"This is EPA working with our sister government to really explore a perfect example of environmental priorities and economic priorities coming together," Jackson said Monday in a telephone interview from Rio.
The forum was prompted by the presidents of both countries.
In March, President Obama traveled to Brazil and met with President Dilma Rousseff. They agreed on a number of measures, including a decision to work together on the issue of sustainability for urban infrastructure - the physical guts of a city, everything from roads to water pipes.
"With the significant investments in sustainable urban growth that Rio is making in the next four years, it is essential that we go there to both learn and share our expertise," Jackson said in an EPA news release Monday. "We want to be part of activities that can create new jobs for American companies and foster cleaner, greener communities for the American people."
Jackson said Nutter was selected because he was a national leader in urban redevelopment and sustainability. He is the only elected official on the trip, and the EPA is picking up the tab.
"Everyone knows what's going on in Philadelphia," she said.
Nutter often says he wants to make Philadelphia the greenest city in the country. His 100-page Greenworks Philadelphia plan sets dozens of ambitious goals for the city, including reducing energy consumption, creating green space, and improving public transportation.
Nutter said the city has "a lot to learn from Rio," but can also offer its own lessons.
Noting Rio's "huge population" - 11.7 million - Nutter said, "How do you deal with managing your water supply? How do you serve such a large population?"
Philadelphia is "perfectly poised for growth and development," he said. "Where else to see what rapid growth and development can mean? This is one of the fastest-growing cities in the world. We think we have a lot to learn."
At a meeting of the Urban Land Institute last week that focused on water, Neukrug said the trip would provide an opportunity to see how Rio's huge investment in sewage treatment and other water projects was progressing.
The Philadelphia Water Department is embarking on a 25-year, $2 billion program to revamp its storm water system that has been praised as a national model.
Instead of building a gigantic underground tunnel, the choice of many other large cities, to hold storm water overflows that currently carry raw sewage and other pollution into area streams, Philadelphia plans to install green projects to stall storm water.
They include vegetative roofs, rain gardens, and porous pavement on streets and parking lots.
Unlike Philadelphia, which is updating an aged water system," Rio is starting fresh in some areas. "Half their population doesn't have sewers," Neukrug said.
One of Rio's projects is much like what Philadelphia envisions - not just a wastewater treatment plant, but a resource recovery system, where everything usable is extracted from the sewage.
"That's the way of the future," Neukrug said. "If they have to build all these sewer plants down there, it's perhaps an opportunity to see what a resource recovery facility looks like from scratch."
Former University of Pennsylvania president Judith Rodin, now president of the Rockefeller Foundation, also is in Rio with the delegation.
Other members of the group include representatives of Morgan Stanley, Microsoft Corp., Alcoa, Harvard University, the global construction company CH2M HILL, and C40 Cities, an international group of cities seeking to tackle climate change.
After the hours-long plane ride, Jackson and Nutter decided they needed to stretch their legs. Jackson joked that on one of the most famous beaches in the world, "here he is looking at the streets and the bike lanes."
The mayor noticed the separate areas for pedestrians, bicycles and vehicles - an initiative that in Philadelphia has drawn some heat. Cyclists want more dedicated lanes, but drivers resent losing traffic lanes and parking.
So which beach was it? Ipanema? Copacabana? Nutter said he didn't know. "It was the beach outside my hotel."
Contact staff writer Sandy Bauers at 215-854-5147, firstname.lastname@example.org, or @sbauers on Twitter. Visit her blog at philly.com/greenspace
Inquirer staff writer Troy Graham contributed to this article.