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Biosolids
Recycling for a better environment
Sydney Water operates a biosolids land application program under the registered business name of BioSoil®. Biosolids are the nutrient rich organic material resulting from the treatment of wastewater. Up to 190,000 tonnes of biosolids are produced annually which are beneficially used in agriculture, composting and land rehabilitation.
How are they produced?
Sydney Water treats about 1,300 million litres of wastewater daily at its sewage treatment plants (STPs) located in the Sydney, Illawarra and the Blue Mountain regions. These plants treat the wastewater from over four million people. The liquid and solids are separated during the treatment process. After processing, the treated liquid (effluent) is released into receiving waters or is recycled. The treated solids (biosolids) are transported from the STP for beneficial use.
Sydney Water currently produces two types of biosolids. These are dewatered biosolids and lime amended biosolids - lime is added after initial dewatering and further processed.
Why use biosolids?
Australia is home to some of the world's oldest soils. These soils tend to lack organic matter, nutrients and are often highly acidic. Biosolids are more than 60 per cent organic matter and contain nutrients such as nitrogen, phosphorous and potassium. These nutrients are released slowly during plant growth increasing crop production, reducing soil erosion and protecting water quality. Ultimately the use of biosolids conserves landfill space while providing benefits to soils.
Biosolids also contain plant essential trace elements and small amounts of other chemicals. All biosolids produced by Sydney Water have undergone a treatment process to reduce levels of pathogens, vector (insect and vermin) attractants and odours within the product.
Biosolids In Agriculture
For the past 15 years, biosolids products have become recognised by farmers for their organic material, which provide benefits to depleted agricultural soils and a range of plant nutrients and trace elements - essential for plant growth.
Applied at agronomic rates, dewatered biosolids are an excellent soil conditioner providing superior water holding properties that can improve pastures and increase crop yields. More than 60 per cent of available biosolids are used in the agricultural sector.
Biosolids are:- so popular that demand outstrips supply
- applied on farms throughout the South Western Slopes, Central Western Slopes of New South Wales.
Biosolids assist in closing the nutrient loop by replacing what cropping takes away from the soil.
Biosolids In Composting
Composted biosolids can be used in large commercial landscaping projects or residential gardens. Like any other fertiliser, composted biosolids are generally applied and mixed into the soil, promoting efficient water usage due to the natural water holding capacity of the compost.
The biosolids are mixed with other organic materials such as sawdust, shredded timber and green waste and formed into windrows (lines of compost material heaped together for processing). The windrows are turned to allow for aeration and to create an even blend. Over a 12-week period, the natural processes of composting develop temperatures above 55 degrees Celsius, destroying most unwanted organisms and breaking down the organic material.
The result is a composted product that can be used for gardening and landscaping activities. By using composted biosolids, you will also be helping the environment.
Biosolids In Land Rehabilitation
Biosolids are fast becoming an alternative soil ameliorant for both land and environmental managers. Degraded soils, that may have soil structure decline, erosion, nutrient depletion, acidity and salinity, are often the result of mining practices, excessive farming and industrial activities.
These soils are often unable to support plant growth. Biosolids products have been used to successfully revegetate mine sites and degraded agricultural land by providing organic matter and plant nutrients.
Disturbed and degraded land responds exceptionally well to high levels of organic matter and plant nutrients in dewatered biosolids. Lime amended biosolids products can improve the pH of degraded soils - giving the land a helping hand.
How Can You Help
There are many factors contributing to the success of Sydney Water's biosolids program. To help improve the quality of biosolids created during the wastewater treatment process, Sydney Water has developed a number of strategies to help keep toxic substances such as chemicals and paints out of the sewerage system and the environment. The trade waste program, which targets industrial and commercial customers, sets standards and charges for the amount and type of substances discharged to the sewer. It encourages industry and small business to treat wastewater before discharging it to the sewerage system.
There are many ways domestic residents can help improve the quality of biosolids. These include:
- don't wash paint, pesticides, medicines or other chemicals down the sink or toilet. Put them in the bin or take them to a chemical collection point
- use low phosphorous or phosphorous-free detergents and pesticides, and only use the recommended amount of detergent for your washing machine and dishwasher
- don't pour grease, oil or milk down the sink.
By improving the quality of waste entering the sewer by not putting improper things into sinks, drains and toilets you ultimately improve what returns to the environment after treatment.
FOR MORE INFORMATION
For more information on biosolids contact BioSoil® on:
NSW Country (freecall) 1800 657 271
Ph (02) 9795 4533 Fax (02) 9795 4545
or via email - BioSoil@sydneywater.com.au