The Australia & New Zealand Biosolids Partnership is managed by the Australian Water Association

The following questions and responses provide general guidance in responding to questions on biosolids. Relevant water authorities should also be consulted in order to provide accurate information on specific biosolids related issues.

The Department of Sustainability and Environment, Victoria, has prepared a series of fact sheets on the processing of biosolids. These can be accessed via the links, below:

What are biosolids?

Biosolids are treated sewage sludges. Sewage sludge is the solids that are collected from the wastewater treatment process but which have not undergone further treatment. Sludge normally contains up to around 3 % solids. Biosolids are a product of the sewage sludge once it has undergone further treatment to reduce disease causing pathogens and volatile organic matter significantly, producing a stabilised product suitable for beneficial use. Biosolids, normally contain between 15 % to 90 % solids. Biosolids are carefully treated and monitored and they must be used in accordance with regulatory requirements.

What is in biosolids?

Biosolids are mainly a mix of water and organic materials that are a by-product of the sewage treatment processes. Most wastewater comes from household, kitchens, laundries and bathrooms. Biosolids may contain:

• Macronutrients, such as nitrogen, phosphorus, potassium and sulphur and
• Micronutrients, such as copper, zinc, calcium, magnesium, iron, boron, molybdenum and manganese

Biosolids may also contain traces of synthetic organic compounds and metals, including arsenic, cadmium, chromium, lead, mercury, nickel and selenium. These contaminants limit the uses to which biosolids can be put, with all applications regulated by appropriate government authorities in each State and federally. Australia has one of the strictest regulatory regimes for biosolids application and use in the world.

What are biosolids used for?

Biosolids can be applied as a fertiliser to improve and maintain productive soils and stimulate plant growth. They are also used to fertilise gardens and parks and reclaim mining sites.

In Australia and New Zealand, biosolids have been used for:

• Co-generation/power production/energy recover
• Land application in agriculture (vine, cereal, pasture, olive)
• road base
• Land application in forestry operations
• Land rehabilitation (including landfill capping)
• Landscaping and topsoil
• Composting
• Incineration
• Landfill
• Oil from sludge (experimental).

Other uses overseas include:

• Bricks and construction material
• Vitrification (glass manufacture)
• Bio-fuel
• Fuel substitute (cement works)
• Additive to road base
• Jewellery

Biosolids are graded according to chemical composition and the level of pathogens remaining after production. Not all biosolids can be used for all applications. Lower qualities are typically used for road based and mine site rehabilitation. Only the highest grade of biosolids can be used to grow crops for human consumption. Regulators, such as State departments of Health and Environment strictly control the application, production and quality of biosolids.

How can biosolids be used/disposed of?

Basically, there are only two options for long term biosolids management:

• Application to land in one form or another, with a range of stabilisation and dewatering/drying options; and
• Incineration (including energy from waste), with disposal of the residue to landfill or land.

Landfill of biosolids is not generally accepted, or will not be accepted in the future, by regulators in Australia and New Zealand.  The accepted waste management hierarchy is: avoidance, reuse, recycling, recovery of energy, incineration, containment and disposal (as a last resort)

What is the difference between biosolids and sludge?

Biosolids are treated sewage sludge. Sludge is typically 3% solids (97% liquids) whereas biosolids are typically 15-90% solids. Because of the treatment and production process, pathogen levels Biosolids are much lower than in sludge.

Regulators, such as State departments of Health and Environment strictly control the application, production and quality of biosolids

How are biosolids made?

What you flush down the toilet and plug-holes in your house eventually requires treatment at a sewage treatment plant. A typical sewage treatment plant uses a range of treatment processes to produce recycled water and biosolids. See visual representations of the wastewater treatment process and the biosolids production process here.

How does the nutrient value of biosolids compare to other fertilisers?

