Philadelphia Energy Solutions, the giant South Philadelphia refinery complex that is a major regional economic engine as well as one of the city's largest environmental challenges, is getting new leadership.

PES announced Wednesday that Gregory Gatta, 41, currently the company's executive vice president and chief operating officer, will become chief executive officer March 31, succeeding Philip L. Rinaldi, who is retiring.

Rinaldi, whose industrial activism made him a lightning rod for environmentalists, announced retirement plans in December and plans to remain on the PES board until the end of 2017. He will turn 71 this year.

Gatta, a protégé of Rinaldi, came from the investment banking and private-equity industry to the refinery in 2012, when the Carlyle Group and Sunoco formed a joint venture to operate the troubled complex, which employs more than 1,000 people.

"Having grown up in the industry under Phil, my view and outlook is not totally dissimilar from his," Gatta said in an interview. "I'm starting with a great base. We've got a great asset, with a great location and great employees, all of whom are focused on building on the successful foundation that Phil laid."

Gatta became chief operating officer in 2015 after an internal shake-up at the refinery and oversaw reductions in workforce and benefits last year to shrink the refinery's overhead, which he said resulted in the loss of 50 to 100 salaried employees, mostly through voluntary reductions.

"We've gone through that period," he said. "We've done everything we're going to do."

Gatta said he has known Rinaldi for 16 years, when Rinaldi operated a refinery in Kansas that was backed by equity firms with which Gatta was associated. Gatta is also a long-term associate of Rodney S. Cohen, the Carlyle managing director who helped engineer Carlyle's takeover of the Philadelphia refinery in 2012 after a complex negotiation involving the United Steelworkers Union, then-Gov. Tom Corbett, and the Obama White House.

The new owners revived the business with $700 million in new investments, including a rail-unloading terminal that allowed the facility to tap into a virtual pipeline of low-cost domestic crude-oil shipments. The workforce increased from 900 to 1,150 employees.

Rinaldi's attempt to take PES public last year sputtered, and the 330,000-barrel-per-day refinery struggled with the drop in crude-oil prices.

Rinaldi has also been active in promoting an "energy hub" in Philadelphia, which has been slow to take off in an atmosphere of low energy prices and political opposition from climate activists.

Before joining PES, Gatta was the managing member of Blue Barn Partners LLC, a private investment and advisory firm he founded. He also has worked with Basso Capital Management LP and Pegasus Capital Advisors LP, where he served on numerous corporate boards of directors.

A native of Holbrook, N.Y., Gatta graduated from Cornell University with a bachelor's in biological science and an MBA from Cornell's Samuel Curtis Johnson Graduate School of Management.