A YEAR ago, Brazilians in a city park here got dressed up in alligator costumes, rode hot air balloons, sang songs, signed petitions, and made speeches to save the Tiete river, an urban waterway made lifeless by pollution.That rally evolved into a popular movement to clean up the river, and helped to galvanize officials. The pollution sources have been mapped and some companies have begun working to treat their effluent. In July, the state government proposed a $2.6 billion four-year cleanup plan. And Sao Paulo governor Luis Antonio Fleury Filho recently went to Washington, where he persuaded the Inter-American Development Bank to lend $450 million for sewage treatment plants, part of the cleanup plan. The plan would construct new sewer systems that include collectors and five new treatment plants, while also investing in industrial treatment to put oxygen back into the Tiets waters. "No one is saying that in four years the river will be totally clean, but it will be much better," says Lineu Alonso, director of pollution control for the metropolitan region at CETESB, the State Company for Technology and Environmental Sanitation. "There will be the beginning of life in the river for flora and fauna, and it will look cleaner." The state of Sao Paulo has already committed $1.15 billion to the plan, part of it from the federal government. Private companies are also pledged to put up $300 million to $400 million, and the World Bank may also help pay the tab, Mr. Alonso says. The pollution is the result of Brazil's rapid industrialization, which began in the 1950s and turned the state of Sao Paulo into a national powerhouse churning out half of the nation's annual GNP, today around $350 billion. "The goal was growth of the city, and in developing countries like ours there weren't ample resources, so they were used for other things, [not environmental protection]," Alonso explains. "Now, society is more aware." Activists add that for many years, officials were unwilling to commit themselves to cleanup projects that would last longer than their terms of office. So far, the city's sewage-treatment system has been unable to keep up with Sao Paulo's rapid growth. The river daily receives untreated waste from thousands of homes and roughly 39,000 companies. Of the latter, CETESB targeted 1,200 companies, responsible for 90 percent of the pollution, and is working with them to implement cleanup plans. The CETESB list of offenders is long and includes subsidiaries of such US-based multinationals as Colgate-Palmolive, Quaker Oats, Avon, and Philip Morris International Inc. A locally owned Coca-Cola bottling franchise ranks sixth on the CETESB list. And the companies are worried. "When our factory was built, over 30 years ago it was on the edge of the city. Now it's in the middle of it," says a spokeswoman for Philip Morris, which owns Industrias Alimenticias Kibon S.A., an ice cream manufacturer. She explains that there is no nearby water treatment plant that functions. "We are concerned with ecology and quality of life, and we are doing what we can to solve the problem," she says. Kibon is considering banding together with other companies to treat sewage. With the same idea in mind, the Sao Paulo State Industrial Federation (FIESP) is helping to bring small companies together to pool needs and resources. Dante Mariutt, director of FIESP's environmental department, organizes seminars on waste treatment technology, especially for small companies. "Larger companies have easier access to technology and money," he says. It was a Sao Paulo radio station called El Dorado that began the ball rolling last year with a series of reports on the state of the Tiete. Done in conjunction with the British Broadcasting Corporation, the reports included the story of how London cleaned up the Thames River. "I never imagined a radio station could be able to move public opinion," says El Dorado director Joao de Lara Mesquita, who was forced to leave his regular duties and spend three months with groups and individuals who wanted to organize a cleanup. "It turned into a campaign, a national event." Especially gratifying, says Mr. Mesquita, is what the campaign taught citizens about democracy, reinstalled here in 1985 after a 21-year military dictatorship. "For the first time I see that the populace is trying to do something, to make the politicians know that [voters] are the most important of all," he says. "The politicians are only the bridge, the mechanism to getting things done. And the Tiete river is the biggest example we have of this." El Dorado radio, three months ago, helped set up the Union for the Tiete River Nucleus. Funded with a $350,000 grant from Unibanco bank, the Nucleus group helps action groups in many of the 208 cities located in the river basin. One project involves turning the river's source into a park; another organized 3,000 photographers to document the river's 680 mile length last August. Mario Mantovani, Nucleus coordinator, says he has been invited to speak in several other Brazilian cities whose rivers are polluted. His group's mission, he says, is "to be a motivating factor, to show that laying pipe and taking care of sanitation also provide votes [to politicians]."