One aspect described herein is a fluid treatment apparatus. The apparatus may comprise a body extending along a flow path between a first end and a second end opposite of the first end along the flow path, the first end comprising an inlet along the flow path, the second end comprising an outlet along the flow path； a flow channel extending inside the body along the flow path to direct a fluid from the inlet to the outlet； and a solid-state radiation source mountable in a cavity of the flow channel to emit radiation into the flow channel along the flow path, the solid-state radiation source comprising a thermally conductive portion positioned to be contacted by the fluid when the fluid is flowing from the inlet to the outlet and the solid-state radiation source is mounted in the cavity. Related apparatus, devices, and methods also are described.
