Crimson Investment has closed a deal for private equity-backed Aqua-Chem.

Aqua-Chem, headquartered in Knoxville, Tennessee, makes water-treatment chemicals and products.

Crimson Investment is a San Francisco private equity firm that invests in middle-market businesses. The firm generally invests in companies with Ebitda between $5 million and $40 million. Crimson's other portfolio companies include Ameda, a breast-pump provider, Tyden Group, which provides security seals and Hydron, a contact-lens manufacturer.

The deal marks an exit for manufacturing-focused private equity firm Altus Capital Partners Inc.  Altus, headquartered in Wilton, Connecticut, bought Aqua-Chem in March 2006 from the Cleaver-Brooks Co., and expanded the company. Under Altus, the target launched more than a dozen new products, including large vapor compression systems, reverse-osmosis water purifiers and copper-nickel heat exchangers. In 2011, Altus added on Enviro-Solutions to Aqua-Chem

BB&T Capital markets advised Aqua-Chem on the deal.