Edu Bayer for the International Herald Tribune Watching a Sikh band performing at a temple in Badalona, a city in Catalonia, which is considering separating from Spain. It has been good for business. Last month, before a giant rally in neighboring Barcelona to support independence, Mr. Shen ran out of the Catalan flags he sells as a wholesaler because customers had snapped up about 10,000 of them in just a week. But as an immigrant who moved here from Shanghai 20 years ago, he is worried by the way separatists advance their case for nationhood with claims to a distinct Catalan national culture, language and identity that set it apart from Spain. "It's always best to be part of a larger country, just like having a bigger family to help you," Mr. Shen said. Immigrants like Mr. Shen illustrate the complexities of identity in Catalonia, where they have helped make the economy both the largest among Spain's regions and the most diverse, alongside Madrid, with sizable populations of Muslims, Sikhs, Chinese and others. As Catalonia prepares for a regional election on Nov. 25 that could become an unofficial referendum on independence, as many as 1.5 million residents of the region, out of a total population of 7.5 million, will not be eligible to vote because they are not Spanish citizens. While these newcomers have played little part in the separatist debate so far, their sheer numbers and their contributions to Catalonia's economy have indirectly reinforced the claims by some politicians that the region should occupy a place in the European Union separate from Spain. With annual output of about $260 billion in goods and services, an independent Catalonia's economy would be larger than a dozen of the union's 27 members. Cities like Badalona, just northeast of Barcelona on the Mediterranean coast, illustrate the social and economic challenges that Catalonia faces, whatever the outcome of the separatist drive. Last year, Badalona, with a population of 220,000, elected a hard-line conservative mayor, Xavier García Albiol, "in part due to his polemical views linking immigrants from Romania and other countries to crime and promising a tougher stance on illegal immigration," the United States Department of State said in its most recent human rights report on Spain. Mr. García Albiol is one of only a few politicians from the governing Popular Party of Prime Minister Mariano Rajoy to win office in Catalonia. In step with his conservative colleagues, Mr. García Albiol opposes separation, and he has cast a large shadow over Badalona's immigrants, to the point that he has been sued based on accusations of inciting hatred against the local Roma population. "One reason I got elected is because people could see that I was ready to identify a problem and take action to resolve it," Mr. García Albiol said in an interview. Asked to explain the problem, Mr. García Albiol said, "A large part of the migrants came here to work, but a small part also arrived with the sole intention of becoming delinquents, stealing and making life generally impossible for all their neighbors." For this minority, he concluded, "the only solution is police pressure, efficient judicial action, and if possible, send them back to their countries." This year, Mr. García Albiol tried unsuccessfully to block the opening of a new mosque in Badalona. The mayor's immigration policies are "a bad joke," said Abdelkrim Latifi I Boussalem, who helps run Amics, an association that offers Islamic teaching and Arabic language classes in Badalona. Still, Mr. Latifi I Boussalem, who left his native Casablanca, Morocco, 22 years ago, said the municipality struggled to accept the Moroccans and Pakistanis who form the bulk of the city's Muslim population even before the city elected Mr. García Albiol. "All the major political parties display some fear of Islam," he said. It's never been easy, but at least other politicians used to talk to us and didn't just call us a problem. Mr. Latifi I Boussalem contended that recent immigrants should have a say in any independence referendum. We're not here to dilute Catalan identity, and are ready to work hard to understand the place in which we live, especially since Catalonia has always been a land of welcome and refuge.