February marked the 10th anniversary of the nation's largest public-private partnership for municipal wastewater operations.

According to the Milwaukee Metropolitan Sewerage District Commission, the MMSD's contract with United Water Inc. reduced rates an average of 16.5% within a year.

But the relationship hasn't been without its challenges: In May 2004 the district dumped 4.6 billion gallons of untreated wastewater into Lake Michigan following a heavy rain, sparking federal and civil lawsuits and prompting the district to sign a new 10-year contract with Veolia Water North America Central in March.