Since Thursday, nine people have been arrested in total, including two in Germany.
The man was identified as Faycal C by authorities but Belgian media reported his full name as Faycal Cheffou.
No weapons or explosives had been found after a search at his home, the prosecutor statement said.
Two other men, identified as Aboubakar A and Rabah N, were also charged with terrorist activities and membership of a terrorist group. Rabah N was also wanted in connection with a recent Paris raid when police said they foiled a terrorist attack.
The prosecutor said one more man, Abderamane A, will be detained for an extra 24 hours.
The newspaper Le Soir reported Cheffou was identified by a taxi driver who drove the suspect Tuesday morning.
Officials said there were no specific threats to the event but explained that police should not be distracted from providing security.
Two explosions occurred on Tuesday March 21 in the departure hall of the Zaventem airport and a metro substation in Brussels.
The Islamic State (IS) group said it was behind the attacks in a statement issued on the IS-linked Amaq agency.
Belgium has raised its terrorism alert to its highest level, after three days of national mourning.