I am trying to calibrate a WWTP on GPS-X and I am getting a feeling that the data I have could be wrong. I have an average of 907, 307, 799, 54.4, and 8.76 coming in and an average of 26.2, 10.5, 4.5, 3.95, 0.86 in the effluent for COD, BOD, TSS, TN, and TP respectively.

I am aware that BOD and TSS content are related. I am getting low BOD (around 2-4 mg/L) as simulated values while the measured ones range between 6-13 mg/L.

I am doubting that something could be wrong with the data but I am not sure. What could possibly increase BOD in effluent while keeping the remaining parameters in range?

Thanks.