The commercial nano-sized TiO2 powder (P25) was immobilized on foamed waste-glass substrates by using the plasma spraying technology. The immobilized TiO2 coatings were applied to treat both the green tide and the red tide under illumination of an UV light. Their photocatalytic characterizations were evaluated as functions of the number of residual algae, transmission as well as pH value with illumination time. It was found that the plasma sprayed nano-TiO2 coatings on foamed waste-glass show a higher photocatalytic activity, which was effective to treat the green tide and the red tide.