Biosolids Recycling

A Program to Help Preserve Agriculture and Protect the Chesapeake Bay

Chesapeake Bay
Biosolids Recycling

In the mid 1800s, stormwater and untreated wastewater flowed from the sewers of Washington, D.C., into the city's nearest waterways—the Anacostia and Potomac Rivers. As the city's population grew, so too did the pollution of streams and rivers. By 1930, the population was approaching 500,000 and the contaminated condition of the nearby waterways compelled the city to develop a plan to treat wastewater flowing from the sewers.

By 1938, the District of Columbia had constructed a 130-million gallon wastewater treatment plant at Blue Plains. Treatment capacity grew to more than 300 million gallons a day from the city and surrounding areas in Virginia and Maryland.

Industrial wastewater is monitored for metals and hazardous compounds, in accordance with state and federal regulation, before it enters the city's sewer system and flows into the Blue Plains plant.

Soil Enrichment

Farmer on a tractor in a field
Soil Enrichment

One valuable product of wastewater treatment is what industry professionals call "biosolids". A biosolid is wastewater transformed into a semi-solid state. Biosolids can greatly enrich soil used to grow feed crops. Biosolids contribute organic material to soil that encourages moisture retention, provides essential micro-nutrients to crops and acts as a liming agent for agricultural lands. Nutrients found in biosolids include nitrogen, phosphorus, zinc, potassium, copper and calcium carbonate as lime. Biosolids often supplement or even substitute for conventional chemical fertilizers. Environmental Protection Agency studies show that biosolids reduce the use of chemical fertilizers needed to produce comparable crop yields. Plants fertilized with biosolids show greater vigor as measured by root growth.

Nutrient Management

Based on nutrient loading rates, the Maryland Department of Environment and the Virginia Department of Environmental Quality regulate and control the application of biosolids to land. Biosolids applicators carefully develop nutrient management plans for each site and submit their plans to the appropriate state regulatory agency. These plans determine the application rate of biosolids for each specific land site based on nitrogen requirements of the crop and the lime needed for optimum soil pH.

Biosolids Recycling Protects the Chesapeake Bay by:

  • Removing nutrients from wastewater treatment plant effluent
  • Providing nutrient runoff buffer zones to streams, lakes and ponds
  • Applying biosolids to crops at nitrogen levels which match plant uptake

Biosolids Recycling Helps Preserve Farming by:

  • Recycling nutrients back to rural farms
  • Providing free nutrients to farmers
  • Reducing dependence on chemical fertilizers

Biosolids Recycling Improves Soil Quality by:

  • Improving soil porosity and infiltration
  • Reducing soil erosion
  • Improving water holding capacity
  • Reducing soil compaction
  • Providing organic matter

Cost-Effective Recycling

The District of Columbia wastewater treatment plant produces approximately 1,200 tons of biosolids each day. This material is distributed for beneficial use by several land application contractors and to several utilization facilities. About 90% is given to farmers for crop fertilization and 50 tons per day go to a compost production facility in Virginia.

From an economic viewpoint, using biosolids improves agricultural yields. From an environmental viewpoint, their use protects our rivers and the life those rivers sustain—including our own.

Creating Biosolids

Biosolids are created in several ways. One method involves piping wastewater into tanks where the heavy organic material, or solids, settles to the bottom and is removed. A second method involves aerating the wastewater in tanks, which allows microorganisms to consume much of the nutrients and organic matter, which then settle to the bottom. A third method combines iron with phosphorus in the wastewater for settling. Finally, biological nutrient removal pulls nutrients from the water. These nutrients are recycled as biosolids.

The various settled solids are dewatered and treated with lime at Blue Plains. Lime stabilization consists of mixing settled solids with lime to reduce unwanted organisms. This creates material called Class B, lime stabilized biosolids. Future plans include building digesters to further treat biosolids to Class A standards, allowing for more recycling options.

A Winning Strategy for You and the Environment

DC Water encourages the recycling of biosolids. To assist in this effort, DC Water has contracted with Maryland Environmental Service, an independent state agency specializing in water and wastewater treatment. The Service provides support for our field inspection programs and public education efforts. Their staff will provide the public with information about analyses of biosolids produced at the DC Water facility, quality assurance issues, contractor information and the delivery of material to our sponsoring sites.

For more information, call 1-800-4RECYCLE, Monday through Friday, 8 a.m. to 4 p.m.

At Your Service

The mission of the DC Water Biosolids Management Program is to provide flexible, environmentally sound, and cost-effective management of biosolids. In doing so, DC Water will help preserve agriculture and protect the Chesapeake Bay.

We invite you to learn more about DC Water's Biosolids Recycling Program. Please contact Chris Peot at 202-787-4329.

What We Do