PARIS, Feb 17 (Reuters) - Ardian is not working on a counter offer to buy French water and waste management company Suez , the investment firm’s chairwoman told a hearing at the French Senate about Veolia’s hostile bid for its smaller rival. “We are not working today on a counter-takeover project,” Dominique Senequier said, adding that it would be important to name a mediator in the Veolia and Suez situation. (Reporting by Sudip Kar-Gupta and Matthieu Protard; Editing by Edmund Blair)