The Dumfries Town Council rejected last night a controversial proposal to impose a curfew on teen-agers and instead adopted a law to prohibit persons of any age from loitering.

Olney Brawner, mayor of the Prince William County town of 3,200, said the council felt essentially more comfortable with the loitering law, which he said gives police the power to arrest persons cxongregating in groups who refuse orders to move on.

The law takes effect immediately, he said, and violators are subject to up to a year jail and a fine of as much as $1,000.

The curfew proposal, which divided the town, stemmed from complaints by residents of a subdivision that teen-agers were hanging out near the residents' homes shouting and playing music. On one occasion a bottle was tossed through a window.

Police Chief Harvey Anderson was among those who were skeptical about the proposal. He expressed reservations, according to Brawner, at a council work session last week.

"Why put something on the books that you can't enforce?" Anderson asked in an interview earlier. "There's too many loopholes, too many chances of being sued."

Jeff Milton, a leader of a homeowners group who pressed for the curfew described himself last night as "disappointed to say the least." But he said the loitering law "has a little bite to it," and that its value will depend on the degree to which it is enforced.