Kitchen wastewater Treatment

Its a school kitchen that generates wastewater of 5000 litres

There is a higher BOD and COD rate. Capacity of kitchen waste-water is 5 m3/day. Could someone please suggest me how to treat this waste-water and what is the reason for too much rate of BOD & COD?

BOD: 4100 mg/L

COD: 7000 mg/L