the cod concentration of kitchen wastewater is between 111 and 1111 mg/L .. The cod concentration of kitchen wastewater mainly comes from ingredients and organic substances in food processing, such as fat, protein and starch. These organic substances will be decomposed into cod in kitchen wastewater, so the cod concentration of kitchen wastewater will be relatively high. At the same time, the scale, business scope, food variety and catering management level of restaurants will also affect the cod concentration of kitchen wastewater. Generally speaking, smaller restaurants will have lower cod concentration, while larger restaurants and restaurants with complicated cooking techniques will have higher cod concentration. Therefore, it is common that the cod concentration of kitchen wastewater is between 111-1111 mg/L.