كاربرد مدل هاي لجن فعال ﴿ ASMS ) در هضم هوازي لجن ثانويه

چكيده انگليسي :

AbstractAerobic digestion is a desirable method of sludge stabilization used in especially small wastewater treatment plants In this process as the available substrate supply is depleted microorganisms begin to consume their own protoplasm to obtain the energy required fortheir cell maintenance reactions giving rise to the endogenous phase in which the death oforganisms cell lysis and predation among the microorganisms cause the active biomass toconstantly reduce Mathematical modeling allows a large number of potential aerobic process designs to betested and the performance of aerobic digesters to be evaluated In applying such models however it is essential to use appropriate models that can neatly explain the kinetics of theprocess In this thesis the simple first order model Adams et al 1974 and the ActivatedSludge Models developed by IWA ASM1 and ASM3 were evaluated For this purpose three batch reactors with initial TSS concentrations of 5 000 10 000 and 20 000 mg L andoperating volumes of 10 L as well as three semi continuous reactors with operatingvolumes of 5 L and mean solids retention times of 5 10 and 20 days with correspondingdaily feed rates of 1000 500 and 250 mL d respectively were operated to investigatetheir performance and to collect the experimental data required for model calibrations Thebatch reactors and the semi continuous ones were monitored for 70 and 60 days respectively Samples taken from the reactors were analyzed for their solids concentrationsand their Chemical Oxygen Demand COD Experimental data revealed that the moreconcentrated the sludge the lower its stabilization rate but the higher the ultimateefficiency of the digester It was also shown that increased mean cell residence time insemi continuous reactors led to higher reductions in biological activity higher suspendedsolids degradation and a more stabilized sludge produced The measured data were thenused to estimate the parameters of the models investigated and the best sets of parametersyielding the best fit of the predicted and measured data were identified for each model andfor each reactor For each of the batch and semi continuous runs representative sets ofparameters were also identified whose total errors over all reactors were minimum Theparameter estimation results for batch and semi continuous runs showed that higher sludgeconcentrations and mean cell residence times were associated with lower cell decaycoefficient values The error values for batch and semi continuous runs calculated byASM3 were found to be lower than those calculated by the simple first order model and byASM1 Comparisons with experimental data proved ASM3 to be superior in its capabilityto predict concentrations in both batch and semi continuous reactors

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كاربرد مدل هاي لجن فعال ﴿ ASMS ) در هضم هوازي لجن ثانويه

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