Private equity firm-backed ProAct Services Corp. has acquired Thermtech Inc., a manufacturer of waste heat and thermal oxidizer systems, for an undisclosed amount. This transaction is ProAct’s fourth add-on acquisition over the last three years.

Thermtech engineers a variety of process systems for thermal and catalytic oxidizers, waste heat recovery packages, burner systems, and combustion and control systems. The Kingwood, Texas-based target manufactures built systems used to heat both liquid and air streams. Thermtech’s products are designed to help reduce the cost of waste disposable by eliminating the heavy water portion of waste.

“The acquisition of Thermtech greatly improves our capabilities in manufacturing thermal oxidizers,” states ProAct CEO Frank Smiddy. “We continue to expand our presence in the degassing market and Thermtech will help drive our continued growth.”

ProAct provides customized services for innovative air and water treatment needs with respect to the requirements of specific environmental issues. The buyer’s services are specifically tailored to processes involving on-site water treatment, industrial degassing and vapor control, environmental remediation, and suspended solids removal. A portfolio company of private equity firm Hammond Kennedy Whitney & Co. Inc., ProAct is based in Ludington, Michigan.

Other middle-market deals involving water treatment systems and materials include: European investment group EQT’s acquisition of Innovyze, a U.S.-based software developer for smart water infrastructure modeling, from Stantec Inc. (NYSE: STN); and Maroon Group LLC’s purchase of Cadence Chemical Corp., a national distributor of chemicals for the water treatment industry.