Discharge water from an aqueous cleaning system should be tested for any banned or limit controlled substances. I doubt you will find any of the other RoHs substanses in the discharge water. Most regions are concerned about substances not common in de-fluxing applications. Historically, lead (in solution and in particulate form) was the primary concern. Ph can be a concern in some regions. Consult with your local regulators to be sure as specific toxic "deal-breakers" vary from city to city.