An air treatment apparatus (10), such as a dehumidifier or latent cooling system, has a desiccant wheel (12) having a plurality of similar internal structures (14), a shroud (16), at least a first fan (18, 20), a motor (30), an axle (32), slip rings (34), and sliding contacts (36). The similar internal structures are coated with a desiccant, and may be shaped as blades, cylinders, boxes, teeth, or corrugations. The shroud divides the wheel into an active area where the desiccant removes moisture to provide treated air (22), and a regeneration area where the desiccant is heated to release the adsorbed moisture from the air (28). Switches, such as magnetic switches, apply electrical power to heaters in the similar internal structures as they rotate into the regeneration area thereby heating and drying the desiccant.