The nutrient content of some organic fertilisers compared to Biosolids is shown below:

Nutrient source	Nitrogen %	Phosphorus %
Animal by-product
Dried blood	13.0	1.0
Bone meal, steamed	3.0	11.0
Dried fish meal	10.0	3.0
Tankage, animal	7.0	4.0
Blood and bone, Bailey's	5.0	3.0
Manures
Cattle manure	2.0-5.0	0.7
Horse manure	2.0-8.0	0.5-1.5
Poultry manure	5.0-15.0	1.3
Pig manure	7.0	1.7
Biosolids (dried)	2.0	0.9
Organic 2000 Turf Start ™	4.0	1.0
Organic 2000 Turf Restore ™	8.0	1.0
Dynamic Lifter ™	3.0	2.5

Modified from:

• ¾ DEPWRC (2001) 'Environmental guidelines for the establishment and maintenance of turf and grassed areas.' Department of Environmental Protection Water and Rivers Commission, Western Australia, Perth.
• ¾ Johnston K (1996) 'Turf Irrigation and Nutrient Study - Turf Manual.' Royal Australian Institute of Parks and Recreation - W.A. Region 1996.

How much biosolids does the average family produce per week?

The average household sewage leads to the production of between 0.5 and 1 kilogram of biosolids (dry weight) per week. This varies depending on the type and effectiveness of the treatment processes to which a particular household's sewerage system is connected and a number of other factors (e.g. industries connected to the sewerage system).

Why should I care about biosolids?

Biosolids are a valuable resource which can be use just like recycled paper, glass and aluminium cans. Biosolids use provides cost savings to the public who pay sewage fees and end-users of the resource, while enhancing sustainability. The fertiliser and soil amendment attributes of biosolids also make it worth using biosolids, thereby completing the nutrient cycle. Biosolids can also be used as a renewable alternative fuel.

How are biosolids generated?

Modern sewage treatment processes lead to the production of water that can be recycled or discharged to the environment and most produce biosolids. The sewage treatment process separates solid material from sewage. These solids, known as sludge, are then further treated using biological processes. The resulting biosolids are a combination of treated sewage sludges and the dead micro-organisms used in the biological treatment process. Biosolids may be further dewatered or composted depending on the use to which they will ultimately be put. Regulators, such as State departments of Health and Environment strictly control the application, production and quality of biosolids. The term biosolids is derived from the most common method of its production: the biological treatment of sewage solids.

The sewage treatment process also produces grit and screenings which are solids removed during either the initial treatment process - where floatable materials are skimmed from the surface or filtered out using coarse screens - or which later settle. Grit and screenings are typically landfilled.

What quantity of biosolids is produced?

There are approximately 360,000 dry tonnes of biosolids produced annually in Australia and New Zealand.

What do biosolids look like?

Before drying, biosolids look like a dark mud, rich in organic matter and some may have a plasticine texture. After drying, they are soil-like in appearance, much like garden mulch or potting mix. In some cases, the dried biosolids are made into pellets and look similar to some commercially fertilisers.

What do biosolids smell like?

Biosolids may have their own distinctive odour depending on the type of treatment it has been though. Some biosolids have a stronger odour that may be offensive to some people, while most biosolids have a slightly musty, ammonia odour. Sulphur and ammonia compounds (both plant nutrients) in biosolids are normally the cause of these odours. Typically odours are reduced after the biosolids have been applied and incorporated into the topsoil. One of the objectives of biosolids management is to ensure that offensive odours minimised.

How is biosolids use and production regulated?

Biosolids are usually regulated by the State Environment Protection Authority (EPA) or equivalent using the guidelines that apply in that State or Territory, or adopting those used in other States or national Guidelines.
The primary objective of regulation is to maximise the sustainable use of biosolids ensuring a high level of protection for both the environment and public health. The various, State, Territory and national Guidelines document the correct procedures for the production and management of biosolids so that the quality of the biosolids produced is matched with the purpose for which they may be used, minimising any associated risks.

The overarching document in Australia is produced under the auspices of the National Water Quality Management Strategy, although frequently the NSW Guidelines are used as a reference.

In New Zealand biosolids safe application to land is carried out under the auspices of Territorial Authorities as per the provisions of Regional Plans. To facilitate the safe application of Biosolids to land, the New Zealand Ministry for the Environment (MfE) and New Zealand Water & Wastes Association (NZWWA) have developed guidelines for the application of Biosolids to land. These Guidelines are used by Territorial Authorities when evaluating applications for consent to apply biosolids to land on a case-by-case basis.

