Swimming pool water is usually treated with chlorinated chemicals to prevent bacteria growth.

chlorinated 是动词 chlorinate 的过去分词形式。chlorinate 由词根 chlor-（表示"氯"）和动词后缀 -ate（表示"使...化"）组成，意思是"用氯处理"。 chlorinated chemicals 指"经过氯化处理的化学物质"，即含有氯的消毒剂。