Some Frequently Asked Questions about Biosolids

What are biosolids?

Biosolids are nutrient-rich organic materials processed and refined from domestic sewage in a wastewater treatment facility. When treated and processed, biosolids can be safely recycled and applied to landscapes and garden soils where they supply plant nutrients and improve the soil. Biosolids are closely regulated by state and federal laws. Biosolids used in composts must, by law, be free of human pathogens.

Is there a difference between biosolids and sludge?

Yes. Sludge is as different from biosolids, as manure is from compost. Wastewater is a combination of solid waste and liquid waste. In the wastewater treatment process, solids are separated from liquids. The solids, after further treatment, are then called sludge. The remaining liquid is called effluent. 

In southern Nevada tertiary treated effluent (the highest level of treatment) is used for irrigating golf courses, schools playgrounds, parks and right of ways. When treated water is put to beneficial use it is called recycled water. Recycled water accounts for 40 percent of our water used in Southern Nevada. In a similar fashion, sludge from wastewater is processed and refined to make biosolids. When treated and processed, biosolids can be recycled and safely applied as fertilizer to sustainably improve desert soils and stimulate plant growth.

The treatment process of wastewater in Las Vegas

What can we do with biosolids?

Biosolids are a solid waste from wastewater. Early in Las Vegas history wastewater was piped directly into the desert to get rid of solid waste. Thirty years ago, thousands of American cities dumped raw sewage directly into rivers, lakes, and bays. Environmental regulations no longer permit this type of disposal. We now have wastewater treatment plants and state and federal regulations that give direction for the safe disposal of solid waste and effluent. Local governments operating wastewater treatment plants currently have three options available for disposing of their solid waste from wastewater; recycle it as fertilizer, incinerate it or bury it in a landfill. In southern Nevada we currently bury our solid waste in landfills.

Are biosolids safe?

The National Academy of Sciences has reviewed current practices, public health concerns and regulator standards and has concluded that "the use of these materials in the production of crops for human consumption, when practiced in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, to crop production and to the environment." Here is what two major Universities say about the safety of biosolids and food crops.

“The use of high quality biosolids, coupled with proper management, should safeguard the consumer from contaminated crops and minimize any potential adverse effect on the environment.”

Michigan State University. Utilizing Biosolids on Agricultural Land, December, 2001.

https://www.msu.edu/~warncke/E2781%20Utilizing%20Biosolids%20on%20Agricultural%20Land.pdf

“The use of manure and municipal biosolids as crop fertilizer is both safe and effective when properly administered.”

University of Florida. Food Safety on the Farm: Good Agricultural Practices and Good Handling Practices—Manure and Municipal Biosolids, Reviewed Feb 2013.

https://edis.ifas.ufl.edu/fs150

Are there differences in biosolids?

Yes. There are three classes of biosolids. Class A biosolids (sometimes called EQ or Exceptional Quality biosolids) contain no detectible levels of pathogens and very low levels of metals. Class B biosolids contain detectible levels of pathogens and should not be used in home landscapes and gardens. Make sure composted biosolids for home or garden were certified as Class A.

Can biosolids be used in my garden?

Yes. Biosolids are used to fertilize agricultural crops. Composted biosolids have been shown to produce significant improvements in crop growth and yield in numerous studies. Nutrients found in biosolids, such as nitrogen, phosphorus and potassium and trace elements such as calcium, copper, iron, magnesium, manganese, sulfur and zinc, are necessary for crop production and growth. The organic nitrogen and phosphorous found in biosolids are used very efficiently by crops because they are released slowly throughout the growing season. This enables the crop to absorb these nutrients as the crop grows. The use of biosolids reduces the need to apply fertilizers and improves soil organic matter. The organic matter improves soil structure by increasing the soil's ability to absorb and store moisture.

How much composted biosolids can I apply to my garden?

Much of that depends on how much soil organic matter is already present and the nutrient content of your soil. Raw desert soils require much more than a productive vegetable garden. Most productive gardens will require somewhere between one to two inches of compost applied to the surface and cultivated into the soil each growing season. A new garden area which never had compost before may need twice this amount the first season. Consult your ViraGrow representative for recommendations.

Are there regulations governing the safe use of biosolids?

The Federal EPA biosolids rule is contained in 40 CFR Part 503. A copy is on file at ViraGrow for public inspection. Otherwise you can read obtain a copy online at http://water.epa.gov/scitech/wastetech/biosolids/503pe_index.cfm

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