Wapora Inc., the Chevy Chase environmental testing and consulting firm that was taken over last year by a New York entrepreneur who ousted founder and president Jacob I. Bregman, reported another quarterly loss and a continued slump in revenues for the third quarter of its fiscal year.

Wapora lost $356,196 through three quarters of fiscal 1983, against earnings of $19,629 (3 cents a share) in the comparable period of 1982. Nine-month revenues dropped to $2.3 million from $4.9 million.

The extent of Wapora's decline is illustrated by the nine-month revenue report of $2.3 million. As recently as 1982, Wapora was taking in nearly that much in one quarter.

The Chevy Chase firm lost $236,210 in the third quarter, compared with a profit of $775 (negligible per-share earnings) last year. Revenues for the quarter were $651,384, compared with $1.4 million.

When Bregman lost control of Wapora to James Schirippa, of Huntington, N.Y., who acquired a majority of the stock in a private transaction, he predicted Wapora would continue to lose money throughout 1983. Schirippa, however, predicted Wapora would resume making a profit in the quarter that will end March 31.

Owens & Minor Inc.; of Richmond, which sells wholesale drugs and hospital supplies, posted earnings of $1.5 million (77 cents) for 1982, compared with $2.6 million ($1.38) the year before.

Revenues grew to $211 million from $182 million.

Fourth-quarter profits were $301,000 (16 cents), compared with $927,000 (49 cents) the year before. Sales increased to $57 million from $50 million in the final quarter of 1981.

Most of the decrease in earnings was attributed to the nonrecurring gain realized when Owens & Minor bought the inventory of Will Ross Division of G. D. Searle at a discount. Other factors include business expansion and higher costs associated with a more aggressive marketing campaign, officials said.

Owens & Minor has just purchased the assets of S&S Hospital Supply Corp. of Oklahoma City, as part of the company's drive to expand in Sun Belt states.