The workers were working on the "equipment" - I think they mean either Kurion's or Toshiba's cesium absorption vessels - that has absorbed radioactive cesium from the highly contaminated water. From the word used in the article below (かぶった), it seems the workers may have been "drenched", not just "splashed" with the water. One of them was wearing the Tyvek suits only.
From Asahi Shinbun (8/31/2011):
TEPCO announced on August 31 that two workers from TEPCO's affiliate company [could be two separate companies] got covered with contaminated water as they were conducting the control work of equipment used to process the highly contaminated water at Fukushima I Nuclear Power Plant. The contamination was wiped off, and the workers' radiation exposure was 0.14 to 0.16 millisievert.
According to TEPCO, the accident happened in the facility where the equipment that absorbed radioactive cesium from the highly contaminated water was stored. One worker was standing on the ladder draining water from the equipment and the other worker was holding the ladder secure. When the worker on the ladder removed the hose [for draining water] at about 9:35AM on August 31, the water leaked.
The worker [on the ladder] was wearing the water-proof jacket, but the worker who was holding the ladder was wearing the Tyvek suits only. The contaminated water penetrated the Tyvek suits and came in direct contact with the skin. The radiation survey meter showed 10 times the standard level. According to TEPCO, there is no possibility that the worker ingested radioactive materials through the nose or the mouth.
"かぶる" in Japanese means one gets covered with a substance falling from above. TEPCO hasn't tested what nuclides are there in the contaminated water during or after the treatment, and has said it has no plans to do so unless it is necessary (meaning when they are ordered to test by the regulatory agency NISA).
TEPCO's people who appear regularly on the press conferences often seem genuinely puzzled why they have to do certain things (like analyzing the treated water for beta radiation or analyzing the filter) without being specifically ordered by the government.