ATG UV Technology’s WF range of UV systems was awarded Norwegian Veterinary Institute (NVI) approval for disinfection of intake water and wastewater from aquaculture installations after 45 weeks of field-testing on board the Norsk Fisketransport-operated wellboat MS Namsos,
which is used for the transport of live salmon from sea cages and for de-lousing operations at fish farms in Norway.
The vessel is equipped with three 1000m3 circular fish holding tanks with separate circulation systems, each of which was fitted with a WF-850-20 medium pressure lamp system, capable of three tank turnovers per hour.
The minimum required UV dose of 25 mJ/cm2 was ensured by operating the system with variable lamp power control according to the UV dose monitoring. UV intensity, flow rate, lamp operating hours, UV dose and chamber temperature were continuously monitored, recorded, and verified against a reference sensor. Water samples were collected weekly for heterotrophic bacteria and Vibrio species analysis which showed an average 2.5 log reduction.
Specifically designed for wellboat and aquaculture applications, the compact units lend themselves to installation in the limited spaces available on a marine vessel whilst also featuring very low pressure head losses.
Erling Lorentzen of Norsk Fisketransport is pleased with the UV equipment: “The atg units meet the capacity, functionality and reliability requirements of our wellboats,” he says. “We have used the UV systems during smolt transport and despite demanding conditions on the transport, the UV systems maintained the required UV dose. Service friendliness and ease of installation mean that we will use these UV systems in the future on our boats.”
The medium pressure lamps have a low operating cost and a UV dose alarm function can be linked with overboard valves, ensuring that no untreated water is discharged into the sea. For on-shore aquaculture sites, atg UV’s Data Stream feature allows monitoring of UV operation at remote sites via an Ethernet connection.