EVALUATION OF THE IWA ANAEROBIC DIGESTION MODEL (ADM1) FOR SIMULATING FULL-SCALE ANAEROBIC SEWAGE SLUDGE DIGESTION

This paper applies IWA's Anaerobic Model No. 1 (ADM1) to the anaerobic digesters in eleven wastewater treatment plants. The eleven plants have treatment capacities ranged from 13 to 350 million gallons per day (MGD), with approximately 12 to 550 dry metric tons (dtpd) sludge produced for digestion per day. The main purpose of this study was to evaluate the ADM1's application on the full-scale sewage sludge digestion by comparing the ADM1 model predictions with full-scale data collected. The results showed that the predictions of the ADM1 steady-state implementation using the suggested physico-chemical and biochemical parameter values were able to reflect the results from the actual digester operations to a reasonable degree of accuracy for eight plants. It was found that the predicted volatile solids (VS) concentration in the digested biosolids, and the digester volatile solids destruction (VSD) are within sixteen percent (16%) of the actual plant data. As a result of questionable plant data for digester feed, the results from the ADM1 may not reflect actual digester performance in three of the eleven WWTPs. Biogas yield (standard cubic feet (SCF) per pound of VS destroyed) is within twenty percent (20%) difference between the model prediction and the plant data. The biogas yield was significantly off for few plants, which might be due to the potential biogas meter malfunction or/and due to the metered biogas volume not corrected for temperature to the standard condition of 20°C. In addition to demonstrating that the ADM1 is a powerful tool for predicting the steady-state behavior of anaerobic digesters treating municipal sludges, this study also proved that the use of a whole plant simulator for fractionating the influent organics into the ADM1 input parameters was successful.