Epidemic Prevention and Water Purification Department

The Epidemic Prevention and Water Purification Department was a department of the Imperial Japanese Army from 1936 to the dissolution of the Army in 1945. While its public mission was to prevent the spread of disease and monitor water supply, the Kwantung Army also assigned their unit the covert mission of manufacturing biological weapons, and former members allege that at least one unit carried out human experimentation.

Organization
The department was organized under the following system:
 * Unit 691 was under control of the Kwantung Army.
 * The central office of Unit 691 was Unit 731, infamous for its secret commitment to chemical and biological weapons.
 * Unit 516 (Qiqihar), a chemical weapons division, operated secretly underneath Unit 731.
 * Other sub-units, which apparently were principally devoted to water purification, were Units 643, 162, 673, 543, and 319.
 * Unit 1855 (Beijing) was under control of the Japanese Northern China Area Army.
 * Unit Ei 1644 (Nanjing) was under control of the Japanese Central China Area Army.
 * Unit 8604 or Nami Unit (Guangzhou) was under control of the Japanese Southern China Area Army.
 * Unit 9420 or Oka Unit (Singapore), under control of the Southern Expeditionary Army Group.

The 1996 book Germ Warfare Units (細菌戦部隊) contains testimonies that all of these units engaged in biological weapon development.

Equipment
Each office was equipped with water purification facilities and trucks to transport water to where it was needed. The water filtration equipment was designed by Shirō Ishii of Unit 731.