| dc.description.abstract | The Bio Win software was used to simulate manure feeding to a separator, anaerobic digester (AD) and activated sludge (AS) nitrification reactor system. The General Bio Win model called integrated AS/AD model was capable of predicting most of the performance parameters involved in an anaerobic digester and nitrification reactor system. Hydraulic retention times (HRTs) were changed through a step increase of 10% to 50% in the influent flow each day for these five cases to determine the effect of HRT on important AD parameters such as methane production, COD removal efficiency and pH. There was a gradual increase in methane production from 335 to 692 L/d with a decrease in HRT from 8.7 to 3 days. At HRT < 3 days, the methane production rate increased faster till its maximum value 5 m3/d at HRT of 0.4 days before the system collapse for all five cases at HRT < 0.4 d. The optimum HRT was observed to be a 1 day for all five cases. The maximum COD removal efficiency of 72% was achieved at HRT of 8.7 days, and remained above 60% till HRT of 1 day in all five cases, while below 1 day of HRT, it decreased swiftly till value of 16% at HRT of 0.2 days. For HRT of 8.7 to 1 days, pH in an anaerobic digester dropped gradually from 7.46 to 7.38, but after HRT of 1day, its value decreased faster and reached to the minimum value of 5.28 at HRT of 0.2 days (system collapse). Solid Retention Time (SRT) has also significant effects on methane production and system stability. The moderate SRT was chosen between 15 days and 60 days for all cases. The increase in readily biodegradable fraction in the feed from 0.01 to 0.7 each day has increased the methane production from 30 to 40 COD g/L (68% to 70%) and COD concentration in the feed from 44 to 56 g/L (33%), while the increase in slowly biodegradable fraction in the feed from 0.01 to 1 each day has decreased the methane production from 33 to 38 COD g/L (69% to 67%) and COD concentration in the feed from 47 to 57 g/L (21%). In nitrification reactor, 99% free ammonia was coverted to nitrates. | |