Details of the guidelines and other relevant documents are accessible on the Guidelines page of this website.

Why do different jurisdictions have different guidelines for management of biosolids?

Just like some specific road rules vary between Australian States and Territories and New Zealand, biosolids guidelines vary too. Each state or country has their own biosolids guidelines to suit their specific conditions while offering adequate protection to human health and the environment.

That having been said, there would be value in standardising the Guidelines across the States and Territories and Federally, and between Australia and New Zealand. The Australian and New Zealand Biosolids Partnership is working to identify inconsistencies and to suggest to legislators improvements that might be made.

A summary of the specific guidelines for biosolids management in Australia and New Zealand can be found here.

How are biosolids classified?

Biosolids are classified in specific State, Territory or national Guidelines. Development of these Guidelines is usually the responsibility of regulatory agencies responsible for the environment. Primarily there are usually two parameters examined when determining the classification of biosolids: the treatment (microbiological) grading and the contamination grading.

Most Australian State guidelines have three or four treatment grades and two or three contaminant grades. The overall combined grade (treatment and contaminant) is usually linked to the different ways in which Biosolids may be used or applied. Grade specifications can be checked with the relevant Guidelines.

What are the different forms of biosolids?

Biosolids is a general term for treated sewage sludges. More specific terms that describe the four most common forms of biosolids are:

• Biosolids cake - raw sludge is stabilised biologically (most commonly by anaerobic digestion) and the liquid biosolids are dewatered to produce biosolids ‘cake'. The cake varies between 15 to 30 % solids for consistency, with the balance being water. The cake can be dried further by air drying. A similar result occurs with lagoon stabilisation and air drying.
• Biosolids pellets - raw sludge or liquid biosolids are dewatered to approximately 20% total solids then further heated in a dryer and dried to 95% total solids and then pelletised.
• Lime amended biosolids - raw sludge or biosolids are first dewatered followed by stabilisation with the addition of lime.
• Composted biosolids - dewatered raw sludge or biosolids are composted, typically with other organic materials, to produce a high quality product suitable for use in domestic gardens as well as public parks and gardens.

Why put biosolids on land?

Biosolids contain organic matter and nutrients which improve soil fertility and the quality and structure of soil. They also contain micronutrients such as copper, zinc and iron and can reduce the need for fertilisers. As many commercial fertilisers are produced using hydrocarbons, the price of such fertilisers is rising, adding to the attractiveness of Biosolids under the right conditions. The application of biosolids returns nutrients to the land, thereby completing the nutrient cycle.

Biosolids also aid forestry and land rehabilitation at mining sites by conditioning and fertilising the soil.

Who can apply biosolids to land?

Land application may be undertaken by a water authority, a contractor engaged by a water authority, or a landowner.

Some classes or qualities of biosolids can be applied with minimal restrictions as environmental and health risks are negligible.

Lower classes or qualities of biosolids can also be applied to land, but there may be restrictions on the amount applied each year. Just like fertiliser, if applied too heavily they can have detrimental impact on the environment.

How are biosolids transported?

Dewatered biosolids are generally transported to the land application sites in covered or enclosed trucks. In the same way commercial fertilisers are transported, biosolids are usually delivered prior to crop planting. Good practice requires cleaning any excess biosolids from the exterior of the vehicle prior to transportation and after unloading.

How do biosolids benefit the environment?

Use of biosolids can benefit the environment, particularly in areas of degraded soils. The use of biosolids also completes the nutrient cycle by returning nutrients to the land from which they were sourced. Organic matter has been used by humans for thousands of years to improve soil fertility and productivity.

When properly applied and managed, biosolids can:

• Provide essential plant nutrients;
• Improve soil structure and moisture retention;
• Add organic matter; and
• Reduce soil erosion.

Research and years of experience in the use of biosolids have demonstrated that properly managed land application of biosolids is beneficial to the environment.

What are some of the concerns and risks arising from land application of biosolids?

