Introduction  Under the guidance of the national water-saving policy for water resource reuse, more and more power plants are using reclaimed water as make-up water for circulating water, which increases the difficulty of treating sewage discharged from circulating water in power plants. This paper proposes a treatment process that combines biological treatment with advanced oxidation to address the issue relatd to excessive COD, total nitrogen, and total phosphorus pollutants in sewage discharged from circulating water.

  Method  Taking a gas turbine power plant in Guangdong province as an example, this paper described the water quality characteristics of sewage discharged from circulating water using reclaimed water as make-up water, and sorted out the discharge standards for sewage discharged from circulating water in different newly-built gas turbine power plants in recent years. Based on the types and characteristics of pollutants exceeding the standard, a "denitrification tank + secondary sedimentation tank + advanced oxidation + aerated biological filter + sand filter" process was proposed, and a thorough analysis of the principles, functions, advantages and disadvantages of various treatment processes was conducted.

  Result  Under anaerobic conditions in the denitrification tank, denitrification reaction can remove the total nitrogen. Fenton and ozone advanced oxidation can decompose and oxidize COD that is difficult to biodegrade in wastewater. As a secondary biochemical tank, the aerated biological filter not only has biological adsorption and oxidation effects but also has solid-liquid separation filtration effects. It can treat the remaining COD in the front-end process together with excess external carbon sources, achieving COD compliance. Total phosphorus and suspended solids can be removed through coagulation, clarification and filtration. This process is an efficient and stable in-depth treatment process for sewage discharged from circulating water.

  Conclusion  It can provide reference for the stable and standard discharge treatment process of sewage discharged from circulating water in power plants.