Nalco Holding Company, a wholly owned subsidiary of Ecolab Inc.; is a Naperville, Illinois-based supplier of water, energy and air improvement solutions and services for industrial and institutional markets.n 2007, Nalco achieved sales of more than US$3.9 billion. In July 2011, Nalco announced a merger with Ecolab, Inc., and it became a wholly owned subsidiary of Ecolab Inc. in December 2011 after the completion of the US$5.4 billion acquisition by Ecolab.