Republican County Executive Lawrence J. Hogan, renewing an effort to place his own nominees in key positions in Prince George's County, has asked the Democratic County Council to appoint James S. Merkle to the Washington Suburban Sanitary Commission.

Merkle, 55, an officer of a local carpenter's union, would replace Johanna Norris, a Democratic holdover whose term expired in 1981.

Last week, Hogan nominated Edgar B. Keller Jr., 41, a D.C. firefighter, to replace John W. Churchill on the Maryland-National Capital Park and Planning Commission. Churchill's term had expired.

The WSSC sets water and sewer rates, and the planning commission oversees housing and recreational planning. Although the council has final say on many actions of the commissions, and must approve the nominees, the positions are among the more powerful patronage jobs controlled by the executive.

The County Council confirmed Keller's nomination Tuesday, after Churchill stepped aside. "I didn't resign," said Churchill, who was first appointed in 1972, and whom Hogan had twice attempted to replace, "I just decided not to fight it. It was dehumanizing. . . It felt like I was groveling for a job," he said. The council will consider Merkle's nomination this week.

Hogan made his first attempt to replace Norris (and his second to replace Churchill) in February, but the all-Democratic council responded to pressure from Norris supporters and made it clear the council would not remove her from the WSSC. Hogan then withdrew his WSSC nominee and the council rejected Hogan's proposed replacement for Churchill.

A spokesman for Hogan said he was hopeful that Merkle would be appointed. "He's a Democrat and a union man, what more could they want?" said Hogan press secretary Carl Gagliardi.

But council chairman Gerard McDonough said the council was not likely to cooperate. "As far as I have determined, they will not remove Jo," McDonough said, "As best I can discern, it's unanimous." McDonough said the council went along with the Keller appointment because both Churchill and Keller are Republicans, "and the council saw no reason to get involved in a Republican fight ."

In January McDonough met with Hogan and agreed to try to persuade the council to replace Norris and Churchill in return for Hogan's reappointing Democrats Andrew Vislosky on the WSSC and Edwin Brown on the planning commission. The agreement was breached when Hogan informed Norris, who then marshalled supporters, including State Sens. Michael Donovan and Edward Conroy, who threatened to introduce legislation stripping the council of the right to make WSSC appointments.