A plant for wastewater treatment is provided by an exemplary embodiment of the present invention. The plant for wastewater treatment includes a reactor into which wastewater and air flow into and depart from; multi-layer sludge separating portions, wherein pollutants in wastewater can be decomposed by increasing an amount of dissolved oxygen because upward moving time of intruded wastewater and air bubbles can be increased by including a reactor divided into upper and lower sides, and fluidity of wastewater may be improved by forming a residential space; and carriers located between the sludge separating portions and including a large amount of microbes, wherein wastewater treatment is performed by a biological reaction caused by contact between the carriers and wastewater.