What biosolids are and how they can benefit you

What are Biosolids?

How are Biosolids produced?

What are Biosolids good for?

How are Biosolids used?

Is land application of Biosolids safe?

Additional information
Click here to view Biosolids Data and Reports.
Additional information on biosolids and biosolids EMS certification may be obtained by visiting the website of the National Biosolids Partnership.

Biosolids are a beneficial byproduct of wastewater treatment. These solids are separated from the wastewater and fully treated to create a safe, stabilized, useful product especially beneficial for re-use due to their nutrient-rich organic material.

But that’s only part of the story. To plants and earthworms, biosolids are food. To soil, they are a valuable resource that can improve soil tilth and structure.

The road from wastewater to biosolids is a long one. The first thing that happens when wastewater enters a treatment facility is screening. In this process, undesirable objects such as plastic, rags, and stringy material are removed and landfilled.

After screening, the wastewater undergoes both primary and full secondary treatment; depending upon specific regulatory requirements, some wastewater receives tertiary treatment. During primary treatment, solids are removed by physical means including settling, skimming, and additional screening.

The wastewater then moves on to secondary treatment, where microorganisms feed on organic materials in the wastewater in the presence of oxygen. After secondary treatment, we're left with clean effluent that can safely be discharged to the waterways, and captured solids known as raw sludge. The work is far from over, though. The raw sludge from all treatment stages must be processed further to produce biosolids.

The additional processing kills disease-causing organisms such as bacteria and viruses, and reduces odors. The Metropolitan Water Reclamation District of Greater Chicago (MWRD) processes these solids in anaerobic digesters which are heated to 95°F and again uses microbes to further reduce odorous and non-odorous volatile organic compounds and pathogens. After digestion, the biosolids are stored in lagoons for a minimum of 18 months to further reduce volatile organic compounds and pathogens. The biosolids are then removed from the lagoons and placed on asphalt pads for air-drying. This process is accelerated by mechanical agitation and the resulting biosolids contain only 35% water. The final product resembles topsoil used by landscapers.

After all this processing, biosolids are ready to go to work. When applied to the land, biosolids improve soils by providing organic matter, which improves the “tilth” and other soil characteristics. Good soil tilth means that soils are easy to dig in and work up. Biosolids organic matter also enhances soil fertility and soil moisture holding capacity. These improvements in soil characteristics provide tremendous benefits for:

Plants – Healthy soil means healthy plants. For instance, improved tilth makes it easy for seedlings to emerge and easy for plant roots to penetrate. Improvements in tilth and structure provide a better balance of water and air in the soil for plant growth and improve the soil’s ability to store water for use by plants.

Improvements in soil fertility produced by biosolids provide all the essential nutrients such as nitrogen, phosphorus, potassium, and sulfur, which plants require for vigorous growth. Biosolids provide these nutrients in organic and inorganic forms. The inorganic forms of the nutrients, like commercial fertilizers, are immediately available to plants, while organic forms are released slowly over several growing seasons insuring long-term enhancement of plant growth.

Soil Organisms –Organic matter also provides food for soil organisms, such as earthworms, which keep the soil healthy and help to change nutrients from organic to inorganic forms. A healthy environment for soil organisms also helps to suppress root borne diseases of plants.

Biosolids are put to a wide range of uses including:

Fertilize agricultural land
Provide organic matter and nutrients to sod farms and nurseries
Top dressing on golf course fairways
Soil conditioner for construction of golf courses, parks, and athletic fields
Soil substitute in final landfill cover

Fischer Farm	Harborside International Golf Course

 

Is land application of Biosolids safe?

In order to be called biosolids, raw sludge must be carefully and extensively processed to meet U.S. Environmental Protection Agency (USEPA) Part 503 regulations. The USEPA’s Part 503 standards are based on a half-century of research and are designed to protect human health and the environment. The regulation sets limits on trace element’s content and requires extensive processing to kill pathogenic organisms. In establishing very stringent safety standards under Part 503 regulations, the USEPA considered numerous pathways by which humans could potentially be exposed to the chemical constituents of biosolids. Pathways included to protect human health were children ingesting biosolids, workers breathing dust at land application sites, and home gardeners using biosolids in their vegetable gardens.

The MWRD has a long history of operating wastewater treatment facilities and has been land applying biosolids successfully for over a quarter of a century. The MWRD has an approved Illinois Environmental Protection Agency (IEPA) biosolids management plan and operates under an IEPA controlled biosolids distribution permit. This means that local biosolids users do not have to seek any additional permitting from the IEPA to utilize MWRD biosolids.

The MWRD goes to great lengths to insure the safety of its biosolids. In addition to processing the biosolids to meet the most stringent standards of the USEPA, the MWRD’s Research and Development Department limits the input of industrial wastes to its treatment plants and studies the behavior of biosolids in the environment. The MWRD conducts more than one million analyses annually to monitor the quality of industrial discharges and the chemical composition of its biosolids products.

The MWRD provides the following technical assistance to users of its biosolids:

Preliminary site evaluation and soil testing

Coordination of deliveries and use

Selection of appropriate crop rotations or vegetative species for each project

Determination of the most suitable application rates and methodologies

Determination of best management practices for successful use and compliance with all regulations

The MWRD biosolids utilization program has received national and international acclaim. Many local farmers, golf courses, municipalities, sod farms, nurseries, and other organizations have already discovered that biosolids are a safe and cost effective alternative to top soil, commercial fertilizers, or composts.

Please click here to view and download our Biosolids FAQs brochure.