"Over the last two years, EQT Infrastructure and E.ON have jointly contributed to EEW's development, allowing EEW to improve its competitive position," it said in a statement.

The firm operates at 19 waste burning sites that produce power, district heat and industrial steam in Germany, Luxembourg and the Netherlands.

In 2014, EEW had sales of 539 million euros (398 million pounds) and 1,210 employees.

The value of the transaction was not disclosed.

(Reporting by Vera Eckert, editing by Kirsti Knolle)