reactors used in drinking water applicationsReading time:
(see also disinfection)
Transmittance should be equal to or better than 85%. This condition determines the nature of pre-treatment to apply.
reactor types and layout
Pressurised chamber or in-line type closed vessel reactors are typically used.The number of reactors is calculated according to the design peak flow and UVC dose; a series or parallel arrangement of the reactors is determined according to maximum head loss allowable and flexibility. An additional parallel train of reactor(s) is required to perform maintenance work on the active reactor(s) trains (replacing lamps, quartz sleeves or seals) without interrupting disinfection.
The Aquaray H2O (photo 15) reactor is a typical example. It comprises six MP lamps and can disinfect up to 2 000 m3 · h–1 of drinking water at a dose of 40 mJ · cm–2 with two units in series. This reactor has a complete control system including a UV sensor that can be easily calibrated with the reactor active using a reference sensor, thus ensuring at all times that the right dose is delivered. The UV sensor also helps modulating the lamps arc current to match the actual flow, thus minimising lamp aging and electrical power consumption.
It is required to systematically provide a quartz sleeve mechanical cleaning system. This system should be easily accessible for maintenance as is clearly the case for the Aquaray H2O reactor. This mechanical cleaning system should be complemented by an in situ chemical cleaning system operating at intervals that are specific to the application.