Muswellbrook and Denman are serviced by similar sewer networks, however the treatment processes for the raw sewage are different in each township.  In general the treatment process follows the schematic below.

Muswellbrook Wastewater Treatment Plant receives sewerage from ten pumping stations, which in turn receive gravity flows from individual residences. As wastewater enters the plant, grit and foreign material are removed by screens and machinery in the intake works, and this is taken to landfill.

Wastewater then goes through a sedimentation process, where heavy materials are taken off to sludge digesters where they are broken down by anaerobic bacteria (ie bacteria that operate in a water environment depleted of dissolved oxygen).  The water remaining after sedimentation is passed through trickling filters where it is treated by aerobic bacteria (those that live in an oxygen rich water environment).  Digested sludge is dried in beds for later disposal, and water from the trickling filters flows out to tertiary treatment ponds.

Simplified wastewater treatment plant process

Muswellbrook sewage treatment plant - May 2004

Water from the tertiary ponds is chlorinated after 30 days detention time and pumped to Council’s reuse customers, e.g. mining companies, who use the water for coal preparation and dust suppression. Muswellbrook’s plant treats up to 1100 ML of raw sewage per annum, and currently 100% of this is reused. Discharge to receiving waters is very rare and occurs, if ever, only after significant wet weather events. Any environmental discharges that do occur during wet weather enter Ramrod Creek, which is 8km upstream of the Hunter River.

This is a very old style of plant and has reached the end of its economic life. Council are currently investigating options for upgrade or reconstruction of this plant to meet the future needs of the community.

Denman sewage treatment plant is a much more modern plant using more current technology.

Denman sewage treatment plant - May 2004

Denman Wastewater Treatment Plant receives sewerage from two pumping stations that collect gravity flows from residences. This wastewater flows through a grit removal chamber, then into an extended aeration tank where aerobic bugs digest the organic component of the sewage. The tank goes through a cyclic settlement phase in which the bugs (sludge) settle to the bottom and clear water is left on top. Some of this clear water is decanted from the tank into an effluent lagoon where it undergoes UV disinfection, while some of the settled sludge is pumped to sludge ponds.

As this sludge in the sludge ponds settles, the clear water left is decanted from the top and returned to the treatment process. Eventually the sludge ponds fill, then the sludge is removed, dried and disposed of. Water exiting the treatment process at the downstream end of the effluent lagoon is pumped to storage, and reused for irrigation of the Denman golf course. One hundred percent of the effluent from this plant is reused, leaving nil discharge to receiving waters (which in this case would be the Hunter River).

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