Efficient and environment-friendly method for reducing COD in sewage

The invention discloses an efficient and environment-friendly method for reducing COD in sewage. The method comprises the following steps: firstly, adding a biological agent and an oxidant into the sewage, and carrying out oxidation treatment on the sewage; filtering and precipitating the sewage, and then adding activated carbon into the sewage for adsorption; then adding a sodium silicate solution into the sewage until the pH value is 8.0-9.0, and carrying out stirring reaction; adding a calcium fluoride solution into the sewage until the pH value is 6.5-7.0, and carrying out stirring reaction; and finally, adding a flocculating agent into the sewage, stirring, carrying out flocculent precipitation on the obtained solution, discharging supernatant by using a thickener, and carrying out plate-and-frame filter pressing separation on precipitated sludge. According to the method, the sewage is mixed with the biological agent and the oxidizing agent and then is added into the sewage, and impurities in the sewage