The District of Columbia announced yesterday an accelerated drive to catch up with water bill collections that have fallen nearly $10 million behind, threatening to balloon the city's expected massive deficit.

More than 120,000 water customers who already have received one bill since the Oct. 1 start of the fiscal year will get a second bill earlier, and it probably will be larger than normal, city officials said.

While admitting the city itself was heavily at fault for past delays and confusion, City Administrator Elijah B. Rogers said the Department of Environmental Services had been ordered to use its new automated billing system to crank out new bills and see that they are paid in full before Sept. 30.

That will require an aggressive collection program, Rogers told a news conference, with the city prepared to cut off service to the most severely delinquent accounts and to use commercial collection services to collect the debt. Enforcement procedures such as water cutoffs were halted in 1977.

The largest groups of customers -- 40,300 in Northwest outside the historic 19th century city boundary at Florida Ave. and 31,700 in Northeast -- will pay a catch-up bill for 11 months of service instead of the normal six-month billing cycle. For a family of three to four persons, the 11-month bill was estimated at $56.

William B. Johnson, acting director of Environmental Services, said the vast majority of bills will be based upon actual meter readings rather than on estimates, as often was the case in the past.

The accelerated bill collection drive is expected to bring in $33 million in revenues for water and sewer services during the rest of the fiscal year, including about half the $9.6 million that was overdue at the end of the past fiscal year. The city already has collected $10.6 million in water revenues this year, bringing the total expected from the collection program to $43.6 million.

By law, water and sewer revenues are put into a special fund to pay for providing those services and cannot be used -- except as a temporary loan -- to pay for other city operations. But if water bills are not collected, Rogers said, tax revenues might have to be diverted from the city's general fund to pay water and sewer costs.That would increase the city's potential deficit beyond the currently threatened $172 million.

By adding to the District's cash flow, Rogers said, the water money will enhance the city's ability to meet its obligations on time. He said the water revenue was taken into account by Mayor Marion Barry in developing his program to avert the deficit.

The accelerated drive on water bills is the second announced effort by the city during its current crisis to collect past-due funds from citizens. The Finance and Revenue Department has begun a crackdown expected to yield an estimated $6 million of the $23 million in taxes listed as delinquent.

Under the new enforcement program, he said, this will not be permitted to happen. Customers will be expected to pay within the normal 30-day grace period. Up to 12 employes will be trained and assigned to bill collection, he said. Extended payment plans will be arranged for customers who owe so much that a single payment would strain their budgets.

Johnson said there will be no cutoff of water service to apartment buildings in which landlords are late in paying a single bill for the entire development. i

Following is the residential billing schedule for each of the four water service areas of the city:

Northwest area south of Florida Avenue including most of Georgetown, 12,500 customers received bills in January and will be billed in April or May for six months of service.

Northwest area, north of Floriad Ave., 40,300 customers received bills in November and will be billed between April and June for 11 months of service.

Southwest and Southeast, 19,300 customers received bills in February and will be billed in June for 10 months of service.

Northeast, 31,700 customers received bills this month and will be billed between July and early September for 11 months of service.

Johnson, the Environmental Services head, said many water customers have "ignored our bills and delinquency notices" in the past.

In addition, 17,306 commercial customers will receive six-month bills in May and August in addition to bills that were sent in January.