LISBON, March 22 (Reuters) - Cocaine use has increased across Europe, an EU-wide wastewater study showed on Wednesday, with the highest levels of residues found in Belgium, Spain, Portugal and the Netherlands. It analysed samples collected over a one-week period between March and April last year for traces of cocaine, amphetamine, methamphetamine, MDMA/ecstasy, ketamine and cannabis and found drug-use was greater than in previous studies. See here for a complete list of exchanges and delays