Through a pilot-scale study of biological aerated filter(BAF)，a new technology to reclaim the low concentrated domestic wastewater as circulating cooling water has been developed. In addition，the experiment can also provide some technical foundations of realizing zero drainage in a heat power plant，then we can conclude that the best hydraulic load for BAF's running under the condition which has low concentrated domestic wastewater in a power plant is 3m³/(m²·h). In this experiment, the average removal efficiency of COD_Cr,BOD₅,NH₃-N，SS is 78.21%，82.53%，86.97%，85.82% respectively. The average quality of the outlet is COD_Cr. 14.17 mg/L,BODS 3.72 mg/L, NH₃-N 0.40 mg/L, SS 3.67 mg/L. In conclusion, using BAF, the outlet of the reclaimed wastewater can meet the water quality standard of circulating cooling water used for the steam condensers which is made of alloy copper pipes.