The Muswellbrook sewage treatment plant utilises a trickling filter process for domestic wastewater treatment. The original plant was constructed in 1939, with a subsequent upgrade in the early 1960s which increased the number of trickling filters to three. A significant portion of the plant, including trickling filters One and Two, has therefore been operational for 70 years. Muswellbrook’s sewage treatment plant facility currently occupies 16,000 m², excluding maturation ponds.

 Muswellbrook sewage treatment plant processes wastewater from households, which is made up of solids, liquids and paper from toilet use, bath and shower water, dishwashing and laundry water. Every 1000L of wastewater typically contains only 1kg of solid wastes. This wastewater is then piped by gravity to one of Muswellbrook’s nine Sewer Pump Stations, where it is collected, hemically dosed for odour control, and sent via pressure mains to the sewage treatment plant. Inflow to the sewage treatment plant averages 2,700KL per day in dry weather (2008 data).

One of the tertiary treatment maturation ponds, Muswellbrook Sewage Treatment Plant.
Photo: One of the tertiary treatment maturation ponds, Muswellbrook Sewage Treatment Plant.

Muswellbrook sewage treatment plant consists of

  • Preliminary treatment - automatic screening and grit removal.
  • Flow balancing and plant bypass.
  • An automatic drum screen for bypass flow screening.
  • Primary treatment - Combination Imoff and Sedimentation tank for sludge separation and removal.
  • Sludge digestion via three cold anaerobic digesters.
  • Sludge storage via two sludge lagoons.
  • Sludge drying in five sludge drying beds.
  • Secondary effluent treatment - trickling filter process via three filters.
  • Humus sludge removal and return via two humus tanks and pump stations.
  • Tertiary effluent treatment via three maturation ponds.
  • Effluent reuse via three pump stations.

Recent droughts and better understanding of water resource management issues have highlighted that fresh water is becoming increasingly scarce. There are a number of competing demands for water, including the mining sector, power generation industries, current and future urban water needs and environmental flows for the Hunter River itself.

Currently effluent from the Muswellbrook sewage treatment plant is fully utilised through reuse initiatives involving the golf course and local mining operations.

Discharge to receiving waters is rare and occurs, if ever, only after significant wet weather events. While there have not been any environmental discharges over the past year, the wet weather discharge point is into Ramrod Creek, which is
8km upstream of the Hunter River.

The simplified plant process is:

  • Raw sewage enters the plant.
  • Flows through grit chamber to remove grit, sand & other inorganic solids.
  • Flows through screens to remove rags, litter & other large objects.
  • Primary settling tanks remove settleable organic solids.
  • Anaerobic sludge digesters change organic solids in sludge.
  • Sludge drying beds reduce volume of solids after treatment for disposal.
  • Biological (trickling) filter converts solids in solution to a form that can be settled.
  • Settling tank removes settleable solids discharged from the filters.
  • Effluent ponds kill off remaining bacteria by starvation and ultra-violet irradiation.
View across the sedimentation tanks, Muswellbrook Sewage Treatment Plant.
Photo: View across the sedimentation tanks, Muswellbrook Sewage Treatment Plant.

Overview of process chart

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