Cities with lower levels of cocaine found in waste water include London, Paris and Amsterdam.
However, Alexander Van Nuijs of Antwerp University’s toxicology department says that the figures are only provisional.
Mr Van Nuijs added that Antwerp’s role as Europe’s second biggest port could account for the relatively high levels of cocaine found in the water.
The samples from Antwerp were taken from the Zuid water plant that collects and cleans up waste water from Hoboken, Borgerhout and Antwerp city centre.
The levels of cocaine found in Antwerp’s waste water point to a daily consumption of ten lines of cocaine par 1,000 population.