Monitoring zinc and ammonia discharges from galvanizing installations

Discharges to surface waters from galvanizing installations are now to be monitored in accordance with guidance note AQ 20(07) from DEFRA. During the galvanizing process, fumes released from the galvanizing kettle can settle on roof and ground surfaces which are mobilised during rain events.

WatStech has performed flow and load surveys of a number of installations immediately before, during and after rain events to record discharge and predict future contributions. Initial laboratory treatment studies using chemical precipitation with caustic or lime and also adsorption media such as granular ferric oxide (hydroxide) and zeolite have shown potential for removal of zinc and ammonia. WatStech has a pilot scale plant which can be used to assess different media for the treatment of run off water prior to discharge.

Previous surveys have revealed high concentrations in the initial ‘first flush’ due to accumulations but levels typically fall rapidly during a rain event. Flow monitoring has allowed for the accurate prediction of future discharges.