When conducted according to regulations, years of research has shown that land application of biosolids is safe. However, concerns do still remain regarding soil and groundwater contamination from trace elements, toxic chemicals, and potentially harmful disease-causing organisms. In response to these concerns, the EPA in the United States of America conducted a comprehensive risk assessment that evaluated the health risk to the general population as well as to a highly exposed individual. To date, there have been no documented cases of negative impacts to human health when a biosolids program has met all the federal and state requirements.

This is the same for Australia. There is no evidence that the beneficial use of biosolids has led to negative human health impacts. To be absolutely sure, the Australian water industry is undertaking further detailed research and risk assessment. Additionally, various Environmental Management Systems and Quality Management Systems are employed. The water industry in Australia and New Zealand complies with regulatory requirements and Guidelines put in place by relevant regulatory authorities in the various Australian States and Territories and federally, and in New Zealand, providing further levels of safety and risk minimisation.

Do biosolids contain pollutants?

As municipal wastewater treatment facilities and systems have improved during the past 20 years and as trade waste discharge licences have become increasingly strict, pollutant concentrations in biosolids have decreased dramatically and are typically well below national and State and Territory Guidelines.

Many of the trace metals in biosolids, including cadmium, lead, copper and zinc, enter wastewater from industrial drains and metal pipes in homes and businesses. Some of these metals, known as micronutrients, are essential in small amounts for plant survival. Others such as cadmium (which is a common ingredient in toothpaste) are monitored very closely in biosolids to ensure they remain well below the Guideline values.

Organic compounds, including pesticides, polychlorinated biphenyls (PCBs) and dioxins, can be found in some biosolids in concentrations near the lowest detectable limits. Studies have found the risks associated with these to be negligible and as many of these compounds are no longer used by the community the risk is diminishing.

In Australia and New Zealand biosolids Guidelines developed or endorsed by State and Territory and national environmental and health-related departments define strict contaminant classifications for heavy metals to ensure sustainable, appropriate uses in Australia and New Zealand.

(See also "Does the application of Biosolids pose a health risk?" below)

Will the metals and pollutants in biosolids enter the food chain?

Protecting human and stock health is a cornerstone of the various Biosolids Guidelines in place in Australia and New Zealand. These Guidelines are usually endorsed by relevant Departments of Health or related regulatory authorities. The Guidelines ensure there is no harmful build-up of metals or pollutants in the soil or in crops.

Many of the trace metals in biosolids are also present in conventional fertilisers and manure. These substances are non-toxic at the low concentrations and low rates at which they are applied.

A summary of the specific Guidelines for biosolids management in Australia and New Zealand can be found here.

Will land application of biosolids pollute ground or surface water?

When applied according to Guidelines and good farming practices, Biosolids will not impact on groundwater or surface water quality.

As with any fertiliser, the chief groundwater issues are nitrogen and phosphorous. Unlike many commercial fertilisers, about 85% of the nitrogen in biosolids is present in a slow-release organic form, making biosolids less likely to cause groundwater pollution from the release of nitrates (the mobile form of nitrogen) or phosphates. In addition, many Guidelines ensure soil pH is taken into account and is managed in establishing the suitability of a site for land application to prevent movement of metals through the soil.

Guidelines for land application of Biosolids usually specify site selection criteria, stormwater controls at the site as well as operating practices to minimise stormwater runoff under extreme events. Please refer to State, Territory and national Guidelines for further detailed information. Links to most of these can be found here

Does the application of biosolids pose a health risk?

Good hygiene practices are essential for persons coming in contact with biosolids. As in many other fertilisers and soil amendments, human sickness may result from exposure to chemicals, toxins or pathogenic organisms. Biosolids may contain some or all of these at various stages, particularly at the time of production. However, there are many barriers available to protect us from these.

The potential health concerns for users of biosolids are excessive levels of toxic metals or chemicals, or presence of potentially pathogenic micro-organisms (e.g.: viruses and bacteria).

All producers of biosolids are required to monitor their product for contaminants. Guidelines published by State, Territory and national governments in Australia and New Zealand ensure that good practice is followed when Biosolids are applied to agricultural land. In these circumstances, there is no danger to health from the resulting crop.

