The world’s largest producer of steel, ArcelorMittal MT , had a problem: Water costs at its huge Galati mill in Romania were escalating, and its effluent water was polluting two nearby lakes. For help, the steel giant called on Ecolab ECL : The St. Paul–based company installed its 3D Trasar technology to act as a high-tech brain for the mill’s cooling system, enabling huge reductions in energy use, corrosion, and waste. The result: 2.2 billion…