Environmental issues

Water quality


Biosolids are an organic solid by-product from treating sewage. Solids produced during the various stages of sewage treatment plants, often called waste-water solids or sewage sludge, are collected and further processed. Once they are suitable for use they are called biosolids. Biosolids Questions and Answers are given below.

The NSW Government's biosolids management policy is to encourage the beneficial use of biosolids where it is safe and practicable and where it provides the best environmental outcome. In cases where beneficial use is not possible, biosolids must be disposed of safely and lawfully.

The NSW Environmental guidelines: Use and disposal of biosolids products (BiosolidsGuidelinesNSW.pdf, 855 KB) will help planners, designers and operators of sewerage systems, and those involved with the processing and end-use of biosolids products, by establishing requirements for the beneficial use and disposal of biosolids products to land in NSW. 

Since the release of these Guidelines in October 1997 there have been some changes to the overarching Legislation for environmental protection in NSW and changes to the regulation of biosolids use and disposal. The Protection of the Environment Operations Act 1997 (POEO Act) and associated regulations commenced on 1 July 1999, replacing a number of Acts and Regulations including the Clean Waters Act 1970 and the Pollution Control Act 1970.  Changes to the POEO Act on 28 April 2008 also simplified waste regulations which are relevant to biosolids use and disposal.

For the regulatory requirements you should refer to current Acts and Regulations relevant to waste management and resource recovery.

Biosolids Questions and Answers

How and why do we use biosolids?

Biosolids are rich in organic matter and contain valuable nutrients. They can be used to improve agricultural soil and in rehabilitating land, such as at former mine sites. Biosolids can also be further treated and mixed with materials such as compost to produce garden soil or potting mix.

In the past sewage sludge was often dumped in the ocean or landfill. By processing sewage sludge into biosolids, we can put the organic matter and nutrients to use and avoid dumping sewage sludge.

How is the use of biosolids controlled?

Biosolids can contain chemical contaminants and pathogens that must be controlled to avoid risk to public health and the environment.

The Environmental guidelines: Use and disposal of biosolids products (BiosolidsGuidelinesNSW.pdf, 855 KB) were developed to control the use of biosolids and these guidelines have been integrated into the environmental regulatory system.

How do the guidelines protect human and environmental health?

The guidelines use a multi-barrier approach to prevent problems. They detail the steps biosolids must pass through before they can be used and place rigorous restrictions on how and where they can be used.

The first step is to analyse the biosolids for chemical contaminants and pathogens. This analysis is combined with information on how the biosolids have been processed to produce a grading, which defines the way in which the biosolids may be used.

When biosolids are used on land, soil samples must be taken and calculations carried out to ensure the land will not become contaminated and the correct amount of nutrients is applied for the types of crops being grown.

There are also strict requirements on how often biosolids can be used; with-holding periods for different crops; and limits on how close biosolids can be used to houses, waterways and other areas. The guidelines ban the use of biosolids in drinking water restricted catchments and environmentally sensitive areas.

How were the guidelines developed?

The guidelines were developed following approximately 10 years and $10 million of extensive research and consultation with government bodies and industry. They were first published in October 1997 and amended in 2000. Consultation with environment and community groups was carried out and the guidelines subject to a full cost benefit analysis prior to release. Further amendments can be made if new scientific information indicates an update is warranted.

How are the guidelines enforced?

It is an offence to use biosolids without following the guidelines. Where failure to meet the guidelines forms a serious offence under the Protection of the Environment Operations Act 1997, including negligently disposing of waste in a manner that harms or is likely to harm the environment, the maximum penalty is $2 million.

OEH carries out field inspections of biosolids application sites and follows up complaints with inspections and investigations. OEH also meets with new biosolids operators to ensure they understand the requirements of the guidelines.

What roles do NSW Health and Sydney Water have in biosolids use?

Sydney Water is the largest producer of biosolids in NSW. It’s biosolids land application program has been in place since 1989 and all of its biosolids are reused.

NSW Health provides advice on how to ensure public health is protected when biosolids are used and was a member of the group that developed the guidelines.

Does anyone else, apart from Sydney Water, produce biosolids?

All sewage treatment plants produce sewage solids but not all process these into biosolids. Many sewage treatment plants in country towns produce relatively small amounts of sewage solids and it can be is cheaper to dispose of these at the local landfill or sewage treatment plant (STP) than to process them into biosolids.

How do the guidelines ensure crops are produced safely?

The guidelines set out specific withholding periods for various types of agricultural activities for biosolids that have been processed to Grade B biosolids. For example, they specify that some crops - from potatoes to lettuce and turf - should not be grown for between 18 months and five years after biosolids have been applied to the soil.

These with holding times allow natural pathogen die-off processes to occur before crops are grown. The most common crops grown using grade B biosolids are wheat, canola and maize. The long lead time from sowing to harvest of these crops provides a safety period in addition to the guideline’s withholding time.

Why is it safe to use biosolids in NSW when parts of the US and European Union don’t?

International studies have shown that biosolids are safe, when treated and managed in accordance with guidelines such those in place in NSW. In 2002 the US National Research Council reviewed the USA’s experience with biosolids use, current science and the US EPA’s biosolids regulation, called the 40CFR Part 503 rule. It concluded that, “there is no documented scientific evidence that the Part 503 rule has failed to protect public health”.


Page last updated: 22 June 2011