The wet material may provide a suitable environment for organisms, and care is required to ensure the health of workers during transportation and application of moist material. After application to farmland, the biosolids decompose quickly into the soil (exposure to sunlight and drying causing rapid die-off of any remaining pathogens) and naturally occurring bacteria become dominant.

Only the highest quality material is able to be used in circumstances such as composting or application to leaf crops. Generally, biosolids are applied to broadacre and grain crops where the time between application, sowing of seeds and harvesting of mature crops can be from three to six months. In the case of grain crops, the crop itself will be subject to further refinement to produce flour and other products.

As is the case with many other foods or products used in conjunction with food production, there are ongoing concerns about various chemicals: that they may be present in very tiny concentrations, or their effects have not yet been identified. It is important to note there have been no identified cases of death or illness from exposure to biosolids that have been used appropriately, in line with relevant Guidelines.

Protecting human health is a cornerstone of the various Biosolids Guidelines in place in Australia and New Zealand. These Guidelines are usually endorsed by relevant Departments of Health or related regulatory authorities. Biosolids applied in accordance with Guidelines to grow crops or graze stock for human consumption presents a negligible risk to the consumer.

A summary of the specific Guidelines for biosolids management in Australia and New Zealand can be found here.

Is it safe to eat food that has been grown using biosolids?

This is one of the major factors considered in formulating State, Territory and national Guidelines. Provided that Biosolids are used in accordance with the Guidelines there is no greater risk associated with biosolids application than with other commercial fertilisers.

The USA has conducted more than 30 years of scientific research including a US Environmental Protection Authority risk assessment of biosolids use. These studies included the independent evaluation of how biosolids could directly or indirectly affect human health and the environment and established minimum safe concentrations for biosolids applications to land. It concluded that if correctly managed biosolids application to land has no adverse environmental or health impacts.

Similar research has been conducted throughout Australia in the past 15 years.

A summary of the specific Guidelines for biosolids management in Australia and New Zealand can be found here.

What are some of the potential benefits when using biosolids?

Biosolids are rich in nutrients and organic matter so are a good natural fertiliser as well as being a soil amendment to enhance the land. The nutrients including nitrogen and phosphorus (two elements essential for crop growth) and micronutrients such as copper, zinc and iron release slowly during plant growth.

Among their benefits, biosolids can:

• Improve crop production
  Land application of biosolids that meet strict quality criteria help improve, replenish and maintain healthy soil by adding important nutrients, boosting soil water-holding capacity and reducing topsoil runoff, all of which serve to increase crop yields. The largest component of biosolids is organic matter. It works as a soil conditioner to promote necessary bacterial activity, loosening clay and improving the consistency of sandy soils. The improved texture of these treated soils promotes dense, healthy root growth, allowing better nutrient uptake by plants.
• Reduce soil erosion and protect water quality
  Land application of biosolids can reduce soil erosion as the organic matter in biosolids binds with soil particles, thereby retaining nutrients and improving water quality. The end results are improved soil properties which enhance root growth and increase the drought resistance of vegetation thus further reducing soil erosion.
• Enrich tree plantations
  Biosolids can promote tree growth and increase forest productivity for certain tree species. Biosolids used on pine stands can shorten pulpwood and lumber production cycles, particularly in marginally productive soils. Because biosolids enhance vegetation growth wildlife populations also benefit from more abundant understorey vegetation.
• Conserve landfill space
  The use of biosolids through land application and other methods offers an environmentally sound alternative to disposal thereby conserving landfill space for non recyclable materials.
• Improves economic returns
  Farming areas with marginal soil characteristics can improve productivity by the addition of biosolids, whichgenerate an income fromwhat would otherwise have been a cost to dispose.
• Provide topsoil for land used for recreational uses
  In our dry climate composted biosolids provide much need organic material to increase soil moisture retention and promote plant growth.

How long have biosolids been in use?

The use of sewage wastes is not a new concept. For thousands of years, Chinese society returned sewage to farmland to maintain soil structure and encourage plant growth. In parts of Europe and elsewhere biosolids have been applied on agricultural land for more than a century.

In the United States, biosolids recycling is as old as farm reclamation. Today thousands of municipalities across the USA successfully use biosolids. Similarly, biosolids use has been practised in Australia and New Zealand for more than 20 years.

