It is not often that Mayor Angelo J. Errichetti of the much-maligned town of Camden, N.J., gets a chance to upstage his sophisticated brethen from Philadelphia and New York City. But he got that chance yesterday - and loved every minute of it.

The scene was Room 1334 of the Longworth House Office Building, where a host of city officials, members of Congress and representatives of the Environmental Protection Agency had assembled to discuss progress in banning the dumping of treated sewage - sludge - into the ocean.

The representatives from Philadelphia and New York City - two of the East Coast's major sludge dumpers - said their cities were making progress, but would oppose proposed legislation setting Dec. 31, 1981, as a cutoff date for dumping.

"The imposition of a statutorily defined end-date freezes both the [Environmental Protection] Agency and ourselves into actions which may not be needed and with which it may be impossible to comply," said Philadelphia Water Commissioner Carmen Guarino.

"If there is no acceptable [sludge-dumping] alternative by Dec. 31, 1981, the city, in the face of legislated cutoff date, would be in helpless violation of the law - a position which we dread," said Robert A. Low, administrator of the New York City Environmental Protection Administration.

"I point with all humility, but with a certain amount of pride to the efforts of my city in meeting the challenge of sewage disposal in a manner which is environmentally sound and economically feasible," said a beaming Errichetti.

"We are proud of what energetic leadership has accomplished in our city in developing an alternative to ocean dumping."

Errichetti went on, "in all humility," to describe the "keystone" of his city's sludge-disposal system to the members of the House Subcommittee of Fisheries, Wildlife Conservation and Environment and the Subcommittee on Oceanography, which held a joint hearing yesterday.

The keystone of the Camden system is six-step process called "aeorbic composting," in which raw sewage is partially dried ("dewatered," the experts say), mixed with wood chips, mixed with "previously dewatered and blended sludge," aerated for 21 days, "cured" for an additional 30 days and then marketed as a soil conditioner and ground cover.

"Our system is complete and online," said Errichetti, again speaking "in all humility."

"We are enthusiasitc . . . We anticipate being out of the ocean for once and for all within the next five months," he said.

He then posed for photographs with members of the New Jersey delegation - in all humility.