Goulburn Mulwaree
Indicator: Discharge to Waters
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What the results tell us for Goulbourn Mulwaree
Effluent generated in Goulburn City is treated at the Goulburn sewage treatment plant. The treated effluent is disposed of through irrigation onto Council owned land, such as the Goulburn Racetrack. Sewage generated in rural areas of the Council is treated by on-site septic tanks.
The New South Wales (NSW) Department of Environment and Climate Change (DECC) regulates most sewage treatment systems owned by state and local government. DECC has licensed the Goulburn sewage treatment plant to discharge treated effluent to utilisation areas. Volume limits are not applicable to this plant; instead it has assessable pollutant limits, as shown in Table 1.
| Assessable Pollutant | Load limit (kg) |
|---|---|
| BOD (Enclosed Waters) | 42780 |
| Nitrogen (total) (Enclosed Waters) | 78520 |
| Oil and Grease (Enclosed Waters) | 23310 |
| Phophorus (total) (Enclosed Waters) | 19630 |
| Total suspended solids (Enclosed Waters) | 58890 |
Source: Department of Environment and Climate Change, NSW
The total suspended solids limit was exceeded on eight occasions in 2005-06 and nine occasions in 2004-05. The Biochemical Oxygen Demand (BOD) limit was also exceeded on seven occasions in 2004-05.
Sewage was discharged to stormwater drains in 2007-08 but the discharges were considered minor. The stormwater discharged is not monitored however gross pollutant traps are installed to prevent solid wastes entering the river. A larger discharge during wet weather provided substantial dilution (Table 2).
During wet weather significantly increased flows are experienced at the treatment plant. This is due to the poor condition of some existing pipes, which are subject to infiltration from prolonged rainfall. Council has implemented a replacement program using trenchless techniques including relining and pipe bursting. This has reduced blockages from over 500 per year to approximately 300 per year.
Council has observed that the treatment plant is struggling to meet environmental guidelines as there has been insufficient land to irrigate in a sustainable manner. A 600 ML wet weather storage facility was completed in 2001 to enable irrigation to cease during wet weather. Additional works completed in 2007 allow additional volumes to be pumped to irrigate additional farmland and sports fields.
| Licensed/ unlicensed |
Volume (ML/year) | Type | Estimated volume discharged illegally (L/year) | Estimated volume discharged accidentally (L/year) | Receiving waters | Mass load of nitrogen (kg) | Mass load of phosphorus (kg) |
|---|---|---|---|---|---|---|---|
| Licensed | 24.1 | Sewage | Nil | Nil | Wollondilly River | Unknown | Unknown |
| Licensed | 0.1 | Sewage | Nil | 0.1 | Mulwaree River | Unknown | Unknown |
| Licensed | 15 | Stormwater (Backwash from Water Treatment Plant) | Nil | Nil | Mulwaree River | Unknown | Unknown |
Source: Goulburn Mulwaree Council
A series of 13 sewage pumping stations collect sewage from sub-catchments within the Council and transfer the sewage to the treatment plant for treatment and reuse. A number of the pump stations are located next to the Wollondilly River and Mulwaree Ponds. This presents environmental concerns during periods of malfunction. Council has recently installed a back up power supply to five pump stations to ensure a continuous power supply during power outages. This will reduce the risk of sewage overflow into the Wollondilly River and Mulwaree River.
Stormwater Discharge
The Water Treatment Plant discharges to a stormwater pit from the settling pond via a 300mm pipe. DECC has licensed the water treatment plant to discharge 200 KL/day.
The water entering the plant is flocculated with Alum to assist sedimentation of larger particles. The water is then passed through multi-media filters before flouride and chlorine are also added. Once treated the water is distributed for use throughout Goulburn.
Comprehensive details for Goulburn Mulwaree Council can be viewed at the National Pollutant Inventory website. The website lists the Goulburn Wastewater Treatment Plant as 31,000 kg a year of Ammonia to land.
Trade Waste Policy
Council has a trade waste policy for businesses in Goulburn to regulate and influence the quality of tradewaste accepted into the sewerage system.
About the data
Information was supplied by Goulburn Mulwaree Council. Additional information was obtained from the DECC’s public register of protection licences.
References
DECC – see Department of Environment and Climate Change
Department of Environment and Climate Change NSW (2008), Public Register for Licences, Applications or Notices, Environment Protect Licence, Section 55 Protection of the Environment Operations Act, viewed at http://www.environment.nsw.gov.au/prpoeoapp/searchregister.aspx on 25 September 2008.
Department of the Environment, Water, Heritage and the Arts (2008) National Pollutant Inventory, Commonwealth of Australia, viewed at http://www.npi.gov.au on 25 September 2008.
DEWHA - Department of the Environment, Water, Heritage and the Arts
Goulburn Mulwaree Council (2008), Goulburn Mulwaree Council: Engineering Services: Water and Sewage, viewed at http://www.goulburn.nsw.gov.au/roads/1440.html on 25 September 2008.
