The federal government has approved more than $6.7 million in loans to two Washington area nonprofit organizations to finance housing for the elderly and handicapped in Fairfax and Montgomery counties.

Plans call for a 100-unit apartment building for the aged in the Aspen Hill area of Silver Spring and facilities for 24 physically and mentally handicapped people in the Mount Vernon neighborhood of Fairfax County.

As the new loans were announced last week by the Department of Housing and Urban Development, construction was beginning on a 100-apartment building for the elderly and handicapped at Lake Ridge in eastern Prince William County. The $5 million loan for the project was approved as part of HUD's fiscal 1981 budget.

The loans for the Aspen Hill and Mount Vernon projects come from $716 million for 15,252 units nationwide provided by HUD's 202 program for the elderly and handicapped.

That program has survived drastic cutbacks in housing funds for low- and moderate-income citizens. It was scaled back to 10,000 units across the country in the budget for fiscal '83, which began yesterday, and will be the only new construction in any category financed by HUD for the fiscal year.

The Section 8 housing construction and rehabilitation program, which has been a major source of funds for low-income housing, much of it for the elderly, has been eliminated.

Section 8 rental assistance survives, however, and will be available to residents of the new Washington area housing. Under the program, tenants pay up to 30 percent of their income for rent, and HUD pays the difference between that amount and the market value of the apartments.

Nonprofit organizations have 40 years to repay the loans at an interest rate slightly higher than the average rate paid by the Treasury in borrowing activities. The rate is now 9 1/4 percent but may change this month.

While funds for facilities have been dropping sharply, demand has remained high. The two local organizations planning housing for the elderly each reported waiting lists of about 200 names, meaning waits of several months.

The National Capital Housing Foundation, part of B'nai B'rith, will receive $5.66 million to construct the Montgomery building half a mile from Homecrest House. That 135-unit apartment house for the elderly, also was paid for with a HUD loan. It opened in 1979 at 14508 Homecrest Road in Silver Spring.

Residents of the new building, which has not been named, will have the services of a full-time activities director and "floor captains" who will check daily on the welfare of each resident, said foundation President Leonard Stein. A bus will transport residents each evening to dinner in the Homecrest House dining room, where kosher meals are served, said Stein.

Approval of plans required by HUD will take from six months to a year, and construction can be completed with a year after that, he said.

HUD requires that the apartments must be rented to persons 62 or older who are in reasonably good health and who have a total income of not more than 80 percent of the median income of the local jurisdiction. In Montgomery and Fairfax counties, this amounts to about $15,000 annually for one person and $17,000 for a couple.

Hartwood Group Homes, a cooperative established by families of mentally handicapped persons, will receive $1.1 million for a residential facility. Co-op leader Judy Rosen, president of the Hartwood Foundation, said the HUD loan will help provide a permanent home for as many as 30 clients. She said the organization plans to buy and renovate structures, and hopes to have the home ready for occupancy within a year.

Rosen said care of residents will cost about $600 per year per family, only half as much as most other facilities because of its "revolutionary" cooperative system in which family members of the handicapped do most of the administrative and operating jobs. The present facility is situated in a former convent on the grounds of St. Louis Church in Alexandria. Professional staff members work daily with nonresident patients.

The Lake Ridge facility on which work has begun is a project of the Fellowship Square Foundation, a nonprofit corporation established by members of Lutheran churches in the metropolitan area. The foundation, set up to provide housing for the elderly and handicapped, already operates two apartment complexes in Reston with a total of 464 units, according to Executive Director Leo E. Berger.

The new building, to be named Lake Ridge Fellowship House, is expected to be ready for occupancy in about 14 months. It will go up next to the site of a planned shopping center in Lake Ridge.

Each unit will be a one-bedroom apartment ranging from 517 square feet for single occupancy and 540 square feet for a couple and will be equipped with emergency call buttons. Ten percent of the apartments will be especially designed for handicapped persons. CAPTION: Picture, At Hartwood House are counselor Lena Purokallas, Eric Metzger, Billy Wade, Janine Wade, Steve Gilbert, in wheelchair, Michael Wade, Marshall Rosen, and Director Cindy Johnson. A cooperative of mentally handicapped persons' families will receive a $1.1 million loan. By M.C. Valada for The Washington Post