Pay for manufacturing and wholesale workers in the District of Columbia will rise Aug. 5 to a minimum of $3.50 an hour, equal to the highest government-set minimum wage in the nation.

The new minimum, ordered by a unanimous vote of the D.C. Wage-Hour Board, applies to 27,700 workers in the affected industries, including printing and publishing.

Since most workers in the affected industries already earn far more than $3.50, the increase is expected to bring raises only to about 1,300 workers, according to Richard R. Seideman, executive secretary to the board.

Seideman said a recent hearing held by the board brought only two objections by employers, along with a union leader's proposal that the minimum be set at $4.50.

With the increase, affected D.C. workers will be paid at the same rate as household workers in the city, who got a $3.50 minimum last year.

Among the industries covered by the new minimums are meat-packing, newspaper publishing, and such wholesale industries as automobile parts, hardware, lumber, paper products and fresh fruits and vegetables.

There will be four exceptions to the new wage floor. They are adult trainees, who may be paid $3.25; workers hired for training under federally hired for training under federally aided jobs programs, who may be paid $2.90; young people hired under the Youth Employment Act, who may be paid $2.65 and full-time students, who may earn $2.46.