only one ditch functioning at any given time. Effluent is aerated, resulting in biological digestion and fed into one of the two sedimentation tanks.

Sedimentation tank supernatant is conveyed to the chlorine detention chamber for disinfection.  Following disinfection, the effluent is transferred to an effluent lagoon.

Lagoon effluent is discharged into Reliance Creek on ebb tides, restricted to a maximum period of four hours under the Mackay City Council Integrated Authority No. NM0250.

Waste Activated Sludge (WAS) drawn from the sedimentation tanks is discharged into one of the three sludge-thickening lagoons. Sludge lagoon supernatant is returned to the head of the plant whilst sludge is alternately directed into one of eight sludge drying beds.  The beds are constructed of a 150 mm layer of coarse river sand on top of 150 mm layers of 10 mm and 20 mm screenings.