The present invention provides an apparatus for carrying out a photocatalytic reaction for wastewater treatment. The apparatus includes at least one spiral rod having a spaced thread profile that swirls helically along the rod wherein the at least one rod is coated with photocatalyst, and a cylindrical sleeve coaxially enclosing the at least one rod enabling a wastewater to flow helically in a space between the thread along the rod while contacting the photocatalyst coating thereon such that organic compounds in the wastewater undergo photocatalytic degradation upon exposure to a light source.