Wastewater and Sewage
Wastewater and Sewage
All forms of household wastewater are infectious, pollutant and a risk to human health and the environment. When managed properly and carefully through sewage treatment processes wastewater can be converted into a valuable resource, known as effluent, and can be reused under certain circumstances.
There are three types of household wastewater:
- Blackwater is wastewater generated from a toilet, bidette or bidet which is heavily and directly contaminated with human faeces and/or urine and may contain contaminated solid material, such as toilet paper. This wastewater is highly infectious.
- Greywater is wastewater which does not arise from a toilet and includes wastewater from a hand basin, shower, laundry and kitchen. Greywater is often contaminated with human faeces, dirt and other materials but to a lesser extent than blackwater and is therefore less infectious than blackwater.
- Sewage is a combination of both blackwater and greywater, and again is very infectious.
Wastewater may be disposed of in three ways:
- Centralised through pipes called sewers into a sewerage system and treated in a single large sewage treatment plant where it can be converted into a resource for selective reuse for car washing, outdoor household garden watering, toilet flushing, golf course watering and irrigation of crops. The treated effluent may also be discharged to rivers and oceans.
- De-centralised through pipes into a local community small sewage treatment plant for local community reuse. A number of these local systems make up de-centralised sewage management.
- On-site single domestic wastewater management where the sewage or components such as greywater must be partially or fully treated for utilisation or reuse within the property boundaries.
NSW Health is involved in on-site single domestic wastewater management through convening the Wastewater Management Advisory Committee. NSW Health also accredits sewage management facilities under the provisions of the Local Government (Approvals) Regulation.
NSW Health supports the reuse of treated effluent, which has been appropriately treated as this can reduce the demand for drinking water and help protect the environment.
NSW Health recommends the use of the Australian Guidelines for Water Recycling: Managing Health and Environmental Risks for the development of recycledwater schemes and in this regard, the Australian Guidelines have replaced the 1993 NSW Recycled Water Co-ordination Committee's NSW Guides for Urban and Residential Use of Reclaimed Water for use with dual reticulation schemes.
The Office of Water (NOW) has also released the guideline document Managment of Private Recycled Water Schemes. This guideline aligns the principles outlined in the Australian guideline to the approvals process for private recycled water schemes (requiring section 68 approval) in NSW. The guideline replaces the NSW Health Interim Guidance for Greywater and Sewage Recycling for Mulit-Unit Dewllings and Commercial Premises (GL 2005/051 previously Cirulcar 2004/71).
More information on these and other relevant NSW recycled water guidelines can be found at the Water for Life web site.
NSW Health has also worked very closely with the Sydney Water Corporation and Sydney Olympic Park Authority on several reuse schemes, including the Rouse Hill Reuse Scheme and the Water Reclamation and Management Scheme (WRAMS). As part of these schemes sewage is collected, treated to a very high standard and supplied to local residents for oudoor use (garden watering and washing cars) and toilet flushing.
Biosolids expert advisory panel
NSW Chief Health Officer, Dr Kerry Chant convened an expert advisory panel to consider community concerns of health risks from the use of biosolids sourced from Sydney Water in response to reports that these products were causing gastrointestinal disease in Sydney residents.
Members of the expert advisory group considered the risk to human health from Grade A and Grade B biosolids was negligible if the recommended treatment and use followed the Environment Protection Authority (EPA) guidelines.
The panel’s findings can be viewed here.