Biosolids valuable for land application
by Brian R. Hook

The Hampton Roads Sanitation District (HRSD) – which provides service for 3,100 square miles around Virginia Beach, Virginia, with nine wastewater-treatment facilities – estimates it is saving money, by the tons, by not dumping its biosolids in a landfill.

Rhonda Bowen, recycling manager at the district, estimates that putting the biosolids in a landfill costs around $315 per dry ton compared with $225 a dry ton for the land application of the biosolids. She said that about 11 percent of the biosolids that the district generates are used for land applications. Another 11 percent of the biosolids generated in the district is composted and sold back to the general public as fertilizer.

“We have several different processes (for disposing of biosolids) to give us diversification. We are not dependent on one method.” Bowen said. The district incinerates the remaining biosolids and only sends it to a landfill as a last option.

HRSD has been recycling biosolids through land application on farmland since 1984. The district first tested the program on a 310-acre farm next door to one of its wastewater treatment facilities. The district still owns and operates the working farm.

“We feel the recycling of our biosolids, both for land application and composting, are the most environmentally sound ways to manage these materials,” Bowen said “There is a huge a benefit received by the farmer who receives these materials.”

HRSD defines biosolids as a nutrient-rich organic material resulting from the natural biological and physical treatment of wastewater. Solids are first separated from the wastewater during the treatment process. These separated solids contain primarily organic material, sand, nutrients, microorganisms, and trace amounts of metal.

HRSD said the solids are further processed by several biological, chemical or physical methods, depending on the end usage. The resulting biosolids are either liquid or a moist to dry soil-like material that generally have a mild organic odor that dissipates after application. The treatment process takes the biosolids to what’s classified as a Class A level, used for composting, or a Class B level, used for farmland applications.

Bowen said Class B biosolids have not been processed quite to the extent as Class A material. Therefore there are additional site restrictions that prevent the general public from being in direct contact with the Class B material. She said that both classes of biosolids meet all quality standards established by federal, state, and local regulators.

Landscapers and home gardeners use Class A biosolids compost to enhance lawns and gardens. Farmers can take advantage of the many plant nutrients and soil enhancement properties provided by Class B biosolids. The HRSD estimates that farmers can save anywhere from $75 to $100 per acre by using biosolids, increasing crop yields, reducing erosion and reducing runoff associated with the use of inorganic fertilizers.

Biosolids are rich in nutrients, containing nitrogen and phosphorus along with other supplementary nutrients such as potassium, sulfur, magnesium, calcium, copper, zinc and iron, according to the HRSD. Bowen said that since most of the nutrients are in the organic form, biosolids acts as a slow release fertilizer and soil conditioner.

“It adds a lot of micro-nutrients that are essential to crops. But the farmers don’t generally apply these micro-nutrients because the costs are extensive. They have added benefit by adding the biosolids and receiving these additional micro-nutrients,” Bowen said. “We are also keeping a valuable resource out of landfills and not using up space.”

Bowen said that composting and land application of biosolids also helps to offset operating costs at the district. “In our situation we are not in this business to make a profit. Our ultimate goal is to clean wastewater. We have to manage those materials in whatever way is available and we feel that composting and land application and other recycling alternatives are the best way to manage those materials,” Bowen said.

Cal Sawyer, director of the Division of Wastewater Engineering at the Virginia Department of Health, said that Virginia is among the top in the amount of biosolids applied across the country annually. He said that 250,000 dry tons of biosolids are applied to a little over 50,000 thousand acres in 20 to 30 counties in Virginia each year.

“It’s the most economical method of the three management options that are addressed in the federal and state regulations,” Sawyer said. The three options include incineration with the disposal of the ash to a landfill, co-disposal mixed with solid waste in a landfill and land application, including pasture, cropland and forestland.

“I think it can be as much as half of the cost for incineration and two thirds of the cost for landfill. It also depends on the availability of landfill space,” Sawyer said.

Sam Hadeed, communications director at the National Biosolids Partnership, said that about 60 percent of the biosolids across the country are used for land application purposes. The not-for-profit based in Alexandria, Virginia is an alliance of the National Association of Clean Water Agencies, Water Environment Federation and the U.S. Environmental Protection Agency. Its goal is to advance environmentally sound and acceptable biosolids management practices. About 80 agencies participate.

Hadeed said some agencies are facing controversy in regards to land application of biosolids, especially in places like Southern California. “They don’t want human waste on farmland. So you have legalities that sometime make it difficult,” he said.

But he said that as agencies start looking at managing their biosolids and realize that landfills are filling up, it is becoming more costly to put biosolids in a landfill. Therefore, he said land application of biosolids becomes a more attractive option.

“It’s going to be more economical and more environmentally friendly if we can recycle this byproduct somewhere in our community,” Hadeed said.