President Reagan has proposed a $1.38 billion operating budget for the Environmental Protection Agency in fiscal 1986, the first time the agency's operating budget would creep above its levels under the Carter administration.

The president's budget also requests $900 million for the Superfund toxic-waste cleanup program, 45 percent more than in 1985, and $2.4 billion for sewage-treatment construction grants, which the administration wants to phase out in four years.

Among increases is a $54 million boost for hazardous-waste disposal programs, which also would benefit from a $28 million "reprogramming" of 1985 funds. The EPA said the 44 percent increase would help it meet new responsibilities for regulating small-quantity waste generators and underground storage tanks and for banning land-disposal of certain toxic wastes.

Research would get a 12 percent increase, most of it focused on acid rain and hazardous waste or channeled into the agency's risk assessment activities for pesticides and toxic substances. Long-range research would be reduced.

The budget for enforcement activities would increase by $34 million, or 21 percent, about two-thirds of that aimed at recovering Superfund expenditures from companies that created toxic dumps.

Among losers in the president's budget are programs to review old pesticides and set food-residue tolerances. Radiation programs also would be pared, and the president's budget seeks less money for monitoring compliance with the National Environmental Policy Act.

Grant programs to help states comply with federal environmental standards would be increased about 5 percent, to $278 million.The president intends to propose legislation to triple revenues for Superfund, apparently without tapping the U.S. treasury. In the past, the federal government has contributed about 12 percent of Superfund appropriations, the rest coming from a chemical-feedstocks tax.