Four years ago land use was the major political issue in Fauquier County.

But this election year finds politicians in the county, which lies southwest of the District along Rte. I-66, largely confident that recent zoning changes will ensure local control over future development. As the hottest campaign issue, land use has been replaced by sludge.

The practice of spreading sludge on farm land is not new to Fauquier, where farmers have for years taken waste material from their private septic tanks and dumped it on their crop land as a way to cut fertilizer costs. It is sludge from outside the county, which some say contains possibly harmful ingredients, that has politicians and some citizens upset.

A lagoon for temporary storage of sludge from a District sewage treatment plant was approved in August by the board of supervisors, who earlier this year adopted an ordinance allowing out-of-county sludge to be stored and spread on county farms. This week, sludge from the lagoon is expected to be spread on 900 acres by a Maryland firm that already has received permission from the state water control board and the state health department.

The controversy is strongest in Lee District, where the lagoon is located, and where Democrat Samuel M. Butler, 47, a dairy farmer, faces two opponents in his bid for a fourth term on the board of supervisors.

Both his rivals are farmers. Janice W. Traver, 56, running as an Independent, is a horse breeder. She is Butler's neighbor and his appointee to the county planning commission.

Howard E. Grove, 69, a Democrat running on an Independent ticket, is a cattle and crop farmer born and raised in the county. Grove held the Lee District seat from 1968 to 1972 and ran unsuccessfully against Butler in 1979.

Both Grove and Traver say Butler's votes supporting the use of sludge from outside the county and the location of the lagoon in Lee District are evidence that the three-term supervisor no longer adequately represents his constituents.

Traver, who has filed suit against the board of supervisors charging in part that the sludge ordinance was improperly implemented, said she opposes spreading sludge from the District's Blue Plains Sewage Treatment plant or other plants outside Fauquier.

Butler's opponents both say the city sludge may contain unsafe levels of bacteria, pathogens and heavy metals that they contend county sludge would not contain.

"Questions remain that have never been answered," said Traver, who has lived in Lee District for 17 years. "I don't really think Fauquier County should be the proving ground for whether this is a successful way to use sludge." Grove agreed with Traver. "There are some questions that haven't been answered that should be," Grove said. "We should learn a little more about it before we turn it loose in the county."

Butler, however, said he prefers to trust the experts. "We wouldn't drink milk if we didn't believe the health department tested milk at the dairy," he said.

The state health department and water control board have approved for use in Fauquier County sludge from Blue Plains and from a treatment plant in Maryland.

According to both state agencies, the heavy metal content of the sludge meets their requirements. They said the processing methods that reduce bacteria and pathogens also meet their approval.

Hugh Eggborn, director of the state health department's Culpeper regional office, said the difference between Fauquier County sludge and sludge from Blue Plains lies in the treatment. Sludge from county septic tanks is untreated, he said, making it Class B sludge. Blue Plains sludge, which is stabilized with lime to reduce the pathogens, is Class A sludge, he said.

"If 25 to 30 years from now I thought sludge would be dangerous to residents of Fauquier County, I certainly would vote against it," Butler said. He does not use it himself, he said, only because his cattle produce enough fertilizer for his farm.

In Cedar Run District, Democrat David A. Botts, 69, is seeking his fourth term. A farmer and retired merchant, Botts is opposed by Charles A. Padgett Sr., 45, a Republican who owns an automotive machine shop.

Board chairman John B. Adams, 69, is unopposed in Scott District. He is an Independent. Center District's Robert Kenefick is not seeking reelection. Vying for that seat are James Rankin, a Warrenton merchant running as an Independent, and Walter A. Hitchcock, also an Independent. Hitchcock, 47, owns a management consultant and construction business.

In Marshall District, incumbent James R. Green Jr., an Independent seeking his second term, is opposed by Republican Madge M. Eicher.

In Fauquier County's constitutional races, the office of county sheriff is sought by former deputy sheriff Ashby W. Olinger, 34, who defeated Sheriff Luther Cox in the June Democratic primary

Running against Olinger is Charles A. Cooper, 43, a Republican and a former Fairfax County police officer who, like Olinger, lives in Warrenton.

Commissioner of the revenue Alice Jane Childs, 57, a Democrat who has held the office for 17 years, faces opposition for the first time since 1971. Her opponent, Beverly L. Ennis, 38, is running as an Independent. Ennis is an associate broker with Rainbow Realty in Warrenton.

Clerk of the Circuit Court Harvey L. Pearson, and Treasurer J.E. Cox, both Democrats, are unopposed.