PROBLEM TO BE SOLVED: To provide liquid for water purification and a water purification method which can efficiently reduce nitrate, nitrite, and the like generated in the natural world, such as a marsh, a pond, a lake, a river, the sea, or wetlands, and a water environment of artificial equipment, such as a water bath for viewing or cultivation.SOLUTION: Liquid for water purification loads an external force to a culture solution containing raw water containing a microbe group including anaerobic microorganisms and particles composed of polyhydroxyalkanoate, and destroys at least a part of a biofilm formed on particle surfaces after cultivation starts before it completes.【課題】例えば、沼、池、湖、河川、海、湿地帯等の自然界や、観賞用や養殖用等の水槽等の人工装置の水環境において生じる、硝酸塩、亜硝酸塩などを効率良く低減することが可能な水浄化用液及び水浄化方法を提供すること。【解決手段】嫌気性微生物を含む微生物群を含有する原水とポリヒドロキシアルカノエートからなる粒子とを含む培養液に対して、培養の開始後終了までの間に、外力を負荷して前記粒子表面に形成されたバイオフィルムの少なくとも一部を破壊してなる水浄化用液。【選択図】図１
