Despite the Stigma, the Future of Sewage May Be to Renew Land

A controversy that developed last week over a plan to fertilize Antelope Valley farmland with Los Angeles sewage sludge highlights a growing reliance across the country on disposing of sludge by applying it to land.

Although there is a stigma attached to sludge, and its use as fertilizer raises environmental concerns, the idea is hardly new and is growing in popularity.

Using sludge to nourish soil and repair scarred land is regarded by many environmental officials and advocacy groups as the wave of the future, and it is the cornerstone of the Environmental Protection Agency’s policy of promoting “beneficial reuse” of sludge.

Although land application is viewed as vastly superior to the old standbys--dumping it in the ocean or landfills--most experts believe the technique is inadequately controlled under current environmental rules.

The EPA has proposed broadening and strengthening its sludge regulations to reduce risks, including pollution of soil and ground water by toxic metals and nitrates, the absorbing of metals into crop roots and the presence of disease-producing organisms in sludge. The rules, which could take effect next year, would set strict limits for 28 toxic substances and for pathogens.

EPA officials and environmentalists said they knew of no documented cases of human illness from land application of sludge. Nonetheless, the new regulations are needed, in part, because of the growing popularity of the option, they said.

There’s “a veritable explosion of land application all over the country,” said Dr. Douglas N. Rader, a senior scientist with the Environmental Defense Fund.

“We think that land application is the way to go,” said Jessica Landman, a senior project attorney with the Natural Resources Defense Fund in Washington, D.C. But “it has to be land application of sludge that is . . . free of . . . harmful levels of toxics.”

Sludge is the mud-like residue made of the solids left by sewage treatment. The best sludge is not much different than the steer manure prized by weekend gardeners. But sludge also reflects the local industrial base, containing traces of cadmium, arsenic, mercury and other harmful substances from industrial discharges and street runoff. Those compounds slosh around in waste water and then are concentrated in the sludge.

Areas with little industry may produce fairly clean sludge, while sludge in industrial cities carries a heavier metal and chemical load. Cities that require waste pre-treatment by industry and that crack down on violators, as Los Angeles has done, are rewarded with cleaner sludge. The purity of Los Angeles’ sludge is about “middle-of-the-road,” said Lauren Fondahl, an environmental engineer with the EPA in San Francisco.

Most officials say the risks of land application are small if those applying the sludge carefully consider the quality of the sludge, the amount and method of application, and local soil and ground-water characteristics.

If metal concentrations are too high or applications too heavy, there’s a risk of metals being taken up in plants. The risk is greater in acid soils, such as in the U.S. Southeast, which tend to promote metal uptake.

Dr. Rufus L. Chaney, a research agronomist with the U.S. Department of Agriculture, cited one recent case in which a North Carolina peanut crop was damaged by zinc and manganese in sewage sludge.

But Chaney said such episodes, although once fairly common, are now rare. The combination “of regulations and advice from the agricultural community has prevented this from being a problem,” said Chaney. “It’s really hard to find any examples anymore.”

Sludge also breeds pathogens--disease-producing viruses and parasites. Most are the type that cause gastrointestinal illnesses that are not life-threatening, said Dr. Marylynn Yates, a microbiologist in the department of soil and environmental sciences at the University of California at Riverside. Yates said sludge can also contain hepatitis A and polio virus--dangerous to those not vaccinated against it.

On the other hand, Yates said, efforts to detect them in the air at sites where sludge was being sprayed have been unsuccessful.

“I would never say there would be zero risk of anybody getting ill . . . but, from everything that I know . . . the risk to public health would be minimal,” Yates said.

There are more than 15,000 sewage treatment plants in the United States, according to the EPA. They produce enough sludge each year to fill nearly 186,000 railroad cars, which, if connected, would stretch halfway across the country.

With two big oceans and an abundance of cheap landfills, the United States was slow to embrace land application, although in some parts of the country, particularly the Midwest, sludge has been spread on farmland for years. Japan and most European countries today reuse a greater percentage of their sludge, according to EPA estimates.

Sludge has also been used in solving unusual problems. In Pennsylvania, for instance, it is used to revegetate barren, strip-mined lands.

California, on the cutting edge of many trends, has been slow to get on the sludge bandwagon. Still, sludge in California is recycled as fertilizer, as it is in every other state. But nearly 45% of California’s sludge is still being put into landfills, although the percentage will dwindle as landfill space grows more scarce.

An additional 21% of the state’s sludge is disposed of by incineration, which has drawbacks. It eliminates the sludge and produces useful power, but incinerators are expensive and complicated, as Los Angeles has found with its $400-million Hyperion Energy Recovery System at Playa del Rey. And, even with sophisticated controls, incinerators leave an ash, which must be disposed of, and produce some air pollution.

About 25% of California sewage sludge is now applied to lands, either directly--as Los Angeles sought to do in the Antelope Valley--or through sale of the sludge to fertilizer plants.

The preferred way to use sludge on land is to compost it first, mixing it with sawdust, wood chips or crop wastes, which speed the biological processes that kill pathogens.

Composting also provides an economic advantage for sludge producers. It makes sludge easier to handle and sell to local fertilizer plants and eliminates the need to truck it to farms many miles away.

The Los Angeles County Sanitation Districts, which serve suburban communities from Pomona to Palos Verdes, rely on a blend of old-school and modern techniques.

About 400 wet tons per day, or 25% of its sludge, is composted at its Joint Water Pollution Control Plant in Carson. The sludge is then sold to Kellogg Supply to make soil improvement products, said Ross Caballero, supervising research engineer with the districts.

The other 75% of the sludge goes to the districts’ Puente Hills landfill.

On the other hand, the city of Los Angeles has scrambled for ways to get rid of its sludge since finally halting ocean dumping in 1987.

The city’s goal is to destroy all its sludge in the Hyperion plant’s sludge burner, but the operation’s sludge drying unit is not working. Because of its experimental nature, some officials are uncertain the plant will ever be reliable.

In the meantime, the city has dumped sludge into landfills, used it as landfill cover and contracted with a private firm to truck it to farms near Yuma, Ariz., and Blythe, in easternmost Riverside County.

In recent months, sludge dumping has become an emotional issue in Blythe, and residents have raised environmental concerns.

Los Angeles officials said they had hoped to divert about 300 tons per day from Blythe to the Antelope Valley to save on trucking costs. From the Hyperion treatment plant, it’s 220 miles to Blythe and about 70 miles to the Antelope Valley.

But last week, some Antelope Valley residents voiced surprise and anger about the plan, and the Los Angeles County Board of Supervisors demanded that the city take its sludge somewhere else.

The “somewhere else” could be Kern County, where supervisors last week approved plans for a composting firm to make fertilizer using Los Angeles sludge.