The Asian Development Bank has awarded a technical assistance grant to Thailand's Provincial Waterworks Authority to boost the nation's efforts to control "nonrevenue" water -- treated water lost through pipe leaks, illegal connections or other problems.

The PWA plans to provide at least 70 percent of the population access to clean piped water by 1990, but the authority needs to reduce the level of nonrevenue water in order to keep costs down.

ADB's technical assistance grant, the size of which was not revealed, will finance a study of Thailand's water supply conducted by consultants with expertise in leak detection, rehabilitation and water-loss management. The consultants will train eight engineers and eight technicians drawn from the 10 administrative regions of PWA to carry out the techniques of water control recommended by the project's findings.

In complementary studies, four Thai towns -- Phattalung, Surat Thani, Ubon Ratchthani and Surin -- will be used as representative samples of the water supply system.

Control of nonrevenue water is an important part of Thailand's plan to bring clean water to provincial areas by the end of the International Drinking Water Supply and Sanitation Decade (1980-90), sponsored by the United Nations.

The ADB has approved a $4 million concessional loan and a $225,000 technical assistance grant to improve Honiara Port, the largest of nine major ports in the Solomon Islands.

With aid from the ADB, the overseas wharf of Honiara Port, the country's principal international port, was extended in 1982 to accommodate cargo ships. But the original portion of the wharf now is deteriorating.

The second Honiara Port project will rehabilitate the original section of the wharf, improve its container-handling facilities, and upgrade the port's information system.

Total cost of the project is expected to be $5.52 million, of which $4.14 million is the foreign exchange cost and $1.38 million the local currency cost.