Ecolab Inc. made its third acquisition in 16 months Wednesday with news that it will buy a small Swedish antimicrobial water-treatment division with $23 million in annual sales.

With the purchase of Purate, a division of Sweden-based Akzobel, St. Paul-based Ecolab now has a patented line of chlorine dioxide programs that kill microbes in industrial cooling towers and systems in power plants, chemical factories, paper mills and other facilities.

Ecolab spokeswoman Lisa Curran said Purate has a very small presence in the United States. “Our plan is to take it globally and use it more in the United States. We are excited about the offering,” she said.

Curran added that the chemistry used is considered safe and cost-effective. As a result, “We hope that it will help differentiate us in the marketplace,” she said.

The deal is subject to regulatory approval. Officials hope to get it by the end of June.

The cautious timeline stems from troubles associated with Ecolab’s recently closed purchase of Champion Technology, bought for $2.3 billion only 15 days ago.

The Champion deal was announced in October but was delayed for months by the U.S. Justice Department, which expressed anti-competitive concerns. The department eventually permitted the purchase but prevented Ecolab from buying a particular division of Houston-based Champion. The division, which helped treat offshore oil operations in the Gulf of Mexico, was sold to a different company.

Champion’s acquisition woes followed Ecolab’s problem-free purchase of Nalco, an Illinois water treatment firm bought in December 2011 for $8.3 billion. Nalco provides water treatment services for paper mills and offshore oil drilling companies.

Ecolab boasts $12 billion in annual revenue and is known as a water treatment, sanitizing and chemical services firm that caters to hotels, restaurants, food processors, hospitals and energy firms.

Ecolab’s stock closed Wednesday at $83.29, down 50 cents.