300-ton class environmental research ship is a class of naval auxiliary ship currently in service with the People's Liberation Army Navy (PLAN). The exact type of this class remain unknown as of 2015, because no official information has been released, despite the ships have already been in service around a decade. 300-ton class is the most commonly referred term when describe these ships. In addition to the usual task of conducting regular environmental sampling, surveillance and research missions, these ships are also tasked with additional task of sewer transfer and treatment from other ships to prevent sewer onboard other ships from overflowing into the sea and thus causing pollution, and thus these ships also act as sewer vessels for vessel sewage discharging.