After a decade of complaints about it, suits over it and odors from it, the sewage sludge of Prince George's County is finally being given a decent burial.
Since July 1, on a farm in the south Piscataway section, a giant "Terra-gator" has been pulling a bank of narrow chisel plows through the fields and injecting sludge as a fertilizer and soil conditioner into the foot-deep furrows.
The injection technique, perfected for large-scale application in the past several years, may have ended the county's desperate and controversial search for an acceptable way to dispose of the 550 tons of sludge produced daily at sewage treatment plants.
The injection method, used successfully in a small number of cities and counties across the country, is both a cheap method of sludge disposal and a solution to the odor problems. As an added bonus, the method will provide area farmers with free tilling and fertilizing of their fields.
"So far I haven't smelled a thing," says James Hancock, a neighbor who lives only 200 yards from where the giant Terra-gator rumbles across the fields six days a week on its 3 1/2-foot-wide tires.
"This injection system is a lot better than that system they had before: just putting it on top" of the ground, said Hancock, referring to one of many sludge disposal methods tried by the county.
The county has buried sludge in deep trenches and at landfills, still incinerates some of it and recently attempted to compost sludge on a large scale.
Though this recycling method is used successfully in Montgomery County and more than 40 urban areas around the nation, the composting in Prince George's was halted almost before it had begun.
When the county's new $6 million Western Branch composting site in Upper Marlboro produced strong odors and strong objections from nearby residents, it was closed by county officials, temporarily last summer and then permanently in April.
That sent county and Washington Suburban Sanitary Commission officials on a frantic search for yet another sludge disposal method. Two sludge injection firms, Bio Gro and Ad+Soil, contracted with WSSC to handle all of the county's sludge, except a small amount that is incinerated. Beginning in August, Ad+Soil will inject about 200 tons a day on farms in Queen Anne's County on the Eastern Shore; Bio Gro injects about 100 tons a day now and next month will handle 350 tons a day on farms both in and outside the county.
The WSSC pays the two firms approximately $30 a ton to dispose of the sludge, about the price it costs to compost it but without the expense of operating and maintaining composting sites. Bio Gro and Ad+Soil truck the sludge directly from the sewage plants to the farmers' fields. The farmers get it free.
Composting, generally considered the cheapest and best of the recycling methods, was rejected in Prince George's while working well elsewhere, apparently more because of political considerations than anything else.
There were musky odors when the Western Branch plant opened, more than at Montgomery's new Dickerson plant, according to officials of the WSSC and the Maryland Environmental Service, the state-owned corporation that built the two plants and operates many of Maryland's water, sewer and recycling projects. However, the odors apparently were caused because the plant was opened before it was complete and because it was composting more sludge than it was designed to handle.
WSSC officials say air inversions also trapped and intensified the odors in the area and the existing sewage treatment plant beside the composting site may also have contributed to the overall problem.
But county officials already were opposed to composting, having just fought all the way to the U.S. Supreme Court in an unsuccessful attempt to keep Montgomery County from building a sludge composting plant at Calverton, near the Prince George's line. Prince George's also recently forced the closing of an experimental federal-state composting project at Beltsville, where composting techniques were developed over the past half-dozen years.
While Prince George's was closing the new Western Branch composting plant, Maryland Environmental Services (MES) was operating its companion Dickerson plant so successfully, and without complaints, that it hasn't been able to meet area nurseries' and garden centers' demands for composted sludge.
"Washington sludge is great stuff, about the best in the country," because it is free of industrial pollutants, said Clinton R. Albrecht, chief MES engineer. "We can't keep up with the demand. We've outsold our (Dickerson) production, sold out until fall."
The sludge, composted with wood chips, is heated until virtually all germs are killed and is safe enough to use in home vegetable gardens, according to state and federal officials. Most of the Dickerson compost is being used for landscaping and soil improvement, Albrecht said.
Because the supply cannot equal the demand, MES just raised its composted sludge price from $3.50 to $4 a cubic yard. "Nurseries are selling it for $10 to $20 a cubic yard and at least one as high as $30," according to Dickerson project manager Joel Thompson.
MES sells wholesale only in dump-truck quantities of 10 to 20 cubic yards, although MES trucks can deliver it.
The injection method, almost as cheap as composting, is one of several "land application" methods tried in the county and the method with the fewest drawbacks, according to the WSSC. The other methods are spreading sludge directly on fields, still done occasionally, and burying large quantities in deep trenches, which is no longer used because the heavy concentrations make the fields unusable for farming for several years.
In the injection method, careful calculations are made to determine the amount of sludge needed for a particular crop in a particular field, based on the nutrients that can be absorbed in one season.
The process has many benefits for the farmer, says Stephen R. Campbell, president of the 4-year-old Bio Grow firm that has set up similar sludge injection systems in Roanoke, Raleigh, N.C., and Oklahoma City and recently proposed a system for the District.
"This is outstanding sludge and a system that provides a farmer, free, with $60 to $80 worth of fertilizer, tills his field, which would cost him $6 an acre to plow, and improves the tilth of his soil and its water-holding capability," said Campbell. State permits for sludge injections are easily obtainable because the sludge is used as a fertilizer rather than a dumped waste, Campbell said.
Bio Gro and Bevard Brothers, a large hauling company in the county, operate the project; Bevard provides special tank trucks made from cement mixers welded together to haul the sludge, which is about 80 percent liquid and the consistency of watery cement.
The Terra-gator also is hybridized. A large vehicle for applying fertilizer and insecticide, it was adapted to pull a gang of narrow chisel plows that have built-in nozzles to pump sludge into furrows.
The injection method has its drawbacks, particularly in winter when the ground is often too hard to plow. Then, Campbell said, "We spray it on top of the ground, because there's no odor when it's cold, or take it to farms in sandy areas like Virginia where the soil is resistant to freezing."
MES engineer Albrecht, an ardent supporter of composting, believes the injection method is a good one, though it may not solve sludge problems year-round.
"But we like to see a good product put to constructive use . . . and if sewage sludge is used for nothing else but to restore bad land, we sure have enough of that" to make good use of all Washington-area sludge.