Can the health of native or domestic animals be affected if they come into contact with biosolids?

Typically the pathogens found in sewage are sourced from human waste and the vast majority are removed during processing of the biosolids. Most of these pathogens, in particular viruses, do not infect other animals as they are specific for humans. However, a few pathogens, such as some strains of the protozoan parasite Cryptosporidium, can infect certain domestic animals, including cattle and the bacterium Salmonella is known to infect young chickens. This is why the various Biosolids Guidelines recommend a withholding period of 30 days before stock is allowed to graze or domestic fowl allowed access to land once Biosolids have been applied.

This withholding period is not required for domestic animals such as dogs and native wildlife as they cannot become infected with these human pathogens.

Will a land application site next to me impact my property value?

There is no evidence that land values in Australia or New Zealand have been negatively affected as a result of the application of biosolids on a neighbouring property. On the contrary, the use of biosolids on farmland helps improve crops and supports continued success of those farming operations, adding to the generally economic wellbeing of the region.

Successful land reclamation projects using biosolids have also raised land values at and around surface mine sites.

Are biosolids tested to ensure safety?

Biosolids must be analysed to ensure they meet the quality standards for land application, as defined in State, Territory and national Guidelines. These tests may include analyses for pathogens, nutrients, metals and any organic chemicals of concern (e.g. polychlorinated biphenyls or PCBs). The frequency of testing is based on the amount of biosolids generated by the treatment facility. In addition, biosolids producers must regularly monitor the treatment process.

A summary of the specific Guidelines for biosolids management in Australia and New Zealand can be found here.

Will I know when biosolids are applied near my property?

Consultation should occur whenever biosolids are applied to land regardless of the quality. In most cases, where high-quality biosolids are applied, consultation with neighbours is all that is required. When biosolids of lower quality are used relevant Guidelines can require erection of prominent signs to restrict access by the general public and stock to the site until vegetation is fully established and withholding periods have passed. Although not always mandatory, authorities or land owners will normally consult with their communities prior to undertaking biosolids application.

Will biosolids be carried in the air?

Biosolids generally will not generate dust or moisture droplets during handling or application. Because biosolids are high in organic matter, once on the ground, they dry and form a crusty material that is resistant to erosion. Dust generated during application of biosolids is usually generated by spreading equipment disturbing the existing soil layer, not from the biosolids being applied.

Do prions pose a risk in the management of biosolids?

Prions are small folded protein molecules containing no genetic information, which are made up of amino acids, the essential building blocks of all proteins. Prion-like proteins that are found naturally in many (perhaps all) plants and animals are folded differently than normal proteins due to slight amino acid changes in certain regions of the protein. The term prion is often used to refer to such abnormally folded proteins (also referred to as proteinaceous infectious particles), when they have the ability to affect other proteins, causing them to change from the normal form to the abnormal form.

In their normal, non-infectious state, prions are believed to be involved in cell-to-cell communications and other important cell functions. In their abnormal form prions have been linked to the transmission of Bovine Spongiform Encephalitis (BSE, or so-called ‘Mad Cow' disease) and Creutzfeld-Jakob Disease (CJD) and variant CJD. There has been discussion about the potential for prions to enter wastewater streams through the discharge of animal waste from abattoirs and similar facilities and thereby passed on to humans through either contact with treated wastewater or biosolids.

The US Water Environment Federation (WEF) reports the following in its Prion Fact Sheet:

"Based on a review of available information and assessments made to date (including a quantitative risk assessment for BSE in biosolids by Gale & Stanfield in the U.K.), it is unlikely that significant levels of prions enter the wastewater collection system and the risk of prion transmission directly to animals and indirectly to humans from biosolids management and effluent land application is extremely low (i.e., practically zero). Prion transmission via biosolids land application seems less likely than other potential food chain pathways."

A copy of the Fact Sheet can be found here

Who can I contact if I have questions or concerns?

Questions and concerns would generally be directed to your State, Territory or National Departments of Health or the Environment.

You can also contact the Australian and New Zealand Biosolids Partnership Project Manager on admin@biosolids.com.au

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