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Indicator: IW-15 Volume of sewage discharged to land

Data

Sludge Production and Disposal Methods (%)

Quantity (1984), 000 tonnes dry solids /year	Agricultural Use (%)	Landfill or stockpile (%)	Incineration (%)	Ocean (%)
300	9	76	2	13

adapted from Source: Priestley, AJ, Report on sewage sludge treatment and disposal - Environmental problems and research needs from an Australian perspective, Department of Primary Industries and Energy, Canberra, viewed 4 Oct 2005, http://www.eidn.com.au/ukcsirosewagesludge.htm, Table 2

Emissions to land from sewerage and drainage services (tonnes)

	2001-02	2002-03	2003-04
ACT	0.0	1.3	2.3
NSW	66.8	58.6	119.4
Qld	0.9	52.6	33.5
SA	0.3	9.1	15.5
Tas	0.0	1.2	2.0
Vic	345.5	426.4	443.4
WA	0.0	0.0	30.0
Total	413.4	549.2	646.2

Derived from data available from Source: National Pollutant Inventory 2005, Download NPI emission data by spreadsheet, viewed 29 Mar 2005, http://www.npi.gov.au/database/download-data.html

Discharge of sewage effluent to land is significantly influenced by land availability, climate, topography, and soil conditions. Many small, mainly inland communities discharge effluent to land. Land discharge in arid or inland regions is often associated with reuse of the effluent for other purposes, such as irrigation. When discharging sewage effluent to land, the goal is to return water and nutrients with the least adverse effect on the soil, on the pasture or crop, and on the ecosystems near the discharge site.

Emissions of substances to land from sewerage and wastewater treatment plants include the following three methods:

• lagoon treatment and effluent polishing through irrigation that rely on microorganisms and sunlight to disinfect the effluent as it passes through the lagoons and irrigation ponds
• land filtration that relies on evaporation and soil filtering
• pasture filtration disposal, or fate management, that relies on bacteria in the soil and pasture to treat the effluent.

Source: National Pollutant Inventory 1999, Emission Estimation Technique Manual for Sewage and Wastewater Treatment, Environment Australia, Canberra, viewed 4 Oct 2005, http://www.npi.gov.au/handbooks/approved_handbooks/pubs/fsewage.pdf.

Biosolids (treated dried sludge) have been used in Australia for soil conditioning and potting mixes, composing, land rehabilitation, landscaping, forestry, brick manufacture, agriculture and siliviculture.

What the data mean

A small amount of sewage is discharged to land each year.

Data Limitations

Sludge stockpiles may not be included in NPI data.

Issues for which this is an indicator and why

Inland Waters - Habitat scale influences - Water Quality (for surface and groundwater) - Other pollutants 

Discharge from sewage treatment plants can contribute to nutrient enrichment in rivers and streams. High nutrient levels, combined with the increased periods of low flow due to river regulation and water extraction, have caused blue-green algal blooms to become a persistent problem in some dams, wetlands and lakes.

Sewage treatment plant discharges are a major source of pathogens. Most sewage treatment plants disinfect their discharges to kill pathogens, but the effectiveness and reliability of disinfection varies with flow and age of the sewage treatment plant.

Wastewater from sewage treatment plants can contain pollutants in high enough concentrations to cause ecological harm. Discharge to land is often regarded as more environmentally beneficial because it reduces the impact on the waterways. Changes in quantity discharged to land, vis-à-vis quantities discharged to water may be indicative of an overall reduction in environmental pressure due to improvements in sewage management.

Other indicators for this issue:

• IW-14 Volume of sewage discharge to surface waters by treatment category (primary, secondary, tertiary) 
• IW-16 Total pesticide use 
• IW-21 Exceedance of pH water quality triggers 
• IW-22 Exceedance of biological and chemical water quality triggers 
• CO-28 Quantity of discharges of different substances from humans activities to coastal and marine waters 

Land - Direct pressure of human activities on the land - Pollution to and from the land 

Some sewage treatment plants discharge directly to the land. Sewage treatment plant discharges are a major source of pathogens. Most sewage treatment plants disinfect their discharges to kill pathogens, but the effectiveness and reliability of disinfection varies with flow and age of the sewage treatment plant. Discharge to land is often regarded as more environmentally beneficial because it reduces the impact on the waterways.

Volume of sewage discharged to land is a direct measure of this pressure, relative to discharges to water ways, and may assist in comparing impacts.

Other indicators for this issue:

• LD-21 Area of land used for landfill 
• LD-22 Rate of violations of residue levels in harvested products 
• LD-36 Emissions to the land 
• LD-37 Emissions from activities that derive contributions from the land 
• HS-53 Total solid waste produced and disposed 
• IW-16 Total pesticide use 

Human Settlements - Pressures created by human settlements on the environment - Waste 

Sewage treatment plant discharges from cities and towns are a major source of pollutants and nutrients in aquatic environments, which, if in high enough concentrations, can cause ecological harm. Discharge to land is often regarded as more environmentally beneficial because it reduces the impact on the waterways. Changes in quantity discharged to land, vis-a-vis quantities discharged to water may be indicative of an overall reduction in environmental pressure due to improvements in sewage management.

Other indicators for this issue:

• HS-53 Total solid waste produced and disposed 
• HS-65 Amounts of hazardous waste 
• HS-66 Gaseous emissions from waste 
• LD-21 Area of land used for landfill 
• LD-22 Rate of violations of residue levels in harvested products 
• LD-37 Emissions from activities that derive contributions from the land 
• IW-12 Catchment nitrogen and phosphorus load 
• IW-14 Volume of sewage discharge to surface waters by treatment category (primary, secondary, tertiary) 
• CO-23 Aquaculture: volume of discharged sediments and nutrients 
• CO-27 Number, frequency, extent and volume of oil spills from all sources 
• CO-28 Quantity of discharges of different substances from humans activities to coastal and marine waters 
• CO-51 Quantity of sewerage and ballast water dumped by shipping 

Further Information

• Report on Sewage Sludge Treatment and Disposal - Environmental Problems and Research Needs From An Australian Perspective (Priestley 1992?) 
• Exploitation of gold in an historic sewage sludge stockpile, Werribee, Australia; resource evaluation, chemical extraction and subsequent utilisation of sludge (Reeves et al. 1999) 
• Melbourne Water - publications